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Reproduction or Cell division

Reproduction or Cell division


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Most of the cells in multicellular organism undergoes cell division through Mitosis.

While most of the single celled organism reproduces through binary fission by mitosis.

In both cases,the offspring are very genetically similar to the mother cell.

But one is defined as Cell division and other is defined as Reproduction.

Why?


Both cells from unicellular organisms (for example, E. coli) and multicellular ones (humans, for example) divide by mitosis - you are correct. The daughter cells are not just very genetically similar, they are identical (if everything goes right, which it usually does). Both of these instances are called "cell division". It's also called "reproduction" in unicellular organisms because the entire organism just reproduced, in an asexual manner - it went from one to two copies of itself. On the other hand, many multicellular organisms (and some unicellular) can or must reproduce sexually. This involves (generally) at least one partner and a cellular process known as meiosis, which produces haploid gametes, which then meet somehow, one gets fertilized by the other, and the resulting diploid cell begins mitosis again.


Essay on Cell Division

Cell division, cell reproduction or cell multiplication is the process of formation of new or daughter cell from the pre-existing or parent cells. In other words, the formation of new cells from the pre-existing ones and their enlargement are important factors in the growth of the plants.

A plant, in fact, it starts its life as a single cell. In course of time the cells undergo repeated division to produce many new cells, as a result of which they grow and develop into mature plants.

Essay # 2. Factors Controlling Cell Division:

There are some factors which can control cell division are:

i. Cell Size:

Cells are capable of division grow for some time, attain a particular size and then undergo division.

ii. Kernplasma or Karyoplasmic Ratio:

rise in cell volume disturbs kernpklasma ratio. It stimulates the cell to divide.

iii. Mitogens:

Mitogens are agents, factors or substances that triger cell division. The common plant mitogen is hormone cytokinin. There are several mitogenic substances known in human beings, e.g., lymphokines, EGF (epidermal growth factor), PDGF (Platelet derived growth factor).

Essay # 3. Significance of Cell Division:

1. Cell Multiplication:

Cell division is a means of cell multiplication or formation of new cells from pre-existing cells.

It maintains continuity of living matter generation after generation.

iii. Asexual Reproduction:

Cell division is a means of asexual reproduction in lower organisms.

iv. Multicellular Organisms:

The body of a multicellular organism is formed of innumerable cells. They are formed by repeated divisions of a single cell or zygote. As the number of cells increases, many of them begin to differentiate, form tissues and organs. In fully formed multicellular individuals, only some of the cells retain the power of division, e.g., bone marrow, germinal tissues, stratum germinativum, meristematic regions (in plants).

Growth of an organism involves growth and division of its cells.

Cell division helps in maintenance of a particular cell size which is essential for efficiency and control of cell activities.

vii. Genetic Similarity:

The common type of cell division or mitosis maintains genetic similarity of all the cells in an individual despite their being different structurally and functionally. It is helpful in proper coordination.

Cell division is a means of repair and healing of injured regions of the body. Old or worn out cells are similarly replaced by new ones.

ix. Regeneration:

Cell division helps in regeneration of a part or whole of the organism

x. Sexual Reproduction:

Sexual reproduction requires a special type of cell division called meiosis.

xi. Reshuffling of Genetic Traits:

Meiosis is a means of reshuffling of genetic traits. It introduces variability

During cell division, there is replication of genetic material. Any change during this activity results in mutations.

Essay # 4. Role of Amitosis in Cell Division:

It is a simple method of cell division which is also called direct cell division. Amitosis was discovered by Remak (1841, 1855) and described by Flemming (1882). In this division there is no differentiation of chromosomes and spindle. The nuclear envelope does not degenerate.

The nucleus elongates and constricts in the middle to form two daughter nuclei. This is followed by a centripetal constriction of the cytoplasm to form two daughter cells. Amitosis is not a regular method of division because it does not divide the nuclear matter equitably.

It occurs in metabolic nucleus (e.g., meganucleus of Paramecium) of some pro­tozoa. The growth of embryonic membrane of some vertebrates is due to this type of cell division. Amitosis also occurs in diseased cells. In Chara, intermodal nuclei divide by ami­tosis.

It is not followed by cytokinesis. This produces a large number of nuclei of unequal size. Some authors include cell division of monerans (e.g., bacteria) under amitosis due to absence of spindle formation. As compared to amitosis, other types of divisions (mitosis and meiosis) are called indirect cell divisions.

Essay # 5. Role of Mitosis in Cell Division:

Mitosis (Gk. mitos- thread or fibril) is that type of division in which chromosomes replicate and become equally distributed both quantitatively and qualitatively into two daughter nuclei so that the daughter cells come to have the same number and type of chromosomes as are present in the parent cell.

It is, therefore, also called equational divi­sion. Mitosis was first observed by Strasburger (1870) in plant cells, Boveri and Flemming (1879) in animal cells. The term of mitosis was coined by Flemming (1882).

It is the most common method of division which brings about growth in multicellular organisms and increase in population of unicellular organisms.

Mitosis occurs in the formation of somatic body cells and is hence often named as somatic cell division. The sites of mitotic cell division in a plant are meristematic regions like stem tip, root tip, intercalary meristem, lateral meristem, growth of embryo, leaves, flowers, fruits, seeds, etc.

In animals, mitosis is found in embryo development and some restricted regions in the mature form like skin and bone marrow. It can be easily studied in smears or sections of root and stem tips.

While the plant cell does not show much change, the animal cell becomes spheroid, more viscous and refractile at the time of mitosis. Depending upon the type of cell and the species, mitosis takes 30 minutes to 3 hours for completion.

The somatic cells or the body cells divide by a much complicated process where the nucleus plays the most important role. The nucleus divides first into two exactly equal daughter nuclei, and that process is followed by cytoplasmic division to make the cell division complete.

i. Karyo­kinesis:

Nuclear division is called mitosis or karyo­kinesis and cytoplasmic division is known as cytokinesis. Vege­tative parts of the plant grow by this method of cell division.

Mitosis (Fig. 133) is a much complicated and continuous process in which the nucleus undergoes a series of changes to divide division, though purely man-made, is recognised in the whole biological world.

a. Prophase (the early phase):

It begins with the earliest recognisable changes in the ‘metabolic’ or resting nucleus. The nucleus slightly enlarges and the crooked chromonemata, which form the reticulum, separate and become quite distinct. They undergo progressive shortening and thickening, and form thread­like bodies, called chromosomes.

The number of chromosomes is always constant for a particular species of plant. Deeply stainable matter, called ‘matrix’, appears in which chromonemata remain embedded. Each chromosome undergoes longitudinal splitting into two equal and identical halves, called chromatids, which may often remain coiled or twisted round each other.

In the meantime the nuclear membrane and the nucleolus gradually disappear, and some fibrils make their appearance in the nuclear field.

It is a short phase when the nuclear mem­brane and the nucleolus completely disappear, and by further extension of the fibrils a bipolar spindle is formed. The two ends of the spindle are the poles and the central portion is called the equator. The chromosomes arrange themselves at the equator, just preparatory to migrating towards the poles.

Each of the chro­mosomes has a spindle-fibre attachment region, called centromere, to which a fibre remains attached (traction fibre). Other fibres of the spindle (supporting fibres) extend from pole to pole.

It is the moving phase when the chromatids are repelled from the equator and move towards the poles. As the attachment regions move first, the chromosomes appear U- or L-shaped, often with unequal arms. One set of chromosomes moves towards one pole and the other set towards the opposite pole. The cause of the movement is still uncertain and has aroused a good deal of controversy. It is likely that a tractive force is exercised by the spindle fibres.

d. Telophase or Reconstruction Phase:

This is the last phase when chromosomes have reached the poles and are crowded together. Their individuality is lost. Matrix disappears and the crooked chromonemata form the reticulum. Nuclear membrane and nucleolus re-appear, and thus two daughter nuclei, with the same number of chromosomes, are reconstructed.

During telophase the fibres of the spindle expand outwards almost touching the lateral walls. Protoplasmic materials accumulate at the equatorial region in form of small droplets ultimately coalesce to form a plate called cell plate. The cell plate are by chemical and physical changes is transformed into the inter­cellular substance, middle lamella, on which cellulose particles are deposited by the protoplasts to form the primary walls.

Somatic mitosis is the most important method of cell division which takes place in all the vegetative parts of the plants. It is usually confined to some regions called meristems, like root-tips and stem-tips. This is equational division, because the distribution of chromosomes in the two daughter nuclei are exactly equal, both qualitatively and quantitatively.

The daughter nuclei are exactly alike the mother nucleus, as they have the same number of chromo­somes. The number of chromosomes is constant for a species. A cell may divide a million times, but the method is such that the number will remain same. The number of chromosome in pea is 14, in onion 16, in tobacco 48, in maize 20.

Some significance of mitosis are:

Somatic cells are formed by mitosis. Therefore, mitosis is essential for growth and development of a multicellular organism. Human baby has about 6 x 10 12 cells. All of them develop from a single celled zygote through repeated mitosis. Plants are able to grow throughout their life due to mitotic divisions in their apical and lateral meristems.

ii. Maintenance of Surface or Volume Ratio:

An overgrown somatic cell is induced to divide so that mitosis helps in maintaining a proper surface/volume ratio.

iii. Nucleocytoplasmic Ratio:

An efficient cell has a high nucleocytoplasmic ratio. Increase in size lowers the ratio. It is brought back to efficient level through division.

iv. Maintenance of Chromosome Number:

Mitosis involves replication and equitable distribution of all the chromosomes so that all the cells of a multicellular organism have the same number and type of chromosomes. This helps in proper co-ordination among different cells.

Mitosis keeps all the somatic cells of an organism genetically similar, resembling the fertilized egg. They, therefore, are able to regenerate part or whole of the organism.

Mitosis is the method of multiplication of unicellular organisms.

It is a mechanism for replacing old or worn out cells. In human body roughly 5 x 10 9 cells are daily lost from surface of skin, lining of alimentary canal, RBCs, WBCs, etc. The same are replaced by new cells formed through mitosis.

An injury or wound is healed by repeated mitotic divisions of the surround­ing healthy cells.

ix. Opportunity for Differentiation:

Mitosis produces multicellular condition. It pro­vides opportunity for differentiation.

Uncontrolled mitotic division leads to cancer.

xi. Evidence of Basic Relationship:

The details of mitosis are similar in the majority of organisms, showing their basic similarity and relationship.

Essay # 6. Role of Meiosis in Cell Division:

Meiosis or reduction division (Fig. 134) is a very complicated method of cell division which is restricted only to the reproductive cells. This method involves two divisions, of which the first division is reductional and the second one is mitotic or equational.

During prophase slender thread-like bodies, the chromosomes, are formed as usual. Two chromosomes approach each other and become very intimately associated. They may remain coiled or twisted around each other, but do not actually fuse.

This selective pairing is called synapsis, which is a fundamental feature of meiosis. Taking arbitrarily, if there are six chromosomes, they are arranged in three pairs. The chromosomes forming the pair are called homo­logous ones, and the pairs are known as bivalents.

Soon, while in contact, each chromosome undergoes longitudinal splitting and become double. In metaphase the split chromosomes move to the equator of the spindle. Since each member of the homologous pair has split longitudinally into two halves the chromosomes at the equator appear as tetrads, consisting of four chromatids.

During the next stage, anaphase, the original chromosomes forming a pair, each consisting of two chromatids—dyads, are separated and move towards the poles. This is separation or disjunction of the two members which formed the homologous pair, since the two chromatids of each dyad constitute an original chromosome.

In the telophase two daughter nuclei with reduced or halved number of chromosomes are reconstructed. This number is designated as haploid or ‘n’ number so the original number is diploid or 𔃲n’. This division is immediately followed by a second division, which is mitotic or equational.

Thus four nuclei are formed at the close of meiosis, each nucleus receiving one of the four chromatids of each tetrad. Now cytokinesis occurs, resulting in the formation of four cells.

Meiosis or reduction division takes place somewhere in the life cycle of all plants having sexual method of reproduction. The gametes, male and female, have reduced or n chromosomes. 𔃲n’ number is restored in the zygote, the product of fusion of the two gametes. Thus the number of chromosomes remains constant in a species.


Section Summary

Prokaryotes have a single looped chromosome composed of double-stranded DNA in the nucleoid. Eukaryotes have double-stranded linear chromosomes composed of chromatin in the nucleus. A full set of matched chromosomes is referred to as diploid. Haploid is having a half a set of chromosomes. Genes are segments of DNA that code for a specific protein. An organism’s traits are determined by the genes inherited from each parent. Duplicated chromosomes are composed of two sister chromatids held together by the centromere. Chromosomes are compacted using a variety of mechanisms during the cell cycle which is necessary for chromosomal segregation during mitosis.

Additional Self Check Questions

1. Define diploid and haploid.

2. Eukaryotic chromosomes are thousands of times longer than a typical cell. Explain how chromosomes can fit inside a eukaryotic nucleus.

AnswERs

1. Diploid is a full set of matched chromosomes inside a cell nucleus. Haploid is a half a set of chromosomes. Diploid is represented as 2n, while haploid is represented as n. 2. The DNA double helix is wrapped around histone proteins to form structures called nucleosomes. Nucleosomes are coiled into a chromatin fiber. During cell division, chromatin is further condensed.


Evolution Connection

Mitotic Spindle ApparatusThe precise timing and formation of the mitotic spindle is critical to the success of eukaryotic cell division. Prokaryotic cells, on the other hand, do not undergo karyokinesis and therefore have no need for a mitotic spindle. However, the FtsZ protein that plays such a vital role in prokaryotic cytokinesis is structurally and functionally very similar to tubulin, the building block of the microtubules that make up the mitotic spindle fibers that are necessary for eukaryotes. FtsZ proteins can form filaments, rings, and other three-dimensional structures that resemble the way tubulin forms microtubules, centrioles, and various cytoskeletal components. In addition, both FtsZ and tubulin employ the same energy source, GTP (guanosine triphosphate), to rapidly assemble and disassemble complex structures.

FtsZ and tubulin are homologous structures derived from common evolutionary origins. In this example, FtsZ is the ancestor protein to tubulin (a modern protein). While both proteins are found in extant organisms, tubulin function has evolved and diversified tremendously since evolving from its FtsZ prokaryotic origin. A survey of mitotic assembly components found in present-day unicellular eukaryotes reveals crucial intermediary steps to the complex membrane-enclosed genomes of multicellular eukaryotes (Table).

Cell Division Apparatus among Various Organisms
Structure of genetic materialDivision of nuclear materialSeparation of daughter cells
ProkaryotesThere is no nucleus. The single, circular chromosome exists in a region of cytoplasm called the nucleoid.Occurs through binary fission. As the chromosome is replicated, the two copies move to opposite ends of the cell by an unknown mechanism.FtsZ proteins assemble into a ring that pinches the cell in two.
Some protistsLinear chromosomes exist in the nucleus.Chromosomes attach to the nuclear envelope, which remains intact. The mitotic spindle passes through the envelope and elongates the cell. No centrioles exist.Microfilaments form a cleavage furrow that pinches the cell in two.
Other protistsLinear chromosomes exist in the nucleus.A mitotic spindle forms from the centrioles and passes through the nuclear membrane, which remains intact. Chromosomes attach to the mitotic spindle, which separates the chromosomes and elongates the cell.Microfilaments form a cleavage furrow that pinches the cell in two.
Animal cellsLinear chromosomes exist in the nucleus.A mitotic spindle forms from the centrosomes. The nuclear envelope dissolves. Chromosomes attach to the mitotic spindle, which separates the chromosomes and elongates the cell.Microfilaments form a cleavage furrow that pinches the cell in two.


Mitosis

The process of mitosis consists of six major steps and results in two identical daughter cells. It is different from meiosis which is used to create sex cells for sexual reproduction. Prior to mitosis beginning, the cell has already copied its chromosomes and the proteins that will create the mitotic spindle were created during the step called interphase.

Prophase

During prophase, the chromosomes coil up tightly and appear thicker. The cells’ nucleolus shrinks in size and disappears. The nuclear membrane starts to break down and the spindle fibers start to form from the proteins created earlier.

Metaphase

Metaphase is characterized by the chromosomes lining up across the midline of the cell and attach to the spindle fibers.

Anaphase

In this phase, each pair of chromatids separates into two identical chromosomes. The spindle fibers then pull each set of chromosomes to opposite ends of the cell.

Telophase

In telophase, the chromosomes unwind and the spindle fibers are broken down. Also in this phase, the nuclear membrane begins to reform.

Cytokinesis

Cytokinesis is when the cytoplasm of the mother cell divides forming two daughter cells. Each daughter cell has DNA that is identical to the mother cell in the number of chromosomes and the genotype.

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The image above shows the steps in mitosis.


The last important instrument of cell cycle is meiosis, it is a type of sexual reproduction the eukaryotic cell can causes, after the replication of the DNA.

In mitotic metaphase, individual chromosomes composed of two identical sister chromatids line up in the middle of the cell, but in metaphase I, homologous ch.

Cells reproduce by replicating themselves. There are two types of reproduction, meiosis and mitosis. Meiosis is what most of us think about when considering .

Different groups and organizations have varying definitions for cloning. The American Medical Association defines cloning as “the production of genetically i.

Mitosis has only one division consisting of prophase, metaphase, anaphase, and telophase, meiosis has two divisions each of the 4 phases listed. Also, meiosi.

Secondly, there is a Metaphase II which is when the chromosomes line up in the middle of the cell, at this point the spindle is fully formed. Later there is .

It is the process of producing female gametes.The sex determination of the embryo has occurred. The occurrence of the SRY gene on the Y chromosome on the m.

Unlike mitosis, there is a pairing of homologous pairs and there are two cell divisions that forms 4 haploid cells. There are two parts to meiosis: Meiosis I.

These nitrogenous bases account for the genome code of A,T,G, and C. The nitrogenous base provides a specific sequence unique to each individual inherited fr.

While we should know that Meiosis only occurs in sexually reproducing organisms. 4) In Mitosis the DNA replicates only one time in one cell division. On the.


Image of the Day: Unusual Fungi Reproduction

Emily Makowski
Oct 30, 2019

R esearchers collected 35 species of marine fungi in the waters off of Woods Hole, Massachusetts, including some that had never been studied before, and found unusual cell division cycles in some species of yeast. Their findings were published in Current Biology October 21.

“There’s hardly anything known about fungi in the marine environment,” says lead author Amy Gladfelter, a cell biologist at the University of North Carolina at Chapel Hill and a research fellow at the Marine Biological Laboratory in Woods Hole, in a news release. “This was an opportunity to understand who might be there and what they’re doing, and also to discover some new fungal systems that might display interesting biology.”

Black yeasts, in particular, showed unexpected reproduction methods. One species, Hortaea werneckii, was found to alternate between fission, the division of a parent yeast cell into two identical daughter cells, and budding, when a new cell forms as a “bud” on the parent cell and then branches off, leaving the original unchanged. Yeasts were previously thought to reproduce through either fission or budding, but not both.

Another species, Aureobasidium pullulans, produced multiple buds at a time, unlike well-studied laboratory yeasts that form them one by one. “The division cycles of these yeasts display far more plasticity and behave in unconventional ways not predicted by the studies from model yeasts,” the authors write in the paper.


Diatoms Reproduction

Reproduction in diatoms can take place by two different processes, sexual and asexual. The following article will help you to gain information regarding subject of reproduction in these tiny single-celled algal species.

Reproduction in diatoms can take place by two different processes, sexual and asexual. The following article will help you to gain information regarding subject of reproduction in these tiny single-celled algal species.

Diatoms are unicellular organisms, which are covered with a cell wall containing silica, which is called frustule. They belong to the major algal group that consists of many types of phytoplankton. These diatoms can exist in colonies, and form shapes like filaments, zigzag and stellated patterns, and ribbon-shaped colonies.

Scientific Classification

Reproduction Process

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Diatoms have a nucleus, cytoplasm, vacuoles, and chromatoplasts as cell components. The silicon wall is porous with different designs at various places for passage of gases and nutrients within the cell. These algae are classified into pinnate and centric groups. The ones belonging to the latter group are round in shape, and the former ones are elongated.

The reproduction process can occur by either sexual or asexual reproduction. All diatoms pass through a seed-like or a spore phase called the resting spore.

Asexual Reproduction

This is the primary form of reproduction, and it occurs by binary fission. In this process, the DNA undergoes replication that causes the chromosomes to divide into two identical halves. This leads to the formation of two frustules or theca. Each daughter cell receives one of the parent cell’s frustules, like other organisms that reproduce asexually. This causes the small frustule or hypotheca to form a larger frustule or epitheca. The parent cell grows larger to divide the two daughter cells by pushing out of the valve. Each daughter cell produces a new cell wall, and such units receive one valve each. This type of reproduction causes reduction in size of a daughter cell from the average size. It eventually leads to shrinkage in the size of cells, which are just one-third their maximum size. This ‘shrinking division’ is a unique mode of asexual reproduction in diatoms. The algae also need to restore their original cell size of population, and therefore undergo sexual reproduction.

Sexual Reproduction

Diatoms are non-motile organisms, and therefore the sperms have flagella. The vegetative cells of diatoms are diploid (2n), and hence, they undergo meiosis. The cells produce sexual gametes that fuse to form a zygote. The males produce sperms and females produce eggs. The female cells tend to bend, and create an opening in the cell wall. This helps the sperms to enter the female cell, and fertilize it. The egg gets encased in an envelope-like structure, which produces its own shell and nucleus. Soon, the diatom will grow to its full size. The parent cell and the new diatom form auxospores, and act as if it is in a dormant stage called ‘resting spores’. This helps the cells to survive long periods of time under unfavorable conditions. Once the cells get proper conditions to grow, they continue with their sexual reproduction.

Diatoms Facts

  • The word diatom is derived from Greek words, dia that means ‘across’ and tome that means ‘cut’. The reason being that diatoms are cut into half by the frustule.
  • They can live in fresh as well as salt water, and even can survive in soil.
  • Diatoms occur in hundreds of different shapes, and their size ranges from 10 millionths to 150 millionths of a meter.
  • The diatomaceous ooze at the bottom of the water bodies is formed by the sedimentation of dead diatoms.
  • Scientists have come across diatom fossils that are about 185 million years old, i.e., from the Jurassic age.

They initially follow the primary modes of reproduction, i.e., asexual reproduction. When the cell size in population decreases considerably, they switch over to sexual reproduction.

Related Posts

Euglena is a genus of unicellular organisms that reproduce by binary fission. Read on to find out more about the process.

A short account of the pros of asexual reproduction in plants is provided in this article.

Reproduction in fungi takes place by asexual or sexual means. Production of spores is observed in both these types of reproduction, though the genetic makeup of the spores varies. Read&hellip


Preap Cell Division Study Guide

1. Chromosomes are Rod Shaped structures made of _________ and ___________.

3. The phases in the life of a cell are called the ______________ _____________.

4. The cell cycle consists of ________, __________, __________, & division.

5. ________________ is a series of ______________ in cell division during which the _____________________ of a cell divides into __________ __________ with ____________ _____________ material.

6. _________________ only occurs in _________________________ cells.

7. The period of cell growth prior to division is _________________________.

8. Interphase consist of what three phases and describe each:
a.

9. The period during which DNA is copied ______________________.

10. DNA replication in a cell results in _________________ ____________________.

11. Replication is the process of copying _______________ ____________________.

12. Cell division is the process by which one _________ produces __________ new identical _________ ___________.

13. Cell division involves 2 Steps called __________________ _____________ ________________________.

14. Step 1 of cell division is called ___________, and step 2 is called ______________.

15. During __________the cytoplasm of the cell divides into _______ new cells called ___________ ___________.

16. The steps or phases of Mitosis are ___________, ____________, ____________, and ________________.

17. _________ is the process by which a nucleus gives rise to ___________ _________ _____________.

18. In anaphase, the sister Chromatids __________________________________.

19. The cell is pinched into two and cytokinesis begins during ____________________.

20. The assembling of microtubules that make up the spindle fibers occurs during _____________.

21. During prophase the _________ and ________ ____________ disappear.

22. The center of the cell is called the ___________ _______________.

23. ________________ condenses into chromosomes of two _________________ ____________________, joined together by the _____________________ during __________________________.

24. The production of offspring from one parent is called ________________________ ________________________.

25. During mitosis, centrioles are present only in _________________________ cells.

26. Most organisms are capable of combining ______________________ from two parents to produce ______________________.

27. The phase of mitosis during which chromosomes move to opposite poles is called ____________________________________.

28. When chromosomes of two parents combined to produce offspring, the process is known as _____________________ _____________________.

29. The chromosomes that combine during sexual reproduction are contained in special reproductive cells called _________________________.

30. In most organisms, ________________ can be either _____________ or _________________.

31. Eggs are _______________ than sperm, but are ______________________.

32. Sperm have ______________________ that help them swim to the ___________.

33. Gametes are formed by _______________________, a type of nuclear division in which _____________________ number is ______________________ and is followed by ________________ ______________________.

34. In humans, specialized reproductive cells with _________ chromosomes, called ____________________ cells, undergo ________________ and ___________ ________________ to give rise to egg or sperm that have only _______ chromosomes, ___________________ cells.

35. Any cell that contains two complete sets of chromosomes is called a _____________________ ______________.

36. A cell with only one complete set of chromosomes is called a ____________________ ______________.

37. When an egg and sperm join to produce a new individual, the process is called _________________________________.

38. The single cell that results from fertilization is called a ____________________.

39. Matching pairs of chromosomes in a diploid cell are called ___________________ _________________.

40. During ______________________, the cytoplasm of a cell and its organelles separate into two New ______________________ _____________.

41. Cytokinesis proceeds differently in animal and plant cells. In animal cells, the cytoplasm divides when a _______________ called the ________________ _________________ forms through the middle of the parent cell. In a plant cell, the material form a ______________ ____________ and __________________ gather and fuse along the equator or middle of the cell.

42. The term cleavage furrow refers to _______________________________________
________________________________________________.

43. The exchange of genes between pairs of homologous chromosomes is called _____________________ – ___________________________ and Only occurs during __________________________________ of meiosis.

44. What equally divides chromatids between offspring cells _________________ ____________________.

45. The time between cell division is called ________________________________.

46. The division of a prokaryotic cell into two offspring cells is called _______________________ ____________________________.

47. What equally divides an animal cell into two offspring cells (daughter cells) ________________________ _______________________.

48. Each protein in an organisms DNA is coded for an individual __________________.

49. If an organism has 12 chromosomes in each body cell, how many chromosomes would you expect to find in the organism’s gametes? _________________

50. During which phase of meiosis do tetrads form? ___________________________

51. The division of the cytoplasm of a eukaryotic cell is called _________________________________.

52. What event occurs during synapsis? ______________________ __________ ___________________________ _______________________.

53. During mitosis and meiosis, kinetochore fibers are thought to move __________________________________.

54. Histones are proteins that _______________ in the _______________ of __________________ in eukaryotic cells.

55. Spermatogenesis results in _______________ _______________ cells.

56. Each offspring cell produced by binary fission contains an ____________________ __________________ of the original cell’s __________________________.

57. Crossing-over results in genetic recombination by permitting the ________________________ of genetic material between ____________________ and _______________________ chromosomes.

58. Two of the 46 human chromosomes are called _______________ _________________________, all others (44) are called _________________________.

59. The production of eggs is called ____________________________.

60. What structure not found in animal cells forms along the midline of a dividing plant cell? _________________________ ____________________________.

Answer the Following questions in paragraph form:

1. What is Cytokinesis? How is it different in plant and animal cells?

2. Explain the difference between Mitosis and Meiosis?

3. What is the Difference (Contrast) between Sex Chromosomes and Autosomes?

4. List 2 ways that meiosis differs from mitosis.

5. Compare the structure of a prokaryotic chromosome with that of eukaryotic chromosomes.

6. What are homologous chromosomes?

7. Explain the difference between a haploid cell and a diploid cell?

8. What is your diploid and haploid Number?

9. What is DNA? What are histones?

10. What is independent assortment, and how does it affect the genetic makeup of offspring cells?

11. What are chromatids and what holds two chromatids together?

12. Describe how you could determine if a dividing cell is a prokaryote or an eukaryote. What structures would you look for?

13. Compare the products of mitosis with those of meiosis II.

14. Describe the events of binary fission and what kind of organisms would use this.

15. What is the cell cycle?

16. How do the products of spermatogenesis and oogenesis differ?

17. What is interphase? What makes up and occurs during each part of interphase?

18. What is mitosis and in order, What are the four phases of mitosis?

19. What are kinetochore fibers and polar fibers? What are their functions?

20. Explain crossing-over, What is it? When does it occur? Why is it Important?

21. In what type of cell, Eukaryote, Prokaryote, or Both, does mitosis occur?
__________________________________________. EXPLAIN WHY?

22. Explain the difference between Mitosis and Cytokinesis.

23. What is the difference between asexual and sexual reproduction? Which has evolutionary value? Why?


Watch the video: Animation How the Cell Cycle Works (February 2023).