Gamete formation in eukaryotes:Meiosis

Question 1

What are the different versions of the same gene called?

Answer 1

Answer: Different versions of the same genes are called different alleles of that gene.

Question 2

On a homologous pair of chromosomes, what is the possible relationship between the alleles of a gene on the two homologous chromosomes?

Answer 2

Answer: On a homologous pair of chromosomes, the two Homologous chromosomes can have the same alleles of a gene, or they can have different alleles

Question 3

What is genetic variation?
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Answer 3

Answer: Genetic variation refers to the differences in the possible combination of the alleles of a gene between individuals of a population

Question 4

Why do so many organisms use sexual reproduction?
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Answer 4

Answer: The main reason is that sexual reproduction leads to genetic variation

Question 5

Question: How does sexual reproduction affect the alleles of the parents in the offspring?
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Answer 5

Answer: It randomly mixes and combines the alleles of the two parents, giving the offspring a unique combination of the two parents genes

Question 6

What advantage does genetic variation provide to a population?
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Answer 6

Answer: Genetic variation gives a population resiliency against extinctions

Question 7

What special type of cell division is required for sexual reproduction?
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Answer 7

Answer: It requires a special type of cell division called meiosis, which results in the formation of gametes

Question 8

Question: What type of cells does meiosis happen to?
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Answer 8

Answer: Meiosis only happens to primary sex cells, the cells that will divide using meiosis to produce gametes

Question 9

Question: What type of cells does meiosis result in forming?
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Answer 9

Answer: Meiosis results in the formation of gametes.

Question 10

What are the names of the male and female gametes?
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Answer 10

Answer: The gametes formed by meiosis are oocytes (Female gamete) and spermatocytes (Male gametes).

Question 11

How many chromosomes do gametes have compared to normal diploid cells?
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Answer 11

Answer: Gametes have half the number of chromosomes of a normal diploid cell

Question 12

What does the term “haploid” (n) mean for gametes?
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Answer 12

Answer: Gametes are haploid (n), meaning that they have half the number of chromosomes that a regular diploid cell has (2n)

Question 13

Question: What is the main effect of meiotic cell division on the chromosome number, in contrast to mitosis?
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Answer 13

Answer: Meiotic cell division reduces the number of chromosomes. Unlike mitosis, the total number of chromosomes is reduced by meiosis to produce gametes.

Question 14

How many rounds of nuclear and cytoplasmic division does meiosis involve?
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Answer 14

Answer: Meiosis involves 2 rounds of nuclear and cytoplasmic division called meiosis one and meiosis two respectively

Question 15

What are the stages of Meiosis I?
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Answer 15

Answer: Meiosis I is made up of stages prophase 1, metaphase 1, anaphase 1 and telophase 1, followed by cytokinesis.

Question 16

Name one difference between prophase I of meiosis and prophase of mitosis regarding chromosome organization.
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Answer 16

Answer: During prophase I, duplicated chromosomes of each type will attach to each other to form tetrads, instead of being organized separately as in mitosis prophase.

Question 17

What is homologous recombination (crossing over) and when does it occur?
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Answer 17

Answer: Homologous recombination occurs during prophase I, while the chromosomes are in tetrads. One chromatid of one homologue can overlap with another chromatid and exchange alleles

Question 18

What is the effect of homologous recombination?
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Answer 18

Answer: It increases genetic variability

Question 19

What is a chiasma?
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Answer 19

Answer: A chiasma is the physical location where the two chromatids overlap and where homologous recombination takes place

Question 20

Question: Name one difference between metaphase I of meiosis and metaphase of mitosis regarding chromosome alignment.
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Answer 20

Answer: During metaphase I, homologous chromosomes line up together as tetrads, instead of individually as in mitosis metaphase

Question 21

What is independent assortment and when does it occur?
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Answer 21

Answer: Independent assortment occurs during metaphase I. The duplicated homologous chromosome that faces each pole of the cell is completely random for every type of chromosome (including sex chromosomes)

Question 22

What is the effect of independent assortment?
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Answer 22

Answer: It increases genetic variability

Question 23

Question: Name one difference between anaphase I of meiosis and anaphase of mitosis regarding centromeres.
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Answer 23

Answer: During anaphase I, the centromeres are not duplicated.

Question 24

Question: What is pulled to the poles during anaphase I of meiosis?
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Answer 24

Answer: The duplicated homologues are pulled apart from each other

Question 25

Name one difference between telophase I of meiosis and telophase of mitosis regarding the state of chromosomes after separation. *

Answer 25

Answer: During telophase I, the chromosomes do not relax back into extended chromatin

Question 26

Question: Name two other differences between telophase I of meiosis and telophase of mitosis regarding the nuclear membrane and the nucleolus. *

Answer 26

Answer: During telophase I, the nuclear membrane does not re-form and the nucleolus does not reappear

Question 27

How does Meiosis II generally compare to mitosis? *

Answer 27

Answer: Meiosis II proceeds almost exactly the same way as mitosis. The source notes that "Meiosis Il is easy!".

Question 28

What is the final result of meiosis (after Meiosis II)? *

Answer 28

Answer: The end result is four haploid gametes, each having only one set of genetic material

Question 29

Name the differences between prophase II of meiosis and prophase of mitosis. *

Answer 29

Answer: In prophase II, the chromatin is already condensed from prophase I, the nuclear membrane is already gone, and the nucleolus is already gone, unlike prophase of mitosis.

Question 30

How do metaphase II, anaphase II, and telophase II of meiosis compare to mitosis? *

Answer 30

Answer: Meiosis 2 metaphase 2, anaphase 2 and telophase 2 are the same as mitosis

Question 31

Is gamete fusion (fertilization) part of meiosis? *

Answer 31

Answer: No, gamete fusion (fertilization) is part of sexual reproduction, but not part of meiosis. It occurs after meiosis. The source states that during sexual reproduction, 2 gametes must fuse to create an offspring.

Question 32

How does gamete fusion affect genetic variability?

Answer 32

Answer: Gamete fusion is a third way that sexual reproduction increases genetic variability, because it mixes the chromosomes (and therefore the combinations of alleles) of two genetically distinct organisms.