Meiosis

Question 1

The nuclear division that reduces the chromosome number from the __ number to the __ number is called meiosis.

Answer 1

Diploid
Haploid

Question 2

A zygote always has the __ number of chromosomes, and gametes have the __ number.

Answer 2

Diploid
Haploid

Question 3

Indicate whether the following statements regarding the role of meiosis are true (T) or false (F):
____ In animals, meiosis is involved in the production of gametes that fuse to form a zygote.
___ Meiosis forms haploid cells in the life cycle of animals.
__
__ Meiosis produces four diploid cells over two divisions.

Answer 3

T
T
F

Question 4

The human diploid number is __ and the human haploid number is __.

Answer 4

46
23

Question 5

Why is it essential that meiosis produces haploid gamete cells rather than diploid like somatic cells?

Answer 5

Two gamete cells will fuse/combine in sexual reproduction, so each gamete must contribute half the genetic material (n + n = 2n)

Question 6

When do the daughter cells become haploid? Identify the stage of Meiosis and explain how.

Answer 6

In Anaphase II when the homologous pairs separate, the cell goes from having two sets of chromosomes (diploid) to only one set of chromosomes (haploid). The nuclei formed in Telophase II are each haploid (n).

Question 7

__ Homologues separate independently.

__ Crossing over occurs.

__ Gametes fuse during fertilization.

I. Zygote carries a unique combination of chromosomes.
II. Gametes carry different combinations of genes.
III. Daughter chromosomes carry different combinations of genes.

Answer 7

II
III
I

Question 8

Explain the process of crossing over and during which phase of meiosis it occurs.

Answer 8

Crossing over (Prophase I) is when homologous chromosome pairs meet up and form a tetrad. The homologous pairs swap sections of genes between the nonsister chromatids, creating recombinant chromosomes.

Question 9

Explain the process of independent assortment and during which phase of meiosis it occurs.

Answer 9

Independent assortment (Metaphase I) is when the homologous pairs (tetrads) are randomly distributed and aligned at the cell equator. There is a random manner to which pole the maternal v. paternal chromosome of each pair will face, leading to greater variety in resulting nuclei.

Question 10

How many different combinations of chromosomes would be possible in gametes produced by humans as a result of independent assortment (human diploid number = 46)? Show your work!

Answer 10

Independent assortment = 2^n (n = haploid number)
2n = 46 so n = 23
2^n = 2^23 = 8,388,608 possible combinations!

Question 11

How might sexual reproduction be advantageous to an organism?

Answer 11

Produces offspring with more genetic variation due to: crossing over, independent assortment, and random fertilization

Question 12

Explain the differences between asexual reproduction and sexual reproduction.

Answer 12

Asexual reproduction = one parent produces offspring; offspring are genetically identical to the parent
Sexual reproduction = two parents produce offspring; offspring are genetically unique from both parents

Question 13

Based on the behavior of chromosomes during meiosis, how does a species with six chromosomes pairs have an evolutionary advantage over a species with two chromosome pairs? (Hint: consider the independent assortment calculation in your response)

Answer 13

Species with n= 6 chromosomes: 2^6 = 64 varieties of independent assortment
Species with n=2 chromosomes: 2^2 = 4 varieties of independent assortment

Species with 6 chromosome pairs has more possible genetic combinations in meiosis, and therefore will have an evolutionary advantage over the species with only 2 chromosome pairs.

Question 14

Label each statement with one of the following choices:
I - meiosis I
II - meiosis II
__ Homologous chromosomes pair up forming tetrads
__ Separation of homologous chromosomes occurs
__ Results in one viable egg cell and two to three polar bodies in human females
__ Results in four viable sperm cells in human males
__ Daughter cells have chromosomes composed of two sister chromatids
__ Daughter nuclei produced have single daughter chromosomes
__ Crossing over occurs

Answer 14

I
I
II
II
I
II
I

Question 15

Does cytokinesis following both meiosis I and meiosis II?

Answer 15

Yes! Meiosis, like mitosis, is the division of the genetic material and must be followed by cytokinesis to divide the cytoplasm and its contents.

Question 16

Is DNA replicated during interkinesis?

Answer 16

No! Chromosomes were already duplicated before meiosis I and the sister chromatids are still attached (duplicated chromosomes are still present) in daughter nuclei of meiosis I.

Question 17

One division
Two successive divisions
Use PMAT stages of division
Daughter chromosomes separate
Homologous chromosomes separate
Daughter cells are produced from one parent cell
Daughter cells with the diploid number of chromosomes
Daughter cells with the haploid number of chromosomes
Somatic (body) cells
Formation of gametes
Daughter cells are genetically unique
Daughter cells are genetically identical

Answer 17

Mitosis
Meiosis
Both
Both
Meiosis
Both
Mitosis
Meisos
Mitosis
Meisos
Meisos
Mitosis

Question 18

_ begins with a diploid nucleus

__ complete after one division

__ requires two successive divisions

__ homologous chromosomes separate

__ produces haploid nuclei

__ produces diploid nuclei

__ normally produces triploid cells

__ occurs during growth and repair of tissues
I. Mitosis only
II. Meiosis only
III. Both mitosis and meiosis
IV. Neither mitosis nor meiosis

Answer 18

III
I
II
II
II
I
IV
I

Question 19

Do cells produced by Meiosis enter and go through the cell cycle again, like cells produced by mitosis do? Explain.

Answer 19

No, the gametes formed by meiosis are haploid and will not divide nor prepare to divide. Gametes produced will simply wait to serve their function.

Question 20

Indicate whether these statements are true (T) or false (F):
____ Meiosis in human males is part of spermatogenesis
____ Mitosis in human females is part of oogenesis.
____ Oogenesis occurs in the testes.
___ A zygote undergoes mitosis during development of the fetus.
____ Oogenesis produces four functional and viable egg cells from one parent cell.

Answer 20

T
F
F
T
F

Question 21

State whether the following processes occur in males (M), females (F), or both (B):
____ gamete formation
____ spermatogenesis
____ oogenesis
____ polar body formation

Answer 21

B
M
F
F

Question 22

Which of the following is NOT a valid contrast between mitosis and meiosis?
A. Mitosis: requires one set of phases; Meiosis: requires two sets of phases
B. Mitosis: occurs when body cells divide; Meiosis: occurs during gamete production
C. Mitosis: results in four daughter nuclei; Meiosis: results in two daughter nuclei
D. Mitosis: results in daughter nuclei with diploid number of chromosomes;
Meiosis: results in daughter nuclei with haploid number of chromosomes

Answer 22

C

Question 23

Polar bodies are formed during
A. Meiosis
B. Mitosis
C. Oogenesis
D. Spermatogenesis
E.!Both A and C are correct

Answer 23

E

Question 24

During anaphase of meiosis II,
A. homologous chromosomes separate.
B. daughter chromosomes separate.
C. daughter centrioles separate.
D. None of the above.

Answer 24

B

Question 25

During interkinesis,
A. chromosome duplication occurs.
B. chromosomes consist of two chromatids.
C. meiosis I is complete.
D. Both B and C are correct.

Answer 25

D

Question 26

By the end of meiosis I,
A. crossing over has occurred.
B. daughter chromosomes have separated.
C. independent assortment has occurred.
D. each daughter nucleus is genetically identical to the parent cell.
E. Both A and C are correct.

Answer 26

E