Mitosis and Meiosis

Question 1

Where is the centromere located in metacentric chromosomes?

Answer 1

Middle

Question 2

Where is the centromere located in a submetacentric chromosome?

Answer 2

between the middle and the end

Question 3

Where is the centromere located in an acrocentric chromosome?

Answer 3

Close to the end

Question 4

Where is the centromere located in a telocentric chromosome?

Answer 4

At the end

Question 5

What is happening in the G1 phase (interphase)?

Answer 5

Active gene expression and normal cell activity. Preparation for DNA synthesis.

Question 6

What happens in S phase (interphase)?

Answer 6

DNA replication and chromosome duplication.

Question 7

What is happening in G2 phase (interphase)?

Answer 7

Preparation for cell division.

Question 8

Describe G0 phase?

Answer 8

Terminal differentiation and arrest of cell division.

Cell is specialized and will eventually undergo apoptosis.

Question 9

Describe prophase (M phase).

Answer 9

Chromosomes condense

Paired centrosomes begin moving towards poles

Nucleolus disappears

Question 10

Describe metaphase (M phase).

Answer 10

Condensed chromosomes line up at metaphase plate. Each sister chromatid connected at kinetochore by by centrosomes.

Mitotic spindle is complete

Question 11

Describe anaphase (M phase).

Answer 11

Daughter chromosomes pulled to opposite poles of the cell.

Question 12

Describe telophase and cytokinesis (M phase).

Answer 12

Nuclear envelope reassembles

chromosomes decondense

cytokinesis divides cytoplasm via cleavage furrow created by contractile ring.

Question 13

What is a bivalent?

Answer 13

2 homologs that have synapsed

Question 14

What is a tetrad?

Answer 14

4 part structure of 2 homologous chromosomes, each with 2 sister chromatids.

Question 15

What is a dyad?

Answer 15

a pair of homologous chromosomes or sister chromatids after nondisjunction in anaphase I or II

Question 16

What is crossing over?

Answer 16

This is when genetic material is exchanged between two of the sister chromatids.

This happens at the chiasmata after synapsis.

Question 17

Which phases of meiosis contributes to genetic diversity?

Answer 17

Prophase 1 - crossing over

Metaphase 1 - random alignment at metaphase plate

Question 18

What cells perform mitosis and what cells undergo meiosis?

Answer 18

Somatic - mitosis

germ-line - meiosis

Question 19

State the cells of spermatogenesis from earliest to latest stage. Label them haploid or diploid. If division occurs state what phase of meiosis it is.

Answer 19

Spermatogonium (germ-line cell) 2n

– growth maturation

Primary spermatocyte 2n

–meiosis I

2 Secondary spermatocytes n

–meiosis II

4 spermatids n

– differentiation

Spermatozoa

Question 20

What is the calculation for possibilities of random alignment?

Answer 20

2^n

n = # of pairs of chromosomes

(2^n)^2 for sperm and egg combinations

Question 21

State the cells of oogenesis from earliest to latest stage and label them haploid or diploid.

Answer 21

Oogonium 2n

— growth and maturation

Primary oocyte 2n

— Arrest at prophase I till puberty

– meiosis I

1 Secondary oocyte (most of cytoplasm) n and small first polar body (degrades) n

— secondary oocyte arrests at metaphase II until fertilization

– Meiosis II

1 Ootid (most of cytoplasm) n and 1 second polar body (degrades) n

– differentiation

1 Ovum n