Lecture 6

Question 1

define Autosome

Answer 1

Chromosomes common to both sexes; one from each parent in each parent in each diploid nucleus

Question 2

What is a cohesin complex?

Answer 2

the structure that holds sister chromatids together

Question 3

what occurs in the S phase of the cell cycle?

Answer 3

DNA replication (S for synthesis of new DNA)

Question 4

Define homolog

Answer 4

copies of the same gene (you should end up with one from each parent)

sister chromatids are identical copies of homologs

Question 5

compare and contrast the cells at the end of meiosis I and Mitosis

Answer 5

Meiosis I cell’s homologs are separated which creates a haploid cell

Mitosis cells have sister chromatids separated which creates diploid, genetically identical cells

Question 6

Compare and contrast cells at the end of meiosis II to mitotic cells

Answer 6

4 haploid daughter cells are created by the end of meiosis II

Mitotic cells create diploid daughter cells that are genetically identical

Question 7

What are the 5 phases of prophase I?

Answer 7

Leptotene

Zygotene

Pachytene

Diplotene

Diakinesis

Question 8

Define the Lepotene phase of Prophase I

Answer 8

Homologs begin to condense/pair

Question 9

Define the Zygotene phase of Prophase I

Answer 9

Homologs pair and synaptonemal complexes form in order to keep the homologs tightly paired

Question 10

Define the Pachytene phase of Prophase I

Answer 10

Synapsis is complete and crossing over begins to occur

Question 11

Define the Diplotene phase of Prophase I

Answer 11

Synaptonemal complex begins to break down so that the homologs can eventually be pulled apart
○ Homologs are still tethered together by the Chiasmata (the “X” formed by crossing over)

Question 12

Define the Diakinesis phase of Prophase I

Answer 12

the chromatids reach maximum condensation (to protect DNA from damage) and the homologs are pulled apart
○ This begins the transition into metaphase

Question 13

Where do primary oocytes arrest during embryonic development?

Answer 13

Meiosis I

Question 14

In order to generate enough gamete egg cells for an entire lifetime, what type of cell division occurs in females?

Answer 14

mitotic division prior to meiotic division

Question 15

until fertilization occurs, at what stage to secondary oocytes arrest?

Answer 15

Metaphase II

Question 16

Describe oocytes compared to sperm. how did they get this way?

Answer 16

they are much larger and complex; polar bodies formed during oogenesis allow this increased cytoplasm

Question 17

at what stages of oogenesis do polar bodies form?

Answer 17

the completion of meiosis I and the completion of Meiosis II

Question 18

where do primordial germ cells (PGC’s) migrate in males? what type of cell division occurs there?

Answer 18

the testis ; mitotic division

Question 19

where does crossing over during the formation of sperm cells occur?

Answer 19

prophase I

Question 20

at one point in spermatogenesis do sperm cells have just one sex cell?

Answer 20

the completion of Meiosis I

Question 21

how many spermatids are present at the end of Meiosis II? are they haploid or diploid?

Answer 21

4 ; haploid

Question 22

describe the path ,along anatomical chambers, of spermatids during their development.

Answer 22

testis ; lumen of seminiferous tubules ; epididymis (where they fully mature)

Question 23

What do Sertoli cells do?

Answer 23

they maintain close contact with sperm cells throughout their maturation process.