Lecture 06

Question 1

How many rounds of cell division and DNA synthesis are undergone during gamete production?

Answer 1

2 rounds cell division

1 round DNA replication

Question 2

When do homologous chromosomes separate?

Answer 2

Anaphase I

Question 3

When do sister chromatids separate?

Answer 3

Anaphase II via separase

Question 4

Leptotene stage of Prophase I

Answer 4

Homologs begin to condense/pair

Question 5

Zygotene stage of Prophase I

Answer 5

Homologs pair, synaptonemal complexes form

Question 6

Pachytene stage of Prophase I

Answer 6

Synapsis is complete; crossing over occurs

Question 7

Diplotene stage of Prophase I

Answer 7

Synaptonemal complex begins breaking down, homologs begin to separate, but remain attached at chiasma

Question 8

Diakinesis stage of Prophase I

Answer 8

Reach maximum condensation; separation of homologs and transition stage into metaphase

Question 9

Synaptonemal complex

Answer 9

Include transverse filaments (important for crossing over) and cohesin complexes (segregating homologs)

Question 10

Nondisjunction

Answer 10

Homologs fail to separate properly - leading cause of spontaneous abortions and mental retardation in humans

Question 11

Aneuploid

Answer 11

Cells with abnormal chromosome number such as Trisomy 21

Question 12

Which type of meiotic error/s is the egg generally responsible? Why?

Answer 12

Nondisjunction, aneuploidy; long arrest in meiosis I

Question 13

Which type of meiotic error/s is the sperm generally responsible for? Why?

Answer 13

DNA mutations (specifically point mutations) due to more mitotic cell divisions

Question 14

What determines whether the gonad is an ovary or testes?

Answer 14

Sex chromosomes in the genital ridge

Question 15

Sry gene

Answer 15

Sex determining region of Y; causes cells to differentiate into Sertoli cells in concert with Sox9

Question 16

What is the default pathway for gonadal development?

Answer 16

Development as a female

Question 17

When is the primary oocyte arrested, and when does meiosis resume?

Answer 17

Prophase of Meiosis I; Resumes at ovulation

Question 18

When is the secondary oocyte arrested, and when does it complete meiosis?

Answer 18

Metaphase II; Resumes after fertilization

Question 19

When does meiosis begin in sperm?

Answer 19

Puberty

Question 20

What are the requirements for capacitation?

Answer 20

Albumin, Ca2+, HCO3- to extract cholesterol and activate adenyl cyclase to produce cAMP

Question 21

Cortical reaction

Answer 21

Cortical granules release contents; prevents polyspermy by inactivating ZP3, cleaves ZP2 to make egg impenetrable

Question 22

What does sperm contribute to zygote?

Answer 22

Centrosomes and centrioles

Question 23

ICSI (Intracytoplasmic sperm injection)

Answer 23

Form of IVF where egg is injected with a single sperm; helpful for men with few motile sperm