MCDB 240: Testes II

Question 1

describe the number of chromosomes in each process of spermatogenesis

Answer 1

1) spermatogonia diploid (2N: 46), at basal of tubule
2) mitosis
3) more diploid spermatogonia (2N), TYPE B
4) spermatocytes (2N), PRIMARY
5) meiosis: halves chromosome number
6) 1 primary spermatocyte -> 4 haploid spermatids, equal in size, very small (23 chromosomes)

Question 2

what’s the difference between the primary and secondary spermatocyte?

Answer 2

secondary produces round spermatids

Question 3

go over the processes of meiosis I and II

Answer 3

Meiosis I: centromeres do not divide

Meiosis II: centromeres do divide

Question 4

define spermiogenesis

Answer 4

• occurs after the blood-testes barrier
• is the MATURATION; spermatids develop morphological traits of a sperm cell
• no growth phase; b/c tiny cells are better at moving
• not active…yet
• no new gene expressions and protein synthesis (cells lack machinery to do so)
• elongate cell, acquire tail, compact nucleus

Question 5

go over the process of nuclear compaction

Answer 5

1) chromatin loses histones, but GAIN promatines (DNA packed more tightly)
2) tight pack means no more transcription
- somatic cell nucleus can be packed 4x in spermatozoa via promatines
- embryo cells divide, inhereit chromatin structure (not all histones divide)
- displacement, if not proper, embryo develops incorrectly
- sperm have 9+2 microtubule structure

Question 6

describe the structure of a sperm

Answer 6

1) acrosome - holds digestive enzymes for fertilization
2) head (nucleus) - holds DNA, fuses w/ zone pellucida
3) midpiece: source of ATP
4) flagellum (tail): locomotion

Question 7

is there or is there not RNA in the head? why or why not?

Answer 7

there is, b/c of need for immediate translation at fertilization

Question 8

what kind of changes are there?

Answer 8

cellular, genetic, and chromatin changes at different stages

Question 9

define fertilization at its basest level

Answer 9

sperm enters –> male pronuclei decondenses –> syngamy

Question 10

go over the significance of apoptosis

Answer 10

fas ligand + fas = apoptosis, essential for quality control spermatogenesis (DNA repair)

Question 11

does sperm length matter?

Answer 11

no; blue whales (56 um) -> fruit flies (58 um) -> human (65) -> mice (110)

Question 12

spermatogenesis: how much spermatozoa is produced daily?

Answer 12

200 million

Question 13

define the WHO standards for sperm

Answer 13

2 mL, 7.2 pH, 20 million sperm/mL, 40 million per ejaculate, 50% motile, >15% normal forms

Question 14

what is the single most common cause of infertility?

Answer 14

male infertility; 30-50% of all cases consist of sperm count/defects

<15% normal forms

Question 15

define oligozoospermia

Answer 15

low number count

Question 16

define asthenozoospermia

Answer 16

poor motility in sperm

Question 17

define teratozoospermia

Answer 17

poor morphology

Question 18

define oligoasthenozoospermia and oligoasthenoteratozoospermia

Answer 18

former: low numbers and poor motility; the latter is all three conditions

Question 19

define azoospermia (obstructive)

Answer 19

• obstructive
• ejaculatory duct obstruction
• congenital bilateral absence of vasa deferntia (CBAVD)
• CBAVD closely correlated w/ mutations of cystic fibrosis transmembrane conductance regulator (CFTR) gene
• in short, in cystic fibrosis, vas deferens is blocked and sperm isn’t ejaculated

Question 20

define azoospermia (non-obstructive), and the two most common genetic association

Answer 20

1) chromosomal abnormalies –> impaired testicular fxn

2) y-chromosome microdeletions –> isolated spermatogenic impairment

Question 21

what is a method of treating male infertility?

Answer 21

intracytoplasmic sperm injection (ICSI)

Question 22

go over ICSI in detail

Answer 22

• IVF first w/ women in ‘78, w/ blocked Fallopian tubes
• micromanipulation techniques used to treat men (subzonal insemination, SUZI, and partial zona dissection, PZD).
• needle puts ONE sperm into an egg, quite precise*