Making sperm

Question 1

Germ cells become enclosed by the ____________ cells

Answer 1

Sertoli

Question 2

Sertoli cells are found ____________ the seminiferous tubules

Answer 2

Inside

Question 3

Leydig cells are found ______________ the seminiferous tubules

Answer 3

Outside

Question 4

Where does spermatogenesis occur?

Answer 4

Seminiferous tubules

Question 5

How much sperm is produced daily?

Answer 5

150-300 million

Question 6

What is the site of sperm maturation and transport?

Answer 6

Epididymis

Question 7

What is the site of sperm transport?

Answer 7

Vas deferens

Question 8

What is the precursor of the male reproductive tract?

Answer 8

Wolffian duct

Question 9

Match the descriptions to either Sertoli or Leydig cells:
a) Synthesize steroids; testosterone and estrogen
b) Harbor and support developing germ cells

Answer 9

a) Leydig cells
b) Sertoli cells

Question 10

What is the length of the seminiferous tubules?

Answer 10

250 m/ testis

Question 11

What are the similarities between Sertoli and granulosa cells?

Answer 11

Derived from the same precursor cells in embryonic gonad
In direct contact with and supporting developing germ cells
Express FSH receptors

Question 12

What are the similarities between Leydig and theca cells?

Answer 12

Derived from interstitial cells of embryonic gonad
Are not in direct contact with germ cells
Express LH receptors
Produce testosterone

Question 13

Identify the following with either oogenesis or spermatogenesis
a) All germ cells produced before birth
b) Germ cells enter meiosis throughout reproductive life
c) Meiosis I before fertilization; meiosis II after
d) Growth and maturation require 3-4 months in humans

Answer 13

a) Oogenesis
b) Spermatogenesis
c) Oogenesis
d) Oogenesis

Question 14

How many gametes are produced at the end of oogenesis and spermatogenesis?

Answer 14

Oogenesis: one
Spermatogenesis: four

Question 15

What is SSC?

Answer 15

Spermatogenic stem cell that has the ability to divide
It produces one stem cell and another committed differentiating cell

Question 16

How long does spermatogenesis take in mouse vs in humans?

Answer 16

Mouse: 35 days
Human: 75 days

Question 17

What triggers meiotic division?

Answer 17

Retinoic acid

Question 18

In spermiogenesis, spermatids are ___________

Answer 18

Haploid

Question 19

Place the following species in order of most to least sperm output: Humans, monkeys, rodents

Answer 19

Monkeys, rodents, humans

Question 20

Where do stem cells reside?

Answer 20

A niche

Question 21

Where is the niche located?

Answer 21

Near the basement membrane of the seminiferous tubule

Question 22

What factor does Leydig cells provide to SSC in the niche?

Answer 22

CSF1

Question 23

What factors are provided for progenitor spermatogonia?

Answer 23

BMP1 and neuregulin 1

Question 24

What factors from the Sertoli cells are provided to the SSC?

Answer 24

GDNF and FGF2

Question 25

What is the problem of tight junctions?

Answer 25

Spermatocytes need to pass through the gap junctions to get to the lumen and would need to be disassembled

Question 26

What is the first cell to differentiate in testis?

Answer 26

Sertoli cell

Question 27

______-chromosome is required to make a Sertoli cell

Answer 27

Y

Question 28

Sperm production in adults is proportional to the number of ___________ cells generated during fetal life

Answer 28

Sertoli

Question 29

Leydig cells produce _____________ mg of testosterone per day

Answer 29

3-10

Question 30

Leydig cells are responsible for __________% of the total testosterone production

Answer 30

95

Question 31

What are some features of the acrosome of the mature sperm?

Answer 31

Covers anterior half of nucleus, derived from Golgi, outer membrane fuses with PM releasing acrosomal contents

Question 32

What are the two enzymes typical of lysosomes in acrosomes?

Answer 32

Acrosin and hyaluronidase

Question 33

What are some features of the tail of sperm?

Answer 33

55 micrometers long in humans, microtubules arranged in 9+2 structure typical of axonemes, outer dense fibres, mitochondria

Question 34

What are some features of the nucleus of sperm?

Answer 34

Extremely condensed DNA, transcriptionally inactive, histones replaced by protamines (rich in arginine and cysteine)

Question 35

Histones are associated with which stage of spermatogenesis?

Answer 35

Mitotic phase, meiosis and post-meiotic phase

Question 36

Transition proteins are associated with which stage of spermatogenesis?

Answer 36

Post-meiotic phase and spermiogenesis

Question 37

Protamines are associated with which stage of spermatogenesis?

Answer 37

Spermiogenesis

Question 38

Chromosome pairing occurs at ________________

Answer 38

Pachytene

Question 39

X and Y chromosomes do not ______________ over most of their length

Answer 39

Synapse

Question 40

Why are unpaired X and Y chromosomes transcriptionally silent?

Answer 40

The chromatin is unpaired

Question 41

What are the consequences of MSCI?

Answer 41

Autosomal genes encoding homologues of X-encoded genes become transcriptionally active in meiotic sperm cells Failure of MSCI causes cell death XXY -> synapsis of Y-chr -> expression of Y-encoded genes -> sterility

Question 42

How is MSCI mediated?

Answer 42

BRCA1 leads to chromosome inactivation BRCA1 activates ATR, ATR phosphorylates H2A.X which activates transcriptional silencing