Chapter 17

Question 1

what are germ cells?

Answer 1

reproductive cells that have materials for initiating bodies in the next generation (immortal)

Question 2

what are cytoplasmic determinants?

Answer 2

maternal substance already inside the cell that changes how the DNA acts for early development

Question 3

what is special about nematode germ plasm?

Answer 3

contains a set of proteins that ensures the DNA doesn’t get activated
-prevents chromosome diminution!!
-gametes need ALL parts of chromosome

Question 4

what is chromosome diminution?

Answer 4

fragmenting of blastomere so only small % of chromosome survives
-only in cells without germ plasm

Question 5

what is the process of oocyte maturation?

Answer 5

1. oogonium (mitosis)
2. primary oocyte (starts meiosis 1)
3. secondary oocyte & polar bodies (starts meiosis 2)

Question 6

what is the fusome –> ring canals?

Answer 6

cytoplasmic bridge where nurse cells attach to the egg
-directional portal to allow the egg to get materials

Question 7

what is the germarium?

Answer 7

nurse cells + egg formation
-contain follicle cells that set up polarity before fertilization

posterior: egg
anterior: nurse cells

Question 8

what are the two ways the nurse cell and egg functions were discovered? how do they work?

Answer 8

in situ hybridization: probed to find mRNA

immunohistochemistry: fluorescent labeled antibodies to find proteins

Question 9

what is the inert genome hypothesis?

Answer 9

cells become germ cells because they are forbidden to become any other type of cell

-stem cells are totipotent (potential to become anything)

-occurs because of germ plasm components that block transcription or translation

Question 10

what are the four germ plasm components that block transcription?

Answer 10

gcl (makes germ cells)
pgc (pole cells, blocks RNA poly)
PIE-1 (inhibits enzymes)
piwi (needed for cell proliferation)

Question 11

what are the three germ plasm components that block translation?

Answer 11

piwi
nanos (posterior end)
vasa (represses somatic cells, differentiation)

Question 12

what are pole cells?

Answer 12

cells that migrate inward to be surrounded by germ line cells

-cells that have remain inert by cytoplasmic determinants
-found using VASA probe

Question 13

describe frog oocyte maturation

Answer 13

takes 3 years
-needs a vitellogenic phase to accumulate proteins and materials needed for survival of the vulnerable baby when born for accelerated growth

Question 14

what are the different parts of a lampbrush chromosome?

Answer 14

string: rDNA
branches: rRNA

Question 15

what are cellular components in an oocyte besides DNA?

Answer 15

mitochondria
RNA poly
DNA poly
histones
DNTP
ribosomes
tRNA
morphogenical factors
cytoplasmic determinants
vitellogenin

Question 16

what are some components made after fertilization?

Answer 16

cyclins
Vg1
cadherins
metalloproteinases (remove cell matrix)
actin
tubulin
reductase

Question 17

how does oocyte maturation work in rabbits & minks?

Answer 17

ovulate during intercourse, no cycles

Question 18

how does oocyte maturation work in deer?

Answer 18

estrus: ovulation triggered by weather
diapause: growth pauses until spring

Question 19

what is the process of human oocyte maturation?

Answer 19

1. stem cell divides via mitosis
   - becomes a primary oocyte before being arrested
2. diplotene (prophase 1) BLOCK
   -chromosomes are crossed over but cannot go into metaphase 1
   -progesterone activates MPF through phosphorylation
3. metaphase 1 –> metaphase 2
   -becomes a secondary oocyte before being arrested
4. metaphase BLOCK
   -fertilization causes a release of Ca2+ that breaks down CSF
5. completion of meiosis 2

Question 20

what is the process of spermatogenesis?

Answer 20

1. spermatogonia
2. primary spermatocytes
3. secondary spermatocytes
4. spermatids
   ————SPERMEOGENESIS (makes tails)————
5. sperm & residual bodies

Question 21

what is different about sperm and oocyte maturation?

Answer 21

spermatogenesis…

• meiosis initiated continuously
• 4 gametes produced
• completed in days or weeks
• no cell arrests

Question 22

what are sertoli cells?

Answer 22

stretch b/w cells and controls the process of spermatogenesis and spermeogenesis

-makes GDNF

Question 23

when during spermatogenesis are BMP-8 and GDNF important?

Answer 23

spermatogonia -> spermatocytes

Question 24

what happens to BMP-8 and GDNF as the spermatogonia matures?

Answer 24

BMP-8: increase in amount as cells divides

GDNF: decreases in amount as cells divides (diluted out)