Devo Lect 4 - Gametogenesis

Question 2

Compare egg and sperm

Answer 2

Size, motility; both haploid, both went through meiosis

Question 3

Gametogenesis (in development)

Answer 3

Germline tissue develop separately from somatic tissue early - primordial germ cells -

Question 4

Spermatogenesis

Answer 4

Seminiferous tubules contain mature sperm in lumen; progress in stages (layers of cells)

Question 5

Leydig cells and sertoli cells

Answer 5

Leydig b/w seminiferous tubules produces testosterone; sertoli in seminiferous tubules secrete GDNF, regulates fate of developing sperm

Question 6

Process of spermatogenesis, and time required

Answer 6

Spermatogonium (diploid) stem cell; primary spermatocytes; secondary spermatocytes; spermatids (haploid); mature sperm; takes 74 days in humans (35 in mice)

Question 7

Spermiogenesis

Answer 7

Differentiation of the haploid spermatid to mature sperm (ie this is part of the process of spermatogenesis)

Question 8

Structure of sperm

Answer 8

Small, little cytoplasm (lighter); nucleus condensed; mitochondria in midpiece; flagella (axoneme); acrosomal vesicle; generally conserved in animals, some plants

Question 9

Acrosomal vesicle

Answer 9

Modified lysosome in head of sperm;

Question 10

Axoneme

Answer 10

Core of flagella; 9 + 2 microtubule arrangement, tubulin; dynein motor causes flagella bending to create movement

Question 11

Gene expression in spermatogenesis

Answer 11

ß-tubulin: meiotic spindles, axoneme; dynein: motor unit; histone genes: chromatin condensation; genes for recognition proteins

Question 12

Kartagener syndrome

Answer 12

mutation in dynein gene; one or both arms absent; results in infertility, problems with cilia too (chest infections, egg doesn’t move in fallopians)

Question 13

Oogenesis differences in species

Answer 13

many eggs or few, depends on species (parental care)

Question 14

Oogenesis in mammal

Answer 14

Oogonium (diploid stem cell); primary oocytes (still diploid); 1 ovum + 3 polar bodies (uneven meiosis required to have correct number of chromosome); controlled by FSH; meiosis often not complete in mature follicle!

Question 15

FSH

Answer 15

affects the follicle to develop into Graafian follicle (contains egg undergoing meiosis); then ovulation occurs; some granulosa cells from follicle become cumulus

Question 16

When does meiosis complete in human egg?

Answer 16

After sperm meets egg

Question 17

Egg structure

Answer 17

large; stores of enzymes, mRNA (for early development), yolk proteins etc;

Question 18

Comparing different eggs

Answer 18

Sea urchin: egg secretes jelly layer outside (glycoproteins), vitelline envelope; mammal: zona pellucida (thick ECM), cumulus layer of cells

Question 19

Parthenogenesis

Answer 19

Some species can reproduce without a gamete from another; aphids, insects, sometimes occurs under unusual circumstances (aquariums); either includes one of the polar bodies (diploid), or viable haploid offspring. NOT mammals; Pro: colonize; Con: low genetic diversity