Reproduction

Question 1

G1 stage

Answer 1

presynthetic gap. Cells create organelles for energy and protein production and increases size.

Question 2

G1 to S restriction point

Answer 2

proper complement of DNA , makes sure the DNA is in good condition for synthesis. If not, the cell goes into arrest under the control of p53 protein

Question 3

S stage

Answer 3

2 chromatids bound at the centromere. The ploidy of the cell does not change but the number of chromatids doubled. Still 2N but not 1C, but 2C.

Question 4

G2/M checkpoint

Answer 4

ensuring cell has achieved adequate size and organelle to support 2 daughter cells. Also under control of p53 protein

Question 5

mechanism differences between mitosis and meiosis

Answer 5

mitosis = one round of replication, one round of division 
meiosis= one round of replication followed by two rounds of division

Question 6

meiosis 1 vs meiosis 2

Answer 6

Meiosis 1= homologous chromosomes separated= haploid daughter cells (reductional division)
Meiosis 2= similar to mitosis in that its the separation of sister chromatids, known as equational division.

Question 7

After s phase of meiosis 1.. how many chromatids, chromosomes and homologous pairs

Answer 7

After s Phase, 92 chromatids in 46 chromosomes, 23 homologous pairs.

Question 8

synapsis

Answer 8

etrads with 4 chromatids, held together by proteins called synaptonemal complex. Close contact causes chiasma

Question 9

chiasma

Answer 9

break point of homologous chromosomes where they can exchange equivalent pieces of DNA (CROSSOVER)

Question 10

Mendel’s second law of independent assortment

Answer 10

inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes. (this is backed up by cross over which can unlink genes)

Question 11

Disjunction

Answer 11

Mendel’s first law of segregation- maternal and paternal homologous chromosome is distributed randomly

Question 12

Segregation

Answer 12

separating two homologous chromosomes

Question 13

hemizygous

Answer 13

many of the genes on the X-chromosome have only one copy.

Question 14

SRY gene

Answer 14

on the Y chromosome- sex-determining region Y- codes for TF that initiates testis differentiation and formation of male gonads

Question 15

two parts of the male testes

Answer 15

1) seminiferous tubules and 2) interstitial cells

Question 16

Cells of Leydig

Answer 16

secrete testosterone and androgens

Question 17

Vas deferens

Answer 17

raise and lower the testis to maintain proper temperature (2-4 C lower than body temp)

Question 18

pathway of sperm

Answer 18

Seminiferous tubulues, epididymis, vas deferens, ejac. Duct, urethra, penis

Question 19

spermatogenesis

Answer 19

Diploid stem cells = spermatogonia which then replicate into diploid primary spermatocytes. FIrst meiotic division will result in haploid secondary spermatocytes and then meiosis 2 to generate spermatids and then they mature to become spermatozoa.

Question 20

oogenesis

Answer 20

All oogonia in women have formed during fetal development. BY birth all the oogonia have undergone DNA synthesis and are at primary oocytes. (arrest at prophase 1)
Then at menarche, once a month a primary oocyte will complete meiosis 1 to produce secondary oocyte and a polar body. (Unequal cytokinesis)

Question 21

male sexual development. FSH stimulates…. LH stimulates

Answer 21

FSH stimulates sertoli cells for sperm maturation. LH causes interstitial cells to make testosterone