Reproduction

Question 0

Control of the cell cycle

Answer 0

G1/S checkpoint: cell determines if the DNA is good enough condition for synthesis
-if there is damage to the DNA, cell cycle goes into arrest until DNA has been repaired, main protein for this is p53
G2/M checkpoint: cell is mainly concerned with ensuring that the cell has achieved size and the organelles have been properly replicated to support two daughter cells

Question 1

Interphase

Answer 1

G1: create organelles for energy & production& & increase in size
S: cell replicates its genetic material; ploidy of the cell does not change even though the number of chromatids has doubled
G2: cell checks to ensure that there are enough organelles & cytoplasm to divide into two daughter cells; checks that DNA replicated correctly
G0: cell is simply living and serving its function, without any preparation for division

Question 2

Molecules responsible for the cell cycle

Answer 2

Cyclins and cyclin-dependent kinases (CDK)

• In order to be activated, CDKs require the presence of the right cyclins
• Concentrations of the various cyclins increase and decrease during specific stages. These cyclins bind to CDKs, creating an activated CDK-cyclin complex.
• This complex can then phosphorylate transcription factors

Question 3

Key differences between mitosis and meiosis

Answer 3

Mitosis: 2n -> 2n
Occurs in all dividing cells
Homologous chromosomes do not pair
No crossing over

Meiosis: 2n -> n
Occurs in sex cells only
Homologous chromosomes align on opposite sides of the metaphase plate
Crossing over can occur

Question 4

Spermatogenesis

Answer 4

Spermatogonia -(S stage)-> Diploid primary spermatocytes- (Meiosis I)-> Haploid secondary spermatocytes- (Meiosis II)-> Haploid spermatids -(Maturation)-> Spermatozoa

Question 5

Production of seminal fluid

Answer 5

Combined effort by:

• Seminal vesicles: contribute fructose to nourish sperm
• Prostate gland (along with seminal vesicles): give the fluid mildly alkaline properties so the sperm will be able to survive in the relative acidity of the female reproductive tract
• Bulbourethral (Cowper’s) glands: produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal