Question

1. The somatic cells of a human male...
A) contain 44 autosomes
B) contain 22 autosomes
C) contain an X and a Y chromosome
D) A and C
E) B and C

2. Which of the following statements is FALSE?
A) The SRY gene triggers development of males
B) The SRY gene is absent in females
C) Embryos develop both male and female reproductive systems at first
D) Males develop by ‘default’, and is prevented by the presence of 2 X chromosomes
E) Female development is prevented by the presence of the SRY gene

3. Horses have 64 chromosomes in their somatic cells, and donkeys have 62 chromosomes in their
somatic cells. The interspecies hybrid between these two animals is the mule. Mules will have ____
chromosomes in their somatic cells
A) 64
B) 63
C) 62
D) 61
E) 60

4. During cell division, polar microtubules separate chromatids by....
A) pushing against each other, making the spindle longer
B) forming a contractile ring in dividing cells
C) transporting attached chromatids in opposite directions
D) both B and C

Answer 1

The correct answers have been highlighted and explanation each has been provided under the question.

1. The somatic cells of a human male...
A) contain 44 autosomes
B) contain 22 autosomes
C) contain an X and a Y chromosome
D) A and C
E) B and C

The somatic cell in humans contains 22 pairs of autosomes (44 autosomes) and two sex chromosomes (X and Y or X and X) also known as allosomes.

2. Which of the following statements is FALSE?
A) The SRY gene triggers development of males
B) The SRY gene is absent in females
C) Embryos develop both male and female reproductive systems at first
D) Males develop by ‘default’, and is prevented by the presence of 2 X chromosomes
E) Female development is prevented by the presence of the SRY gene

If Y chromosome is absent, the bipotential gonad develops into ovaries by default. Ovaries produce oestrogen which enables development of Mullerian duct into female reproductive organs.

If Y chromosome is present, it contains the SRY gene which signals the bipotential gonad to develop into testes. Testes form and secrete two important hormones

1) Anti-Mullerian duct hormone / Mullerian inhibiting substance (MIS) by Sertoli cells

2) Testosterone – masculinizes the fetus (stimulates formation of male anatomy) by Leydig cells

3. Horses have 64 chromosomes in their somatic cells, and donkeys have 62 chromosomes in their
somatic cells. The interspecies hybrid between these two animals is the mule. Mules will have ____
chromosomes in their somatic cells
A) 64
B) 63
C) 62
D) 61
E) 60

The mule would have 32 chromosomes from the horse and 31 chromosomes from the donkey, which equals to 63 chromosomes.

4. During cell division, polar microtubules separate chromatids by....
A) pushing against each other, making the spindle longer
B) forming a contractile ring in dividing cells
C) transporting attached chromatids in opposite directions
D) both B and C

Polar microtubules push the spindle poles away from each other with the help of motor proteins. They grow and slide past one another thus increasing the length of mitotic spindles pushing the poles far apart.