Tag: sex determination in humans

Each pregnancy has a 50% chance of resulting in a boy or girl and this does not include the possibility of multiples. Having 3 daughters previously does not affect the chances of any resulting pregnancy. The chance of having a boy remains at 50%. Thus, the correct answer is option C. 

Human follows XX- XY mechanism of sex determination. Human females have 46 chromosomes arranged in 22 homologous and homomorphic autosomes and two copies of X chromosomes as sex chromosomes (44+XX). Males have 22 homomorphic pairs and one heteromorphic pair, the XY pair (44+XY). During meiosis, all the gametes produced by females contain only the X chromosome (22 + X), whereas males produce two kinds of gametes, 1/2 gametes with X- and 1/2 with Y-chromosome (22 + X and 22 + Y). Fertilization of egg (22 + X) with sperm carrying 22+X chromosomes results in female child (44 + XX). Fertilization of egg (22 + X) with the sperm carrying 22+Y chromosomes results in a male child (44A + XY) as the zygote is a diploid structure and consists of two complete sets of chromosomes. Thus, the correct answer is option A.

Sex determination seen in humans is XY sex determination. Ovum carries X chromosome, whereas sperm can carry either X or Y chromosome. The genetic makeup of a female is XX and genetic makeup of male is XY. Therefore, if the zygote is formed by receiving the X chromosome from the father, the resulting zygote will be a female. 

The karyotype of a normal human contains 22 pairs of autosomal chromosome and one pair of sex chromosome called as allosomes. Female contains 2 X chromosomes and 46 autosomes and male contains 1 X and 1 Y chromosome and 46 autosomes.

In human, the genetic makeup of female is XX and that of male is XY. Female ovum carries X chromosome, whereas the male sperm may carry either X chromosome or a Y chromosome. Therefore, if the sperm is carrying Y chromosome fertilizes an egg with X chromosome, the zygote develops into a male child.

Humans have 22 pairs of chromosome of which one pair of sex chromosome is not always a perfect pair. Women have a perfect pair of X chromosome but, men have a mismatched pair of X and Y chromosome. Therefore, (c) is the correct answer.

All animals do not contain chromosomes. In some cases, sex is determined by environmental variables (such as temperature) or social variables (e.g. the size of an organism relative to other members of its population). Therefore, (d) is the correct answer.

There is one X chromosome present in a male. Sex pair of chromosome XY represents the male human.

There are two X chromosomes present in a female. Sex pair of chromosome XX represents the female human.

When a sperm containing Y chromosome fertilises an egg with X chromosome, the zygote develops into a male child with XY as the sex chromosome. Because Y chromosome is only found in males.