Tag: mendel's law of inheritance

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.

A zygote is diploid. Hence it will have 44 autosomes. A sperm can have either of the two sex chromosomes X or Y while the egg has only one sex chromosome X. If the sperm containing the X chromosome fuses with the egg, the child born will be a female. If the sperm containing the Y chromosome fuses with the egg the child born will be a male. Thus the correct answer is option A.

XX chromosomal pair determines that a child is a female. XY combination determines that the child is a male. Thus, an egg of a female will always contain and X chromosome. 50% of the sperms contain X chromosome and 50% of sperms contain Y chromosome. Thus when an egg is fertilized by a sperm containing X chromosome, the combination of XX is paired thus giving birth to a girl child.

In humans, males and females have differences in sex chromosomes. Human cells are having two types of chromosomes: autosomes and allosomes. Allosomes present in a male is XY and those present in a female are XX. There are no differences in the cytoplasm or membrane. The chromosome is present inside a nucleus, so you can think of the nucleus also as the correct answer but when a chromosome is given as an option, it is a better choice.