Question

what is chromosome? state its any two typical features? Describe chromosomal basis of sex determination in human life. ​

Answer 1

$\underline\bold {\huge {ANSWER \::}}$

■Inside a cell, there is the nucleus .

■The nucleus contains most of the cells DNA which is organised into discrete units called chromosomes .

■Each chromosome contains one long DNA molecule associated with histone proteins .

■Chromosomes

are highly coiled and condensed chromatin fibres .

■It is 40% DNA and 60% histones.

Features:-

■As a cell prepares to divide the chromatin fibres coil and condense further eventually becoming thick enough to be distinguished as chromosomes .

■Each chromosome consists of two chromatids joint at some point along the length and this point of attachment is called centromere .

$\underline\bold {\huge {Sex determination \::}}$

■In a human, the female has XX chromosomes and the male has XY chromosomes.

■The sex of the child depends upon the kind of sperm that fertilizes the egg .

■The egg contains only one x chromosome but half of the sperms released into the genital tract of the female during sexual intercourse are X bearing and the remaining half are Y bearing .

■It is a matter of chance as to which type of sperm fuses with the ovum .

● If the egg (X) fuses with the X bearing sperm the resulting combination is XX that is female (daughter ).

● If the egg (X) fuses with the Y bearing sperm the resulting combination is XY that is male (son).

■This is the process of sex determination in humans.