State its any two typical features ? Describe chromosomal basic sex determination in humans.
Answers
Male have two types of sex chromosome (X and Y chromosome)
Female has only one type of chromosome ( two X chromosome)
During fertilistion, when the male gamete sperm fuse with the female gamete the ovum. Two events can occur:
#EVENT I: X chromosome from male and X chromosome from female fuse together, this leads to fomation of XX chromosome which develops as a female
#EVENT II: Y chromosome from male and X chromosome from female fuse together, this leads to fomation of XY chromosome which develops as a male.
Note:
1. Sex is determined by the father.
2.Male gamete shows heterogamety (two types of chromosome X and Y)
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 .
■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.
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