Answer:
(a) The term homogametic and
heterogametic refers to the organism depending upon whether all the gametes
contain one type of sex chromosome (homo same) or two different types of sex
chromosomes (hetero different).
Humans show XX/XY type of sex
determination, i.e., females contain 2 copies of X-chromosome and males contain
1 X and 1 Y-chromosome. Therefore, ova produced by females contain the same sex
chromosome, i.e. X.
On the other hand the sperms
contain 2 different types of chromosomes, i.e.,50% sperms have X and 50% have
Y-chromosomes (meiosis). Therefore, the sperms are different with respect to
the composition of sex chromosome. In case of humans, females are considered to
be homogametic while males are heterogametic. Yes, there are examples where
males are homogametic and females are heterogametic. In some birds the mode of
sex determination is denoted by ZZ (males)and ZW (females). Certain moths and
butterflies also show homogametic males and heterogametic females.
(b) As a rule the heterogametic
organism determines the sex of the unborn child. In case of humans, since males
are heterogametic it is the father and not the mother who decides the sex of
the child. In some animals like crocodiles, lower temperature favour hatching
of female off springs and higher temperatures lead to hatching of male off springs.
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