. Genetics


 Explain the following terms:
(a) Heterozygous
(b) Homozygous
(c) Pedigree chart

 

 

Best Answer

(a)  Heterozygous:  The condition in which a pair of homologous chromosomes carries dissimilar alleles for a particular character.

For example -

(i) A daughter (XXo) from a normal homozygous mother for colour vision (XX) and a colour blind father has one normal and one defective allele (XoY).

(ii) Certain tongue rollers are heterozygous with Rr genotype.

 

(b)  Homozygous:  The condition in which a pair of homologous chromosomes carries similar alleles for a particular character.

For example -

(i) A colorblind daughter (XoXo) will have both the X chromosomes with defective alleles.

(ii) A non-roller will have rr (homozygous) genotype.

(c)  Pedigree Chart:  A pedigree chart is a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next. In the pedigree chart, males are shown by squares and females by circles.

 

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