Q3 of 32 Page 27

Can there be a heterozygous recessive? Explain.

No, it is not possible because recessive gene is not expressed when paired with dominant gene. Recessive genes are only expressed when paired with another recessive gene. Hence, in such a situation the dominant allele will express its character while the recessive will remain unexpressed.

Note: Homozygous is the condition where both the alleles governing a particular trait is same. For example, dwarfness of plant (tt)


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1

Approximately, how many genes have been Discovered in humans?

 2

Define the following terms:

(i) Allele …………………………………


(ii) Dominant gene ………………………


(iii) Genotype ………………………………..


(iv) Phenotype ……………………………


(v) Heterozygous dominant ……………………

 4

List any four traits in humans which you can easily study just by observing and making family charts.

(i) ……………………………


(ii)……………………………


(iii) …………………………


(iv) ………………………

 1

Who discovered for the first time the basic principles of genetics?