Question

Recessive gene express itself only in ________________
(a)Homozygous condition
(b)Heterozygous condition
(c)All of the above
(d)None of the above

Answer 1

Hint: These genes show phenotypic expression only when two same alleles of the gene are present together. Sickle cell anemia disease is an example of a recessive gene disorder.

Complete answer:
According to the Mendelian concept of the gene, there are two forms of alleles based on its expression: dominant and recessive. Dominant alleles are defined as an allele that is expressed whenever it is present either homozygous or heterozygous. Whereas recessive is an allele that is masked whenever the dominant allele is present. Thus, to express the recessive allele should present in homozygous form.

Additional Information: -Genes are discrete particles inherited in Mendelian fashion and responsible for the expression of specific phenotypic characters.
-Dominant and recessive alleles both influence an organism’s phenotype.
-A condition where the inheritance of a lethal combination of alleles results in the death of the organism is called lethality.
-When a single gene affects two or more traits is termed as pleiotropy.
-Height, weight, skin color, etc are traits affected by many genes which are known as polygenic inheritance.
-A trait like a flower color in four- o'clock which is determined by a single gene with two alleles is known as monogenic inheritance.
So, the correct answer is, ’ Homozygous condition.’

Note: -The term ‘gene ‘ was coined by W. Johansen in 1909.
-The gene is the unit of genetic information for each organism which controls a specific aspect of the phenotype.
-The gene is arranged on the chromosome in the linear order which contains codon on the special region or locus.