Question

Lethal genes are
A. Causative for appearance of ancestral traits
B. Always recessive
C. Genes present on different chromosomes but influencing single trait
D. Killer in homozygous state

Answer 1

Hint: Lethal genes are a result of mutation in genes which can be recessive, dominant or conditional. If the organism carries lethal genes then it causes the death of that organism.

Complete answer:
Lethal genes are those genes which cause the death of organisms but only when they are present in the homozygous state. Generally these genes can be recessive, dominant or conditional.
Recessive lethals- When an organism carries a pair of identical alleles then it results in death of that organism and these are known as recessive lethal. It also codes for dominant or recessive traits but it for sure causes death when present in homozygous condition.
If we look at options now, option A is Causative for appearance of ancestral traits. This option is incorrect as lethal genes are not causative for the appearance of ancestral traits but these are killer when they are present in a homozygous state. Therefore this option is incorrect and it gets eliminated.
Moving to option B which is Always recessive. This option is incorrect as lethal genes can be dominant, recessive or conditional depending on the other gene. Therefore, this option is incorrect and it gets eliminated.
Moving to option C which is Genes present on different chromosomes but influencing single traits. This option is incorrect as lethal genes are not the genes which are present on different chromosomes but influencing a single trait. They are the genes which result in death of an organism. Therefore, this option is also incorrect and gets eliminated.
Last option D is Killer in a homozygous state. This option is the correct one since lethal genes are the genes which kill the organism when it is present in the homozygous state. Therefore, this option is correct.

Thus, the correct answer is option D which is Killer in a homozygous state.

Note: Since from all the above given options, lethal genes are those genes which kill in a homozygous state. Therefore, the most correct option is D and this gene can be recessive, dominant or conditional. The recessive lethal gene carries a pair of identical genes and it results in death which means that it results in death when present in a homozygous state.