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In which mode of inheritance do you expect more maternal influence among the offspring ?
A
Autosomal
B
Cytoplasmic
C
Y-linked
D
X-linked
Detailed Solution
Besides the nucleus, genes are also present in the cytoplasm, in the DNA of mitochondria and chloroplasts (plasmagenes).
At fertilisation the egg contributes almost all the cytoplasm of the zygote, while the male gamete contributes practically only its nucleus.
So the cytoplasmic genes of the offspring come almost entirely from the mother.
Characters controlled by them are transmitted only through the female parent; this is called cytoplasmic or maternal inheritance, and reciprocal crosses give different results.
Examples are leaf variegation in Mirabilis jalapa and cytoplasmic male sterility in maize.
In autosomal and X-linked inheritance both parents contribute genes, and Y-linked genes pass only from father to son.
So more maternal influence is expected in cytoplasmic inheritance.
At fertilisation the egg contributes almost all the cytoplasm of the zygote, while the male gamete contributes practically only its nucleus.
So the cytoplasmic genes of the offspring come almost entirely from the mother.
Characters controlled by them are transmitted only through the female parent; this is called cytoplasmic or maternal inheritance, and reciprocal crosses give different results.
Examples are leaf variegation in Mirabilis jalapa and cytoplasmic male sterility in maize.
In autosomal and X-linked inheritance both parents contribute genes, and Y-linked genes pass only from father to son.
So more maternal influence is expected in cytoplasmic inheritance.