Question

2. Which of the following is TRUE about cytoplasmic inheritance?

a. It refers to chromosomal genes.

b. It is independent of the gender of the parent.

c. It follows Mendel’s law of segregation.

d. It originates from plasmids in the cytoplasm.

e. It is based on the widely different amount of cytoplasm that male and female parents provide when gametes are formed.

Answer 1

cytoplasmic inheritance , also known as extranuclear inheritence . it is the inheritance of extranuclear genetic material i.e genetic material which is situated outside the nucleus or chromosome . cytoplasmic organelle such as mitochondria and plastid ( and also may be cellular parasite) also carry DNA or genetic material . and that genetic material ( mitochondrial DNA and plastidial DNA ) are also transmitted to the offspring through cytoplasm . this transmission of mitocondrial and plastidial DNA to the offspring is known as cytoplasmic inheritance . male gamet and female gamet produce zygote . and female gamet or egg cell contribute the cytoplasm of zygote mainly . so all the cytoplasmic organelles ( like mitochondria , plastid , golgi bodies) of the zygote are actually transmitted from egg cell to the zygote ( only centrosome is transmitted to zygote came from male gamet . but centrosome does not carry any genetic material ) therefore offspring's mitocondrial DNA = egg cell's mitochondrial DNA . and this cytoplasmic genetic material will be inheritated from generation to generation through maternal ( egg cell's ) cytoplasm . shell coiling in Limnaea , transmission of kappa particle in paramoecium are the example of cytoplasmic inheritance . in case of Limnaea , shell coiling are controlled by mitochondrial DNA . so offspring gets their shell coiling type according to their mother .

option a is wrong option . because cytoplasmic inheritace is extranuclear ( outside the nucleus) inheritance . it never refers to inheritance of chromosomal  genes .( chromosomal gene belongs to nucleus only ) so option a is completely wrong .

option b is also wrong because it is not gender ( of parents) independent . cytoplasmic inheritence depends on female because of more contribution of maternal cytoplasm to the zygote . ( cytoplasm of zygote = mainly maternal cytoplasm or egg cell cytoplasm ) so option b is wrong .

option c is wrong also because cytoplasmic inheritance does not follow rules of mendel's law about genetics . cytoplasmic inheritance is known as non mendelian segregation .

option d is wrong because cytoplasmic inheritance originates from mitochondria and plastid , the genes of plasmid usually incorporated with the nuclear DNA and transmitted through nuclear inheritance . the cytoplasmic inheritance is the transmission of mitochondrial DNA and plastidial DNA through egg cell cytoplasm .

option e is the right option . because cytoplasmic inheritance is based on the cytoplasm of zygote ( or actually cytoplasm of gamet cells produced by male and female ) , male and female contribute totaly different amount of cytoplasm ( widely different amount of cytoplasm . ) to the zygote . generally maternal effect on cytoplasmic inheritance is observed because ovum or egg cell contributes the maximum cytoplasm to the zygote and sperm cell generally does not contribute any cytoplasm to the zygote or may contribute almost negligible amount of cytoplasm ( plant )