Question

In the nematode C. elegans, females have both male and female germ lines, and can make both their own sperm (male gametes) and oocytes (female gametes) and fuse them together by self-fertilization. Body shape is determined by alleles of a single gene. The recessive d allele causes a short dumpy shape, while the D allele results in the wild-type shape. If a heterozygous Dd nematode undergoes self-fertilization, what proportion of its self-progeny will have a dumpy body shape?

Explain your answer

Answer 1

In Nematode C. elegans, female can make both sperm (male gamete) and oocyte (female gamete) and then fuse them together for self fertilization.

The body shape is determined by alleles of a single gene.

D allele is dominant and results in wild type body shape.

d allele is recessive and results in short dumpy shape.

The nematode is Heterozygous Dd. So it will produce allele D or d as sperms and oocytes. It undergoes self fertilization.

Parent :- Dd

Gametes :- D & d (sperm) × D & d (oocyte)

Offsprings :-

Punnett square

Sperms⬇️/ oocytes➡️	D	d
D	DD	Dd
d	Dd	dd

DD and Dd will be having wild type body shape. And dd will be having dumpy body shape.

Wild type : dumpy type = 3:1

The proportion of self progeny having dumpy shape is 1/4 or 0.25 ( or 25%).