Question

Problem 6-56: (beetle) (a) Mode of inheritance of the three phenotypes (b) genotype of ії.3 Black eye Eyeless Brown eye 1 2 34 5 2 34 IV Problem &-56 EleventhEdition

Answer 1

a)Based on the information provided in the question Black filled means Black eye, cross mark means eyeless and white filled means brown eye.

The black eye is autosomal dominant because parents II-1 and II-2 are affected but their progeny is not affected with a black eye so this dominant trait that is both parents are Bb so Bb*Bb can have bb offspring, here B is dominant allele which causes Black eye and b is recessive allele is normal,

	B	b
B	BB	Bb
b	Bb	bb ( normal)

and both males and females are affected in a similar way.

Eyeless is an autosomal recessive trait because of individuals III-2 and III-3 are parents of IV-1 here both parents are normal for eyeless phenotype but their progeny is affected this shows both parents carry recessive alleles which are passed to their offspring that is parents are Ee, E for normal allele and e is the allele for eyeless phenotype.

Ee*Ee

	E	e
E	EE	Ee
e	Ee	ee ( affected)

and both females and males are affected in a similar way.

Brown eye is also an autosomal recessive trait individuals II-2 and II-1 are parents of III-1 both parents do not have brown eyes but their progeny has brown eye this shows the trait is autosomal recessive so parents carry a recessive allele that is R- allele for normal eye r-allele for brown eye and Rr*Rr

	R	r
R	RR	Rr
r	Rr	rr( affected)

and both males and females are affected in a similar way.

b) individual II-3 has a brown eye so is rr and one of her parents has the eyeless phenotype(ee) so II-3 got one e from mother so she is Ee and she has no black eyes so bb

so genotype is bbEerr