Question

three autosomal genes (Z, E and T) in seahorses. Each gene sorts independently and each gene has two alleles. The Z allele forms zebra stripes which are completely dominant over no stripes, z. The E allele codes for crossed eyes which is dominant over uncrossed eyes, e. Lastly, the T allele codes for jellyfish-like tentacles,which are dominant over (t) squid-like tentacles. You have two parents that are completely heterozygous for all traits. What is the probability they have offspring that have:

a.Zebra Stripes, uncrossed eyes, and squid-like tentacles? ________________

b.All dominant traits?_______________________________

c.Have the genotype ZZeeTt?_________________________

d.True breeding for zebra stripes, crossed eyes and squid-like tentacles?______________

e.All dominant alleles or all recessive alleles?________________

f.The first progeny is a male with zebra stripes and the second progeny is a male with no stripes?(assume sex probabilities in zebrafish is similar to humans)

Answer 1

Three genes in seahorse. And each have an allele.

Z = zebra strip -------dominant

z = no strip ----recessive

E = crossed eye -------dominant

e = uncrossed eye ----recessive

T = jelly-fish like tentacles -------dominant

t = squid-like tentacles ----recessive

When parents with complete heterozygous for all traits cross. The progenies will be:

Heterozygous parents genotype = Zz Ee Tt for both parents

Perform the cross ---> ZzEeTt X ZzEeTt

We will use fork-line method to perform the cross. Punnett square can also be made but it's a complex for more number of genes.

Gametes for Zz X Zz

	Z	z
Z	ZZ	Zz
z	Zz	zz

1/4 = ZZ ; 2/4 or 1/2= Zz ; 1/4 = zz

Gametes for Ee X Ee

	E	e
E	EE	Ee
e	Ee	ee

1/4 = EE ; 2/4 or 1/2 = Ee ; 1/4 = ee

Gametes for Tt X Tt

	T	t
T	TT	Tt
t	Tt	tt

1/4 = TT ; 2/4 or 1/2 = Tt ; 1/4 = Tt

Cross is as in image :

Phenotypic ratio = 27:9:9:9:3:3:3:1

Ans d) true breeding for Zebra stripes, crossed eyes and squid-like tentacles. P = 9/64

Ans e) all dominant allele = 1/64

All recessive allele = 1/64

Thank you...

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