Question

4. Snifits are fictional diploid animals. You cross pure-breeding red long-nosed snifits with pure-breeding blue short-nosed snifits. All the F, snifits are red with short noses. Using the letters of your choice, write the genotypes of both parents and the F. (3 points) Next, you cross your F, snifits with pure-breeding blue short- nosed snifits. Draw a Punnett square showing this cross. Include both the genotype and phenotype in each square. Indicate the overall phenotype ratio expected from this cross. (8 points)

Answer 1

Answet 4)

All F1 are red with short stiffed nose. This suggests that red and short stiffed nose are dominant traits. Let S allele encodes short stiffed nose and it is dominant over s allele. s allele encodes long nose in homozygous recessive condition.

R allele encodes red colorand it is dominant over r allele. r allele encodes blue color in homozygous recessive condition.

Parents genotype: RRss (red nose, long sniffed) and

rrSS ( blue, short sniffed)

F1 genotype: RrSs ( red short sniffed)

The F1 is crossed with homozygous blue and short sniffed individual.

RrSs × rrSS

Punnet square:

Gametes	rS
RS	RrSS ( red short sniffed)
Rs	RrSs ( red short sniffed)
rS	rrSS ( blue short sniffed)
rs	rrSs ( blue short sniffed)

Phenotypic ratio: red, short sniffed (2): blue short sniffed (2) or 1: 1

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