alleryStart learning →Two mice heterozygous at both the A and C genes are crossed. What phenotypic ratio of agouti to solid to albino results?
A9 to 3 to 4
B9 to 4 to 3
C12 to 3 to 1
D9 to 6 to 1
Answer & Solution
Correct answer: A. 9 to 3 to 4
1. Take the cross AaCc with AaCc and split it by gene.
2. At the C gene the offspring are 3/4 with at least one C allele and 1/4 cc.
3. At the A gene the offspring are 3/4 with at least one A allele and 1/4 aa.
4. Any mouse that is cc is albino whatever its A alleles, so the albino class is 1/4, which is 4/16.
5. Among the pigmented 3/4, those with a dominant A are agouti: 3/4 times 3/4 gives 9/16.
6. The remaining pigmented mice are aa with a dominant C: 1/4 times 3/4 gives 3/16 solid coloured.
7. Multiplying by 16 gives 9 agouti to 3 solid to 4 albino, and the parts total 16 as expected for a two-gene interaction.
8. The 9 to 3 to 3 to 1 dihybrid pattern has collapsed because the two smallest classes both became albino.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 12 "Mendel's Experiments and Heredity", section 12.3 Laws of Inheritance_
Keep practising Mendel's Experiments and Heredity
Browse all Mendel's Experiments and Heredity questions for NCEA Level 2, or explore more Biology topics.
Related questions
Sort each clue by its dominance patternOrder the steps of crossing overKnock out the false allele claimsHow many genes contribute to eye colour in humans, at minimum?A single characteristic gives a phenotypic ratio whose parts total 16. What does that usuaIn shepherd's purse, seeds are ovoid only when both genes are homozygous recessive. What rAgouti coat colour needs a dominant A allele, but pigment of any kind needs a dominant C aIn an epistatic pair of genes, what are the alleles being masked called?