In cases of double epistasis, the dominant allele of one of the involved genes inhibits the expression of the other gene. <em>The </em><em>phenotypic ratio</em><em> of the </em><em>offspring</em><em> in the </em><em>F1 generation</em><em> is </em><em>12:3:1.</em>
<h3><u>Available data</u></h3>
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- Two genes are involved in color expression
- One of the genes controls the color
- The dominant allele B codes for blue kernels
- The recessive allele b codes for red kernels
- The other gene determines whether or not that color will actually appear
- The dominant allele A inhibits the color ⇒ kernels are white
- The recessive allele a allows the color expression
Since the dominant allele A is the one that inhibits the expression of the color, we can assume it is <u><em>dominant epistasis.</em></u>
<h3>What is dominant epistasis?</h3>
- When talking about epistasis, we are referring to an interruption.
- These are interactions between genes located in different loci in the same chromosome.
- An epistatic gene can alter, influence, or suppress the expression of a hypostatic gene.
- When the epistatic gene is dominant, the interaction is known as dominant epistasis.
- In dominant epistasis cases, the dominant epistatic allele inhibits the expression of the hypostatic gene.
- Observing the altered phenotype proportions of the offspring can reveal which interaction is operating in the trait determination.
- The ratio 12:3:1 belongs to dominant epistasis.
Now, let us perform the cross.
Cross: a plant that is heterozygous for both traits is self crossed
Parentals) AaBb x AaBb
Gametes) AB, Ab, aB, ab AB, Ab, aB, ab
Punnett square) AB Ab aB ab
AB AABB AABb AaBB AaBb
Ab AABb AAbb AaBb Aabb
aB AaBB Aabb aaBB aaBb
ab AaBB Aabb aaBb aabb
F1) Genotypes
- 1/16 AABB
- 2/16 AABb
- 1/16 AAbb
- 2/16 AaBB
- 4/16 AaBb
- 2/16 Aabb
- 1/16 aaBB
- 2/16 aaBb
- 1/16 aabb
Phenotypes
- 12/16 White kernels ⇒ AABB, AABb, AAbb, AaBB, AaBb, Aabb
- 3/16 Blue Kernels ⇒ aaBB, aaBb
- 1/16 Red kernels ⇒ aabb
The phenotypic ratio of the progeny is 12:3:1 → <em>12 white, 3 blue, 1 red. </em>
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<em>You will learn more about </em><em>epistasis</em><em> at</em>
<em>brainly.com/question/17387527</em>
<em>brainly.com/question/25217589</em>
