Amoeba sisters video recap questions + answers, video: Incomplete Dominance, codominance, polygenic tratis, and epistasis

Amoeba sisters video recap questions + answers, video: Incomplete Dominance, codominance, polygenic tratis, and epistasis

1. Amoeba Sisters Video SELECT Recap: Incomplete Dominance, Codominance,
Polygenic Traits, and Epistasis (Non-Mendelian Inheritance)
In some guinea pigs, having hair is associated with the presence of a dominant allele “H.”
Hairless guinea pigs do not have the dominant allele “H.” This is a Mendelian trait.
1.Show a Punnett square with a Mendelian cross between two guinea pigs that are Hh x Hh.
2.According to your work, complete the following phenotype ratio: 3 Have Hair: 1 Hairless
3.According to your work, complete the following genotype ratio:1 HH: 2 Hh: 1 hh
4.The traits covered in this video are non-Mendelian traits, unlike #1. What does it mean
for a trait to be non-Mendelian?
5.Describe how incomplete dominance and codominance, two
non-Mendelian traits, are different from each other.
6. There are a variety of ways to represent the alleles for incomplete
dominance, codominance, and other non-Mendelian traits. Many times,
there are different pros and cons for how alleles are represented as well as
different preferences. How do you plan to represent the alleles for
incomplete dominance and codominance, and how are you planning to
keep them separate in your mind?
7. Pleiotropy, not discussed in the video, is when just one gene can affect several traits! How is this vocabulary term
different from a polygenic trait, which is discussed in the video?
A non-Mendelian trait is one that does not follow Mendel's laws of inheritance. These traits can
involve incomplete dominance, codominance, polygenic inheritance, pleiotropy, and epistasis,
among others.
Incomplete dominance occurs when the heterozygous phenotype is an intermediate blend of the two homozygous
phenotypes, such as pink snapdragons (Rr) resulting from red (RR) and white (rr) parents. In contrast, codominance occurs
when both alleles in the heterozygote are fully expressed without blending, such as in speckled chickens (BW) where black
(B) and white (W) alleles are both visibly expressed. While incomplete dominance creates a mixed phenotype, codominance
allows both traits to appear distinctly in the organism.
HH Hh
Hh hh
Incomplete Dominance: Use uppercase letters with subscripts or different letters (R for red, r for white, Rr for
pink).
Codominance: Use different uppercase letters to represent each allele (B for black, W for white, BW for
speckled).
Pleiotropy: A single gene affects multiple traits. For example, the gene causing Marfan syndrome affects the heart, eyes, and bones.
Polygenic Trait: Multiple genes contribute to a single trait. For example, human height is influenced by many genes.

2. Amoeba Sisters Video SELECT Recap: Incomplete Dominance, Codominance,
Polygenic Traits, and Epistasis (Non-Mendelian Inheritance)
Codominance can be observed in some breeds of chicken. Black chickens can result from BB alleles. White chickens can
result from WW alleles. A chicken with alleles BW can be speckled with black and white.
8.Show a Punnett square with a Mendelian cross between two chickens that are BW x BW.
9.According to your work, complete the following phenotype ratio: 1 Black: 2 Speckled: 1 White
10.According to your work, complete the following genotype ratio: 1 BB: 2 BW: 1 WW
Incomplete dominance can be observed in snapdragons. Snapdragon
flowers that have two RR alleles have a red phenotype. Snapdragon flowers
with a rr have a white phenotype. Snapdragon flowers that are Rr are pink.
11.Fill in the two Punnett squares in diagram at right.
12.This is a non-Mendelian trait, but how could this be different if the trait
was Mendelian?
13. Explain the Graphic! How does this relate to epistasis?14. Apply the Vocab! The below graphic is a follow-up from
the graphic in #13. Circle genotypes below that you would
expect to result in white coloration and explain why.
Red (RR): 1/4
Pink (Rr): 1/2
White (rr): 1/4
Epistasis: Occurs when one gene masks or
suppresses the expression of another gene. In the
graphic, one gene may be affecting the expression of
another gene, resulting in a different phenotype
than expected.
If the trait were Mendelian, the heterozygote (Rr) would show the dominant phenotype (red)
instead of an intermediate phenotype (pink).
In the graphic, the genotypes that would result in white coloration
would be those where the recessive gene is homozygous (e.g., "aa"
or "bb"), as these genotypes would not allow the expression of the
dominant color.
BB BW
BW WW
RR Rr
Rr rr