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Genetic interactions

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Wize University Biology Textbook > Mendelian Genetics

More Complex Genetics [Blood Type, Pleiotropy, Epistasis and Polygenic Inheritance]

6 Activities

Two unlinked loci effect mouse hair color. BB or Bb mice are Black. Mice with genotype bb are white because all pigment production and deposition of pigment in hair is blocked. At the second locus, the A allele (black coat) is dominant to the a allele (brown coat). A mouse with a black coat is mated with a white mouse of genotype aabb. Half of the offspring are white, one quarter are black, and one quarter are brown. What is the genotype of the black parent?
More More Complex Genetics [Blood Type, Pleiotropy, Epistasis and Polygenic Inheritance] Questions:
Match the non-mendelian inheritance terms with the correct definition.
Which of the follow involve 2 or more genes/loci?
Suppose a white-furred sloth breeds with a black-furred sloth. All of their offspring have
grey fur. What does this most likely tell you about the gene that codes for fur colour in
sloths?
Imagine that you are an alien scientist who has been asked to figure out why some aliens that have landed on Earth look the way they do. You see an alien child that has green skin with scales, and you follow it until it grows up and mates with a similar alien with green skin and scales (assume the same genotype). After mating the parents give rise to
many alien eggs which hatch into aliens with the following phenotypes:
21 green with scales, 7 blue with scales, 6 green without scales, and 2 blue without scales.
Suppose a white-furred sloth breeds with a black-furred sloth. All of their offspring have
grey fur. What does this most likely tell you about the gene that codes for fur colour in
sloths?
Imagine a set of genes that code for climbing speed of a sloth where there are slow, medium and fast climbers. The slow gene (S) and the fat (F) genes are the two loci that control climbing speed. If you produce a dihybrid cross of sloths from these two genes you get 9 slow, 3 medium and 4 fast. What type of interaction most likely exists between F and S?
Imagine that you are an alien scientist who has been asked to figure out why some aliens that have landed on Earth look the way they do. You an alien child that has green skin with scales, and you follow it until it grows up and mates with a similar alien with green skin and scales (assume the same genotype). After mating the parents give rise to many alien eggs which hatch into aliens with the following phenotypes:
21 green with scales, 7 blue with scales, 6 green without scales, and 2 blue without scales.
What can you conclude about the genetics surrounding alien skin appearance?
Practice: Epistasis
There are 2 genes in an alien species that have an epistatic interaction (meaning, one gene affects the expression of the other). Recessive alleles at the “bald” gene (bb) inhibit the expression of different alien antennae lengths (AL for long, AS for short and AN for no antennae where AL>AS>AN). Individuals who are homozygous recessive for the bald gene will show the AN phenotype regardless of their other antennae alleles. Individuals with at least one normal bald gene (B) express their antennae as expected from their genotype. If two parents are heterozygous for long antennae (ALAS) and heterozygous for the bald allele (Bb) mate, what is the probability that they have a child with no antennae?
There is no single gene responsible for hair loss in men, it is believed to be a combination of genes. This is an example of what?
If a heterozygote's phenotype lies exactly in the middle of the phenotypes of both homozygotes, what is this called?
When one character is affected by many genes this is considered what?