Extension to Mendel's Laws Flashcards
What is the meaning of Incomplete Dominance? And Codominance? Make an example.
Incomplete dominance: has an intermediate phenotype.
For example, red and white flowers of the four o’clock plant can produce pink flowers in the F1 generation.
Codominance:
neither dominant nor recessive and all are expressed.
For example, black and white chickens can produce speckled chickens with both black and white feathers in the F1 generation.
What does polymorph mean?
a given gene can have multiple variants or alleles in a population.
For example, the gene for blood type in humans has three alleles: IA, IB, and i.
What does pleiotropy mean?
a single allele can determine distinct phenotypes or affect more than one trait.
For example, the allele for cystic fibrosis in humans causes multiple symptoms, such as lung infections, digestive problems, and infertility.
Explain polymorphism in human blood type determination.
different blood types in humans, due to different molecules attached to red blood cells.
The blood type is determined by two genes: AB0 and Rh.
AB0 gene has three alleles: IA, IB, and i. IA and IB are codominant
both dominant to i.
Rh gene has two alleles: Rh+ and Rh-.
Rh+ allele is dominant,
Rh- is recessive.
The combination of these alleles results in different blood types, such as A+, B-, AB-, or O+.
What is the problem with lethal alleles as yellow fur in mice?
the allele that determines yellow fur is dominant for fur color, but recessive for lethality.
mice that are homozygous for this allele die before birth
mice that are heterozygous have yellow fur.
This alters the expected ratio of phenotypic classes in the F2 generation from 3:1 to 2:1.
Which are the types of inheritance due to 2 factors?
No interaction: the combination of alleles can generate new traits.
For example, lentil seed color can be brown, grey, tan, or green, depending on the alleles of two genes.
Complementation: the combination of both dominant alleles is required for the trait.
For example, sweet pea flower color can be purple or white, depending on the presence of both dominant alleles of two genes.
Recessive epistasis: one recessive allele masks the phenotypic effect of any allele at another gene.
For example, coat color in Labrador retrievers can be black, chocolate, or yellow, depending on the presence of a recessive allele that prevents the expression of another gene.
Dominant epistasis: one dominant allele masks the phenotypic effect of any allele at another gene.
For example, summer squash color can be white, green, or yellow, depending on the presence of a dominant allele that overrides the effect of another gene.
Redundancy: one dominant allele of either gene is sufficient to determine the trait.
For example, flower color in snapdragons can be red or white, depending on the presence of a dominant allele of either gene.
How are the multifactorial inheritance patterns different from single inheritance patterns?
multifactorial:
more than one gene that determines one phenotype.
results in more complex and diverse phenotypic classes and ratios,
Single inheritance pattern:
involves one gene that determines one trait, and** follows Mendelian ratios of 3:1 or 1:2:1**.
