Hereditary- Inheritance Beyond Mendelian's Law Flashcards
(11 cards)
What are multiple alleles? Provide an example of a trait in humans that exhibits multiple alleles. (2)
Multiple alleles refer to the existence of more than two allelic forms of a gene.
In humans, the ABO blood group system is an example, with three possible alleles: IA (A), IB (B), and i (O).
How does the concept of multiple alleles differ from Mendel’s traditional concept of dominant and recessive alleles? (3)
Mendel’s traditional concept involves two alleles, one dominant and one recessive.
However, multiple alleles involve more than two variants of a gene.
These alleles can still follow a dominant-recessive pattern, but the inheritance is more complex because of the presence of more than two allele forms.
How do multiple alleles contribute to genetic diversity within a population? (2)
Multiple alleles contribute to genetic diversity by allowing for a greater variety of phenotypes and genotypes.
The more alleles there are, the more combinations can occur, leading to increased variation in traits across individuals in a population.
What are sex-linked traits? How do they differ from autosomal traits? (2)
Sex-linked traits are genes located on the sex chromosomes (X or Y).
They differ from autosomal traits, which are located on non-sex chromosomes.
Why are males more likely to inherit sex-linked traits such as color blindness? (2)
Males are more likely to inherit sex-linked traits like color blindness because they only have one X chromosome.
If they inherit the recessive allele for a sex-linked trait on the X chromosome, they will express the trait because there is no second X chromosome to carry a dominant allele.
What is the difference between a carrier and an affected individual for a sex-linked recessive trait?
A carrier is a female who has one normal allele and one recessive allele on her X chromosomes, so she does not show the trait but can pass it on.
An affected individual is someone who has two recessive alleles for a sex-linked trait (females) or one recessive allele (males) and expresses the trait.
What is incomplete dominance? Provide an example. (2)
Incomplete dominance occurs when neither allele is completely dominant over the other, resulting in a blended phenotype.
For example, in certain flowers, a cross between red (RR) and white (WW) flowers results in pink (RW) flowers.
How does incomplete dominance differ from Mendelian dominance?
In Mendelian dominance, one allele completely masks the expression of the other (dominant vs. recessive).
In incomplete dominance, the heterozygous phenotype is a blend of the two parental traits, as neither allele is fully dominant.
What is codominance? Provide an example. (2)
Codominance occurs when both alleles contribute equally and visibly to the organism’s phenotype. An example is the coat color of certain cows, where both red and white spots appear in the heterozygous offspring.
What is non-nuclear inheritance? Give an example. (2)
Non-nuclear inheritance refers to the inheritance of traits determined by genes located in organelles such as mitochondria or chloroplasts.
An example is mitochondrial inheritance, where mitochondrial DNA is inherited maternally.
What is phenotypic plasticity? Provide an example. (2)
Phenotypic plasticity is the ability of an organism to change its phenotype in response to environmental factors, even if the genotype remains the same.
An example is the darkening of skin in humans when exposed to ultraviolet light, which stimulates the production of melanin.
