Lecture 19 - Multiple Alleles and Extensions to Mendel Flashcards
When in a meiotic cycle does segregation of alleles occur? What is its importance?
Anaphase I. Segregation of alleles occur so that each gamete carries only a single copy of each gene.
Differentiate between sex-linked, sex limited, and sex influenced.
Sex influenced is defined as traits controlled by autosomal genes that are usually dominant in one sex but recessive in the other.
Sex-linked are traits that are inherited with sex chromosomes (usually the X).
Sex limited genes are generally found on autosomes, however may only be expressed in one gender.
Explain the concept of codominance. Give two examples of a codominant trait in humans.
The full effect of both alleles can be seen in the phenotype of the heterozygote.
Examples include haemophilia the ABO blood group
What is a monohybrid cross?
A monohybrid cross is a mating between two individuals with different alleles at one genetic locus of interest.
Compare and contrast between codominance and incomplete dominance.
In both codominance and incomplete dominance, both alleles for a trait are dominant. In codominance a heterozygous individual expresses both simultaneously without any blending, while in incomplete dominance a heterozygous individual blends the two traits.
Explain the concept of multiple alleles. Give an example.
Multiple alleles involves more than just the typical two alleles that usually code for a certain characteristic in a species. ABO blood group is an example of this.
Explain the concept of phenocopy and pleiotropy. Give an example for both.
Pleiotropy is when a single affects many features of the phenotype. Exp. Sickle-cell anaemia and Marfan syndrome
Phenocopy is a result of an environmental factor that mimics the phenotype of an inherited condition (genotype). Exp. meromelia (caused by ingestion of thalidomide during pregnancy)
Can phenocopy be inherited?
Nooo
Explain the concept of expressivity and reduced penetrance. Give an example of trait that describes both.
Expressivity describes the varying degree or range in which the phenotype is expressed.
Reduced penetrance describes how an individual with a specific genotype may not show the expected phenotype.
Example: Polydactyly
Describe the concept of lethality. Differ between lethal recessive and lethal dominant genes.
Lethality refers to an allele, genotype, or mutation which results in death.
A recessive lethal is only lethal if the individual is homozygous to that allele. While a dominant lethal is lethal as long as there is one copy of that allele.
