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What is a mutant allele?
Rare allele, that usually decreases or eliminates protein synthesis or function activity. It is normally inherited recessively.
What is an essential gene?
Gene that codes for a protein without which the organism cannot survive. (.333 of all genes)
What is a lethal allele?
Allele that causes the organism to die and is inherited in a recessice manner.
What is a conditional lethal allele?
An allele that will kill organism only if or when certain environmental conditions arise.
What is a semilethal allele?
An allele within a population that will kill some organisms and not others.
What is huntingtons disease an example of? (Describe the gene location and what causes the disease.)
- A lethal allele.
- It is on the short arm of C4.
- Repeating CAG.
What is Incomplete dominance?
Two alleles produce intermediate results; Heterozygotes produce an intermediate phenotype. (i.e. Red, pink, White flowers)
What are Multiple alleles?
- Alleles that code for the same trait but have many different phenotypic outcomes.
- C : full coat
- Cch : Chinchilla pattern (partial defect)
- Ch : Himalayan pattern ( Temp sensitive; extremeophiles only)
- c : Albino
What is codominance?
Results in an equal expression of two alleles. (i.e. White spotted red flowers)
What is over dominance?
- Heterozygous advantage.
- Two different alleles that produce proteins with slightly different amino acid sequences. Which allows an individual to function over broader range of conditions or become less susceptible to illnesses.
What are two examples of overdominance? (describe each)
- Cystic fibrosis : carriers are more resistant to water loss illnesses.
- PKU : embryos are more resistant to miscarriages due to fungal toxins.
What is hybrid vigor?
- Hybrids display traits superior to other non hybrids due to multiple alleles.
- Most is due to intraspecific crossing of sub-species, varieties, breeds, strains, or populations.
What is Incomplete pentrance? (Give an example)
- Phenomenon in which a dominate allele does not always penetrate into the phenotype of the individual. At the population level 60% show the dominate trait in heterozygous individuals.
- Polydactyly ( extra fingers and toes)
What does it mean to have sex influenced inheritance? (Give an example)
- An allele can be dominant in one sex and recessice in the other.
- Baldness : Autosomal trait (chromosome 4)
What is a sex limited trait?
- A trait that only occurs in one of the sexes.
- Occurs on the sex chromosome.
What is gene interaction?
Expression of a phenotypic trait is the result of the expression of many different interacting genes.
Give an example of Gene interaction.
Glucose metabolism. This requires the production of various enzymes to complete, each having their own gene.
What is epistasis?
- An example of gene interaction.
- Alleles of one gene mask the phenotypic effects of the alleles of another gene.
- Can have two or more genes coding for different protiens in an enzymatic pathway producing a single product. (Flower pigment color)
- The ratio is 9:7 for a epistatic gene.