Extensions To Mendel's Rules Part II Flashcards
What is the effect of gene interaction?
Effects of genes at one locus depend on the presence of genes at other loci.
What is epistasis?
The interaction of genes that are not alleles, in particular the suppression of the effect of one gene by another.
One gene masks or influences the effect of another gene.
What is an example of recessive epistasis?
The expression of the ABO antigen depends on alleles at the H locus.
What is an example of dominant epistasis?
Yellow pigment in summer squash that is produced in a two-step pathway.
What is duplicate recessive epistasis?
Both enzymes are required for the cascade to result to at least one dominant allele at each locus is needed to get brown snails.
If either locus is dominant recessive, the cascase is blocked resulting in white snails.
What is an example of epistasis?
Coat color.
It depends on two genes, and the epistatic gene determines if pigment will be deposited in hair or not.
What is pleiotropy?
When one gene can affect multiple traits.
People who are heterozygous for cystic fibrosis disease usually do not show symptoms of cystic fibrosis. What type of dominance is this?
Complete dominance.
Heterozygout individuals for cystic fibrosis have channels at a membrane, as well as channels trapped in the ER from the diseaesed allele. What type of dominance is this?
Co-dominant.
Those who are heterozygous for cystic fibrosis have somewhat high levels of chloride in the sweat than those of normal people. Those who are homozygous have very high levels of chloride in sweat. What type of dominance is this?
Incomplete dominance
What is complementation?
It determines whether mutations are at the same locus or at different loci.
Complementation from one gene can determine the other.
True or false: genes that encode sex-influenced traits are expressed differently in males and females.
True
A sex limited characteristic is encoded by autosomal genes that are expressed in only one sex.
:-)
An example is cock featering. It is recessive and only expressed in roosters. Hens do not have it.
How are sex-limited characteristics inherited?
According to Mendel’s principles.
An example is precocious puberty in humans.
What are sex-influenced and sex-limited characteristics?
Genetic maternal effect
Genomic imprinting: differential expression of genetic material depending on whether it is inherited from the male or femal parent.
Epigenetics: phenomena due to alterations to DNA that do not include changes in the base sequence; often affect the way in which the DNA sequences are expressed.
What is genomic imprinting?
Differential expression of genetic material depending on whether it is inherited from the male or female parent.
What are imprinted genes?
Genes whose expression is determined by the parent that contributed them.
They violate the usual rule of inheritance that both alleles in a heterozygote are equally expressed.
Does Prader-Willi syndrome result from a deleton on the maternal or paternal allele?
Paternal
Does Angelman syndrome result from a mutation on the paternal or maternal allele?
Maternal
What is anticipation?
It is the stronger or earlier expression of traits in succeeding generations.
A genetic trait becomes more strongly expressed or is expressed at an earlier stage as it is passed from generation to generation.
Why does anticipation occur?
Due to an expansion of an unstable region of DNA from generation to generation.
What is an example of a disease that results from anticipation?
Huntington’s Disease
Fragile X syndrome
True or false: the more repeats there are of CGG int he 5’ untranslated region of the FMR1 gene, the more severe fragile X syndrome is.
True
What is a temperature sensitive allele?
An allele whose product is functional only at certain temperatures.
