Extensions to Mendel's Rules (Lec 6 & 7) Flashcards
What is it called when the phenotype of the heterozygote is the same as the phenotype of one of the homozygotes
dominance
True or False?
Cystic Fibrosis is considered to be a recessive disease.
true
In cystic Fibrosis mutated form of CFTR causes channels to remain closed and this ion remains within cells
Cl-
In regards to Cystic Fibrosis, heterozygotes produce both normal and mutated CFTR at the cellular level, this can be considered what? At the phenotypic level it can be considered what?
co-dominance; normal
What is it called when the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes?
incomplete dominance
What is it called when the phenotype of the heterozygote includes the phenotypes of both the homozygotes?
co-dominance
What is penetrance?
percentage of individuals having a specific genotype that express the expected phenotype
What is expressitivity?
the degree to which a character is expressed
Type O blood carriers are called what? Type AB?
Type O - universal donor
Type AB - universal recipient
The masking of one gene by another gene at a different locus is called what?
epistasis
The epistatic gene is the gene that does what?
masks the other gene
The hypostatic gene is the gene that does what?
gets masked
What is dominant epistasis?
homozygous dominant or heterozygous genotypes mask the effects of the hypostatic gene
What is recessive epistasis?
presence of either of two homozygous recessive genotypes will mask the hypostatic gene
What does a 9:3:4 phenotypic ratio indicate?
recessive epistasis
what does a 12:3:1 phenotypic ratio indicate?
dominant epistasis
What does a 9:7 phenotypic ratio indicate
duplicative recessive epistasis
What does a 15:1 phenotypic ratio indicate?
duplicative dominant epistasis
When does complementation occur?
when an individual organism possessing two recessive mutations has a wild-type phenotype
What are sex-infuenced characteristics determined by?
autosomal genes
How much penetrance do sex-limited characteristics (also determined by autosomes) have in the opposite sex?
zero
What are some characteristics of cytoplasmically inherited traits?
present in males and females, usually inherited from one parent (usually the maternal parent), reciprocal crosses give different results, exhibit extensive phenotypic variation
What is the genetic maternal effect?
phenotype of the offspring is determined by the genotype of the mother
Differential expression depending on whether it is inherited from the male or the female parent is called what?
genomic imprinting
note: due to DNA methylation differences in sperm and eggs
What are characteristics of Prader-Willi Syndrome?
small hands and feet, short stature, poor sexual development, mental retardation, voracious appetites, mutation is always inherited from father
What are characteristics of Angelman Syndrome?
exhibit frequent laughter, uncontrolled muscle movement, large mouth, unusual seizures, mutation is always inherited from mother
The phenotype of a sex-linked characteristic is determined by what?
genes located on the sex chromosome
What are discontinous characteristics?
characteristics with only a few easily distinguishable phenotypes
ex: tall pea plant vs short pea plant
What are continuous characteristics?
characteristics characterized by a continuous distribution of phenotypes; often polygenic
ex: human height/weight
Characteristics encoded by genes at multiple loci are called what?
polygenic characteristics
ex: kernel color in wheat
Characteristics that are polygenic and also influenced by environmental factors are called what?
multifactorial characteristics
ex: human intelligence
Define pleiotropy
one gene affects multiple characteristics
ex: lethal allele for yellow coat color in mice
What is the phenomenon in which a genetic trait becomes more strongly expressed and/or is expressed at an earlier age in succeeding generations?
anticipation
ex: huntington’s disease, fragile-x syndrome
