Exam Study Flashcards
Amorphic alleles
Also known as null alleles
Type of recessive mutation
- a non functional protein is produced or
- no protein is produced
Hypomorphic alleles
- type of recessive mutation
- a poorly functioning protein is produced
- reduced amounts of normally functioning protein is produced
Recessive mutations include
Null/amorphic alleles
And
Hypomorphic alleles
Dominant mutations include
Hypermorphic alleles
And
Neomorphic alleles
Hypermorphic alleles
- type of dominant mutation
- negative phenotypic consequences due to over production of a normal protein
- negative phenotypic consequences due to production of a protein with increased activity levels
Neomorphic alleles
- negative phenotypic consequences due to the presence of an altered protein that has a new function
- negative phenotypic consequences when altered protein interferes with the wild type protein
Incomplete dominance
All genotypes aa AA and Ab differ phenotypically
Ex. Flowers red white and heterozygous is pink
New one is an intermediate btw the phenotypes
Codominance
AA aa and Aa all differ phenotypically BUT Aa exhibits phenotypes of both homozygotes. Ex. Marble cow
Allelic series
Describes the dominance hierarchy of multiple alleles
A null allele is nonfunctional
A hypomorphic allele had partial function
ABO blood type example of codominance
Gene I encodes for the transferase enzyme
IA encodes for transferase which adds acetylgalactodamine
IB encodes for one that adds galactose
i encodes for nonfunctional one
Individuals with tupe AB blood type have both proteins
Wildtype allele
A functional enzyme or other protein is produced
Sometimes refers to the most common allele in the wild
Often dominant over loss of function allele
Loss of function allele
An enzyme or other protein is no longer being produced, is produced at lower levels or is non-functional
Haplosufficiency
Half as much protein is synthesized, yet this is enough/sufficient to achieve the wild type phenotype
Gain of function mutations
Mutant allele produces a protein that has increased detrimental function
Ex, huntingtons disease
Dominant allele can be a loss of function as well
Haploinsufficiency
In the heterozygote, half as much protein is synthesized and this is not sufficient for a normal phenotype
Ex. Tailless cats
Recessive lethal alleles
Cause death in only homozygotes
Ex. Yellow mice (effect on colour is dominant)
yy white
Yy yellow
YY death
Another ex, manx cats
mm normal tail
Mm no tail
MM lethal
Dominant lethal alleles
Can be expressed in both the heterozygotes and homozygotes
Ex. Huntingtons
BB lethal
Bb lethal
bb not lethal
Tay sachs gene is an example of
Recessive lethal genes
tsts is only lethal genotype
a+
Wild type allele
Produces functional polypeptide
= wild tupe phenotype
a
Recessive amorphic allele
loss of function
Produces a partially functional polypeptide
= severe mutant phenotype
a^h
Recessive hypomorphic loss of function allele
Produces a partially functional. Polypeptide
= a mild mutant
a^D
dominant negative allele
Produces a polypeptide that interferes with the wildtype polypeptide
= severe mutant phenotype
Penetrance
Proportion of individual organisms having a particular genotype that express the expected phenotype
- you either have it or you don’t
Expressivity
Degree of which a phenotype is expressed
Mild to severe
Variation within the individual
Piebaldism
Is an example of Expressivity
Abscence of skin melanocytes
What causes incomplete Penetrance and Expressivity
Due to effects of other genes and the environment
Environmental factors that can effect phenotypic expression
- age
- sex
- temperature
- chemicals
Norm of reaction
The range of phenotypes expressed by a single genotype under different conditions
Ex, heart attack and excercise I think
Temperature sensitive allele
Ex. In Himalayan 🐰, dark pigment only develops in low temperatures
necessary for that pigment production
Enzyme inactivated at higher temperatures so the extremeties which are colder (ears and paws) are darker in colour
Phenocopy
A change in phenotype arising from the environment that is the same as the phenotype produced by a mutation in gene
Genetic interactions
Many genes can contribute to a single phenotype due to interaction last the cellular or biochemical level
Dilute gene
Dilute effect In cat coat colour is autosomal recessive
A cat requires two copies for the colour to be diluted
DD dense pigmentation
Dd carrier of dilute gene
Dd coat colour is diluted
Complementation
Occurs when two strains of an organism with different homozygous recessive mutations that produce the same phenotype produce offspring with the wildtype phenotype when mated/crossed
It will only occur if the mutation is in different genes
The other genome supplies the wildtype allele complement to the mutant allele
Ex, deafness
Genetic epistasis
Masking of the expression of one gene by another
No new phenotypes are produced
Epi static gene does the masking
Hypo static gene is masked
Phenotypic ratio of 9:3:4 indicates
Recessive epistasis
Phenotypic ratio 12:3:1
Indicates dominant epistasis
Phenotype ratio 3:1
Complete dominance
Phenotype ratio 1:2:1
Incomplete dominance
Phenotype ratio 2:1
Recessive lethal allele
Phenotype ratio 9:7
Complementation
Pleiotropy
A single gene can be responsible for a number of distinct and seemingly unrelated phenotypic effects
Ex. Sickle cell disease can be chronic infection and/or joint pain
Cystic fibrosis can be digestion problems and mucus infections
