Variation and Inheritance Flashcards
Both alleles are expressed and the heterozygote manifests a third phenotype with properties of both alleles (blood type, red hairs and white hairs make red and white haired individual)
Codominance
A single gene impacts two or more (seemingly unrelated) traits
Pleiotropy
Variation due to this does not matter for evolution
Variation due only to environmental effects. Evolution is concerned with variation due to genes
When there are no categories, anything size related (like height)
Continuous variation
How do you perform a test cross?
Cross unknown genotype with homozygous recessive genotype
During gamete formation, alleles segregate randomly so each gamete receives one or the other
Mendels law of segregation
Alters larger sections of DNA, sections of chromosomes can get extra copies of missing parts
Unequal crossing over
Example of pleiotropy
Holt Oram syndrome. Defective allele leads to abnormal heart and upper limbs
What is Mendelian inheritance also known as?
Particulate inheritance
Heterozygote results in a third unique phenotype, alleles are “blended” together (red hairs and white hairs make pink hairs)
Incomplete dominance
Example of dominant not meaning common
Huntington’s chorea (Huntingtons disease, CAG repeats)
How can mutations be predictable?
Bacterial resistance. Mutation occurs randomly but others die and the mutation gets passed on in the pop
Provided a theory of heredity
Mendel
What is simple dominance?
When there are two alleles, one dominant and one recessive
How do mutation and recombination occur?
Randomly
4 parts to Mendel’s law of segregation
- Genes are passed on unchanged and alleles account for variation and inherited characters
- Individuals inherit 1 allele from each parent
- Two alleles of gene pair segregate randomly and equally into gametes, which combine randomly and equally in next gen
- Traits may not show up in an individual but can still be passed on
What was Mendel’s law of dominance?
There exists a form of a gene (allele) that will be the expressed phenotype over the other allele
During gamete formation, segregating pairs fo alleles assort independently of other pairs (ability to form every combination, brown hair and brown eyes go to different gametes, etc.)
Independent assortment
What does a higher h2 value mean for selection?
There is a stronger response to selection
How did Mendelian genetics explain the problems of blending?
Blending caused rare variants to be blended out of the population by Mendelian genetics allowed rare variants to persist and become established in the population
Example of recessive disease
Tay-Sachs Disease (neurological impairment due to accumulation of fatty acid derivatives in neurons)
What is total variation (phenotypic variation) equal to?
Vp = Vg (genotypic variation) + Ve (environmental variation)
Why did Darwin need Mendel?
Darwins theory of natural selection almost required heredity to be Mendelian
Mutation altering single nucleotides
Point mutation
What do heritabilites of 0 and 1 mean?
1 = completely due to genes 2 = completely due to environment
Is the act of ducks following their mom genetic or learned?
Both. Genetic = imprinting, Environmental = what to follow (mom)
What is the equation for heritability?
h2 = Vg/Vp h2 = Vg/(Vg+Ve)
Several genes may make products that contribute to phenotype; phenotype determined by interaction of multiple genes (eye color)
Polygenic traits
What ration does a cross of first generation hybrids create?
3:1 in dominate
Way of determining if a phenotype is environmentally or genetically determined by having common gardens for animals and having offspring raised by parents other than their own
Cross fostering
One gene interferes with expression of another gene (bald gene interfering with widows peak gene)
Epistasis
What were Mendel’s three contributions?
Dominance, segregation, and independent assortment
Way of determining if a phenotype is environmentally or genetically determined that determines whether phenotypes are inherited according to expectation of Mendelian laws
Controlled crosses
Mechanism of heredity Darwin favored that said all cell lines contribute to gametes
Pangenesis
How can we determine the genotype of an unknown individual displaying the dominant trait?
Test cross
What is sickle cell anemia an example of?
Point mutation. T substituted for A
Way of determining if a phenotype is environmentally or genetically determined that raise offspring under identical conditions and test effect of particular variables
Common garden experiments
The proportion of variation that can be attributed to genotype
Heritability
The ultimate source of all heritable variation
Mutation
What happens when generation 1 dihybrids are crossed?
9:3:3:1 ratio
What controls mutation rate?
Nothing, although mutations can be propagated or inherited randomly
Theory of heredity that is supported that said certain cells (germ) are responsive for gamete production
Weismann’s germplasm theory
What kind of estimate is heritability?
Population wide, not individual
What kind of heritability do things under high selection have?
Low heritability bc they have low genetic variation
Multiple forms within a species
Polymorphism
How do traits highly correlated with fitness influence heritability?
High fitness = lower heritability
Low fitness = higher heritability
The interaction between these two is key
Genetics and environment
When there are different categories; this is anything categorical (like color)
Discrete variation
Shuffles existing variation into new combinations; creates new combos leading to greater levels of phenotypic variation
Recombination
