Patterns Of Inheritance 1 Flashcards
(17 cards)
What is a codominant allele?
Both alleles are expressed in the heterozygote resulting in a different phenotype
What is epistasis?
When one gene influences the expression of another they can effect or mask it
What is a dihybrid cross?
When two genes are being inherited at the same time
E.g Mendel and his peas
What must be shown in all genetic crosses:
Parental genotype
Parental phenotype
Gametes
Offspring genotype
Offspring phenotype
Proportion of phenotypes
When will there be a 9:3:3:1 ratio?
When there is a dihybrid cross where both parents are heterozygous for both genes
Unless autosomal linkage, crossing over or epistasis
What is crossing over?
Crossing over is swapping of sections of the chromatid between non sister chromatids of homologous pairs overlapping resulting in new combinations of alleles in the gametes
Effects predicted ratio of dihybrid punnet square
What is autosomal linkage?
This is when both genes that are being considered in a dihybrid are on the same chromosome
Reduced the amount of possible gametes that can be make because they are linked on one chromosome
Why can chi squared be used in inheritance?
Becasue we are counting how many individuals are in a category
What is directional selection?
One of the extreme traits has the selective advantage, this is usually when there is a change in environment, modal trait changes
What is stabilising selection?
The modal trait has the selective advantage so individuals with extreme traits decrease, standard deviation would decrease
What is speciation?
Creation of a new species, this happens when the original population of a species become reproductively isolated from the rest of the population. The two populations can no longer breed together results in difference in their gene pools so that they are not able to interbreed to produce fertile offspring so are two different species
What is allopathic and sympatric speciation?
Allopatric is when there is a geographic, physical barrier between populations that causes reproductive isolation. This could be a river, mountain, natural disaster.
Unable to reproduce because of physical barrier, over time both populations will have different beneficial mutations to help survive in their environment. Over time that cannot interbreed becasue of differneces in gene pool
Sympatric speciation is when the populations are in the same area but become reproductively isolated becaause of changes in how they reproduce or behaviours. E.g random mutation that affects courtship ritual, invidivuals reproduce at different times of year.
No gene flow
What is genetic drift?
A change in the allele frequency from one generation to the next
A substantial drift is called evolution
There is a larger impact on smaller populations so evolution happens rapidly in smaller populations
What is a genetic bottleneck?
This is when there is a significant decrease in the population of a species. This results in a very small gene pool. So when animals in the population reproduce, there is less genetic diversity so genetic diseases that exist in the population are likley to be passed on
What is teh founder effcet?
A few individuals from an existing population isolate themself and reflate. This results in a small population so a small gene pool so less genetic diversity and increased risk of existing diseases to be passed on
How does genetic variation occur?
Natural or artificial selection
What are gene banks?
A way of maintaininggenetic material for selective breeding
E.g seed banks
They store biological samples. Selective breeding often involves inbreeding, genetic banks can be used to increase genetic diversity by outbreeding.
This reduces the risk of homozygous recessive diseases in offspring
