inherited change Flashcards
what is the definition for genotype
genetic constitution of an organism ( the alleles it has)
what is the definition for phenotype
the expression of the genetic constitution
what is the defintion for recessive allele
an allele only expressed if no dominant allele is expressed
what is the definition for dominant allele
an allele that will always be expressed in the phenotype
what is the definition for codominant
both alleles are equally dominant and expressed in the phenotype
what is the definition for multiple alleles
more than two alleles for a single gene
what is the definition for sex linkage
a gene whose locus is on the X chromosome
what is the definition for autosomal linkage
different genes that are located on the same chromosome
epistasis definition
when one gene modifies or masks the expression of a different gene on a different locus
monohybrid definition
genetic inheritance cross of a characteristic determined by one gene
dihybrid definition
genetic inheritance cross for a characteristic determined by two genes
what can also alter a persons phenotype
the enviroment
what phenotypic ratio will you always get in a dihybrid cross with heterozygous parents for both genes
9:3:3:1
when does this ratio change
- crossing over in meiosis
-autosomal linkage
-epistasis
what does autosomal linkage mean
both genes will be inherited together
what is the new ratio in a dihybrid cross with autosomal linkage for heterozygous parents
3:1
what is the null hypothesis for chi squared
there is no significant difference between the expected and observed frequency of X phenotype
how do you conclude for chi squared
- if our calculated value is less than the criritcal value at 0.05 then
- more than 5% probability that the results are due to chance
-accept the null hypothesis - there is no significant difference between the expected vs observed
if our calculated value is more than the value at 0.05 critical value
- there is a less than 5% probability the difference between observed vs expected due to chance and we can reject the null hypothesis and there is a significant difference between the expected vs observed
what is the other format you can get for chi squared exam questions
-sometimes you are given a table which is just a p value and the change
- for this if the p value is <0.05 this means there is less than 5% probability the change is due to chance and we reject the null hypothesis
what is meant by the term phenotype
phenotype is the characteristic from the genetic constitution of alleles and the characteristic due to enviroment
what is the hardy weinberg pricniple
The proportion/frequency of alleles
- Will stay constant from 1 generation to the next
- Providing there’s : NO mutation / NO selection / the population’s large / pop. genetically isolated / mating is random
what are the two equations used for the hardy weinberg principle
p + q = 1
- where p is the frequency of the dominant allele
- where q is the frequency of the recessive allele
P2 + 2PQ + Q2 = 1
- where P2 is the frequency of the homozygous dominant genotype
- where Q2 is the frequency of the homozygous recessive genotype
- where 2PQ is the frequency of the heterozygous genotype
what must you remember and look out for in hardy Weinberg principle questions
- what the question is looking for , is it looking for the frequency of the allele or the frequency of the genotype
- never divide 2PQ by 2 it stays as 2 ( think of a genetic cross diagram - 2x probability of heterozygous )
what are the assumptions of the hardy Weinberg principle
- no selection occurs
- no mutations so no new alleles formed
- no migration / immigration
- large population
- random mating
- questions may ask if the hardy Weinberg principle stands for these points , eg if there is a small population size then the principle will not stand
what is a selection pressure
a selection pressure determines which traits are successful
what is disruptive selection
selection pressure towards the extremes , creating two modal values
this selection forms speciation as you evolve 2 seperate populations
what is stabilising selection
selection pressure towards the centre increases the number of individuals at the modal value - extremes are selected against
what is directional selection
selection pressure toward one extreme moves the mode in this direction
- causes evolution
what is intraspecific competition
intraspecific competition is competition within a species for the same resources
what is interspecific competition
interspecific competition is when organisms of different species compete with eachother for the same resources
what are the downsides of interspecific competition
population sizes of both can decrease as there might be less energy for growth and reproduction . it can mean the resources available for both species decreases but sometimes one species will out compete another
