Patterns Of Inheritance And Variation Flashcards
what are the two types of variation
genotype
phenotype
what is genotype and what is it caused by
it is the genetic makeup of an organism caused by GENETIC factors
what is a phenotype and what is it caused by
it is the expression of a genotype caused by GENETIC AND ENVIRONMENTAL factors
what are the sources of genetic factors
- mutations
- crossing over during meiosis
- independent assortment during meiosis
- random fusion of gametes at fertilisation
what are the sources of environmental factors
- diet
- etiolation in plants (chlorosis)
this occurs due to lack of light, mineral deficiencies and virus infections
what are the two types of reproduction
- asexual
produces genetically identical offspring - sexual
random fusion of gametes producing genetic variation in offspring produced by meiosis
continuous variation
polygenic
environmental and genetic
normal distribution
larger standard deviation, more variation
discontinuous variation
genetic
bar chart
what is a gene
the base sequence of DNA which codes for the amino acid sequence of an polypeptide
what is an allele
different versions of the same gene
recessuve allele
allele which requires 2 copies to be expressed
dominant allele
allele which is expressed when there is one copy
homozygous
2 identical alleles
hetrozygous
2 different alleles where the dominant allele is always expressed
what is monogenic inheritance
inheritance of a characteristic coded for by one gene
#f1 gen
codominance
this is when both alleles are expressed in the phenotype if they are inherited tgether
what is multiple alleles
when there are more than two alleles for the same gene
female chromosomes
male chromosomes
xx
xy
how many alleles does a female need to express a RECESSSIVE characteristic
2 recessive alleles on each X chromosome
how many alleles does a male need to express a RECESSSIVE characteristic
1 recessive allele on one x chromsome
if women only have one recessive allele are they a carrier or do they have the disease
carrier
what is dihybrid inheritance
this is inheritance of 2 characteristics which is controlled by 2 different genes
how to work out dihybrid inheritance
FOIL if 4 different alleles are present
punnet square
what is haemophilia
blood which clots extremely slowly due to the absence of the protein blood clotting factor
what makes a gene linked
when the loci of two different genes are on the same chromosome, they are likely to be inherited together
what way will genes not be inherited together
if crossing over separates them during meiosis
what is autosomal linkage
it is if two genes are on the same pair of homologous chromosomes they are kinked, alleles on the same chromosome are more likely to be inherited together.
they go on tp the same daughter cell and is only separated if crossing over takes place
what is epistasis
this is the interactions of genes at different loci, alleles of one gene masks the expression of alleles of another gene
what is the chi squared test
shows if there is a significant difference between the observed phenotypic ratio and expected phenotypic ratio
what iss evolution
it is the change in allele frequency which is affected by natural selection
what are the factors which affect evolution
- muations
- gene flow
- genetic drift
- natural selection
- sexual selection
what is gene flow
the movement of alleles between populations
what is the gene pool
describes all the alleles in a population
higher genetic diversity …… gene pool
larger
what is population genetics
it is the investigation of how allele frequencies within a population change over time
what limits the size of a population
- density independent factors
dependent on population size - density dependent factors
affect populations of all sizes in the same way
what is the founder effect
this is when small groups split to form new populations ‘ organisms start a new colony’
low number of different alleles and there is low genetic diversity leading to a higher rate of genetic disease
what is the genetic bottleneck
this when a population has been reduced due to external factors
it reduces the gene pool and the genetic diversity
what are the 3 types of selection
- directional
- stabilising
- disruptive
directional selection
alleles for an extreme phenotype is most likely to be selected for
triggered by the environment
genetic variation occurs
stabilising selection
this is when the alleles for an average phenotype is selected
occurs when environmental factors remain stable
disruptive selection
extremes are selected for norms are selected against
results in sympatric speciation
what is speciation
it is the formation of new species through the process of evolution
what is the two types of speciation
- allopatric
2.sympatric
allopatric speciation
species is seperated due to geographical isolation
variations occur due to random mutations
different areas have different selection pressures
they are reproductively isolated
what is sympatric speciation
occurs in populations within the same habitat
mutations result in reproductive isolation
separate gene pools
disruptive selection
cannot interbreed
what is reproductive isolation
when populations cannot interbreed succesfully
hardy weinberg theory
