Patterns of Inheritance Flashcards
continuous variation
variation that produces phenotypic variation where the quantitative traits vary be very small amounts between one group and the next
discontinuous variation
genetic variation producing discrete phenotypes- 2 or more non-overlapping categories
quantitative genetics
the study of genetics of such inherited characteristics
directional selection
type of natural selection that occurs when an environmental change favours a new phenotype and so results in a change in pop mean
founder effect
when a small sample of an original population establishes in a new area and gene pool is not diverse
genetic bottleneck
sharp reduction in size of population due to environmental disasters which reduced genetic diversity and as pop expands, gets less diverse
stabilising selection
natural selection leading to constancy within a population, extreme phenotypes are selected against so removed from population, reduces genetic diversity
allele frequencies
the number of alleles at a particular locus of a population
artificial selection
selective breeding of organisms involving humans choosing desired phenotypes and interbreeding those phenotypes individually
inbreeding depression
during stages of selective breeding when individuals with desired characteristics/few undesired are bred, reducing genetic diversity in the gene pool and increasing the chance of inheriting 2 copies of recessive harmful alleles
hybrid vigour
when breeders outcross individuals belonging to 2 different varieties to obtain individuals that are heterozygous at many gene loci
examples of gene banks
rare breed farms, botanic gardens/zoos, seed banks, sperm banks, frozen embryos etc
selective breeding in livestock
IVF, artificial insemination, embryo cloning, embryo transplantation
selective breeding in plants
tissue culture, asexual reproduction
why did mendel study pea plants
easy to grow, naturally self-fertilising so easy to cross artificially
traits mendel compared in pea plants
stem height, seed shape, seed colour, pod shape, pod colour, flower arrangement, flower colour
heterozygous
not true-breeding so have different alleles at a gene locus on a pair of homologous chromosomes
homozygous
true breeding so have identical alleles at a gene locus
monogenic
determined by a single gene
dihybrid
involving two gene loci
codominance
where both alleles present in the genotype of a heterozygous individual contribute to the phenotype
multiple alleles
characteristic for which there are 3 or more alleles in the populations gene pool
allopatric speciation
formation of two different species from one original species due to geographical isolation
speciation
the splitting of genetically similar population into 2 or more populations that undergo genetic differentiation and reproductive isolation, leading to isolation of 2 or more species
sympatric speciation
formation of 2 diff species from one original species, due to reproductive isolation while the populations inhabit the same location
population
members of a species, living in the same place and at the same time, that can interbreed
persistent mutation
transmitted through many generations without change
random mutation
not directed by need on the part of the organism
deletion
part of a chromosome lost
inversion
section of a chromosome breaks off, turns 180’ so genes may be too far form their regulatory nucleotide sequences to be expressed
translocation
piece of one chromosome breaks off and becomes attached to another, may interfere with regulation of genes
duplication
piece of chromosome duplicated, too many certain proteins may disrupt metabolism
non-disjunction
one pair of chromosomes fail to separate, leaving one gamete with an extra chromosome e.g. down syndrome
aneuploidy
chromosome number is not an exact multiple of the haploid number so chromatids fail to separate
polyploidy
if a diploid gamete is fertilised by a haploid gamete, resulting zygote will be triploid e.g. lumpy strawberry
sex-linked
gene present on (one of) the sex chromosomes
gene-linked
gene on the same chromosome (linkage group)
factor 8
one of the genes on non-homologous region of X chromosome which codes for a blood-clotting protein (mutated form in sufferers of haemophilia A)
codominant
where both alleles present in the genotype of a heterozygous individual contribute to the individuals phenotype
autosomal linkage
gene loci present on the same autosome (non-sex chromosome) that are often inherited together
linked
when two or more gene loci are on the same chromosome
epistasis
interaction of non-linked gene loci where one masks the expression of the other
hypostatic
when the alleles at the first locus are epistatic to those at the second locus so they are also epistatic to the first locus
how is epistasis often explained
how the genes work to code for two enzymes that work in succession, catalysing sequential steps of a metabolic pathway
calculated value of chi-squared is not significant when
it is larger than the critical value at p=0.05 so we accept the null hypothesis
gene locus
the position of an allele on the chromosome
genotype
the combination of alleles possessed by an organism
allele
an alternative version of a gene
recessive
allele only expressed when homozygous / in absence of dominant allele
