Terminology Flashcards
Locus
A unique chromosomal location
Allele
different variants of the same coding sequence (locus)
Homozygous
identical maternal and paternal alleles
Heterozygous
non-identical maternal and paternal alleles
Hemizygous
only having inherited one allele
Genotype
genetic characteristics/ combination of alleles in an organism
Phenotype
observed genetic characteristics/traits shown by the individual
mutation
process that gives rise to chages in base sequences or the outcome i.e. the altered sequence
substitution
the change of one nucleotide to another
deletion
one or more nucleotides are deleted (can also occur with larger chromosome fragments)
insertion
on or more nucleotides are inserted (not a copy of the ones around)
(can occur with both small and larger segments)
duplication
a copy of the sequence directly close by is inserted (can occur with both small and larger segments)
inversion
original nucleotide sequence is reversed and flipped 180 degrees (can occur with both small and larger segments)
conversion
sequence copied from another site in the genome replacing the original sequence
balanced structural variation
the DNA variant has the same content but some of it is located somewhere else in the genome
translocation
two different DNA molecules (chromosomes) receive a double strand break and exchange fragments without any change in content
Indel
collective name for insertion/deletion
unbalanced structural variation
DNA variants that differ in DNA content compared to the reference
CNV
copy number variation eg. large indels or tandem duplications
De novo mutation
a new variant apparent in neither of the biological parents
Genetic mosaicism
a state which an individual has 2 or more genetically different sets of cells in his/her body occurs eg if mutations occurs early during embryonic development
SNP
single nucleotide polymorphism. A DNA variant that only spans one base pair, Needs to be present in at least 1% of the population
Neutral variation
variation which has little to no effect on the phenotype
Population genetics
The science of allele frequencies and how they differ between populations and subpopulations
Haplotype
combination of alleles at the same chromosomal segment
gene pool
all alleles at a given locus across a population
The Hardy Weinberg Equation
a mathematical equation that can be used to calculate the genetic variation of a population in equilibrium. p^2+2pq+q^2=1
p+q=1
Linkage Disequilibrium
the tendency of some alleles to be transmitted together more or less often than expected by chance alone. usually caused by close proximity of genes on the same chromosome
Haplotype blocks
Blocks of the genome that are created by correlated SNPs inherited together
genetic drift
changes in allele frequencies due to chance
Heterozygosity measure (Nei’s statistics)
probability that two alleles at a locus drawn at random from a population will be different from each other
population mutation parameter Ꝋ
the diversity per nucleotide that is expected due to the balance between mutation creating new alleles and drift to fixation eliminating them
Diversity: the bottle neck effect
a drastic reduction of effective population size, leaving only a lower random set of alleles
Founder effect/event
when a small number of individuals form a new population with their set of alleles
negative selection or purifying selection
the selective removal of alleles that are deleterious
dN/dS
the ratio of nonsynonymous to synonymous substitutions
positive selection (darwinian selection)
promotes frequency of advantagous DNA variants
Fst (st subscripted)
a measure of how different two (sub)populations are by considering how much heterozygosity would be gained if the two were a single random-mating population (F= 0 –> identical populations F=1 compleate separation)
genealogical ancestry
individuals who would feature in your genealogy if you were able to trace it all the way back
Genetic ancestry
Individuals from whom you inherit significant parts of your genome
coefficent of inbreeding
the probability that an individual recive two alleles at a given locus that are identical by decent
coefficent of relationship
the proportion of alleles two individuals share that are identical by decent
Identical by state (IBS)
the same DNA sequence but might not be from the same descent
Identical by descent (IBD)
the same DNA sequence (alleles) that are due to same ancestry
effective population size
proxy of the number of individuals in a population that contribute their genes to the next generation
Mutation-drift equilibrium
variation is gained by mutation at the same rate as it is lost by drift and selection (–> the effective population size stays the same)
autosome
A chromosome which is not a sex chromosome
p-arm
the short (petite) arm of the chromosome
q-arm
the large arm of the chromosome
centromere
part of the chromosome which separates the p and the q arm