Block Test 1 (Up to lecture 23) Flashcards
What is a missense mutation?
Single base mutation leading to a change in 1 amino acid.
What is a nonsense mutation?
Single base mutation in which the amino acid change results in the formation of an early stop codon. (UGA)
What is a silent mutation?
Single base mutation that does not affect the amino acid that is coded for.
What is a frameshift mutation?
A frameshift mutation is when INDELS (insertions/deletions) cause the entire downstream amino acid sequence to change.
What does copy number variation refer to?
Copy number variation refers to repetitive sequences of DNA in eukaryotes, such as:
- Tandem repeats like micro and minisatellites.
- Interspersed repeats such as transposons.
What is an allele?
An allele is an alternative form of a gene that is located at a specific position on a specific chromosome.
How do you calculate allele frequency?
Allele frequency = number of alleles / number of chromosomes.
What is meant by the wild type allele?
The wild type allele is the allele associated with the normal / most common phenotype.
What is meant by the major allele?
The major allele is the most frequent or common allele.
What is meant by the minor allele?
The minor allele is the least frequent allele.
What is meant by codominant alleles?
Codominant alleles: Both alleles are fully expressed in a heterozygote, both alleles contribute to the phenotype of the heterozygote.
What is meant by genotype?
The genotype refers to the combination of 2 alleles that an individual has at a particular locus/gene.
What is meant by haplotype?
A haplotype refers to a set of linked genes that tend to be inherited together in blocks.
- SNPs do not assort independently because they are so close together on the chromosome.
- The block is not interrupted by genetic recombination during meiosis.
What is linkage disequilibrium?
Linkage disequilibrium is the nonrandom association of alleles at different loci.
1 = 100% inherited together, 0 = never inherited together.
Why do we use class 2 restriction enzymes?
Because the cleave within a known recognition site.
What are isoschizomers?
Isoschizomers are different enzymes that recognise the same sequence and cleave it in the same way.
What are neoschizomers?
Neoschizomers are different enzymes that recognize the same sequence and cleave it in different ways.
What can RFLP be used for?
RFLP can be used to detect point mutations.
What does “S” stand for as a measure of genetic diversity?
S = Number of segregating sites. (Sites where bases are not identical)
What does “P” stand for as a measure of genetic diversity?
P = Proportion of polymorphism.
What does “pi” stand for as a measure of genetic diversity?
pi = nucleotide diversity or average pairwise difference. (Average number of nucleotide differences per site between two randomly selected DNA sequences).
- the likelihood of heterozygosity when comparing 2 randomly selected chromosomes from a population.
What is microevolution?
Microevolution refers to small scale changes within populations or species.
What is macroevolution?
Macroevolution refers to large scale changes across species.
What is a species?
A species is a group of actual or potentially interbreeding organisms that are reproductively isolated in nature from other groups.
What is a population?
A population is a group of organisms of the same species that live in a particular area.
What is speciation?
Speciation is the formation of new species.
-Anagenesis
-Cladogenesis
What is anagenesis?
Anagenesis is an evolutionary change of a single lineage in which one taxon is replaced by another without branching.
What is cladogenesis?
Cladogenesis is an evolutionary change of a particular species in which new species are branched off from a common ancestral species.
Reproductive isolation drives speciation, what are the two types of reproductive isolation?
Prezygotic isolating mechanisms and postzygotic isolating mechanisms.
What are prezygotic isolating mechanisms?
Prezygotic isolating mechanisms prevent organisms from mating in the first place, no zygote is ever formed.
- Geographic mechanism
- Temporal mechanism (incompatible mating seasons)
- Behavioral mechanism
- Physiological mechanism
What are postzygotic isolating mechanisms?
Postzygotic isolating mechanisms refer to when mating and fertilization occur but the zygotes are non-viable or sterile.
- Developmental sterility. (Hybrids are sterile due to abnormal gonad development)
- Segregational sterility (Hybrids are sterile because of abnormal chromosome segregation)
There are three types of geographically related speciation, what are they?
- Allopatric speciation.
- Sympatric speciation.
- Parapatric speciation.
What is allopatric speciation?
Allopatric speciation is when species diverge from each other due to geographic isolation.
What is sympatric speciation?
Sympatric speciation is the evolution of new species from a surviving ancestral species while both continue to inhabit the same geographic region.
What is parapatric speciation?
Parapatric speciation is the evolution of geographically adjacent populations into distinct species.
What are hominids?
Hominids refer to a large group that includes all the great apes, past and present, including chimps, humans, guerillas, and orangutangs.
What are hominins?
Hominins are a group of direct but extinct ancestors of humans, as well as modern humans.
Why is mtDNA useful?
High copy number, high mutation rate, no genetic recombination, maternal inheritance only.
What is phylogenetics?
Phylogenetics is the study and reconstruction of evolutionary history/relationships among a group of organisms or a set of DNA sequences.
What are orthologs?
Orthologs are genes that are similar in different species because they are the result of a speciation event.
What are paralogs?
Paralogs are similar genes that are the result of a gene duplication event within a species.
What are homologs?
Homologs are a general term referring to the similarity of genes due to any common ancestry. Both orthologs and paralogs are homologs.
What is topology?
Topology refers to the branching structure of a phylogenic tree.
What does HWE describe?
HWE describes the relationship between allele frequencies and genotype frequencies in an ideal population.
- Infinitely large population.
- Random mate selection.
- No mutation.
- No migration.
- No selection.
How do you calculate the carrier frequency?
Carrier frequency = heterozygote frequency = 2pq
What is mutation?
Mutation is the origin of new genetic capabilities in populations, the ultimate source of genetic variation.
What is natural selection?
Natural selection is the process of evolutionary adaptation whereby the genotypes best suited to survive and reproduce in a particular environment give rise to a disproportionate share of the offspring.
What is migration?
Migration is the movement of organisms among subpopulations.
What is genetic drift?
Genetic drift is random, undirected changes in allele frequency.
List some causes of mutation:
- Replication errors.
- Chemical damage.
- Radiation damage.
- Transposition.
- Viral insertion.
- Unequal crossing over.
What is the mutation rate (u)?
The mutation rate refers to the number of new mutations produced in a given gene per number of gametes or per generation.
u = the number of newly affected / number of chromosomes in the population.
u per nucleotide = the number of newly affected / number of nucleotides.
What are kimuras contributions to genetics?
- Kimura’s infinite sites model: assumes that each new
mutation occurs at a site that has not mutated before - Kimura’s neutral theory: Vast majority of base substitutions
are neutral or deleterious , very few are beneficial - Molecular clocks: mutations accumulate at a regular rate
over time; we can count number of mutations that differ between twoclosely related species, to determine how long ago the two species diverged
What is admixture?
Admixture is the result of interbreeding between two or more previously isolated populations.
- New population is a hybrid.
What are the effects of admixture on genes?
- Gain of heterozygosity in hybrid pop compared to parent pops
- Gene swamping: admixture has been known to slow local adaptation by introducing foreign, unadapted genotypes
- Hybrid vigour or heterosis, is the improved or increased function of any biological quality in a hybrid offspring. E.g. In plants causes increased rapidity of growth, its height and general robustness
- Introgression, refers to the movement of a gene (gene flow) from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species.
What is the effective population size?
The effective population size Ne is defined as the number of individuals in a population with an equal probability of contributing gametes to the next generation
What are the different mating strategies?
- Monogamy: one mate
- Polygamy: many mates
- Polygyny: one male with many female mates
- Polyandry : one female with many male mates
- the mating system of humans is considered to be moderately polygynous
What is genetic distance?
Genetic distance is a measure of the genetic divergence between species, or of the genetic divergence between populations within a species.
What is positive assortive mating?
Positive assortive mating: similar genotypes are more likely
to mate than different genotypes
What is negative assoritve mating?
Negative assortive mating: different genotypes are more
likely to mate than similar genotypes
What is the Wahlund effect?
Wahlund effect refers to
reduction of heterozygosity in a population caused by
subpopulation structure.
