Genetics/ Evolution Flashcards
Alleles
Alternative form of genes. Can be dominant ( only need one allele to show ,will show even with recessive trait) or recessive ( need 2 alleles to show ,will show only with other recessive trait not dominant).
Genotypes
Allelic configuration of a gene.
Homozygous- contains the same allele.
Heterozygous- contains different alleles.
Complete dominance
Person contains one dominant allele and one recessive
Phenotype
Physical manifestation of a gene.
Codominance
Contains two dominant alleles that are equally expressed.
Incomplete dominance
Has no dominant alleles, recessive traits are a mix of them.
Penetrance v. Expressivity
Penetrance is the proportion of the population who express a phenotype of a given gene.
Expressivity is the strength by which the phenotype is expressed.
What are Mendel’s two laws?
Law of segregation ( Mendel’s first law)- alleles of a gene segregate during meiosis with each gamete having one allele.
Law of independent assortment ( Mendel’s second law) - alleles segregate without being influenced by the other.
Griffith Experiment
Discovered the transforming principle by demonstrating that heat killed virulent bacteria converted nonvirulent live bacteria virulent.
Avery- MacLeod- McCarty
Lead to DNA being discovered as holding genetic information by degrading DNA, causing no transforming.
Hershey- Chase Experiment
Confirmed DNA housed genetic material because it was the only thing found in radiolabeled bacteriophage- infected bacteria.
Gene pool
All of the alleles of a gene in a population.
Point mutations v. Frameshift mutations
Point mutations in the DNA that involves removing one nucleotide for another.
Frameshift mutations are mutations that disrupt the reading frame of DNA.
Describe the following type of point mutations:
- Silent mutations
- Missense mutations
- Nonsense mutations
- Insertions and deletions
- Silent mutations are mutations where the nucelotide switched leads to no change in amino acid.
- Missense mutations are mutations that leads to different amino acid.
- Nonsense mutation- premature stop codon coded causing shortened protein.
- Insertions= adding nucleotide v. Deletions= removing nucleotide = causes frameshift mutation.
What are chromosomal mutations? Describe the following chromosomal mutations:
- Deletion
-Duplication
- Inversion
- Insertion
- Translocation
Chromosomal mutations are larger scales of chromosomes that doesn’t happen at the amino acid/ protein level.
- Deletion mutations- large portion of DNA.
- Duplication - Large portion of DNA are duplicated.
- Inversion- segment of DNA is reversed.
-Insertion - portion of chromosome is removed from one chromosome to another.
- Translocation - when a chromosome is swapped with another segment of chromosome.
Genetic leakage
Flow of genes between species resulting in hybrid offspring.
Genetic drift
When the gene pool of a population changes due to random things ( chance).
Founder effect
When something ( ie. natural disaster) decreases the population considerably causing a bottleneck. This causes inbreeding and more homozygous genotypes.
Why do we use punnett squares?
We can determine genotypic and phenotypic ratios formed from the mating of parents.
- Parent generation (P) - parents.
- Filial generation (F)- offspring.
- Monohybrid cross = cross involving one gene. Dihybrid cross= cross involving two genes.
Recombination frequency
- Represented by theta symbol.
It’s the likelihood of genes being seperated during meiosis during crossing over. - Genes closer together are less likely to be separated than genes further apart.
Genetic maps
Maps of chromosomes by using recombination frequency with the unit being in centimorgans.
Hardy- Weinberg
With certain criteria being met a population is in equilibrium ( allele frequencies doesn’t change). Referred to as hardy- weinberg equilibrium.
Describe the theory of natural selection
Individuals that has advantageous variations of a trait survive (therefore has increased fitness) and are able to pass on these genes to offspring. Those with deleterious variations of traits die off and traits doesn’t get passed ( get selected against).
Fitness
Ability for an individual to survive in their environment, compete for resources, and pass on their genes.
Modern Synthesis model ( neo-Darwinism)
Differential reproduction
Inclusive fitness
Fitness of an individual that includes the number of offspring, the offspring being able to support others, and being able to support offspring.
Stabilizing selection
Selection for the average phenotypes and selection against the extremes.
Directional selection
Selection of an extreme phenotype
Disruptive Selection
Selection of the two extremes of a phenotype. Can lead to speciation.
Adaptive radiation
When multiple species evolve from a common species. Each of the evolved species occupy their own ecological niche.
Species
large group of individuals that are able to reproduce and produce viable offspring.
Divergent evolution
When two species that come from a common ancestor become more different as they evolve from that common ancestor.
Parallel evolution
two species come from common ancestor but evolve similarly to each other due to similar evolutionary pressures.
Convergent evolution
When 2 species that don’t come from a common ancestor evolve to become more similar due to similar evolutionary pressures.
Molecular clock model
The amount of difference between species is correlated to the amount of time that passed from when they evolved from their common ancestor.
- Earlier they evolved the more they will be different.
- Later they evolved the less different they will be.
Sexual selection
A form of directional selection in which certain phenotypic traits are picked for mating even when they don’t serve to increase the fitness of the organism or even decrease it.
What is a population?
Members of a species that live in an area and mate with each other.
What are the conditions for a population to be in H-W equilibrium?
- Population must be large.
- No mutations
- No migration into or out of population
-Mating within population is random
- Natural selection is not at work
Genetic drift
Changes in allele frequencies due to chance events. More susceptible is small populations than large populations because they already have a smaller gene pool.
Bottleneck event
When a catastrophic event causes a decrease in the population which causes the effects of genetic drift.
Can lead to the prevalence of bad alleles because the change in allele frequencies are random.
Gene flow
The changes in the gene pool due to migration.
If it happens in one direction it can lead to an increase in genetic diversity but if it happens both ways it leads to a decrease in genetic diversity.
Natural selection
Proposed by Charles Darwin. States that beneficial alleles are chosen for, and detrimental alleles are chosen against and purged out of the population.
An allele that confers an advantage is able to survive and reproduce, passing on those alleles.
Selection pressures can be different between populations and can lead to convergent or divergent evolution.
Evolutionary fitness
Measured in terms of being able to survive and be able to produce.
Inbreeding v. Outbreeding
Inbreeding - mating of individuals with shared ancestry. Causes a decrease genetic diversity because it increases homozygosity.
Outbreeding- mating of individuals without shared ancestry. Causes an increase in genetic diversity because it promotes heterozygosity.
What happens when mating between species happens?
Produce hybrid offspring which can be fertile or infertile, viable or inviable.
Reproductive isolation
When mating between species leads to inviable or infertile offspring.
Adaptive radiation
When natural selection causes the evolution of multiple forms of a species. Think Darwin’s finches.
Neutral theory of molecular evolution
States that most mutations are neutral and doesn’t cause a positive or negative effect.
Whats the hardy weinburg equation?
P^2 + 2Pq + q^2 = 1
P+q=1
