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Name an example of artificial selection in which multiple common vegetable crops are actually all the same species.
Brussel sprouts, broccoli, cabbage, and kohlrabi are all from the same species (wild cabbage) but are artificially selected for particular traits.
What are the four postulates of natural selection?
- Individuals in a population vary.
- Some of this variation in heritable.
- Not all individuals survive and reproduce equally well.
- Non-random subset of population survives and reproduces better than others.
What is referred to as midoffspring and midparent when some trait is being looked at?
Midoffspring is the mean of all offspring of a given set of parents for some trait (such as beak depth). Midparent is the mean of both parents for the given trait in question.
How can you infer heritability?
Heritability can be inferred by the degree that offspring resemble their parents.
What are some links between natural selection and evolution?
- NS and Evo are dynamic (not random, but not “progressive” either).
- NS acts on individuals within a generation. Evo acts on populations between generations.
- NS acts on a phenotype. Evolution consists of changes in genotype frequencies.
- NS and Evo are not “forward looking”. NS is imperfect.
- NS is neither moral or immoral. NS acts on individuals, not “for the good of the species” because selfish mutants can invade population.
Natural selection acts on _____________, ___________ a generation. Does natural selection act on phenotypes or genotypes?
Individuals; within … phenotypes
Evolution acts on ___________, ____________ a generation. Does evolution act on phenotypes or genotypes?
Populations; between … genotypes
When you find a species of plant that can express orange flowers and yellow flowers, and you can form true-breeding orange and yellow lines of these flowers, which postulates of natural selection have you just confirmed?
That there is variation in the population, and that this variability is heritable.
If you find that orange flowers are more often visited by bees than yellow flowers, and that this results in a greater number of offspring for the orange flower, what postulate of natural selection have you just confirmed?
That not all individuals survive and reproduce equally well and that this different in fitness is non-random (i.e. consistently happens to orange flowers).
Long-term evolutionary change requires an accumulation of ________.
Name three causes of mutation and list examples.
- Environmental stress (radiation, chemical mutagens)
- Imperfect cellular processes (mistakes in DNA replication)
- Heritability of mutations (somatic vs germline, strictly germline heritability)
Name four types of mutation with significant evolutionary impact.
- Point mutation
- Chromosome inversion
- Gene duplication
- Genome duplication
What is a synonymous mutation?
A point-mutation of a nucleic acid that does not result in a change in amino acid in the final product.
What is a non-synonymous mutation?
A point-mutation of a nucleic acid that results in a change in amino acid in the final product.
What is a missense mutation?
A type of non-synonymous mutation that renders the protein product non-function.
What is a nonsense mutation?
A type of non-synonymous mutation that changes the nucleic acid sequence into a stop codon, prematurely stopping transcription and resulting in an incomplete protein.
What is a readthrough mutation?
A type of non-synonymous mutation that changes a stop codon into a non-stop codon, resulting in a much longer transcription and most likely a non-functional protein.
What is a frameshift mutation?
An insertion or deletion of a number of nucleotides other than multiples of three that cause the transcriptional factors to shift where each codon is read, resulting in a drastically different transcription, and therefore a likely non-functional protein.
What is an inframe mutation?
An insertion or deletion of 3, 6, 9, 12 (and so on) nucleotides that doesn’t shift the reading of the gene, but still results in new amino acids being mixed into the protein, resulting in a possibly altered or non-functional protein.
What is a neutral mutation?
A type of non-synonymous mutation that changes the amino acid, but the change is a neutral one that has no bearing on the protein at large.
What kinds of chromosomal rearrangements are there?
What is aneuploidy?
An abnormal number of chromosomes, usually caused by a non-disjunction.
What is a non-disjunction?
Is the failure of chromosomes to properly segregate.
What are the two big effects of chromosomal inversions?
The segment of DNA that is inverted is read backwards. The segment also cannot properly cross-over with the homologous chromosome.
What causes gene duplication?
What is the consequence of gene duplication?
The extra copy of the gene is free to mutate as much as it wants without taking away the effect that the other copy of the gene has. It’s a great source of new genes. Dimers are also often the result of gene duplication.
What is the difference between large and small effect mutations?
Large effect mutations are nearly always deleterious. Small effect mutations are usually a lot less deleterious, and sometimes may even be beneficial.
What are housekeeping genes? Why are they unlikely to mutate?
Housekeeping genes maintain required transcription in the cell. A mutation usually results in death, so mutations are rare in such genes.
How does the sex of an individual affect the mutation rate in the germline?
Male gametes are constantly produced throughout the life of a male, while female gametes are produced only once in the beginning of life, then stored. Mutations can accumulate in female gametes. However, such mutations can also cause the egg to not be released, or to malfunction. Female gametes are more susceptible to mutations that prevent the formation of a zygote than male gametes.
What is the difference between the balance theory and the neutral theory?
The balance theory states that heterozygosity is mostly beneficial, while the neutral theory states that most alleles are equivalent and maintained by genetic drift instead.
What kinds of environments would increase mutation rates?
Unpredictable/changing environments might increase mutation rates in a given population if there is enough variability among individuals for mutation rate (i.e. different individuals have different efficiencies of proofreading mechanisms). So long as that variation is heritable, then natural selection might select for individuals that mutate more because they come across a phenotype better adapted to new environment faster than those individuals that mutate slower.
What are the five hardy-weinberg conditions/assumptions?
- No mutation
- No migration
- No sex selection
- No genetic drift
- No unequal fitness
What letters denote relative and absolute fitness?
- Absolute fitness – W
- Relative fitness – w
What is absolute fitness?
Concerning a particular genotype, it is the ratio between the number of individuals with that genotype after selection to the number of individuals with that genotype before selection.
What is relative fitness?
Relative fitness is the average number of surviving progeny of a particular genotype compared with the average number of surviving progeny of competing genotype after one generation.
What two factors affect the rate of evolution?
The starting frequencies and the strength of selection.