Genetics & Evolution Flashcards
When did the big bang occur?
13.7 bya
How old is the earth?
4.5 billion years
What is the Panspermia hypothesis?
Life arrived from another planet. (E.g. Fossil bacteria from Mars).
What is the ‘seeded’ hypothesis?
Life was ‘seeded’ on earth by other, advanced civilisations.
What would be needed for life to evolve on earth?
1) Simple monomeric compounds 2)Assembly of them into longer molecules 3) Replication of nucleic acids 4) Restriction of interacting molecules into compartments 5) Production of increasing variety of proteins/polypeptides.
What is a monomeric compound?
Nucleotide bases, amino acids - monomers
What was the Miller-Urey experiment?
Simulation of early earth - ammonia, methane, water. This yielded amino acids, purines and pyrimidines.
What is a ribozyme?
An RNA molecule capable of acting as an enzyme.
How did proteins become involved in an RNA world?
Amino acids may have been added as cofactors and aided RNA ribozymes in replication, leading to greater RNA production. Amino acids found in meteorites in 1969.
What is a species?
Smallest evolutionary unit that is independent (barriers to gene flow).
Biological species concept?
Independent = reproductive isolation. Members of populations that actually or potentially interbreed in nature, not according to similarity of appearance.
Phylogenetic species concept?
Independent = evolved separate traits. Shared evolutionary history.
Morphospecies concept
Based on anatomical appearance.
What did Darwin conclude?
1) Factors causing variability are passed from parents to offspring. 2) Some individuals are more successful (fit). 3) This success is linked to variation and selection. 4) Fitness is relative to the rest of the population.
What did Peter & Rosemary Grant do?
Studied Geospiza fortis on the galapagos island. Bigger beaks better at eating bigger seeds. 1977 drought - more big beaks in later generations.
What is directional selection?
Individuals at one end of phenotypic range survive or reproduce more successfully than at mean.
What is stabilizing selection?
Mean phenotype favoured.
What is disruptive selection?
Both extremes favoured, mean selected against.
What causes sexual selection?
Differences in reproductive success in obtaining mates. E.g. Grey treefrog - Females prefer males with long calls = directional selection on call length in males.
What is the neutral theory?
Mutations have little impact on evolution - genetic drift has more impact.
What is a synonymous substitution?
Silent - not influenced by mutation, occur by drift. More common.
What is a non synonymous substitution?
Replacement - occur at lower rate as deleterious so eliminated.
What is kin selection?
Natural selection that favors altruistic behavior by enhancing indirect fitness.
What is indirect fitness?
Reproduction of relatives.
Why should parents look after young altruistically?
Ensuring survival of 2 young = genetically equivalent to surviving yourself.
What is batesian mimicry?
Mimic species evolves to look like model species, which has defence mechanisms.
What is aposematism?
Warning colouration.
What are the outcomes of Hardy-Weinberg?
Frequencies of alleles in a population expected to be in equillibrium between generations. Allows prediction of genotype frequencies from allele frequencies in the population.
The conditions of Hardy-Weinberg equillibrium
1) No natural selection 2) No mutation 3) No migration (isolated pop.) 4) No genetic drift 5) Random-mating
What does selection do?
Remove mutations by deleting them.
What does migration mean?
Movement of alleles.
What is genetic drift?
The gradual change in the frequencies of alleles due to “sampling error” when gametes combine and chance variation. Smaller populations are more volatile and quickly become fixed for one allele - Founder effect, bottleneck.
What is linkage disequilibrium?
Non-random association of alleles at 2 or more loci. May be due to proximity of loci and one ‘drags’ the other during crossing over. Genetic hitchiking.
Why are plants good to study?
1) Grown in large numbers. 2) Many seeds. 3) Short generation time. 4) Many can self-fertilise. 5) Easy to control mating pairs.
What is the stigma?
Where pollen lands
What are the anthers?
Tip of stamen - site of pollen production.
What is the stamen?
Male sex organ.
What is the ovary?
Female sex organ.
What is a reciprocal cross?
Mating in opposite directions - swapped traits.
What did Josef Gottlieb Kolreuter prove?
Male & female parents contribute equally to offspring characteristics.
Why was Mendel’s plan a good one?
He selected peas that could easily be observed for heritable characters and traits. He used characters with well-defined alternative traits - purple/white, spherical/wrinkled. He used true breeding parents.
What are the progeny of the P parent cross called?
First Fillial (F1)
What is a monohybrid cross?
One character (seed shape) and different traits (spherical/wrinkled). 3:1 ratio.
Which trait was dominant in Mendel’s peas?
Spherical.
Mendel’s conclusions
1) Particulate theory. 2) Each pea has 2 units of inheritance for each character. 3) During production of gametes, only 1 of the pair passed to gamete. 4) During fertilisation, zygote gets 1 unit from each parent, restoring pair.
What is particulate theory?
Units that are responsible for inheritance are discrete particles that exist in pairs and separate during gamete formation.
What is the law of segregation?
Mendel’s 1st law. Each gamete receives one member of a pair of alleles.
What is a gene?
A portion of chromosomal DNA that resides at a particular locus. It codes for a particular character.
How did Mendel verify his hypothesis?
He performed a test cross.
What is the law of independent assortment?
Mendel’s 2nd law. Alleles of different genes assort into gametes independently of each other.
What is a dihybrid cross?
A cross between individuals who are identical heterozygous. 9:3:3:1
How to determine probability of independent events both happening.
Multiply the probabilities of the individual events.
How to calculate the probabilities of the outcomes of dihybrid crosses.
Multiply outcomes from monohybrid components.
