Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
40 Cards in this Set
- Front
- Back
|
A common misconception about evolution... |
That individuals evolve and Natural selection acts on individuals It’s a population that evolves change occurs over time. |
|
|
Microevolution |
Change in allele freq. in population over time |
|
|
3 mechanisms that cause allele changes |
1. Natural selection: survival of the fittest 2. Genetic drift: about chance events that alter allele freq. 3. Gene flow: transfer of alleles btw populations. Individuals coming into a pop and bringing their alleles Only natural a selection causes adaptive evolution |
|
|
Prerequisite for evolution.. |
Variation in heritable traits Mendel provided evidence of discrete heritable units (genes) |
|
|
Genetic variation |
Caused by differences in genes or other DNA segments Phenotype is a combo of inherited and environmental (build muscles) Natural selection can only act on variation with a genetic component |
|
|
Either-or |
Phenotype differences are determined by a single gene |
|
|
Continuum |
2 or more genes contribute Polygenic |
|
|
Gene variability |
Average heterozygosity The avg number of loci that are heterozygous in a population Means there is a lot of variation of more |
|
|
Nucleotide variability |
Measured by comparing the DNA sequences of 2 or more individuals Rarely results in phenotypic variation due to noncoding regions (introns) of DNA Variations that occur in coding regions (Exons) rarely change the amino acid sequence of the encoded protein |
|
|
Phenotypic variation |
Does not result from genetic differences among individuals but rather from environmental influences Only genetically determined variation can have evolution changes |
|
|
New genes and alleles can arise by... |
Mutation or gene duplication |
|
|
Results in genetic variation by recombining existing alleles... |
Sexual reproduction |
|
|
Mutations and new alleles |
Change in DNA sequence Only mutations in cells that produce gametes can be passed onto offspring |
|
|
Point mutation |
A single nucleotide in DNA sequence |
|
|
Effects of point mutations can vary |
Mutations that alter phenotype are often harmful Harmful mutations can be hidden (in recessive alleles) Mutations can be beneficial rarely |
|
|
Neutral variation |
Point mutations in noncoding regions Nether advantage or disadvantage |
|
|
Altering gene number or position |
Mutations that delete, disrupt, or rearrange loci are often harmful Duplication of smaller pieces increases genome size and is less harmful |
|
|
Duplicated genes |
Can take on new functions my further mutation An ancestor carried just one odor-detecting gene. It was duplicated and benefitted humans who have 380. Mice have about 1200. Humans used to have 1000. Mice still rely on it. |
|
|
Rapid reproduction |
Mutation rates are low in animals and plants: 1 in 100,000 genes per generation Often lower in prokaryotes but shorter generation times allow mutations to accumulate rapidly Viruses have high mutation rates and short generation times |
|
|
Recombination |
During sexual reproduction allows for genetic variation Shuffles existing alleles into new combos through: Crossing over, independent assortment, and fertilization |
|
|
For evolution to occur.. |
One or more factors that cause evolution must be at work Genetic variation is required but does not guaranteed |
|
|
Population |
Localized group of individuals capable of interbreeding and producing fertile offspring Populations are not always geographically isolated but usually only breed with own members |
|
|
Gene pool |
All allleles for all loci in a population |
|
|
A locus is fixed when.. |
All individuals in a population are homozygous for the same allele |
|
|
If there are 2 or more alleles for a locus... |
Diploid individuals may be either homozygous or heterozygous |
|
|
The frequency of an allele in a population can be calculated |
Diploid organisms: total number of alleles at a locus is the total number of individuals times 2 Total number of dominant allele at a locus is 2 alleles for each homozygous dominant individual plus one allele for each heterozygous individual Same for recessive |
|
|
Frequencies and alleles |
2 alleles at a locus, p is usually dominant, q is usually recessive The frequency of all alleles in population add up to 1 p+q=1 or %+%=100 |
|
|
Example |
320 red flowers 160 pink flowers 20 white flowers Calculate number of copies of each allel: p= (320x2) + 160= 800 q= (20x2)+160=200 800+200= 1000 |
|
|
Same example but for frequency of alleles |
320 red, 160 pink, 20 white P=800/1000=.8=80% q=1-p=.2=20% |
|
|
Hardy-Weinberg equation |
Used to determine Genetic makeup we expect for a population that is not evolving at a particular locus If it differs from expectations, it suggests population may be evolving |
|
|
Hardy-Weinberg equilibrium occurs only if... |
5 things |
|
|
Hardy-Weinberg equilibrium in a gene pool |
p=.8, q=.2 |
|
|
Frequency of alleles calculated |
Frequency of genotypes can be confirmed using a Punnett square |
|
|
1. No mutations |
The gene pool is modified if mutations occur or if entire genes are deleted or duplicated |
|
|
2. Random mating |
Inbreeding or mates with neighbors stops random mixing of gametes and genotypes change |
|
|
3. No Natural selection |
Allele freq. changes when individuals with different genotypes show consistent differences in their survival |
|
|
4. Extremely large population |
In small populations, allele freq. fluctuate by chance over time due to genetic drift. Think of beetles that get eaten out of the 8 |
|
|
5. No gene flow |
Moving alleles in or out of population changes allele freq |
|
|
Example using PKU |
Back (Definition) |
|
|
Wait |
Next set |
