Sheet 14--Final Exam Flashcards
What is balancing selection, and what is balanced polymorphism?
balancing selection–number of selective processes by which multiple alleles are actively maintained in the gene pool of a population at frequencies above that of gene mutation
balanced polymorphism- situation in which two different versions of a gene are maintained in a population of organisms because individuals carrying both versions are better able to survive than those who have two copies of either version alone—-This is maintained through balancing selection
what is frequency dependent selection?
fitness of a genotype depends on its frequency
what is kin selection and what is altruism?
apparent strategies in evolution that favor the reproductive success of an organism’s relatives, even at a cost to their own survival
altruism-selflessness is the principle or practice of concern for the welfare of others
what kinds of evidence support the existence of microevoultion?
.
what is industrial melanism?
darkness—of the skin, feathers, or fur—acquired by a population of animals living in an industrial region where the environment is soot-darkened.
what is the best example of microevolution in human beings?
aids resistence with CCR5
why do we think that the frequency of sickle cell anemia is much higher in central africa?
Selective force in Africa is presence of malaria. Maintenance of allele has adaptive value in Africa
since sickle cell anemia is usually lethal, why hasnt it been eliminated by natural selection?
.
why do humans living in tropical regions have dark skins while those in the north have light skins?
.
What are the two general ways in which DNA is altered?
radiation and chemical mutagens
What are the 3 ways mutations arise?
1) DNA damage
2) chromosomal Rearrangement
3) Transposition
what are four types of mutations?
1) point mutations–base changes
2) small deletions or insertions– frame shifts
3) large deletions or insertions
4) rearrangements of large pieces of DNA
What are point mutations?
involve small numbers of bases
- -can include base substitutions and indels–both insertions and deletions
- -affect one gene
what is an indel?
short way to refer to insertions or deletions
what are base substitution mutations?
chagne in the base that results in:
- -change in the amnino acid sequence
- -change in the stop codon
- add or remove an intron splice site
- –substitution is a type of point mutation
what are indels? what are they lumped together?
- -mutations resulting from an insertion or a deletion of bases
- -causes a frameshift
why are indels usually more deleterious than base substitutions?
indels change the entire message
–CAT CAT CAT
—-remove A
CTC ATC ATC
What are the two ways DNA gets damaged?
- -mistakes during DNA replications
- -chemical decomposition
what sorts of spontaneous mutations occur during and what occur after DNA replication?
During DNA replication:
- –mispaired bases
- – misaligned bases
After DNA replication:
- -Deaminatino of C to U
- -depurination–loss of A or G
what are the two classes of mutagens?
radiation and chemicals
what sorts of mutations are caused by X-Rays?
double stranded breaks cause deletions, insertions, and rearrangements
What mutations are cuased by sun tanning?
UV causes formation of thymine dimers
–point mutatinos
what sorts of mutations are cause by cigarette smoke?
base substitution
what sorts mutations caused by intercalating chemicals?
insert into DNA and cause frame shift mutations
what are the 3 ways that genetic recombination can alter hereditary information?
1) chromosomal rearrangement
2) gene transfer
3) transposition
how can chromosomes get rearranged, and how can this chagne the genetic information?
Rearrangement of chromosomes is due to:
- -unequal recombination during crossing over
- improper repair of broken chromosomes including inversions
- -translocatinos, deletions, insertions
Genetic information is changed due to:
- mutations
- -information placed in a new setting; informations is added or lost
how can genes get transferred between organisms?
transfer of plasmids
–viruses- add their genome to host genome
how can plasmids get transferred between bacteria?
- -bacteria copy of plasmid
- -sex pilus forms conjugation bridge
- -bacteria can also pick up naked DNA
how can viruses transfer genes?
viruses insert their viral genome into the host DNA
what are the two classes of transposons, what is the main difference between them?
Transposons– mobile piece of DNA, inserts into genes at random, the insertion is one of most significant causes of mutation
types:
1) simplest transposons (insertion sequence)
—transposase gene and its recognitino sequence
—frequently get more complicated
———acquire drug resistanec genes and move into plasmids
2) retro viruses (nucleic acid is RNA)
- —resemble retro viruses; some genes and lifestyle
- —make RNA copy
- –revese transcriptase makes DNA copy of RNA
- -integrase inserts DNA copy at new site of host DNA
why do we think that retrotransposons and retro viruses are closely related?
same genes and lifestyle
- -use reverse transcriptase to make DNA copy
ex. HIV
why do transposons cause mutations?
insert into genes; encoded protein has a large meaningless chunk inserted into it, disrupting its structure
—this is insertional inactivation
why do we distringuish between evolution of genes and evolution of genomes?
genome contains many elemets other than genes, often coding sequences are less than 5% of genome
what are the 3 classes of human DNA sequences, and what do you find in each class?
1) highly repeated sequences (satellites)
- –code for nothing
- –millions/cell
- –make chromosomes longer
- –found near centromere or ends of chromosomes(telomeres)
2) moderatly repeatd sequences
- -thousands/cell
- —–a) transposons
- —–B) structural
- ———–centromeres
- ———–matrix attachement: DNA sequence to attach extended loops to scaffold
- ———–telemoeres protect chomosome ends
- ——C) multigene families: histones
- —–D) microsatellites==excess cause many diseases (used for human DNA/fingerprinting because vary alot)
3) unique= most genes
What are the structural elements, and what kinds of structural elements do we find in genomes?
centromeres
–scaffolding attachment regions
what are microsatellites and how can they affect humans?
nucldeotide repeats, sometimes 6-30 or 20-200
–excess cause disease
what is copy number variation and why is it important to human health?
individual humans differ gentically by 10 million base pairs
- -these frequently has to do with the number of copies of a certain gene then have in tandem
- -susceptibility to many disease, includng aids, has been correlated with the number of copies of particular genes
what is the difference between macroevoultion and micro evoultion?
Macroevoultion– formation of new species gradual
–due to microevoultion
Microevoultion– chagne in the frequencies of alleles in a population over time
evoultion– the change in the frequencies of alleles in a population over time
what is a population and why must we study population to understand evoultion?
- -group of individuals of same species in same area, can interbreed
- -populations evolve, not individuals
what is population genetics?
study of how genes behave in a population?
what is a gene pool?
sum of all alleles in all individuals in the population
why do populations geneticists measure allele frequencies and how do they measure them?
chagne in allele frequencies= evoultion
–use Hard Weinberg equilibrium
Why is Hardy weinberg equibrium rarely achieved and why is it useful?
it predicts equibrium–no change, no evoultion
–this never occurs in nature
Useful:
- -population geneticists compare observed frequcies with those predictd by H-W to identify whats happening
- -this provides a starting point for studying changes in the gene pool of a population
what are 5 main causes of microevoultion, which of these factors is most likly to be adaptive?
1) mutation
2) migration (gene flow)
3) genetic drive
4) non random mating
5) natural selection–*most adaptive
what is genetic drift and what is the differenec between genetic drift and gene flow?
genetic drift
- -changes in allele frequency in small population
- -small isloated population become very differnt (random)
- -includes founder principle and bottleneck effect
Gene flow= migration: movement of individuals from one population to another
- -alters composition of gene pool
- tends to homogenie allele frequency in populations
difference between founder effect and genetic bottleneck?
founder effect:
- -few individuals start a new, isloated populations
- -an allele that is rare in source population may become significant new population
- -important in oceanic island evoultin
bottleneck effect:
–populations randomly greatly reduced in size
– surviving individuals represent random genetic sample of orginal population
ex cheetahs
why is inbreeding an unwise practice?
homozygosity–increases liklyhood of genetic disorders
why are many breeds of pure bred dogs “going to the dogs”
difficult to predict genetic outcomes
what is hybrid vigor?
heterozygote is better adapted than either parent
- -useful in corn breeding for example
- AA x aa=Aa
How does heritable variation arise?*
mutation and recombination
which of the following mutations is most likely to be lethal to an organism?
deletion of a single base near the start of a coding sequence
why do many retrovirses cause cancer?
they have added and oncogene from a former host to their genome, which they then add to the genome of each new host
what is the difference between microevoultion and macroevoultion?
microevoultion is changes in the populations gene pool, macroevoultion is formation of a new species
beardless females?
square root of 0.01
