molec bio 20+27+28

what is genetic variation?

differences in alleles of genes found within individuals in a population

what is natural selection?

one of the processes that guides the process of evolution

what is evolution?

changes is inheritable traits overtime

what is studied in population genetics?

• the properties of genes in a population

• evolution results in a change in the genetic composition of a population

what is genetic variation?

the raw material for selection

what can change allele frequencies?

• natural selection

• poly morphism

• SNP (single-nucleotide polymorphisms)

what is allele frequency?

finding out:
what % of alleles are dominant?
what % of alleles are recessive?

what is genotype frequency?

finding out:
what % of genes are homozygous dominant (HH)?
what % of genes are homozygous recessive (hh)?
what % of genes are heterozygous (Hh)?

what is phenotype frequency?

finding out:
what % of a phenotype exists
(eg. what % of flowers in a flower field are white/purple/pink? )

what is the Hardy-Weinberg principle?

proportions of genotypes do not change in a population if…

1. no mutations take place

2. no genes are transferred to or from other sources

3. random mating is occurring

4. the population size is very large

5. no selection occurs

if all of the Hardy-Weinberg principles are correct/true, what is that called?

Hardy-Weinberg equilibrium

how do you calculate the frequency of genotypes/alleles

with the hardy-weinberg equation:

p²+2pq+q²=1

p=frequency of dominant allele
q= frequency of recessive allele

what is a mutation?

• main source of genetic variations

• makes evolution possible, without mutation, there would not be any genetic variations

• other evolutionary processes are usually more important in changing gene frequency

what is gene flow?

• movement of alleles from one population to another

• animal physically moves into a new and different population

• drifting of gametes or immature stages into an area

• mating from adjacent populations

what is nonrandom mating?

• assortative mating

  • phenotypically similar individuals mate together

  • increases proportion of homozygous individuals (HH)

• disassortative mating

  • phenotypically different individuals mate

  • creates excess of heterozygotes (Hh)

what is a genetic drift

• in small populations, allele frequencies may change by chance alone

• magnitude of genetic drift is related to the population size

what is the bottleneck effect?

most of a population does not survive, some of the phenotypes (and genotypes) do not survive and are eliminated from the gene pool

what is the founder effect?

movement of a small population to a different area, and then some of the phenotypes (and genotypes) are eliminated in the same way a bottleneck effect is.

what is artificial selection?

human made changes to get a desired result.

ex. golden retrievers or food like corn

what is natural selection

non human change

ex. giraffe necks becoming longer to reach leaves over time

what are the 3 conditions for natural selection?

1. variation must exist among individuals in a population

2. variation among individuals must result in differences in the future generations

3. variation must be generically inherited

what is evolution?

the historical record of change over time

are evolution and natural selection the same?

no, they are different. evolution is driven by natural selection.

what is survival of the fittest?

fitness means how many offspring survive

if a large bug lays lots of eggs, but dies early and a small bug dosent lay lots of eggs , that that means the intermediate bug who lays a good amount of eggs and lives a long time is the fittest

what is frequency-dependent selection?

fitness of a phenotype depends on its frequency within the population

what is negative frequency-dependent selection

rare phenotypes can be favored by natural selection

what is positive frequency-dependent selection?

• favors the common form

• tends to eliminate the variation

• oddballs stand out

what is oscillating selection

selection favors one phenotype at one time and another at another time

why do heterozygotes have more of an advantage than homozygotes?

because it keeps both alleles in the population than just the dominant

why is sickle cell not eliminated from the gene pool?

being a sickle cell carrier is advantageous to malaria, giving resistance to malaria as the disease cannot enter the sickled cells.

what is disruptive selection

acts to eliminate intermediate types.

what is directional selection?

acts to eliminate one extreme

stabilizing selection

acts to eliminate both extremes and makes the intermediate more common by getting rid of the extremes

how do we track evolution over time/in the past?

we studied fossil evidence and also genomes and DNA from the past.

we can also study populations in a lab with short lifespans (ex. fruit flies) or in field experiments

in the guppy experiment, why do the guppies upstream lose their bright colors?

because of the predators, the guppies had to evolve into duller colors to blend in with their environments and to be safe from the predators.

why does copper resistant grass end up in random fields where there is no copper soil?

because of genetic drift, and wind can carry the copper genotype (in pollen) out elsewhere.

why is there a limit to selection?

you can only go so far with genotypes, and get so many different variables of genees.

the creatures can only be mutated so much and they themselves have physical limits.

does every phenotype have a genetic basis to it?

not every phenotype does. fly eyeballs are “generated” at random, so are human fingerprints. they’re all different.

what are the characteristics of a virus

• no cell membranes

• can be DNA or RNA based

• may or may not have enzymes

• do not have ribosomes

• do no produce ATP

how do viruses make their protein coats without ribosomes?

by stealing host cells ribosomes and using them for making proteins

what are visuses? (whats their function?)

they are

obligate intracellular parisites
(they HAVE to live inside of host cells and steal off of the host cell)

what is the basic structure of a virus?

nucleic acid, with optional enzumes, wrapped in a CAPSID protein coat (made out of capisomeres) and some have an optional viral envelope with also optional protein spikes

what is a virion?

virus when it is outside of the cell

in virions…

• some viruses store specialized enzymes with nucleic acid cores

• many animal viruses have an envelope made out of host cell membrane viral proteins

characteristics of viruses:

• found in every kind of organism

• there is more kinds of viruses than organisms

how does a host range affect viruses and their host cells?

each type of virus has a limited host range,

ex. HIV → immune cells
HEP. → liver cells

rabies → neurons

can viruses be dormant?

they can. the chickenpox virus can stay in the system forever after it has been treated.

how does a virus replicate their DNA for replication?

they hijack host cells and take their ribosomes to create new virus DNA.

what kind of virus shape is this?

helical

what kind of virus shape is this?

polyhedral / icosahedral (soccer ball shape)

what kind of virus shape is this?

complex like bacteriophages

what kind of virus shape is this?

enveloped virus

what are some DNA viruses?

• double stranded | dsDNA

• single stranded | ssDNA

what are some RNA viruses?

• double stranded | dsRNA

• single stranded | ssRNA POS

• single stranded | ssRNA NEG

• retrovirus | RNA → DNA

what do bacteriophages do?

they are viruses that infect bacteria from the inside out

what are the stages of the lytic cycle of a bacteriophage?

1. ATTACHMENT: bacteriophage attaches to a bacteria

2. PENETRATION: injects bacteriophage dna into bacteria

3. BIOSYNTHESIS: bacteriopgage DNA and structure is being synthesized with the host ribosomes

4. MATURATION: new bacteriophage are existing inside of the host cell

5. RELEASE: new mature bacteriophages burst out of the host cell and are ready to infect other bacterias

what happens in the lysogenic cycle?

1. after the penetration phase of the lytic cycle, the bacteriophage DNA instructions on how to build other phages is synthesized into the host cell DNA without beginning to build new phages.

2. host cell undergoes mitoses as usual with the new bacteriophage replicating

3. cell can resume in a dormant state OR go back into the lytic cycle to begin new phage synthesis

what is the HIV infection cycle?

1. ATTACHMENT: virus attaches to a human T cell with its own enzymes

   1. ENTRY into the T cell

2. REVERSE TRANSCRIPTION: the enzymes that the virus had brought, initiates reverse transcription from the HIV dsRNA → dsDNA

3. INTEGRATION: new retrovirus DNA gets included into the host T cell DNA, host cell lives on with new DNA

4. DORMANCY: T cell chills out with the dormant DNA

5. BIOSYNTHESIS: begins making new HIV viruses

6. ASSEMBLY: HIV virus is assembled

7. RELEASE: HIV leaves out the cell without popping or killing the cell

what are ways that medicine can prevent viruses from affecting us? (4 items)

1. blocking entry

2. blocking replication with reverse transcriptase inhibitors

3. blocking integration into host cell DNA

4. blocking maturation