Bio 102 Exam 1

Central Dogma

information only flows from

DNA -> RNA -> Protein

mRNA Processing

location: nucleus

the transcript must be modified to become mature mRNA

capping, Poly-A tail, and splicing occur

Capping

5 inch guanine nucleotide at the end of the pre-mRNA shortly after the start of transcription.

- This protects the mRNA from degrading

Polyadenylation

The poly-A tail is added to the 3' end of the mRNA. the tail protects the mRNA from degrading and assists in the export of MRNA

- determines how much protein should be made

Splicing

the removal of introns which is junk DNA

this is done by the spliceosome

Exons

Sequences that will be translated aka coding

Introns

non coding sequences

Transcription

Location: Nucleus

Process: DNA sequence of a gene is copied into a messenger RNA (mRNA) which then carries the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm.

Transcription Unit

promoter

start site

terminator

3 types of RNA

mRNA, tRNA, rRNA

mRNA

type of RNA that carries instructions from DNA in the nucleus to the ribosome

tRNA

type of RNA that carries amino acids to the ribosome

rRNA

type of RNA that makes up part of the ribosome

Translation

location: cytoplasm

Mature mRNA is used as a template to synthesize a protein. this process takes place on ribosomes, which are either free floating or on the rough ER.

Ribosome

site of protein synthesis (makes proteins)

decode mRNA

form peptide bonds

Codon

A block of 3 DNA nucleotides corresponding to an amino acid

3:1 ratio

Ex) UUA, UGA, UAG

anti-codon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

Hardy-Weinberg equilibrium

Proportions of genotypes do no change in a population if...

- No mutation takes place

- No genes are transferred to or from other sources

- Random mating is occurring

- The population size is very large

- No selection occurs

Used to calculate allele frequencies.

Natural Selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

ex) tall neck giraffes are more likely to live with food at higher elevation than small neck giraffes.

gene flow

movements of alleles from one population to another

genetic drift

in small populations, allele frequency may change by chance alone.

Founder effect

when a new population is created, only some genes are transferred because not all of the population goes.

ex) the red birds making their new group loose the yellow ones that were previous, loosing genes.

Bottleneck Effect

- loss of genes through die off/ endangered species

- genetic drift can lead to the loss of alleles in isolated populations

ex) a tsunami wipes out almost half of a population because they died

Assortive mating

phenotypically similar individuals mate

Dissortive mating

phenotypically different individuals mate

Hardy-Weinburg Equation

P+q=1 P^2+2pq+q^2=1

P= dominant frequency allele q= Recessive frequency allele

P^2= homozygous dominant q^2= homozygous recessive

2pq= heterozygous

Fitness

individuals with one phenotype leave more surviving offspring in the next generation than individuals with an alternative phenotype.

ex) brown beetles leave more offspring than yellow beetles

conditions for natural selection to occur

1. Variation must exist among individuals in a population

2. Variation among individuals must result in differences in the number of offspring surviving in the next generation

3. variation must be genetically inherited

Disruptive selection

acts to eliminate intermediate types

ex) birds with intermediate-sized beaks are at a disadvantage with both seed types- they are unable to open large seeds and too clumsy to efficiently process small seeds.

Directional selection

acts to eliminate one extreme

- often occurs in nature when the environment changes

ex) in Drosophila, artificially selected flies that moved toward the light on one side

Stabilizing selection

Acts to eliminate both extremes

ex) in humans, infants with intermediate weight at birth have the highest survival rates

Heterozygote advantage

heterozygotes are favored over homozygotes

works to maintain both alleles in the population

ex) sickle cell anemia

Artificial Selection

Selection by humans for breeding individuals with certain phenotypic traits, so they can pass specific genes to the next generation.

ex) taking fruit flies with not a lot of abdomen hair and breading another like that until they bread one with no hair.

industrial melanism

phenomenon in which darker individuals come to predominate over lighter ones

- pollution control resulted on dark color being lighter again

Absolute Dating

age of fossils is estimated by rates of radioactive decay

- rate of decay is known as an isotope's half-life

Transitional Fossils

Fossils that provide patterns of evolutionary change from the early ancestors to modern life forms.

ex) oldest known bird fossil is the archaeopteryx (which was a dinosaur)

Vestigial Structure

Have no apparent function, but resemble structures their

ancestors possessed

ex) Hip bones in boa constrictors

- Evolutionary relicts

homologous structures

Structures with different appearances and functions that all derived from the same body part in a common ancestor

ex) bones in the forelimb of mammals

- different functions, same ancestor structure

Convergence

Similar forms having evolved in different, isolated areas because of similar selective pressures in similar environments.

ex) bats and birds both have wings and can fly; however, they evolved these traits seperately

allopatric speciation

geographically separated populations appear much more likely to have evolved substantial differences leading to speciation.

Speciation

the evolution of a new species from an existing species

sympatric speciation

one species splits into two at a single locality, without the two species ever having been geographically separated

Gradualism

accumulation of small changes

standard view for a long time

Prezygotic isolating mechanisms

prevent formation of zygote

Temporal Isolation

form of reproductive isolation in which two populations reproduce at different times

ex) one flower is in early spring and one is in summer

Behavioral Isolation

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding

ex) if male boobie doesn't do the write song or dance, the female will not mate with the male

mechanical isolation

structure of the male and female copulatory organs may be incompatible

ex) bees carry pollen that have to release on the receptive structure on flower

Gamete fusion

In animals that shed gametes directly into water; the eggs and sperm derived from different species may not attract or fuse with one another

postzygotic isolating mechanisms

operate after fertilization has occurred to ensure that the resulting hybrid remains infertile

hybrid sterility

hybrids fail to produce functional gametes and have abnormal sex organs

ex) a mule is able to live a healthy life but will not be able to have offspring

Polyploidy

individuals that have more than two sets of chromosomes

Reinforcement

Initially incomplete isolating mechanisms are reinforced by natural selection until they are completely effective

- favor breading within a population

ex) if 2 species of frogs have different mating calls, and hybrids between them are less fit, natural selection will favor frogs that have even more distinct calls making it less likely for interbreeding.

character displacement

Natural selection in each species favors those individuals that use resources not used by the other species

- greater fitness

- species will diverge

ex) a bird eating a specific seed and doesn't have to compete for food because not every bird likes them.