bio ch 23

Natural selection

works on an individual

Population

evolve over time

Microevolution

A change of alelle frequencies in a population over time

3 Mechanism cause microevolution to happen

1. Natural selection
2. Genetic drift (chance mutation events)
3. Gene flow (transfer of individuals into/out of population

What is the mechanism of natural selection

Natural Selection is only mechanism of Adaptive evoultion

Adaptive

Improves the match between organism and environment

What makes Evolution possible?

Genetic Variation

What is genetic variation?

Differences among individual in DNA composition (genes)

How the genetic variation is revealed?

Is revealed as a phenotypic variation

How are determined some phenotypic characteristics?

Determined by a single gene locus

different alleles produce…

different phenotypes

Other phenotypic characteristics vary along

a continuum

Determined by 2 or more genes

height in humans

What can also be result of a combination of factors?

Phenotype

Is all phenotypic variation heritable?

NO all

What has evolutionary consequences?

Only genetic component of variation has evolutionary consequences

What makes phenotypic differences?

To diet chemicals NOT genes

How new genes and new alleles originate?

ONLY by mutation

Gene

genetic code for protein

Locus

location of gene on chromosome

Alleles

Same gene; same/different sequences

Homologous chromosomes

1 from each parent

Homologous chromosomes

occurs during crossover, form new allele combinations

How we can differences the homologous chromososmes

Using FISH/ Flourescent in Situ Hybridization

Karyotype display

Genetic variation that wvolution depends on has various origins

1.Mutation


2. Gene duplication
3. Sexual reproduction

Types of Chromosome mutation

Duplication

Deletion

Translocation

Inversion

What is the ultimate source of new alleles

Mutation

Mutation

change in nucleotide sequence of organism’s DNA

Mutation can be…

detrimental

What is the point mutation?

Is the change of a single base in gene (sickle cell disease)

Can mutation alter gene number or position?

yes

Can mutation be harmless?

yes

What is the majority of genome

Majority of genome is NONcoding

What redundancy in the genome do?

Allows some mutayions without change in protein

What may not alter protein shape or function?

Point mutation

Can mutation increase adaptability with environment?

yes

ONLY mutations in cells that form gametes

Pass to next generation

Gene mutation

Insertation

Deletion

Substitution

Full-color map of the chromosome

Spectral karyotype

Gene duplication occurs due to…

Erros during miosis

Slippage during replication

Transposable element activities

Are large duplication usually harmful

yes

Duplicated segments can persist and

provide new loci, that take on new functions by futher mutation or subsquent selection

Neutral variation

genetic variation that does not help or harm

Mutation rates vary

from organism to organism

1 mutation

per 100,000 genes in animals and plants

major (KEY) source of genetic variability

Mutation

Rate of mutations quickly **accumulate** in microorganism (bacteria)

due to their fast life cycle

sexual reproduction produces

unique combinations of alleles

Majority of genetic variation is

from the unique combinations of alles

Variant alleles originate

from past mutations

Alleles

matching genes, one from the mother and one from the father

Variants get

shuffled and dealt at random to produce unique combos

3 mechanisms contribute to suffling of variants

\-Crossover during meisis

\-Independent assortment of alleles into gametes

\-jFertilization brings together gametes to create unique allelic combinations

Source of different allelos

mutation

Crossover, Independet assortment, Fertilization ensure each generation contains

new combos

Genetic variation

makes evolution possible

Natural selection is countered by mechanisms that

preserve or restore variation

Preserve or restore variation can be

Diploidy and Balanced Polymorphisms

Diploidy

2N (one maternal & one paternal)

Diploidy means to have?

The state of having 2 chromosomes per somatic cell

Having different alleles on homologous chromosomes

Increases variation

Balanced polymorphism

Prevent the elimination of recessive alleles via selection

Recessive alleles do NOT afect the phenotype of heterozygotes.

Recessive alles are not selected against, hide in genomes

Balanced polymorphisms may end up harboring

a benificial trait over time-sickle cell trait

sickle trait mean

A person has inherited the sickle cell gene from one of his parents

Homozygous dominant

AA (do not have sickle cell)

Hetereozygous

Aa

Homozygous recessive

aa (leads to sickle cell trait)

Gene pool

genetic composition of a population

Population Genetics

Describe the genetic positon of population and how it changes over time

To describe the gene pool you need to know the….

**number of alleles** and **genotypes** and their **frequencies** (%)

Hardy-Weinberg Equilibrium

A population allele and genotype frequencies are constant UNLESS theres is a type of evolution force acting upon them

Population

same species

can breed with each other

fertile offspring

G

dominant allele

g

recessive allele

G

0\.6

g

0\.4

5 assumptions of Hardy Weinberg Equilibrium

No selection

No mutation

No migration

Large Population

Random manting

Small population are more vulnerbale to

genetic drift

5 assumptions of Hardy Weinberg Equilibrium is real?

No

Allele frequencies

p + q = 1

Genotype frequencies

p’2 + 2pq + q’2 = 1

(G) (G)(g) (g)

For what Hardy-Weinberg equation uses frequency of alleles and genotypes

to determien whether a population is evolving

Hardy-Weinberg Principle

Describes gene pool of a population that is NOT evolving

What states Hardy Weinberg Equilibrium that **shuffling alleles** during meiosis and **random fertilization**

does NOT change allele frequency in population

No mutation

The gel pool is modified if mutations occur or if entire genes are deleted or duplicated

No natural selection

allele frequencies change when individual with different genotyoes show consistent differences in their survival or reproductive success

No gene flow

By moving alleles into or out of populations, gene flow can alter allele frequencies

Random mating

if individuals mate within a subset of the population such as neighbors, random mixing of gametes does nto occur and genotype frequencies change

Large populatiom

small population, alleles frequencies fluctuate by chance over time by genetic drift

Genel pool

total agregate of all alleles

for all loci

for all the individual in a population

Population

Group of individuals of same species

live in same area

interbreed to produce offspring

allele

R or W

genotype

RR, RW, WW

Alter allele frequencies in a population

natural selection, genetic drift and gene flow

Genetic drift

In small populations there is a greater chance of random mutation

usually occurs through the random loss of alleles

Founder Effect & Bottleneck Effect

2 types of genetic drift

ways in which genetic drift can have a significant effect on population

Founder effect

Isolated from larger population

Is more pronounced the chance of genetic drift in a founder effect?

yes

Due to such a small gene pool

any aberration is dramatically increased