Genetics Final

Population Genetics

Combine Darwinian selection and Mendelian inheritance

Study of genetic variation within a population

Population

Localized group of individuals of the same species

Species

Group of population whose individuals have the ability to breed and produce fertile offspring

Gene pool

Total of all genes in the population

Hardy-Weinberg Theory

Non-evolving population

Large population size, no migration, no net mutations, random mating, no natural selection

Hardy-Weinberg Equillibrium

Allele frequency doesn’t change over generations

Where does evolution occur?

Within populations

Microevolution

Change in allele frequencies in a gene pool

Causes of microevolution

Genetic drift, natural selection, gene flow, mutation

Genetic drift

Altercation of the gene pool of a small population due to chance

Bottleneck effect and founder effect

Polymorphism

Existence of two or more forms of a character

Geographic variation

Difference between gene pools due to environmental factors

Cline

Graded variation in individuals that correspond to gradual changes in the environment

Mutation

Change in an organism’s DNA

How do new alleles originate?

Mutations

Diploids

Hides genetic variation in the form of recessive alleles

Balanced polymorphism

Natural selection maintains stable frequency in at least two phenotypes

Heterozygous advantage

Heterozygous has greater survival and reproductive success than homozygous

Frequency-dependent selection

Survival of phenotype declines if too common

Neutral variation

Genetic variation with no competitive advantage

Darwinian fitness

Contribution of an individual to the gene pool

Relative fitness

Contribution of a genotype to the next generation

Directional selection

Favors individuals at one end of the phenotype range

Diversifying selection

Favors extreme phenotypes

Stabilizing selection

Favors intermediate phenotypes

Intrasexual selection

Direct competition of same sex for opposite sex mates

Intersexual selection

One sex is choosy over opposite sex mate

Natural selection __

Doesn’t produce perfect organisms

Autosomal dominant disease example

Widow’s peak, Hunington’s disease

Autosomal recessive disorder

Sickle cell anemia

Characteristics of autosomal recessive disorder

Often skip generation

X-linked dominant characteristics

Affected fathers pass to ALL of their daughters

Y-linked characteristics

All sons of an affected man are affected

Oncogenes

DNA that codes proteins that promote normal cell growth and division

Tumor Suppressor Gene

Inhibit cell growth and prevent tumor formation

Hereditary Mutation characteristics

Multiple, early, bilateral tumors

Sporadic mutation

Single, unilateral, late tumors

P53

Gene located on short arm of chromosome 17

Karyotyping

Looking for abnormalities

Top part of chromosome

Upper arm

Lower part of chromosome structure

Lower arm

Circle connecting chromatids

Centromere

Separated chromosome

Sister chromatid

Chromosome with no upper arms

Telocentric

Chromosome with short upper arms

Afrocentric

Chromosome with almost equal arms

Submetacentric

Chromosome with equal arms

Metacentric

Trisomy

Three copies of a chromosome, down syndrome

Monosomy

One copy of chromosome, turner syndrome

Single nucleotide polymorphism (SNP)

One nucleotide is different than the others

RFLP

Restriction Fragment Length Polymorphism

Catalyze cleavage of phosphate bonds

Sickle cell disease

Interfere with body’s ability to make hemoglobin

Heterozygous - carrier, trait

Homozygous - disease

Symptoms - amenia, periodic blood clots, compromised spleen, heart attacks

On chromosome 11

Two copies

Recessive disease

Recognition site of Sickle Cell Anemia

Mostly

CRISPR

Clustered Regularly Interspaced Short Palindrome Repeats

Part of antiviral system

Spacer and CAs protein protect the immune system by adding viral DNA

gRNA

If encountered with foreign DNA that matches spacer sequence, invader’s genome is chopped

Mechanism of Action

Results in small inversions, deletions or other mutations

Loss of function

Selective breeding

Edit breeding pattern to increase desirable traits through CRISPR

PAM site

TGG, sends signal to create double stranded break

Gene that allows taste of PTC compound

TAS2R38 gene

Have III Restriction Digest

C is replaced with G

PCR

Polymerase Chain Reaction

Amplify specific segments of DNA

Taq polymerase from Thermus aquaticus bacteria used

Requirements for successful PCR

Template DNA, primers, DNA nucleotides, DNA taq polymerase

Haelll shape

Straight

PCR extra information

Every cycle doubles number of DNA strands

Most DNA product are the same length as distance between primers

Dramatic amplification exists between primers

20 cycles = 1 million fold applications

PCR and contamination extra information

Most important consideration is contamination

Smaller contamination can affect amplification

Labs put effort to avoid cross contamination