Exam 2

Incomplet Dominance

Blending inheritance (red + white = pink) Neither parental phenotype is shown in the F1 generation

Codominance

Both parental phenotypes appear. Blood type and fur-coats

Pleiotropy

One gene produces multiple phenotypes

Genetic Heterogeneity

Mutations in multiple genes give the same phenotype

Complementation

Only in recessive genes. When you test cross two mutants and see if the mutation is on the same gene

Same Gene

Mutant x Mutant = Mutant

Different Gene

Mutant x Mutant = Normal

Lethal Alleles

Typically recessive only. When you need both copies of the gene for it to harm you

Influence of Environment

Mutations due to what happens around you. Hormonal influence

Sex - limited Traits

Traits that appear only in one sex

Sex - Influenced Traits

Causes differences between the sexes. Due to autosomal genes

Variable Expressivity

Same genotype of severity of phenotype can vary (down syndrome)

Incomplete Penetrance

Not everyone with affected genotype is affected

Anticipation

Phenotype gets progressively stronger over generations

Polygenic Inheritance

A phenotype that is controlled by more than one gene (coats in dogs)

Epistasis

One gene blocks another

Bombay Phenotype

hh is epistatic to I

Ploidy

Number of sets of chromosomes / number of copies

Polyploidy

>2n chromosomes (Odd #'s are usually sterile) (Common in plants)

Clochicine

Can cause chromosomal abnormality (damages spindle microtubutals)

Aneuploidy

Variations of chromosome numbers (down syndrome / Edward syndrom)

Recombination

Crossing over / X ray machines

Hot Spot

Recombination happen frequently

Cold Spot

Recombination doesn't happen frequently

T.H. Morgan

Sex linkage

Barbra Mclintock and Harriet Creighton

Recombination is due to crossing over

Herman Muller

X rays sped up mutations

Calvin Bridges

Looked for sex-linkage / found what chromosome the mutations where on

Alfred Sturtevant

Fine scale mapping / looked at R.F

Dosage Compensation in Flies

Hyperactivate X to match the females

Dosage Compensation in Nematodes

Hypoactivate XX to bring down to males

Dosage Compensation in Mammals

Use of a bar body to deactivate an X to bring it down to males

Sex Determination in Turtles

Temperature

Sex Determination in Bees

Haploidiploidy (# of chromosomes present)

Sex Determination in Nematodes

Hermaphrodite (can self fertilize) (XO)

Sex Determination in Birds

ZW system (Male = ZZ Female =ZW)

Sex Determination in Mammals

XY system (XX = Female XY = Male)

SRY Gene

Sex determining region on Y chromosome (encodes TDF protein)

TDF

Activates the production of testosterone (Activates MIS)

MIS

Mullerian Inhibiting substance

Androgen Receptor

Allows the body to respond appropriately to the hormones