Gregor Mendel

"Father of Modern Genetics" Austrian monk who took care of the monastery gardens

Homologous chromosomes

Paired chromosomes, one inherited from each parent. Same stuff

Gene

a unit of information a piece of DNA on a chromosome that codes for a specific trait

Locus

The exact position a gene is found on a chromosome

Alleles

different forms of the same gene -like a different color of flower

Homozygous

2 identical alleles in a given gene pair

Heterozygous

2 different alleles in a given gene pair

Heterozygous

Aa

Homozygous

AA or aa

Dominant allele

the allele that is expressed in a heterozygous individual

Recessive allele

the allele that is not expressed or is masked in a heterozygous individual

Genotype

the actual genetic makeup that an individual has for a trait

Homozygous dominant

AA

Homozygous recessive

aa

Phenotype

the actual physical or physiological expression of a gene pair

Genetic Cross

A cross (mating) between 2 parents resulting in offspring

Monohybrid cross

a genetic cross involving the inheritance of one trait (4 box Punnett square)

Dihybrid cross

a genetic cross involving the inheritance of two traits simultaneously (16 box Punnett square).

P generation

Parental generation

F1 generation

First filial generation 1st generation of offspring from parents

F2 generation

Second filial generation 2nd generation of offspring from F1 parents

Complete (True) Dominance

– 2 possible alleles exist for a trait – 1 is dominant, 1 is recessive – Heterozygous individuals express the dominant form of the trait

Incomplete Dominance

– 2 possible alleles exist for a trait – No dominance exists – Heterozygous individuals express both alleles simultaneously --> results in a 3rd phenotype

Multiple Alleles

– More than two possible alleles exist for a trait – Multiple phenotypes possible

Autosomal inheritance (complete dom)

traits carried on autosomes (non-sex chromosomes)

Sex-linked inheritance

traits carried on sex chromosomes (chromosomes that determine gender)

X-linked traits

Traits carried on X chromosome only (sex-linked inheritance)

Incomplete Dominance Heterozygous

express both alleles (red)+(white) simultaneously----> results in a 3rd phenotype (pink)

Incomplete Dominance in humans

Handedness H^R H^L = ambidextrous-Can use both hands equally

Phenotypic and genotypic ratios are identical in:

Incomplete Dominance

Multiple Alleles

More than 2 possible alleles exist for a trait =multiple possible phenotypes

Human Blood typing (ABO)

is in Multiple Alleles the 3 possible I^A=A I^B=B i=O

Blood type A

I^A I^A (homozygous) or I^A i (heterozygous)

Blood type B

I^B I^B (homozygous) or I^B i (heterozygous)

Blood type O

ii (homozygous recessive)

Blood type AB

I^A I^B (heterozygous) -I^A and I^B are contaminate alleles

Antigens

proteins produced by red blood cells – Recognize similar blood types

Antibodies

are protein molecules produced by white blood cells – Reject or are against foreign blood types

Blood type A produces

– A antigens and anti-B antibodies

Blood type B produces

B antigens and anti-A antibodies

Blood type O produces

No antigens and anti-A and anti-B antibodies

Blood type AB produces

A and B antigens and no antibodies

Epistasis

The interaction between genes --one gene pair can alter or affect the expression of a second gene pair

Polygenic Inheritance

multiple gene pairs influence the expression of one trait (skin color)