Theoretical genetics

Handedness

Tongue rolling?

Genotypes and Phenotypes• Genotype: alleles possessed by an organism• Phenotype: characteristics of an organism

• Homozogous: two identical alleles of a gene• Heterozygous: two different alleles of a gene

• Dominant allele: allele that has same effect on the phenotype whether it is present in the homozygous or heterozygous state

• Recessive allele: allele that has an effect on the phenotype only when it is present in the homozygous state

• E.g. Earlobe attachment (F dominant and f recessive) – Genotype: FF (Homozygous dominant) or Ff (Heterozygous) – Phenotype: Free earlobe

– Genotype: ff (Homozygous recessive) – Phenotype: Earlobe attached

Theoretical Genetics

Preformation

Idea that an exact miniature replica of parent existed inside sperm/egg cell

Mendel: The grandfather of genetics

• Grew up on parents’ small farm in Austria

• University of Vienna (1851)• Monastery (1857)

– Breed garden peas to study inheritance

• Contributions: – Factors (alleles) were responsible

for characteristics – Consider probability of combination

of offspring

Peas

Why peas? – Distinct traits– Large flower allow

easy manipulation of crosses

The flower structure

What Mendel did

Mendel’s cross pollination experiment

• Pure breeding plants = plants that always produce offspring with identical traits

• P = Parental generation (yellow, green)

• F1 = first filial generation• F2 = second filial

generation

Punnett square

• Red blood cells: transport oxygen

• White blood cells: help fight infection

• Platelets: help blood clot

• Plasma: medium that carries these cells

Review: Your blood

Each blood type has a specific…

• Antigen = surface markers on your red blood cell (your blood cell’s ID)

• Antibody = proteins produced by white blood cells, recognize certain antigens and trigger an immune response

What is special about the ABO blood grouping system?

1. Multiple alleles: IA, IB and i2. Codominance: both alleles are expressed• IA, IB codominant alleles• i is recessive

Genotype Phenotype Protein on RBC (antigen)

Antibody in blood plasma

IAIA or IAi Type A A Anti b

IBIB or IBi Type B B Anti a

IAIB Type AB A and B

ii Type O Anti a and b

Agglutination – what happens when antigen meets specific antibody

Clumped red blood cells can crack and cause toxic reactions

Predict: Does antibody bind to antigen when you…

Mix Anti-A with Group AB?

Mix Anti-B with Group AB?

Mix Anti-A with Group O?

Mix Anti-B with Group O?

http://www.nobelprize.org/educational/medicine/bloodtypinggame/

4.3.5 Sex chromosomes

4.3.6-4.3.7 Sex chromosomes

• some genes are present on the X chromosome and absent from the shorter Y chromosome in humans

• Sex linkage = genes carried on the sex chromosomes, most often on the X chromosome

4.3.8 Red/Green Color blindness• Carrier = an individual has

one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele

• Female carriers do not show the disease, but can pass it on to half of their male offspring

4.3.8 Hemophilia

• X-linked recessive disorder characterized by inability to form blood clots