handedness - the biology...
TRANSCRIPT
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