Cystic Fibrosis
- autosomal recessive
- pleiotropy
- 1/2500 Europeans
- high extracellular chloride concentration which makes mucus really thick
- mucus builds up in lungs, pancreas, digestive stuff
- untreated = die before 5, treated = live to 30
Sickle Cell Anemia
- autosomal recessive
- can be codominant
- 1/400 Africans
- makes red blood cells crescents instead of round
- sickles clump together and clog when O2 is low
- weakness, pain, organ damage
- carriers have some symptoms (codominance)
- heterozygote advantage: resist malaria & aren’t in pain
Albinism
- autosomal recessive
- epistasis
- lack of pigment in skin
- 1/22,000 people
Phenylketonuria (PKU)
- autosomal recessive
- accumulation of phenylalanine in the blood
- food warnings for people with this
- mousy odor, broad shoulders, mental retardation, albinism, difficulty walking
Tay Sachs
- autosomal recessive
- lipid accumulation in brain cells
- death in childhood
- 1/300,000 (mostly Jewish people)
- babies are normal at birth, blind by age 1, dead by 5
Achondroplasia
- autosomal dominant
- dwarfism
- 1/25,000
- pleiotropy
Huntington’s Disease
- autosomal dominant
- degenerative brain disease
- starts deterioration at 35-45
- fatal and irreversible
- kids of a parent with this have 50% chance of it
- 1/100,000
- can be tracked down by a karyotype
Red-Green Color Blindness
- sex linked recessive
- only sees 25 (out of 150) colors
Hemophilia
- sex linked recessive
- inability to form blood clots
Duchenne Muscular Dystrophy
- sex linked recessive
- progressive weakening and loss of muscle
- 1/3500 males
- rarely live past their 20s
- absence of a muscle protein on a specific loci on the X chromosome (baldness)
Multifactorial Disorders
most genetic diseases have a genetic component and an environmental influence
Before Gregor Mendel…
- people thought traits were always blended (tall & short person always made a mid-height person)
- mom and dad contributed 100% equally
- this was called the blending hypothesis
Gregor Mendel’s Experiments
- garden peas
- stamen: boy pollen
- carpet: girl eggs
- stigma: where pollen sticks
True Breeding
-offsprings are like both parents and each other, parents are like each other
Hybrids
-offsprings are a mixture of parents that are different (always heterozygous, Aa)
Law of Independent Assortment
distribution of the number of one pair of chromosomes into gametes is independent of other pairs (whether an offspring gets AA or aa doesn’t affect whether it gets BB or bb)
-crossing over and independent assortment
Law of Segregation
the members of a pair of factors separate during the formation of gametes (A & a have a 50/50 chance of which allele will go to the offspring)
-crossing over and independent assortment
Probability
- ranges on a scale of 0 to 1
- all possible outcome probabilities add up to 1
Rule of Multiplication
- use the word “and”
- 1/2 x 1/2 = 1/4 (1/4 is the chance that both coins tossed at one will both land on heads, 1/2 and 1/2 are the chances of one coin landing on heads)
Rule of Addition
- the chance of an event that can occur in 2 or more independent ways is the sum of their individual chances
- if you cross 2 dogs with Bb, what are the chances of one of their offsprings being Bb?
- Bb x Bb
- 1/2B x 1/2b = 1/4 Bb *add 1/4 & 1/4
- 1/2b x 1/2B = 1/4 Bb -final: 1/2 Bb
Incomplete Dominance
- neither allele is completely dominant over the other
- red (AA) & white (aa) roses make pink (Aa)
Codominance
- both alleles are fully expressed
- blood types
Multiple Alleles
- a person can only have 2 alleles for a particular gene but that doesn’t mean that there are only 2 alleles in the population for that trait
- blood groups
Epistasis
- the product of one gene can modify the phenotype of another
- albinism
- 9:7 dihybrid ratio
