Mendel The Gene Idea Mendelian genetics Vocab Character
Mendel & The Gene Idea
Mendelian genetics Vocab • Character inheritable feature- fur color • Trait variant for a character -brown • True-bred all offspring of same variety • Hybridization crossing of 2 different truebreds • P generation parents • F 1 generation first filial generation • F 2 generation second filial generation
Genetics Vocab. -Monohybrid cross with 1 character -Dihybrid cross a cross with two characters -allele alternate version of a gene -dominant allele an allele that masks another allele -recessive allele an allele that is masked -punnett square- shows possible genetic outcomes
Blending Model of Inheritance • Stated that two different alleles “blended” when crossed • This doesn’t happen with complete dominance
More Genetics Vocabulary…… • Homozygous: pair of identical alleles for a character • Heterozygous: two different alleles for a gene • Phenotype: an organism’s traits (looks) • Genotype: an organism’s genetic makeup • Testcross: breeding of a recessive homozygote X unknown dominant
Test Cross 1 phenotype, 2 possible genotypes Homozygous recessive
The Law of Independent Assortment • Each pair of alleles segregates independently of other pairs of alleles.
Rules of Probability • Addition Rule- probability that any one of two or more mutually exclusive events will occur is calculated by adding the individual probabilities. Example- the chance of getting heads or tails on a coin toss heads- ½ tails – ½ ½ +1/2 = 1
Rules of Probability Multiplication- probability that two or more independent events will occur together Ex- What is the chance that two coins tossed together will both land heads up? probability of 1 head- ½ probability of 2 heads ½ x ½ = 1/4
Probability Problems • Chance of rolling a three on a die? 1/6 • Chance of getting any other number other than three? 5/6 • Chance of rolling a 1 and then a 2 and then 4? 1/6 x 1/6 = 1/216 • Parents are PP and pp- chance that offspring will be Pp? 1 x 1 = 1 • Parents are Pp. Yy x Ppyy chance that offspring will be pp. Yy? Pp= ½ x ½ Yy= ½ x 1 total=1/8
Non-single genetics • Incomplete dominance: offspring appear between the phenotypes of the 2 parents. Ex: snapdragons • Use two different letters for solution • Ex. -Tay-Sachs disease
Non single genetics • Codominance- both alleles affect the phenotype in separate ways • Example-roan coat color in cattle involves the dual expression of the pigmented gene and the non-pigmented gene in coat color
Non single genetics • Pleiotropymultiple phenotypic effects • Example- Sickle cell anemia
Non-single genetics • Epistasis: a gene at one locus (chromosomal location) affects the phenotypic expression of a gene at a second locus. • Ex: mice coat colorblack is dominant over brown but the “coat “gene is also involved
Non single genetics • Polygenic Inheritanceadditive effect of two or more genes • Example- eye color or skin color
Polygenic Inheritance • Trait is controlled by several different genes • Each gene adds to the effect
Nature or Nurture? • Traits are affected by environment • Can create a range of phenotypes • Example- colors of flowers can be affected by acidity of the soil
Pedigree Analysis • Used to predict inheritance based on past phenotypes
Autosomal Recessive Inheritancecystic fibrosis Generation skipped
Autosomal Dominant Inheritance. Huntington Disease Generations are not skipped
Sex-linked Pedigrees • Primarily one gender shows the disease • Dominant sexlinked does not skip generations.
Human disorders • The family pedigree • Recessive disorders: • Cystic fibrosis • Tay. Sachs • Sickle-cell • Dominant disorders: -Huntington’s
Genetic Diseases to Know • PKU • Tay Sachs • Huntington’s disease • Hemophilia • Sickle cell anemia
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