Fundamentals of Genetics

Introduction to Genetics 1. GREGOR MENDEL - “Father of Genetics” Austrian monk, teacher, scientist, gardener Formulated basic laws of heredity in the early 1860s Simplified problems; was meticulous with data collection; think quantitatively

2. Worked with garden peas because: Easy to grow and had a short generation time Could be self-pollinated 3. Chose true-breeding varieties for his experiments Means no genetic variation for a trait Studied 7 simple traits

4. Mendel cross-pollinated plants P 1 = parental generation F 1 = first-generation (sons/daughters) F 2 =second-generation

5. Principle of Dominance and Recessiveness F 1 plants resembled only one of the parents F 1 hybrids contained two factors for each trait one dominant; (stronger, masks recessive); one recessive; (seems to disappear)

6. Principle of Segregation Organism contains two factors for each trait. Factors segregate during formation of gametes. Each gamete contains one factor for each trait.

7. Principle of Independent Assortment Each trait is independent of another Genes of one pair of traits assort independently All combinations of genes occur in gametes

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IN: P12 Why did Mendel select pea plants to study?

OUT: P 12 Pick any dominant and recessive trait. Complete and diagram the 3 types of monohybrid crosses below. 1.Homozygous x Homozygous 2.Homozygous x Heterozygous 3.Heterozygous x Heterozygous....

Chromosomes, Genes, and Genetic Crosses 1.Homologous Chromosomes contain genes (locations) for the same traits 2.Traits are controlled by alleles (alternative forms of a gene). 3.Genotype refers to the alleles an individual receives at fertilization 4.Phenotype refers to the physical appearance of the individual.

5. Homozygous dominant genotypes = two dominant alleles for a trait. (BB) 6. Homozygous recessive genotypes = possess two recessive alleles for a trait (bb) 7. Heterozygous genotypes = one of each allele for a particular trait (Bb)

8. Punnett Squares Show probabilities of future offspring Monohybrid crosses = crosses between individuals that involve one pair of contrasting traits.

9. Monohybrid Crosses (Examples) Ex 1: Pure Tall x Pure Short TT=Tall tt =short F1 F2T t t Tt TtTt TT Tttt 100% Tall 25% pure tall 50% hybrid tall 25% pure short (Homozygous x Homozygous) (Heterozygous x Heterozygous)

10. Test Crosses A cross of an individual of unknown genotype with an individual of known genotype Tells if individual is heterozygous or homozygous Very important to breeders

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Dominance Has Degrees 1. Incomplete dominance Offspring are intermediate between two parental phenotypes Neither allele is completely dominant over the other Both alleles influence phenotype 3 phenotypes

Ex: Japanese Four o’clocks RR = redRR’ = pink R’R’ = white RR R’ RR’ R R’ RRRR’ R’R’ All Pink1 red : 2 pinks : 1 white

2. Codominance Both alleles of a gene are expressed. A person with AB blood has both A and B antigens on their red blood cells. Neither allele is dominant or recessive

RED WHITE ROAN

Ex: Red Coat - RR White Coat – WW White & Red Mixed – RW (“roan”) R WWWW R W R WR W RR RW WW All Roan – both red and white hair 1 red : 2 roan : 1 white

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IN: P 28 My Steps for Dihybrid Crosses 1. Underline: What’s dominant, recessive, and the parents 2. Genotype and phenotype possibilities 3. Write genotypes of parents 4. Diagram possible gametes 5. Do cross 6. Answer question asked X

OUT: P 28 Prepare Data Table Count Kernels (C or D) PREDICT GENOTYPE of PARENTS purple and smooth are Dominant Purple Smooth Purple Wrinkled Yellow Smooth Yellow Wrinkled

Dihybrid Cross Feather color = ORANGE or blue CREST or no crest

A cross involving two pairs of contrasting traits Example: DominantRecessive Yy, YY = yellowyy = green Rr, RR = roundrr = wrinkled

Example cont. P1RRYYxrryy round, yellowwrinkled, green(homozygous) RY ry RrYy Offspring are all heterozygous

RrYy X RrYy Law of Independent Assortment Genes for different traits are inherited independently R, r, Y, y go to sperm/egg independently of each other Can recombine in four ways: RY, Ry, rY, ry

RY Ry rY ry RRYY RY Ry rY ry

. 9 round,yellow : 3 round, green : 3 wrinkled, yellow : 9:3:3:1 1 wrinkled,green RY RyrYry rY Ry RRYYRRYyRrYYRrYy RRYyRRyyRrYyRryy RrYYRrYy rrYYrrYy RrYyRryyrrYy rryy