BELL RINGER If a green pea pod plant is crossed with a yellow pea pod plant, what will the offspring look like? X ALL the offspring will be green!

Father of Genetics GENETICS: study of heredity HEREDITY: passing of traits from parent to offspring TRAITS: characteristics Learned about these patterns by studying PEAS

MENDEL’S PEA TRAITS

How do traits get passed from parent to offspring? Through GAMETES: sex cells Male gamete is the SPERM Female gamete is the EGG FERTILIZATION: union of egg & sperm ZYGOTE: fertilized egg

GENES VS. ALLELES Each form of a gene is called an ALLELE EXAMPLE: Segment of DNA that codes for one protein/trait Most traits are determined by TWO genes. Remember chromsomes have a homologous match…two chromosomes with similar genetic information EXAMPLE: hair color eye color height in pea plants Each form of a gene is called an ALLELE EXAMPLE: brown or blond blue, hazel, brown tall, short

Law of Dominance DOMINANT (allele) Always expressed if present Only need ONE dominant allele to be expressed EXAMPLES: dark hair, brown eyes, tall peas RECESSIVE (allele) May be present but will not be expressed if paired w/ dominant allele Requires TWO recessive alleles for recessive trait to be expressed EXAMPLES: light hair, blue eyes, short peas

Law of Segregation Gene pairs separate during formation of gametes (meiosis) Each gamete gets ONE allele from a pair Each parent passes down one allele to their offspring ( Offspring get 2 alleles (one from each parent)

Preparing for Genetic Crosses Letters will represent alleles Use the first letter of the dominant trait Capital letter = dominant trait Lower case letter = recessive trait EXAMPLE: height in pea plants TALL is dominant over short, so… T = tall t = short

All possible combinations using T, t: TT, tt, Tt, tT Genotype vs. Phenotype All possible combinations using T, t: TT, tt, Tt, tT GENOTYPE: actual genes in the pair; can’t see…they’re on chromosomes…but they determine the individual’s traits Use terms: homozygous: both genes the same (TT, tt) heterozygous:genes different; 1 dominant, 1 recessive (Tt, tT) PHENOTYPE: the trait that is expressed; the ‘physical’ appearance P G TT…tall (homoz dom) tt….short (homoz rec) Tt….tall (heterozygous) tT….tall (heterozygous

Mendelalian Traits Traits that have 2 alleles EXAMPLE: cleft chin If a person inherits two dominant alleles (CC) or one dominant & one recessive (Cc), they will have a cleft chin (top) If a person inherits 2 recessive alleles (cc), they will not have a cleft chin (bottom)

Solving Genetic Crosses Use PUNNETT SQUARES Shows POSSIBLE GENOTYPES of offspring The parents gametes go on outside of square (one parents’ gametes across top; other parents’ gametes down left side Remember: each gamete has only ONE allele