Mendel Heredity Gregor Mendel Father of Genetics Austrian

Mendel & Heredity

Gregor Mendel “Father of Genetics” – Austrian monk who completed breeding experiments with the garden pea plant, Pisum sativum – Wanted to learn more about how traits were passed from one generation to the next • Terms to know: • Character ~ physical features inherited (Ex: color) • Trait ~ several possible forms of character (Ex: purple, white) • Hybrid ~ results from crossing different traits (Ex: purple with a white) • Generation ~ a group of offspring from a given group of parents (P= parental, F= filial)

More Terms to Know • Allele: one of the alternative forms of a gene that governs a characteristic • Homozygous: Having identical alleles for a trait • Heterozygous: Having different alleles for a trait

And Even More Terms • Genotype: Combination of genes for one or more specific traits • Phenotype: organism’s appearance or other detectable characteristic that results from the organism’s genotype and environment

Mendel’s results

Mendel’s Theory • Why did that happen? Purple one generation, purple and white for another generation • ALLELES – Diff. versions of traits (Ex: White trait represented by “p” allele & Purple trait represented by “P” allele) – Get one from each parent – Dominant ~ always fully expressed (P) – Recessive ~ only expressed when there is no dominant (p)

Mendel’s Laws • Law of segregation ~ each pair of alleles is separated (meiosis) & each gamete has equal chance receiving either allele (GENETIC VARIATION) • Combination of alleles for a character = genotype (Ex: PP or Pp or pp) • Combination of alleles for a trait = phenotype “physical” (Ex: PP or Pp = purple, pp = white) • Two of same alleles = homozygous (Ex: PP or pp) • Two diff alleles = heterozygous (Ex: Pp)

Mendel’s Laws con’t • Law of Independent Assortment – The allele of each gene segregate independently – One trait won’t affect another – If traits are not located close to 1 another on chromosome

Good ol’ Mendel • Why are Mendel’s Laws and work so important? Punnett squares ~ Predict the likely ratio of the genotype of a given cross – Monohybrid homozygous ~ always result in 0: 4: 0 genotype & 4: 0 phenotype offspring (Yy dominant trait expressed) – Monohybrid heterozygous ~ will result in 1: 2: 1 genotype (1=YY, 2=Yy, 1=yy) & 3: 1 phenotype (3 dominant trait expressed, 1 recessive trait expressed)

Punnett Practice • A plant has two alleles of a gene for stem length, long (L) and short (l). Two plants that are both heterozygous for the gene are crossed. Use a Punnett square to estimate the chances of getting heterozygous offspring.

Punnett Practice • A plant has two alleles of a gene for stem length, long (L) and short (l). Two plants that are both heterozygous for the gene are crossed. Use a Punnett square to estimate the chances of getting heterozygous offspring.

Punnett Practice • A plant has two alleles of a gene for stem length, long (L) and short (l). Two plants that are both heterozygous for the gene are crossed. Use a Punnett square to estimate the chances of getting heterozygous offspring.

Punnett Practice • A plant has two alleles of a gene for stem length, long (L) and short (l). Two plants that are both heterozygous for the gene are crossed. Use a Punnett square to estimate the chances of getting heterozygous offspring. Parents are “Ll” 1 LL : 2 Ll : 1 ll 2/4 are Ll (heterozygous) L l L LL Ll ll 50% chance

Punnett Practice • A cat is heterozygous for long hair (Hh), and its mate is homozygous recessive, giving it short hair (hh). If they mated and had a litter of eight kittens, how many short hair kittens would you expect to find?

Punnett Practice • A cat is heterozygous for long hair (Hh), and its mate is homozygous recessive, giving it short hair (hh). If they mated and had a litter of eight kittens, how many short hair kittens would you expect to find? Looking for “hh” 2 Hh : 2 hh 2/4 are hh (homozygous recessive) ½*8=4 H h h Hh hh