Mendel and His In-Gene-ius Idea… Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes.

Essential Knowledge 3A3: The chromosomal basis of inheritance provides an understanding of the pattern of passage of genes from parent to offspring.

… “particulate” hypothesis is the idea that parents pass on discrete heritable units (genes)… Gregor Mendel 1822-1884

Mendel’s Peas… Planned experiments using characters (flower color) and traits (purple/white)

He Experiments… Mendel mated 2 contrasting, true-breeding varieties  hybridization True-breeding parents = P generation Hybrid offspring of P generation = F1 generation When F1 individuals self-pollinate = F2 generation is produced

Purple = dominant White = recessive 3:1 Ratio

Mendel’s heritable factor = gene Alternate versions =alleles

IA Video

Law of Segregation and I.A. apply to genes on diff. chromosomes.

Genes near each other on same chromosome tend to move as a unit Probability of segregation is a fxn of the distance b/t them.

Dominant vs Recessive Use Punnett Squares to predict heredity outcomes. Dominant alleles: Use upper case. Ex: S Recessive alleles: Use lower case. Ex: s

Homozygous: alleles for a trait are same Homozygous: alleles for a trait are same. Ex: SS or ss or TT (true breeding) Heterozygous: alleles for a trait are different. Ex: Ss or Tt

Ratios Receive 2 types of info: genotype and phenotype. Genotype: genetic trait that you cannot see (genes) Phenotype: trait or behavior you can see physically.

Genotype Phenotype Use probability to analyze passage of single gene traits from parent to offspring

Punnett Squares!!

One Factor Punnett Square One trait = monohybrid cross. Ex: Cross a tall dominant homozygous pea plant (TT) w/ short recessive homozygous pea plant (tt).

Monohybrid Cross TT is a parent who is Tall tt is a parent who is Short Both are homozygous that make heterozygous offspring.

Ratios to Know TT x tt = 100% Dominant, but heterozygous Tt x Tt = 75% Dominant, 25% Recessive, 3:1

Two factor Punnett Square Cross 2 traits = dihybrid cross. Example: Cross a dominant green, smooth pea plant (GGSS) with a recessive yellow, wrinkled pea plant (ggss)

Ratios to Know SsTt x SsTt = 9:3:3:1 9 dominant in both traits 3 dominant in one trait or the other trait 1 recessive for both traits

Human Genetic Disorders Can be received by inheriting a single gene trait or specific chromosomal change Ex: Tay-Sachs Disease: Mutation on Chrom. 15 causing deterioration of nerve cells.

What’s This??

Punnett Square Sample Probs