What is the probability of rolling a 1 and 5 in two separate rolls? Agenda for Tuesday March 30 th Mendel notes Punnett Squares

Law of Segregation Chromosomes separate during meiosis and unite during fertilization

Law of Independent Assortment Random distribution of chromosomes occurring during meiosis – Genes on separate chromosomes sort independently

The point? It’s all random – Which alleles we get (genes) (traits) – Crossing over – Etc.

What is a trait? Agenda for Thursday March 31 st 1.Mendel 2.Punnett Squares

Mendel Father of genetics Loved nature Austrian monk – taught natural science – worked on plant breeding experiments using pea plants Developed basic understanding of genetics and inheritance

Mendel’s Work It took him 2 years to select the pea plant He collected data for 10 years. His sample sizes were large; he tabulated results from 28,000 pea plants. He replicated his experiments. Published work but was dismissed – Found later

Mendel’s Experiment P Generation – parent generation F 1 generation – first filial generation, offspring of parents F 2 generation – second filial generation, offspring of F 1 generation Ratio of 3:1

Mendel’s Results P1P1 F1F1 F2F2 F 2 ratio smooth X wrinkled seeds all smooth5474 smooth 1850 wrinkled 2.96:1 yellow X green seeds all yellow6022 yellow 2001 green 3.01:1 axial X terminal flowers all axial651 axial 207 terminal 3.14:1 red X white flowersall red705 red 224 white 3.15:1 inflated X constricted pods all inflated882 inflated 299 constricted 2.95:1 green X yellow podsall green428 green 152 yellow 2.82:1 tall X dwarf plantsall tall787 tall 277 dwarf 2.84:1

Collected 6022 yellow and 2001 green 3:1 ratio

Conclusions 2 forms of seed traits in the pea plants – Alleles – forms of a gene passed on to each generation Green and yellow pea seeds – We use letters to represents alleles/genes/traits – Individuals are diploid so we use 2 letters **Genes are on the chromosomes

Dominant and Recessive Dominant – the trait we see (expressed with capital letter, A) Recessive – trait that is masked (expressed with lower case letter, a) Which is better, dominant or recessive?

Dominance Mendel’s experiment, green color was masked – Recessive Organism with two of the same allele – homozygous – AA, aa Organism with two different alleles – heterozygous – Aa – Dominant trait observed (notice the dominant allele)

Homozygous (pure bred) Same HH hh

Heterozygous (hybrid) Different Hh Rr

Genotype Allele makeup of an individual Tt T Ttt RRRrrr

Phenotype Observable characteristics of an individual

Punnett Squares Let’s Practice

Practice A Tt (tall) plant is crossed with a tt (short plant). What percentage of the offspring will be tall? A green pea sead (gg) is crossed with a hybrid yellow seed (Gg). What will be the genotypic and phenotypic ratios of the offspring?

Practice A heterozygous plant (Tt) is crossed with another heterozygous (Tt) plant. What percentage of the offspring will be tall? In guinea pigs, rough coats are dominant over smooth coats. If an Rr guinea pig is crossed with an Rr guinea pig. What are the chances of each genotype and phenotype? Include genotypic and phenotypic ratios.

Define homozygous, heterozygous, phenotype, and genotype Agenda for Friday April 1 st 1.Quiz 2. More practice with Punnett Squares

A Tt (tall) plant is crossed with a tt (short plant). What percentage of the offspring will be tall? Quiz Review Punnett Squares Making Dragons

A Rr (round) seed is crossed with a Rr (round plant). What are the phenotypic and genotypic ratios? Finish making dragons Comparing ratios of Punnett squares to actual ratios lab

What is the process of combining two gametes called? Finish Comparing Punnett Square ratios Dihybrid Crosses

Dihybrid Cross a cross between of two individuals that differ in two traits of particular interest For example: GGbb/ggBb or RRYY/rryy

What is a dihybrid cross? Dihybrid Review Gene Linkage and Polyploidy – Mapping Chromosomes

Genetic Recombination New combination of genes produced by crossing over and independent assortment Why is genetic recombination important?

Gene Linkage Genes on same chromosomes are said to be linked – Travel together during Meiosis Not always true – crossing over occurs Genes close together cross over more frequently – Make chromosome maps based on that info.

Chromosome Map Map genes A, B, C, D Frequency of crossing over – AD = 25% – AB = 30% – CD = 15% – BD = 5% – BC = 20%

Polyploidy Most cells are Diploid (2n) Polyploidy – one or more extra sets of chromosomes – Triploid – 3n In humans polyploidy is lethal – Other organisms it is not – Roughly 1 in 3 plants are polyploidy Increased vigor and size