Genetics

Tossing Coins If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

Vocabulary Genetics: Allele- Trait- the scientific study of heredity one of a number of different forms of a gene Trait- specific characteristic that varies from one individual to another

Bb Vocabulary Phenotype- Genotype- physical characteristics of an organism Genotype- genetic makeup of an organism Bb

Vocabulary Homozygous- Heterozygous- term used to refer to an organism that has two identical alleles for a particular trait. Heterozygous- term used to refer to an organism that has two different alleles for the same trait.

Vocabulary Hybrid True-breeding- - offspring of crosses between parents with different traits True-breeding- - term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

Vocabulary Probability Punnett Square - likelihood that a particular event will occur. Punnett Square - diagram showing the gene combinations that might result from a genetic cross.

Genetic Notes 1. Genes and Dominance a. Mendel studied different traits with contrasting characteristics b. Traits- a specific characteristic such as seed color or plant height that varies from one individual to another. c. Hybrids- Offspring of parent crosses with different traits d. Genes- chemical factors that determine traits (height) e. Alleles- different forms of a gene (short or tall)

Genetic Notes f. Principle of dominance: Alleles can be dominant or recessive i. Dominant: trait is always seen Ii. Recessive: trait is seen if dominant is not present

Genetics Notes 2. Genetics & Probability Probability- the likelihood that a particular event will occur The principles of probability can be used to predict the outcomes of genetic crosses

3.Punnett Squares Ii. Lowercase letters for recessive alleles a. Punnett Square is a diagram used to determine the gene combinations that might result from a genetic cross (the offspring from two chosen parents) b. Letters in the squares represent alleles i. Capital letters for dominant alleles Ii. Lowercase letters for recessive alleles

TT Tt c. Homozygous- organisms that have two identical alleles for a particular trait (TT or tt) : are true-breeding d. Heterozygous- organisms that have two different alleles for a particular trait (Tt) : are hybrid

Phenotype- physical characteristics Genotype- genetic makeup e. Offspring can have the same phenotype but different genotypes Phenotype- physical characteristics Genotype- genetic makeup

4. Probability and Segregation a. Mendels results showed i. Homozygous dominant = ¼ (25%) ii. Heterozygous = ½ (50%) iii. Homozygous recessive = ¼ (25%) b. The ratio of tall plants to short is 3:1 c. Due to the 75% dominant traits showing and 25% recessive traits showing, Mendel concluded that segregation occurs

Review What is probability? What is a punnett square? The likelihood that a particular event will occur. What is a punnett square? A diagram that shows all gene combinations that might result from a genetic cross.

Review How are the principles of probability used to predict the outcomes of genetic crosses? The way which the alleles segregate is random and probability allows the calculation of the likelihood that a particular allele combination will occur in offspring.

Review What are dominant and recessive alleles? Dominant allele: allele whose from of a trait always show up in an organism if the dominant allele is present Recessive allele: allele whose form of a trait shows up only when the dominant allele is not present.