Introduction to Mendelian Genetics

Objectives Define key terms used in Mendelian Genetics

Key Terms Heredity: The passing of characters from parents to offspring. Genetics: The branch of biology that focuses on heredity. Traits: Specific characteristics that vary from one individual to another. Ex. Hair color, skin color Gene- a specific nucleotide sequence of DNA that codes for a protein

Key Terms Allele –alternative forms of a gene. Ex. flower color –purple (P) or white (p)

Key Terms Phenotype- organism’s expressed traits; Ex. Brown coat Genotype – An organism’s genetic makeup; the combination of alleles in the homologous chromosomes. Ex. - BB, Bb, bb Homozygous – having identical alleles for the trait – Ex. WW, ww Heterozygous – having two different alleles for the trait- Ex.Ww.

Definitions Dominant- an allele that determines the phenotype of heterozygote. (Ex. YY-yellow plant or Yy). Recessive – the allele that is masked by the dominant allele in heterozygotes; not observed in the phenotype unless homozygous recessive (yy-green plant).

Purpose of Punnet Square Examines the probability of getting a particular phenotype based on combination of gametes Trait resides on the homologous chromosomes Each square in a monohybrid cross (i.e. one trait) represents 25% chance Summarize result with genotypic ratio and phenotypic ratio

Practice Problem Draw a Punnett square for the following cross: Tt X Tt Give the genotypic and phenotypic ratio.

Practice Punnett Square Problem A plant that is heterozygous for green (G) pods is crossed with a plant that has yellow (g) pods. Green pod is dominant and yellow pod is recessive. What are the probable genotypic and phenotypic ratios in the offspring from this cross? What is the probability that plant will produce yellow pods?

PROPERTY OF PIMA COUNTY JTED, 2010 Paraphrase Write down two genetic terms you learned today Write the definitions of those terms in your own words 6. Paraphrase student writes down one or two main ideas directly from the text or notes student now paraphrases these ideas in their own words teacher provides feedback PROPERTY OF PIMA COUNTY JTED, 2010 6 PROPERTY OF PIMA COUNTY JTED, 2010 10

Human Traits

Detached Earlobes

Hitchhiker’s Thumb

Tongue Rolling

Dimples

Cleft Chin

Widow’s Peak