Understanding Biological Inheritance

Biology 40S Genetics – The Study of Heredity Weblink – Mendel’s Genetic Laws

Sort & Predict

Place the following words into categories Each category must have a title You must make at least two categories Do not name one “words I don’t know”!!

Dominant Mendel Genotype Gene Heterozygous Heredity Yellow seed coat

Word List

Punnett square Recessive Hybrid DNA Purebred Chromosomes Blue eyes Homozygous Pea plants Phenotype Allele Carrier Sex-linked trait Brown hair

Gregor Mendel

Austrian monk & mathematician “The Father of Genetics” Experimented with garden peas (Pisum sativum) Grow & reproduce quickly Matings can be controlled Show a number of distinct traits that are easy to observe Studied peas for 8 years!

Designed simple experiments and observed only one trait at a time Used math to formulate his conclusions – Mendel’s Laws Use the weblab to make some crosses!

Traits that Mendel studied:

Mendel’s Laws:

1. Genes in pairs Characteristics are controlled by unit factors (genes) that exist in pairs in organisms and are passed from parents to offspring When two parents produce an offspring, each parent gives one of the factors from each pair Mendel’s garden

Mendel’s Laws

2. Law of Dominance: In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.

One factor is dominant and the other is recessive

Mendel’s Laws

3. The Law of Segregation: During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. When hybrids are crossed, the resulting ratio of phenotypes is 3 dom: 1 rec.

Mendel’s Laws

4. The Principle of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

Basic Human Genetics

Complete the following chart: Trait & description Dimples – present/absent Tongue rolling – Yes/no # Yes # No Dom/rec??

Mid-digit hair – yes/ no Thumb – bent/straight Widow’s peak – present/absent Eye colour – Blue/ not blue Eye sight – glasses/no glasses P.T.C. – taste/ no taste