WELCOME BACK! Time to jump start your brain!

• What’s the purpose of mitosis?

• What’s the purpose of meiosis?

• How many chromosomes do somatic cells have?

• How many chromosomes do gametes have?

Heredity and Genetics

Mendel and Our Understanding of the Gene Pool

Gregor Mendel

• Gregor Mendel was an Augustinian friar who enjoyed gardening and science

• Though people had an idea about how traits were passed from parent offspring, it was Gregor Mendel who proved it using science

• Between 1856 and 1863, he raised pea plants, which he used to study genetic inheritance

• He is now known as the “Father of Genetics”

What did Mendel prove?

• The Law of Segregation - The two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes. Half the gametes carry one allele, and the other half carry the other allele.

• The Law of Independent Assortment - Genes for different traits assort independently of one another in the formation of gametes.

The Experiment

• There are three things that Mendel paid attention to in his experimental design:– He controlled over breeding– He used purebred plants– He observed only either/or traits, or traits that

manifest in only two forms• He followed 7 traits: pea shape, pea color,

flower color, flower position, pod shape, pod color, plant height

Vocab Check

• A gene is a piece of DNA that provides a set of instructions to a cell to make a certain protein.

• An allele is any of the alternative forms of the gene that may occur.

• A genome is all of an organism’s genetic information.

Punnett Squares

Types of Crosses

• Monohybrid Cross – involves the crossing of only one trait– Test Cross – A cross between an unknown

genotype and a recessive phenotype

Types of Crosses

• Dihybrid Cross – involves the crossing of two different traits

Mendel’s Second Law

• The Law of Independent Assortment – states that allele pairs separate independently of each other during gamete formation (meiosis)

Heredity Probabilities

• Probability is the likelihood that an event will occur

Genetic Variation

• One of the benefits of sexual reproduction (over asexual reproduction) is that it provides for abundant variation.

• There can be 8 million different combinations of chromosomes produced through meiosis.

• Crossing over occurs when homologous chromosomes exchange segments during meiosis.

Genetic Variation

• Each chromosomes contains hundreds of genes

• How do genes show independent assortment if they are on the same chromosome?

• Genes located close together on the same chromosome are said to display genetic linkage.