exploring mendelian genetics

CHAPTER 11 SECTION 3SC B-46: PREDICT INHERITED

TRAITS BY USING THE PRINCIPLES OF MENDELIAN GENETICS

(INCLUDING SEGREGATION, INDEPENDENT ASSORTMENT, AND

TYPES OF DOMINANCE)

Exploring Mendelian Genetics

Essential Question

How would you explain the inheritance patterns beyond dominant & recessive?

Dihybrid Crosses

Mendel also performed an experiment to follow 2 different genes as they passed from parents to offspring

Mendel chose true-breeding round, yellow peas crossed with true-breeding wrinkled, green for F1

(RRYY) x (rryy)

What genotype/phenotype will the offspring have?

Mendel’s 2nd Experiment

The Inheritance of 2 Traits

Does the inheritance of 1 characteristic influence the inheritance of another characteristic?

For example: Does pea shape influence pea color?

F1 Generation allowed to self-pollinate

Results:

Mendel’s plants produced 556 seedsround & yellow: 315wrinkled & green: 32combinations of parent phenotypes: 209

Mendel’s conclusion:Alleles for seed shape & color segregate

independently when gametes forming

Law of Independent Assortment

Genes from different traits can segregate independently during the formation of gametes.

This accounts for the many genetic variations observed in plants, animals, & other organisms

Summary of Mendel’s Principles

1. Inheritance of biological characteristics is determined by individual units called genes. Genes are passed from parents to their offspring.

2. If there are 2 or more alleles of a gene for a single trait, some forms may be dominant & others recessive

3. In most sexually reproducing organisms, each individual has 2 copies of a single gene (1 from each parent) & they separate when gametes are formed

4. Alleles for different genes usually separate independently of one another.

Incomplete Dominance

Cases where neither allele is dominant the heterozygous individual will have a phenotype that is a blend of the 2 alleles.

Codominance

Both alleles for a gene are expressed in the phenotype of a hybrid individual

Multiple Alleles

genes that have >2 alleles

Polygenic Traits

Traits controlled by the interactions of several genes

Genetics & the Environment

Genes provide a plan for development but how that plan unfolds also depends on the environment

Name that type of inheritance

Name that type of inheritance!