Biology 1BChapters 11 and 14

Heredity

1. Define heredity and identify the units of heredity.

2. Discuss the design, results and conclusions of Mendel’s monohybrid cross experiment.

 3. Explain the principle of dominance and the

principle of segregation

Section 11.1 Objectives

From the same root word as “inherit”

Heredity describes the passing of traits from parents to offspring

Give examples of traits shared with family members:

Heredity

ProblemHow are traits passed from parents to offspring?

Many children resemble an aunt, uncle or grandparent more than they do their parents.

Some traits seem to “skip generations”Often traits are expressed in children that are

not observed in any other family member

ANY ACCEPTABLE HYPOTHESIS SHOULD BE ABLE TO ACCOUNT FOR THESE OBSERVATIONS

More Background

Alternative Hypotheses:Traits are inherited

from only one parentThis seems true in

many cases, because many children have a strong resemblance to either their mother or their father

Traits are inherited from both parentsThis seems true in

many cases also, because many children resemble both parents, and often have one trait similar to their father and another trait similar to their mother

Gregor Mendel – Historical PerspectiveMendel was an

Austrian monk in the mid 1800’s

Monks make contemplation and study a lifestyle.

Life at the monastery is largely self-sufficient. It is common for Monks to grow their own food.

Gregor Mendel’s ExperimentsMendel grew peas

for food at the monastery, and observed that the pea plants had a variety of distinct traits, such as flower color, that appeared to be inherited traits.

Inherited Traits in Pea Plants

Mono = oneHybrid = cross breedMendel picked one trait at a time (“mono”)

for his experiments, and cross bred (“hybrid”) pea plants for each trait to see what would happen

To track the effect of inheritance from one parent compared to the other, the parents must be different with regard to the trait being studied (“hybrid”)

The first generation in the experiment is labeled “P1”

P for Parents, 1 for 1st generation

“Monohybrid Cross”

Monohybrid Cross – P1 Generation

• This is a “hybrid” cross, because the parents are different for the trait being studied.

• What trait is being examined in this experiment?

Resulting offspring (F1)F1, F for filial (greek

for brothers) and 1 for 1st generation

In a cross between one purple flower parent and one white flower parent, all the offspring had purple flowers.

What hypothesis does this support?

4. Use punnett squares to predict the probability of genetic crosses

 5. Discuss the design, results and

conclusions of Mendel’s dihybrid cross experiment.

6. Explain the principle Independent Assortment

Section 11.2 Objectives

7. Explain the following forms of inheritance: Incomplete dominance Codominance Multiple alleles Polygenic inheritance

8. Use pedigrees to analyze inheritance of alleles within families

9. Explain ABO blood type and Rh factor, and explain the inheritance of both traits

Section 11.3 Objectives:

10. Define the terms haploid and diploid. Relate the terms to the life cycle of plants and animals.

11. Describe the process of meiosis.

12. Explain what is happening in each stage of meiosis 13. Use the chromosome theory to contrast between “linked”

genes and those inherited by independent assortment

14. Compare and contrast mitosis and meiosis

Section 11.4 Objectives: