Chapter 10

Section 1


Objectives:

• Compare and contrast the blending hypothesis and the particulate hypothesis of inheritance.
• Describe the methods Mendel used in his plant-breeding experiments.

1. Compare and contrast the blending hypothesis and the particulate hypothesis of inheritance.

Both the blending hypothesis and the particulate hypothesis believe that traits are inherited from the parents. In the blending hypothesis, scientists believed that different traits from parents would blend to create the offspring traits. For example, if a red flower was crossed with a white flower, the offspring would be pink, and so would its offspring. The particulate hypothesis believed that parents pass traits that are "separate and distinct factors" to their offspring , which are "responsible for inherited traits". Mendel thought that these factors would be the same generation after generation.

2. Describe the methods Mendel used in his plant-breeding experiments.
He bred pea plants for seven years. One of his methods included tying a little cloth bag around the flowers that way pollen from other plants couldn't fertilize it. He also crossed true-breeding plants to test the particulate hypothesis.

Section 2


Objectives:

• Explain Mendel's principle of segregation.
• Describe how probability applies to genetics.
• Contrast genotype and phenotype.
• Explain Mendel's principle of independent assortment.

1. Explain Mendel's principle of segregation.

"Two alleles for a character segregate during the formation of gametes, so that each gamete carries only one allele for each character. The union of gametes during fertilization reforms allele pairs in the offspring"

2. Describe how probability applies to genetics.

You can use probability to "predict particular outcomes if you know the genetic make-up of both parents".

3. Contrast genotype and phenotype.

A phenotype is an observable trait, while a genotype is the "genetic make-up,or combination of alleles".

4. Explain Mendel's principle of independent assortment.

It states that during gamete formation in an F2 cross, a particular allele for one character can be paired with either allele of another character.

Section 3

Objectives:

• Describe how alleles interact in intermediate inheritance.
• Describe inheritance patterns involving multiple alleles.
• Explain how polygenic inheritance can result in a wide range of phenotypes.
• Describe how environmental conditions affect phenotype expression.

1. Describe how alleles interact in intermediate inheritance.
In some organisms, neither allele is dominant. This pattern doesn't support the blending theory, because parent phenotypes can reappear in the F2 generation.

2. Describe inheritance patterns involving multiple alleles.
One pattern involving multiple inheritance is codominance. Codominance is when the heterozygote expresses both traits. It shows the traits of both alleles.

3. Explain how polygenic inheritance can result in a wide range of phenotypes.
Polygenic inheritance is when two or more genes affect a single trait. The more genes that affect a single character, the more possible phenotypes.

4. Describe how environmental conditions affect phenotype expression.
Temperature, nutrition, exercise, illnesses, and exposure to sunlight are environmental factor that could affect phenotype expression.

Section 4


Objectives:

• Summarize the chromosome theory of inheritance.
• Explain how genetic linkage provides exceptions to Mendel's principle of assortment.

1. Summarize the chromosome theory of inheritance.

Genes are located on chromosomes, and the behavior of chromosomes during meiosis or fertilization accounts for the inheritance patterns.

2. Explain how genetic linkage provides exceptions to Mendel's principle of assortment.

If two genes are on the same chromosome, they will not be separated, or assorted, and therefore there will be less variation.

Section 5

Objectives:

• Explain how sex-linked genes produce different inheritance patterns in males and females.
• Explain why most sex-linked disorders are more common in males.

1. Explain how sex-linked genes produce different inheritance patterns in males and females.
Sex-linked genes are located on the X chromosome, so females carry two copies of the gene for the trait, and males carry one.

2. Explain why most sex-linked disorders are more common in males.

Sex-linked disorders are more common in males because if the male receives a trait just from the mother, then he will have the disorder. In females, they must receive the trait from both their parents, which is rare.