Theme 4A

Question 1

Blending Theory of Inheritance

Answer 1

Hereditary traits blend evenly in offspring through the mixing of the parents’ blood like coffee and cream

Question 2

What is a Character?

Answer 2

A heritable characteristic (i.e fur colour)

Question 3

What is a Trait?

Answer 3

A particular expression of a character in an individual i.e brown fur

Question 4

What is the principle of segregation?

Answer 4

Mendel’s hypothesis that the pairs of alleles that control a character separation as gametes formed; half the gametes carry one allele and the other half carry the other allele

Question 5

What is a genotype?

Answer 5

A particular combination of alleles present in a given organism

Question 6

What is a phenotype?

Answer 6

The expression of a trait (or traits) in an individual

Question 7

How is variation in phenotypes generated?

Answer 7

By simple to complex variation in an organism’s genotype

Question 8

What is transmission genetics?

Answer 8

Deals with the way genetic differences among individuals are passed from generation to generation

Question 9

Why is the blending theory of inheritance problematic?

Answer 9

The variation would be lost over time

Question 10

Mendel’s Work

Answer 10

• tested hypothesis of blending vs. particulate inheritance
• used true-breeding varieties of peas
• many varieties with different characters

Question 11

Three Important Distinctions of Mendel’s Work

Answer 11

1. True breeding strains (“good” phenotypes)
2. Focused on a single trait at a time
3. Quantitative: counted the progeny

Question 12

Mendel’s Hypotheses

Answer 12

• Adult plants carry two copies of factors (genes) that govern the inheritance of a character
• If an individual’s pair of genes consists of different alleles, one allele is dominant over the other
• Diploid organisms get one allele from each parent

Question 13

What is a monohybrid cross?

Answer 13

A cross between two heterozygotes (for a single gene)

Question 14

What does homozygous mean?

Answer 14

The two alleles are the same, therefore produce only one type of gamete

Question 15

What does heterozygous mean?

Answer 15

The two alleles are different, therefore produces two types of gametes

Question 16

What is the gene responsible for Mendel’s white and purple pea flowers?

Answer 16

• Gene encodes a transcription factor required to activate genes that synthesize pigments to make purple pea flowers
• White flowers contain a nonsense mutation in this gene

Question 17

How do you determine if you have a heterozygote?

Answer 17

• A test cross is mating to an individual with the homozygous recessive genotype
• Highly informative: homozygous individuals carry only the recessive allele

Question 18

Test Cross Steps

Answer 18

• Procedure: cross individual with dominant phenotype to a homozygous recessive
• If heterozygous (Pp), then see 1:1 of dominant and recessive phenotypes
• If homozygous (PP), then see all dominant phenotype

Question 19

What is Incomplete Dominance?

Answer 19

• One allele is not completely dominant to the other allele

- Heterozygote exhibits an intermediate phenotype compared to the homozygous phenotypes

Question 20

What is Co-dominance?

Answer 20

• Codominant alleles have equal effects (dominant alleles fight for expression) - heterozygote exhibits both homozygote phenotypes i.e white + black feathers instead of solid white or black

Question 21

Discrete Trait Variation

Answer 21

Traits that can be sorted into bins/categories

Question 22

Continuous Trait Variation

Answer 22

Traits of individuals can be anywhere along a continuum i.e height