Mendel's Experiments and Heredity

Question 1

Describe the scientific reasons for the success of Mendel’s experimental work

Answer 1

-Simple experiment design: Mendel followed seven visible characteristics each with two contrasting traits which made for easier analysis of data

-Good quantitative records: made statistical analysis possible

Question 2

Evaluate the outcome of a monohybrid cross

Answer 2

-1:2:1
-Determined law of segregation

Question 3

Explain Mendel’s principle of segregation

Answer 3

Genes must segregate equally into gametes such that offspring have an equal likelihood of inheriting either factor.

Question 4

Evaluate the outcome of a dihybrid cross.

Answer 4

9:3:3:1

Question 5

Explain Mendel’s principle of independent assortment.

Answer 5

Alleles segregate independently of each other pair of alleles during gamete formation.

Question 6

When does segregation occur

Answer 6

anaphase 1 and 2

Question 7

Define epistasis

Answer 7

When one gene masks another

Question 8

Mendel chose to study pea plants because:

Answer 8

-many pea character variants available
-cheap
-single season generation time
-large number of progeny per cross
-controlled mating
-baseline knowledge of the model system

Question 9

Allele

Answer 9

Alternative form of a gene

Question 10

Mendel’s 5 Element Model

Answer 10

1. Parents transmit discrete inherited factors
2. For each trait, an organism inherits 2 alleles from each parent
3. Not all copies of a gene are identical
4. Alleles remain distinct, no blending
5. Presence of allele does not guarantee phenotypic presentation

Question 11

List the possible gamete genotypes from a dihybrid individual:

Answer 11

AABB
AABb
AAbb
AaBB
AaBb
Aabb
aaBB
aaBb
aabb

9 possible genotypes

Question 12

Incomplete dominance

Answer 12

If the phenotypes of the heterozygote fall between the phenotypes of the two homozygotes, dominance is incomplete.
Ex: red and white snapdragons make pink

Question 13

Codominance

Answer 13

-Joint expression of both alleles
-No complete dominance or recessiveness
Ex: AB blood types

Question 14

Pleiotropy

Answer 14

When one gene encodes for multiple phenotypes

Question 15

Hybridizations

Answer 15

Cross between two true-breeding plants with different traits

Question 16

P Generation

Answer 16

Original parental generation

Question 17

F1 Generation

Answer 17

First filial generation

Produced from two true-breeding strains

All F1 resembled only one (dominant) parent

Question 18

F2 Generation

Answer 18

Second filial generation

Resulting from self-fertilization of F1 generation

3:1 ratio

Question 19

Chromosome Theory of Inheritance

Answer 19

Each gene resides at a specific locus on a specific
chromosome

Question 20

Locus

Answer 20

Specific place on a chromosome occupied by an allele

Question 21

The yellow allele in mice is dominant in terms of coat color but recessive in terms of survival; therefore, the mutation behaves as

Answer 21

a recessive lethal allele

Question 22

Autosomal

Answer 22

Trait appears equally in both sexes

Question 23

How could you distinguish between an autosomal
recessive trait with higher penetrance in males and an X-linked recessive trait?

Answer 23

X-linked recessive traits are only passed to sons from mothers, not from fathers.

Question 24

When does independent assortment occur

Answer 24

metaphase 1