Chapter 7 CMB Mendel's Law

Question 1

What are the 3 Mendel’s Laws?

Answer 1

1. the Law of Dominance
2. the Law of Segregation
3. the Law of Independent Assortment

Question 2

What is the genotype for TT?

Answer 2

Homozygous DOMINANT

Question 3

What is the genotype for Tt?

Answer 3

Heterozygous dominant

Question 4

What is the genotype for tt?

Answer 4

Homozygous RECESSIVE

Question 5

What is a phenotype?

Answer 5

Physical appearance of a trait

Question 6

What is the Law of Dominance?

Answer 6

In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.

Question 7

What is the genotype vocab and phenotype for the genotype symbol TT?
T- Tall
t- Short

Answer 7

Genotype symbol: Homozygous DOMINANT or pure tall
Phenotype: Tall

Question 8

What is the genotype vocab and phenotype for the genotype symbol Tt?

Answer 8

Genotype symbol: Heterozygous or hybrid
Phenotype: Tall

Question 9

What is the genotype vocab and phenotype for the genotype symbol tt?

Answer 9

Genotype symbol: Homozygous RECESSIVE or pure short
Phenotype: Short

Question 10

What is the Law of Segregation

Answer 10

During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then “recombined” at fertilization, producing the genotype for the traits of the offspring.

Question 11

What is the Law of Independent Assortment?

Answer 11

Alleles for different traits (alleles) are distributed to gametes or sex cells (& offspring) independently of one another.

Question 12

What do homologous chromosomes contain?

Answer 12

Homologous chromosomes contain DNA that codes for the same genes.

Question 13

Difference between sister chromatids and homologous chromosomes?

Answer 13

Sister chromatids are exact replica, but homologous chromosomes are not

Question 14

What is the ratio of a dihybrid cross?

Answer 14

9:3:3:1

Question 15

What is test cross used for?

Answer 15

Determine unknown genotypes

Question 16

What is polygenic?

Answer 16

Human traits that are complexed and are affected by several genes

Question 16

How can an unknown genotype be revealed?

Answer 16

By mating between an unknown genotype and a homozygous recessive

Question 17

State examples of polygenic inheritance

Answer 17

Hair and eye color, intelligence and musical ability

Question 18

What are the 4 patterns of inheritance?

Answer 18

1. Recessive: trait can skip one generation
   - Recall short phenotype in F1 generation
2. Dominant: trait appears in all generations
3. Autosomal: trait is carried on autosomes
   - Huntington disease is an autosomal dominant trait
   - Cystic fibrosis is an autosomal recessive trait
4. Sex-linked: trait is carried on X chromosomes

Question 19

What is the purpose of a family pedigree?

Answer 19

Family pedigrees are used to determine patterns of inheritance and individual genotypes

Question 20

What happens to those traits exhibiting recessive gene action? (Recessive Pedigree)

Answer 20

1. Unaffected parents can have affected offspring
2. Affected progeny are both male and female

Question 21

What are recessive disorders caused by?

Answer 21

They are caused by autosomal recessive alleles

Question 21

What happens to those traits exhibiting dominant gene action? (Dominant Pedigree)

Answer 21

1. Affected individuals have at least one affected parent
2. The phenotype generally appears every generation
3. Two unaffected parents only have unaffected offspring

Question 22

What type of chromosomes do mammals have?

Answer 22

In mammals, a male has one X chromosome and one Y chromosome (XY) and a female has two X chromosomes (XX)

Question 23

What gene does the Y chromosome contain?

Answer 23

Has genes for the development of testes

Question 24

Absence of Y chromosome allows ________?

Answer 24

Allows ovaries to develop

Question 25

What are sex-linked human disorders caused by?

Answer 25

1. Are due to recessive alleles
2. Genetic mutation on the X-chromosomes

Question 26

Why are sex-linked human disorders mostly seen in males and provide examples.

Answer 26

It is because a male receives only a single X-linked allele from his mother hence will have the disorder while a female has to receive the allele from both parents to be affected

Examples: Hemophilia, red-green color blindness

Question 27

What are some examples of autosomal RECESSIVE disorders? (6 examples)

Answer 27

1. Cystic Fibrosis*
2. Albinism*
3. Sickle-cell disease*
4. Tay-Sachs disease
5. Phenylketonuria
6. Hemochromatosis

Question 28

What are some examples of autosomal DOMINANT disorders? (3 examples)

Answer 28

1. Huntington disease*
2. Polycystic kidney disease*
3. Neurofibromatosis*

Question 29

What is the offspring and law for this parent cross? (TT x tt)

Answer 29

Offspring: 100% Tt and Tall
Law of Dominance

Question 30

What is the offspring and law for this parent cross? (Tt x Tt)

Answer 30

Offspring: 75% tall and 25% short
Law of Segregation

Question 31

What is the offspring and law for this parent cross? (RrGg x RrGg)

Answer 31

Offspring: 9 RG, 3 Rg, 3, rG, 1rg (9:3:3:1)
Law of Independent Assortment

(where RG is round green, Rg is round yellow, rG is wrinkled green, rg is wrinkled yellow)