Chapter 9 (genetics)

Question 1

Q: How many mutated alleles must an individual have to be affected by an autosomal recessive disorder?

Answer 1

A: Both alleles must be mutated.

Question 2

Q: What are homozygous and compound heterozygous individuals?

Answer 2

A: Homozygous have two identical mutations, while compound heterozygous have two different mutations in the same gene.

Question 3

Q: Who is typically affected by autosomal recessive disorders?

Answer 3

A: Males and females are affected equally, often with no prior family history.

Question 4

Q: What is the risk of offspring being affected if both parents are carriers

Answer 4

A: There is a 25% risk.

Question 5

Q: What is the significance of consanguineous parents?

Answer 5

A: They have a higher risk of having affected offspring due to shared ancestry.

Question 6

Q: Give examples of autosomal recessive disorders.

Answer 6

A: Sickle cell disease, cystic fibrosis, Tay-Sachs disease, thalassemias.

Question 7

Q: How does X-linked recessive inheritance affect males and females?

Answer 7

A: Males are typically affected due to having one X chromosome, while females are usually unaffected because they have a second, “good” X allele.

Question 8

Q: What is a key characteristic of X-linked recessive inheritance?

Answer 8

A: No male-to-male transmission and an absence of affected females.

Question 10

Q: What is the risk for male offspring of female carriers of X-linked recessive disorders?

Answer 10

A: There is a 50% risk of being affected.

Question 11

Q: Provide examples of X-linked recessive disorders.

Answer 11

A: Hemophilia A, color-blindness, Duchenne muscular dystrophy.

Question 12

Q: How does X-linked dominant inheritance differ from X-linked recessive?

Answer 12

A: Both males and females can be affected, but more females are typically affected.

Question 13

Q: What is the risk for offspring of affected females?

Answer 13

A: All offspring have a 50% risk, regardless of sex.

Question 14

Q: Give examples of X-linked dominant disorders.

Answer 14

A: Rett syndrome, incontinentia pigmenti.

Question 15

Q: How does genetic counseling help families?

Answer 15

A: It assesses the odds of children inheriting genetic disorders based on family history.

Question 16

Q: What tests can determine the presence of genetic disorders?

Answer 16

: Amniocentesis and chorionic villus sampling can test for suspected disorders.

Question 17

Q: What is a pedigree?

Answer 17

A: A diagram that shows the occurrence of a genetic trait across generations in a family.

Question 18

Q: How do you perform a monohybrid cross using a Punnett square?

Answer 18

Use a 2x2 grid to predict offspring ratios for one trait based on parental genotypes.

Question 19

Q: How do you perform a dihybrid cross using a Punnett square?

Answer 19

Use a 4x4 grid to predict offspring ratios for two traits.

Question 20

Q: What is an allele?

Answer 20

A: An alternate version of a gene.

Question 21

Q: What does codominant mean?

Answer 21

Both alleles contribute to the phenotype distinctly.

Question 22

Q: What is a dominant allele?

Answer 22

The allele that is fully expressed in a heterozygote.

Question 23

Q: What is F1?

Answer 23

The first filial generation of offspring in a breeding experiment.

Question 23

Q: What is F2?

Answer 23

The second filial generation of offspring in a breeding experiment.

Question 24

Q: What is a gene?

Answer 24

A unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses).

Question 25

Q: What did Gregor Mendel discover about genetics?

Answer 25

Mendel discovered that parents pass on discrete genes to offspring, which retain identity across generations.

Question 26

Q: What is the law of segregation?

Answer 26

A: Each organism has two alleles per gene that separate during gamete formation, with each gamete receiving one allele.

Question 27

Q: How did Mendel demonstrate the law of segregation?

Answer 27

A: By breeding pea plants and observing a 3:1 dominant-to-recessive trait ratio in the F2 generation.

Question 29

Q: What is the law of independent assortment?

Answer 29

A: Alleles for different traits separate independently during gamete formation, leading to varied trait combinations.

Question 30

Q: How did Mendel show independent assortment?

Answer 30

A: Through dihybrid crosses, showing a 9:3:3:1 phenotype ratio in the F2 generation.

Question 31

Q: What are the rules of probability in genetics?

Answer 31

A: Use multiplication for combined events and addition for events occurring in multiple ways.

Question 32

Q: What is incomplete dominance?

Answer 32

A: A heterozygote’s phenotype is intermediate between two homozygotes (e.g., pink snapdragons from red and white parents).

Question 33

Q: What is pleiotropy?

Answer 33

A single gene impacts multiple traits, such as in sickle cell anemia.

Question 33

Q: What is codominance?

Answer 33

A: Both alleles are fully expressed in a heterozygote (e.g., AB blood type).

Question 34

Q: How does epistasis affect gene expression?

Answer 34

A: One gene can mask or alter the expression of another, as seen in coat color of mice.

Question 35

Q: What does “multifactorial” mean in genetics?

Answer 35

Traits influenced by both genes and environmental factors (e.g., hydrangea color varies with soil acidity

Question 36

Q: What is polygenic inheritance?

Answer 36

A: Multiple genes additively affect a single trait, like human height.

Question 37

Q: How is Mendelian inheritance studied in humans?

Answer 37

Through pedigree analysis, which shows inheritance patterns across generations.

Question 38

Q: What is autosomal dominant inheritance?

Answer 38

A single copy of the dominant allele causes the trait or disorder.

Question 39

Q: What are the characteristics of autosomal dominant inheritance?

Answer 39

Affected individuals usually have an affected parent, and there’s a 50% chance of passing the trait to offspring.

Question 40

Q: What are examples of autosomal dominant disorders?

Answer 40

Huntington’s disease, Marfan’s syndrome, and familial hypercholesterolemia.