Chapter 9 (genetics) Flashcards
Q: How many mutated alleles must an individual have to be affected by an autosomal recessive disorder?
A: Both alleles must be mutated.
Q: What are homozygous and compound heterozygous individuals?
A: Homozygous have two identical mutations, while compound heterozygous have two different mutations in the same gene.
Q: Who is typically affected by autosomal recessive disorders?
A: Males and females are affected equally, often with no prior family history.
Q: What is the risk of offspring being affected if both parents are carriers
A: There is a 25% risk.
Q: What is the significance of consanguineous parents?
A: They have a higher risk of having affected offspring due to shared ancestry.
Q: Give examples of autosomal recessive disorders.
A: Sickle cell disease, cystic fibrosis, Tay-Sachs disease, thalassemias.
Q: How does X-linked recessive inheritance affect males and females?
A: Males are typically affected due to having one X chromosome, while females are usually unaffected because they have a second, “good” X allele.
Q: What is a key characteristic of X-linked recessive inheritance?
A: No male-to-male transmission and an absence of affected females.
Q: What is the risk for male offspring of female carriers of X-linked recessive disorders?
A: There is a 50% risk of being affected.
Q: Provide examples of X-linked recessive disorders.
A: Hemophilia A, color-blindness, Duchenne muscular dystrophy.
Q: How does X-linked dominant inheritance differ from X-linked recessive?
A: Both males and females can be affected, but more females are typically affected.
Q: What is the risk for offspring of affected females?
A: All offspring have a 50% risk, regardless of sex.
Q: Give examples of X-linked dominant disorders.
A: Rett syndrome, incontinentia pigmenti.
Q: How does genetic counseling help families?
A: It assesses the odds of children inheriting genetic disorders based on family history.
Q: What tests can determine the presence of genetic disorders?
: Amniocentesis and chorionic villus sampling can test for suspected disorders.
Q: What is a pedigree?
A: A diagram that shows the occurrence of a genetic trait across generations in a family.
Q: How do you perform a monohybrid cross using a Punnett square?
Use a 2x2 grid to predict offspring ratios for one trait based on parental genotypes.
Q: How do you perform a dihybrid cross using a Punnett square?
Use a 4x4 grid to predict offspring ratios for two traits.
Q: What is an allele?
A: An alternate version of a gene.
Q: What does codominant mean?
Both alleles contribute to the phenotype distinctly.
Q: What is a dominant allele?
The allele that is fully expressed in a heterozygote.
Q: What is F1?
The first filial generation of offspring in a breeding experiment.
Q: What is F2?
The second filial generation of offspring in a breeding experiment.
Q: What is a gene?
A unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses).
Q: What did Gregor Mendel discover about genetics?
Mendel discovered that parents pass on discrete genes to offspring, which retain identity across generations.
Q: What is the law of segregation?
A: Each organism has two alleles per gene that separate during gamete formation, with each gamete receiving one allele.
Q: How did Mendel demonstrate the law of segregation?
A: By breeding pea plants and observing a 3:1 dominant-to-recessive trait ratio in the F2 generation.
Q: What is the law of independent assortment?
A: Alleles for different traits separate independently during gamete formation, leading to varied trait combinations.
Q: How did Mendel show independent assortment?
A: Through dihybrid crosses, showing a 9:3:3:1 phenotype ratio in the F2 generation.
Q: What are the rules of probability in genetics?
A: Use multiplication for combined events and addition for events occurring in multiple ways.
Q: What is incomplete dominance?
A: A heterozygote’s phenotype is intermediate between two homozygotes (e.g., pink snapdragons from red and white parents).
Q: What is pleiotropy?
A single gene impacts multiple traits, such as in sickle cell anemia.
Q: What is codominance?
A: Both alleles are fully expressed in a heterozygote (e.g., AB blood type).
Q: How does epistasis affect gene expression?
A: One gene can mask or alter the expression of another, as seen in coat color of mice.
Q: What does “multifactorial” mean in genetics?
Traits influenced by both genes and environmental factors (e.g., hydrangea color varies with soil acidity
Q: What is polygenic inheritance?
A: Multiple genes additively affect a single trait, like human height.
Q: How is Mendelian inheritance studied in humans?
Through pedigree analysis, which shows inheritance patterns across generations.
Q: What is autosomal dominant inheritance?
A single copy of the dominant allele causes the trait or disorder.
Q: What are the characteristics of autosomal dominant inheritance?
Affected individuals usually have an affected parent, and there’s a 50% chance of passing the trait to offspring.
Q: What are examples of autosomal dominant disorders?
Huntington’s disease, Marfan’s syndrome, and familial hypercholesterolemia.
