Lecture 6: Genetic Risk Assessment Flashcards
Which of Mendel’s law states:
- During gamete formation, two hereditary units that determine traits separate from each other
- Each gamete carries one gene variant that influences expression of phenotype
- Two gene alleles alleles are randomly reunited in offspring during fertilization
A. Law of Independent Assortment
B. Law of Segregation
C. Dominance
B. Law of Segregation
Which of Mendel’s Laws states that gene alleles that determine various independent trait phenotypes are distribute to gametes independently from one another?
A. Law of Independent Assortment
B. Law of Segregation
C. Dominance
A. Law of Independent Assortment
In a cross between true breeding parents for contrasting trait alleles, only one form will appear in the F1 generation.
The phenotype of offspring that are hybrid for trait alleles will reflect trait alleles that is ____
dominant
In a monohybrid cross where P1 is tall x short, F1 will be all ____ while F2 will be _____
tall
F2 = 1:3 (short:tall)
True or False: Occulocutaneous albinism is an example of genetic heterogeneity
True
Type 1 OCA (occulocutaneous albinism) is caused by loss of function mutation in the ____ gene, which encodes tyrosinase
TYR
True or False: Reduced production of melanin pigment in skin, hair, and eyes is a feature of OCA
True
In two carrier parents with OCA, what are the phenotype odds? genotype odds?
Phenotype = 1 Albino: 3 Pigmented
Genotype = 1AA:2Aa:1aa
If both parents are heterozygous carriers of autosomal recessive alleles for albinism AND deafness, what are the expected genotype and phenotype ratios?
9/16 = A_ ; D_ : Pigment/Hearing
3/16 = A_; dd : Pigment and Deaf
3/16 = aa; D_ : Albino/Hearing
1/16 = aa;dd : Albino and Deaf
What is the probability of obtaining a 2 on a 6-sided dice AND a head in a coin flip?
1/6 * 1/2 = 1/12 (8.3%)
multiplication rule
What is the probability of obtaining a 2 on a 6-sided dice OR a tail in a coin flip?
1/6 + 1/2 = 2/3 (6.7%)
What is the probability that a couple planning to have 3 children will have all girls?
A. 100%
B. 50%
C. 37.5%
D. 25%
E. 12.5%
E. 12.5%
= 1/2 * 1/2 * 1/2
= 12.5%
What is the probability of 3 boys or 3 girls?
12.5 % + 12.5% = 25%
(all girls) (all boys)
Rare recessive genetic disorders can have a very high prevalence in some populations due to ____
Founder effects
What are three rare recessive genetic disorders caused by founder effects?
Tay Sachs
Sickle Cell
CF
Why do males affected with CF have a high incidence of infertility?
CAVD (congenital absence of vas deferens)
____: describes the predictable relationship between allele frequencies and genotype frequencies in AUTOSOMAL RECESSIVELY inherited genetic disorders
Hardy-Weinberg Equilibrium
True or False: HW Equilibrium predicts allele frequencies within a population
True
What assumptions does HW Equilbrium make?
- Non-random mating
- High new mutation rate
- Unequal allele freq among sexes
- Small population size
- Selection
P(AA) = p2
- Which rule applies: addition or multiplication?
P(aa) = q2
- Which rule applies: addition or multiplication?
Multiplication rule
P(Aa) = 2pq
- Which rule applies: addition or multiplication?
Addition Rule - chance of A allele from one parent x chance of a allele from other parent OR the opposite
What is the carrier frequency of CFTR mutations in caucasians of European descent if the incidence in caucasians is: 1/2500 births?
To determine what is the probability that a Caucasian couple of unknown genotypes will have a child with CF, what two risk factors should you consider?
- Probability/risk of each parent being a carrier for CF
- Probability/risk of the couple having an affected child IF both are carriers.
What is the probability that a woman that is a known
CF carrier and her new partner of unknown genotype
will have a child with CF?
What is the probability that a woman affected with CF and
her husband of unknown genotype will have a child affected with CF?
A. 100%
B. 25%
C. 4%
D. 2%
E. 1%
What is the carrier frequency for autosomal recessive
polycystic kidney disease in a population if the birth
prevalence is 1 per 20,000?
A. 25%
B. 14%
C. 1.4%
D. 0.01%
C. 1.4%
Conditional probabilities can be applied to consider ___ information in a pedigree to asses relative probability of two or more alternative ___ possibilities and predict risk based on that info
phenotypic; genotypic
Conditional probabilities are also known as ____
Bayesian Analysis
What is the probability that a Caucasian couple of unknown genotypes will have a child with CF?
[Note: carrier frequency for CF is 1/25 for caucasian]
What is the probability that a woman that is a known CF carrier and her new partner of unknown genotype will have a child with CF?
[Note: carrier frequency for CF is 1/25 for caucasian]
Conditional probabilities are also known as ____
Bayesian Analysis
Why is the risk of this women having a 7th child that is affected with her new partner so low?
The risk estimates for couple’s future kids using the knowledge can be refined, given that their previous 6 offsprings have not been affect.
Therefore, probability that woman’s new partner is a carrier is much lower.
____ _____: can be applied to consider phenotypic information in a pedigree to assess relative probability of two or more alt. genotypic possibilities and predict risk based on that
Conditional probabilities
