Question 1

How are the linkage scores from multiple families combined?&#10;A) Added&#10;B) Subtracted&#10;C) Multiplied&#10;D) Averaged&#10;E) Cannot be combined

Accepted Answer

Linkage scores from multiple families are typically combined by adding them together to increase the statistical power of detecting linkage.

Question 2

What property is associated with the co-inheritance of marker alleles at frequencies that deviate from that expected based on the allele frequencies?&#10;A) Marker association&#10;B) Linkage disequilibrium&#10;C) Recombination&#10;D) Marker phasing&#10;E) Marker coupling

Accepted Answer

Linkage disequilibrium is the non-random association of alleles at two or more loci. This can occur when the loci are physically close together on the same chromosome, or when they are linked by other genetic mechanisms.

Question 3

A false positive association that results from the use of a mixed population in an association study is caused by which of the following?&#10;A) Linkage disequilibrium&#10;B) Population stratification&#10;C) Genetic diversity&#10;D) Genetic drift&#10;E) Gene flow

Accepted Answer

Population stratification can lead to false positive associations in genetic studies because it refers to differences in allele frequencies between subpopulations due to systematic ancestry differences. If not properly accounted for, it can appear as if certain genetic variants are associated with a trait when in fact the association is due to the structure of the population rather than any causal relationship between the genetic variant and the trait.

Question 4

Using the following groups, compose a formula for the odds ratio for a disease-marker association.
a. Affecteds who have marker allele of interest
b. Affecteds who lack the marker allele of interest
c. Controls who have the marker allele of interest
d. Controls who lack the marker allele of interest

A) ab/cd
B) ac/bd
C) ad/bc
D) cd/ab
E) cb/ad

Accepted Answer

The odds ratio for a disease-marker association is calculated as (a*d)/(b*c), where 'a' represents affected individuals with the marker allele, 'b' represents affected individuals without the marker allele, 'c' represents controls with the marker allele, and 'd' represents controls without the marker allele. This formula compares the odds of having the marker among the affected to the odds of having the marker among the controls.

Question 5

Which of the following situations would support use of positional cloning for disease gene identification?&#10;A) Disease pathogenesis is poorly understood&#10;B) Candidate genes are not apparent&#10;C) Chromosomal rearrangements highlight regions of interest&#10;D) Many disease alleles can be present in the disease gene&#10;E) All of the above

Accepted Answer

Positional cloning is a strategy used to identify disease genes based on their location on a chromosome, rather than the function of the gene or the nature of the disease. It is particularly useful when the pathogenesis of a disease is poorly understood (A), when there are no obvious candidate genes (B), when chromosomal rearrangements point to specific genomic regions (C), and when there are multiple alleles of a gene that could contribute to the disease (D).

Question 6

Deviation from independent assortment of alleles is known as:&#10;A) Linkage&#10;B) Association&#10;C) Haplotype&#10;D) Recombination&#10;E) Meiotic segregation

Accepted Answer

Linkage refers to the phenomenon where genes that are located close to each other on the same chromosome tend to be inherited together, thereby deviating from the principle of independent assortment which assumes that alleles of different genes are distributed independently of one another during gamete formation.

Question 7

Which of the following is a nonparametric linkage method?&#10;A) Linkage analysis in phase-unknown pedigrees&#10;B) Linkage analysis in phase-known pedigrees&#10;C) Affected sib-pair analysis&#10;D) Case-control study&#10;E) A or B

Accepted Answer

Affected sib-pair analysis is a nonparametric linkage method because it does not assume a specific genetic model. It evaluates the genetic similarity of affected siblings to identify genes that contribute to a trait or disease, without making assumptions about the mode of inheritance, allele frequencies, or the effect size of the gene.

Question 8

Which of the following is true ONLY for linkage analysis, as compared to association studies?&#10;A) Families can be used in the analysis&#10;B) Makes use of the correlation between recombination and genetic distance&#10;C) Recombination events within families can be highly informative in this analysis&#10;D) Model-free methods are available&#10;E) Can use thousands of markers in the analysis

Accepted Answer

Recombination events within families can be highly informative in this analysis, as they can help to identify the location of the disease-causing gene.

Question 9

What is the likely explanation for the smaller size of the linkage disequilibrium (LD) blocks in African populations compared to non-African populations?&#10;A) Increased selection in Africa&#10;B) Increased genetic drift in Africa&#10;C) More generations since the African population was founded&#10;D) Population bottleneck when humans moved out of Africa&#10;E) Increased recombination in African populations

Accepted Answer

The answer of What is the likely explanation for the...

Question 10

In this type of gene mapping, one looks for the inheritance of a particular segment of the genome in conjunction with the trait of interest.&#10;A) Association study&#10;B) Linkage analysis&#10;C) Family-based association test&#10;D) Radiation hybrid mapping&#10;E) Haplotype mapping

Accepted Answer

Linkage analysis is used to study the co-segregation of a trait with specific genomic regions within families, which helps in identifying the chromosomal location of genes associated with that trait.

Question 11

Which of the following does a logarithm of odds (LOD) score allow you to estimate?&#10;A) The recombination frequency between a marker and a trait locus&#10;B) The recurrence risk of a trait in a family&#10;C) The population attributable risk of a mutation&#10;D) The heritability of a trait&#10;E) The amount of selection on a trait

Accepted Answer

The answer of Which of the following does a logarithm...

Question 12

Which of the following is an assumption that must hold for large-scale association studies to be successful?&#10;A) The risk allele is in a coding region&#10;B) Only one gene is involved in the trait&#10;C) The mutation giving rise to the risk allele occurred only once&#10;D) The risk allele must not occur in the control group&#10;E) All of the above

Accepted Answer

The answer of Which of the following is an assumption...

Question 13

Which of the following are possibly explanations for a positive result in an association study?&#10;A) Population stratification&#10;B) You have found the allele that confers risk of your trait of interest&#10;C) The allele you have found is in LD with the risk-conferring allele&#10;D) It is a false positive caused by the number of markers examined in the study&#10;E) All of the above

Accepted Answer

The answer of Which of the following are possibly explanations...

Question 14

Which of the following is true ONLY for association studies, as compared to linkage studies?&#10;A) Can use thousands of markers in the analysis&#10;B) Can identify the functional risk allele for the trait of interest&#10;C) Families can be used in the analysis&#10;D) Makes use of the correlation between recombination and genetic distance&#10;E) Requires model specification

Accepted Answer

The answer of Which of the following is true ONLY...

Question 15

What do tagSNPs define?&#10;A) Genes&#10;B) Exons&#10;C) All variation&#10;D) Chromosomes&#10;E) Haplotypes

Accepted Answer

The answer of What do tagSNPs define?&#10;A) Genes&#10;B) Exons&#10;C) All...

Deck 10: Identifying the Genetic Basis for Human Disease