Q: Which formula is used to calculate the recombination frequency (RF) between a polymorphic marker and a disease locus in a pedigree?

$$RF = \frac{\text{number of recombinant events}}{\text{total number of possible observable recombination events}}$$

Question 1

In pedigree analysis, what is the primary purpose of using polymorphic markers such as microsatellites?

Accepted Answer

To map the location of a disease locus by tracking inheritance patterns

Question 2

A pedigree shows an autosomal dominant inheritance of polydactyly. If the disease trait always co-segregates with the A2 allele of a marker, what does this suggest about the relationship between the marker and the disease locus?

Accepted Answer

The marker is closely linked to the disease locus

Question 3

Which formula is used to calculate the recombination frequency (RF) between a polymorphic marker and a disease locus in a pedigree?

Accepted Answer

$$RF = \frac{	ext{number of recombinant events}}{	ext{total number of possible observable recombination events}}$$

Question 4

If a pedigree shows 2 recombinant events out of 20 informative meioses, what is the genetic distance in centimorgans (cM) between the marker and the disease locus?

Accepted Answer

$$10\ 	ext{cM}$$

Question 5

Why is it important to sequence both affected and unaffected family members when mapping a disease locus using pedigree analysis?

Accepted Answer

To confirm that the mutation is unique to affected individuals and not a common variant in the population

Question 6

A missense mutation in the PCSK9 gene is found in a family with high LDL cholesterol. What is the most likely effect of this mutation?

Accepted Answer

It leads to increased LDL levels

Question 7

Which of the following best describes a haplotype?

Accepted Answer

A group of contiguously linked SNPs/alleles inherited together

Question 8

In a case study, a nonsense mutation in PCSK9 is associated with very low LDL levels. What type of mutation is a nonsense mutation?

Accepted Answer

A mutation that introduces a premature stop codon

Question 9

Which statement best explains why finding a mutation in only two affected and two unaffected family members is not definitive proof of causation?

Accepted Answer

The mutation could be a common variant in the population and not causative

Question 10

What is the significance of the LDL/HDL ratio in cardiovascular disease risk assessment?

Accepted Answer

A higher LDL/HDL ratio indicates increased risk of cardiovascular disease

Question 11

Which of the following is a key limitation of pedigree analysis in mapping disease loci?

Accepted Answer

Small family sizes may limit the number of informative recombination events

Question 12

In linkage analysis, why are recombination events between a marker and a disease locus informative?

Accepted Answer

They indicate the physical distance between the marker and the disease locus

Question 13

A pedigree shows that all affected individuals inherit the M3 allele of a microsatellite marker. What is the most likely conclusion?

Accepted Answer

The disease locus is linked to the M3 allele

Question 14

Which of the following is NOT a reason why association does not equal causation in genetic studies?

Accepted Answer

Sequencing only affected individuals guarantees causation

Question 15

If the recombination frequency between a marker and a disease locus is 0.01, what is the genetic distance in centimorgans?

Accepted Answer

$$1\ 	ext{cM}$$

Question 16

Which of the following best describes the principle behind using haplotypes in disease mapping?

Accepted Answer

Unrelated disease families often share haplotypes associated with the phenotype

Question 17

A family with hypercholesterolemia is found to have no mutations in LDLR or APOB genes. Linkage analysis maps the disease to chromosome 1. What is the next logical step?

Accepted Answer

Sequence candidate genes in the mapped interval to identify possible mutations

Question 18

Which of the following is a real-world application of pedigree analysis in human genetics?

Accepted Answer

Identifying genetic risk factors for cardiovascular disease by mapping LDL levels in families

Question 19

How does a nonsense mutation in PCSK9 affect LDL cholesterol levels?

Accepted Answer

It leads to lower LDL levels

Question 20

Which of the following best explains why more families are needed in genetic mapping studies?

Accepted Answer

To increase the number of informative recombination events and narrow down the disease locus

Pedigree Analysis- Sep 24

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