FINAL - CH 8

Question 1

linkage

Answer 1

When genes are inherited together because they are on the same chromosome

Question 2

Crossover is more likely between

Answer 2

loci that are far apart on chromosomes 3than between those that are close together

Question 3

Recombination in linkage

Answer 3

When markers do not show up due to recombination, even when the disease is present in the patient

Question 4

Recombination frequency (1 out of 8 people)

Answer 4

if 1 out of 8 individuals in the generation do not show the correct genotype, the recombination frequency in 1/8 = 12.5%

Since the percentage is less than 50%, the disease gene and the marker are on the same chromosome

Question 5

LOD

Answer 5

logarithm of the odds

Measures the chance that the linkage relationship found was due simply to chance

Question 6

LOD is unnecessary in studies with ________ but in _______ it maybe relevant

Answer 6

very large numbers of pedigrees

small pedigree sample studies

Question 7

LOD score of ____ or higher is considered definitive evidence that 2 genes are linked

Answer 7

3

Question 8

LOD score of ___ or lower is definitive evidence that the 2 genes are NOT linked

Answer 8

–2

Question 9

Linkage Equilibrium:

Answer 9

NO preferential association between the disease gene and the specific allele at a linked marker locus

Question 10

Linkage Disequilibrium:

Answer 10

Preferential association between two linked loci

Question 11

Linkage Disequilibrium is determined by:

Answer 11

observing specific allele forms for each of the two loci that are found together in greater frequency than would be expected if each of their frequencies in pop were considered to be independent. Non-random association.

Question 12

Linkage vs. Association:

Answer 12

Linkage implies 2 genes are located on the same chromosome

Association shows an increased frequency of one marker allele form with a specific disease. These 2 genes may be on the same chromosome (linked) or on a different chromosomes (unlinked)

Question 13

Associations can help map chromosomes location of disease IF

Answer 13

2 genes located on same chromosome (linked)

Ex: hemachromatosis and A3 allele of HLA locus. Helped localize hemachromatosis gene on chrom 6

Question 14

Associations can result from ________ between a specific ____ and _____

Answer 14

causal relationship
allele
disease

EX: ankylosing spondylitis

Question 15

______ has greater linkage ____ with DM than locus A because it is ____ to DM

Answer 15

locus B

disequilibrium

closer

Question 16

Various biomarkers used for linkage and association studies

Answer 16

STRs (short tandem repeats)
RFLPs (Restriction fragment length polymorphism)
SNPs (Single nucleotide polymorphism)

Question 17

____ are the basis of all 23andme results

Answer 17

SNPs

Question 18

Haplotype

Answer 18

Specific alleles for a set of genes linked on the same segment of a chromosome

Question 19

SNP

Answer 19

Variant at a single nucleotide position on a chromosome

Question 20

Informative vs uninfomrative

Answer 20

Informative: has a clear and consistent associated allele with the disease

Uninformative: Does NOT have a consistent allele associated with the marker and the disease

Question 21

Ankylosing Spondylitis and ______

Suspected reason for association:

Answer 21

HLA-B27

HLA system is key element in immune response. Since AS is autoimmune disorder, certain alleles in immune genes may contribute to disease.

Question 22

Linkage disequilibrium exists between:

Answer 22

myotonic dystrophy (DM) locus and two linked loci, A and B

Question 23

DM mutation first arises on:

Answer 23

chromosome with A1B2 haplotype

Question 24

After many generations, most chromosomes carrying DM mutation still have ________ But due to _______, DM mutation also found on _______ (less freq)

Answer 24

A1B2 haplotype

recombination

other haplotypes

Question 25

Evidence for Linkage disequilibrium in DM:

Answer 25

A1B2 haplotype seen in 70% of DM chromosome, but only in 25% of normal chromosome