2H- Gene mapping and cloning

Question 1

What is Genetic mapping?

Answer 1

the frequency of meiotic crossovers between loci (specific location of a gene or DNA sequence on a chromosome) is used to estimate distances between loci.

Question 2

What is physical mapping?

Answer 2

involves using cytogenetic, molecular, and computational methods to determine the actual physical locations of disease-causing mutations on chromosomes.

Question 3

What are “linked” genes?

Answer 3

genes located near one another on the same chromosome are transmitted together rather than independently.

Question 4

What is a haplotype?

Answer 4

a combination of alleles at adjacent locations on a chromosome that are transmitted together.

Question 5

What is recombination?

Answer 5

new rearrangements of alleles. Crossover does not always lead to recombination because a double crossover can occur between two loci, resulting in no recombination.

Question 6

What is a Centimorgan?

Answer 6

a unit of measure for distance between two loci. One cM (centimorgan) is approximately equal to a recombination frequency of 1%.

Question 7

What is Syntenic?

Answer 7

Loci that are on the same chromosome.

Question 8

How far apart must syntenic chromsomes be to be unlinked?

Answer 8

50 cM

Question 9

What is the linkage phase?

Answer 9

the arrangement of alleles of linked loci on each chromosome

Question 10

What are markers?

Answer 10

polymorphisms that are used as “markers” to follow a chromosome with a disease-causing allele.

Question 11

What is a Recombination hot spot?

Answer 11

regions where recombination frequency is at least 10-fold higher than anywhere else on the chromosome.

Question 12

What is Uninformative mating?

Answer 12

a mating generation in which it is impossible to determine linkage phase.

Question 13

What is Functional cloning?

Answer 13

the use of a gene product and its function to pinpoint the gene.

Question 14

What is positional cloning?

Answer 14

locating a disease-causing gene by starting with a known linked marker near the gene of interest and then searching around that region to find it.

Question 15

What are Artificial chromosomes (YACs, BACs, PACs)?

Answer 15

DNA is partially digested with restriction enzymes to produce overlapping fragments. These fragments are then cloned into vectors such as YACs, BACs, and PACs using recombinant DNA techniques

Question 16

What is a contig map?

Answer 16

a physical map of a chromosome region constructed by isolating overlapping (contiguous) DNA segments.

Question 17

What are Sequence tagged sites (STSs)?

Answer 17

Their chromosome location has been established, making them useful as indicators of physical positions on the genome

Question 18

What are Expressed sequence tags (ESTs)?

Answer 18

Since they are derived from cDNA libraries, these small sequences represent portions of expressed genes.

Question 19

What is a Chromosome-specific library?

Answer 19

a library that consists mostly of DNA from only one chromosome because it is created by using flow cytometry to separate chromosomes according to the fraction of AT base pairs in each one

Question 20

What are CG islands?

Answer 20

About 60% of human genes are unmethylated CG dinucleotides found near the 5’ end.

Question 21

What is Exon trapping?

Answer 21

method for isolating exons by using an in vitro cell system to artificially splice out the introns.

Question 22

What is a linkage map?

Answer 22

a genetic map that shows the relative positions of known markers in terms of recombination frequency

Question 23

How can you measure distance on a linkage map?

Answer 23

distance can be approximated by using recombination frequency: each % of recombination frequency is approximately 1 cM in distance.

Question 24

What is the purpose of a likelihood ratio and LOD score?

Answer 24

to determine whether or not the results of a linkage study is due to chance

Question 25

What is the LOD equation?

Answer 25

LOD score = log10(likelihood linked/likelihood unlinked). If the LOD score is 3.0 or more, it shows that there is linkage

Question 26

What are important about Highly polymorphic loci?

Answer 26

Highly polymorphic markers will ensure that most parents will be heterozygous for the marker locus, allowing a linkage phase in families to be established. Without highly polymorphic markers, the mating will most likely be considered uninformative.

Question 27

What is association?

Answer 27

the co-occurrence of two traits or events more often than expected by chance.

Question 28

What is linkage equilibrium?

Answer 28

lack of preferential association of alleles at linked loci.

Question 29

What is linkage disequilibrium?

Answer 29

a nonrandom association of alleles at linked loci in populations.

Question 30

What is the relationship between haplotype and equilibrium?

Answer 30

If the actual frequency of a haplotype is the same as the predicted, there is statistical independence there is linkage equilibrium. If the actual frequency deviated from the predicted, then there is linkage disequilibrium

Question 31

What is the main difference between loci and association?

Answer 31

Linkage is the position of the loci on the CHROMOSOMES. Association is the relationship between 2 traits in the general POPULATION.

Question 32

What does deletions show in gene mapping?

Answer 32

the localization of a disease-causing gene

Question 33

How can you use translocation in gene mapping?

Answer 33

It works by obtaining two patients with the disease with balanced translocations between one shared chromosome (the one in which the disease lies) and one different one. By analyzing the breakpoints of the translocations on the shared chromosome, a more refined location can be obtained.

Question 34

What is a candidate gene?

Answer 34

A candidate gene is a gene with a known protein product that makes it a likely candidate for causing a specific genetic disease