1-18 Linkage and Recombination-Shrimpton

Question 1

Direct vs indirect testing

Answer 1

indirect - testing for genetic disorders using linked DNA sequences call markers (not ideal)

direct testing - testing for genetic disorders using the mutated sequence itself

Question 2

DNA variation, mutation types

Answer 2

mutation - permanent, heritable change in genomic DNA sequence

polymorphism - sequence variant found in at least 1% (2% pop heterozygous)

rare genetic variant - mutation with frequency less than 1%

Question 3

informativeness regarding the question being asked

Answer 3

a marker is informative if it can be used to determine the sperm and egg that produced the individual

Question 4

linkage? recombination?

Answer 4

2 genes sufficiently close on chromosome, often transmitted together in meiosis more freuqnetly than chance. together form a haplotype

recombination is sequence by which DNA is shuffle to produce offspring with different combos.

Farther apart genes are on chromosome, more likely they will be separated onto different chromosomes during recombination

Question 5

crossing over

Answer 5

the reciprocal exchange of DNA between chromosomes (normally homologous).

Question 6

double crossing over

Answer 6

refers to when a crossover occurs twice. it is the only way to remove flanking markers from a gene of interest.

Question 7

interference

Answer 7

the removal of one (single crossover) or two (double crossovers) markers from a gene of interesst

Question 8

Phase: Cis & Trans haplotypes

Answer 8

2 different genes found on same homologue are in cis.

Two different genes found on different homologs are in trans.

Two linked genes = haplotype

Question 9

linkage disequilibrium

Answer 9

when 2 genes so closely linked that they are transmitted together more than would be expected by chance

Question 10

Lod Scores (Z)

Answer 10

value given by the log of the likelihood ratio of a crossover event occurring.

recombination distance (theta) which gives highest LOD score is the most likely recombination distance for the genes in question

Question 11

genetic linkage analysis

Answer 11

process by which linked gene markers are used to trace the inheritance of genetic disorders

Question 12

_______ are likely to me more variable and thus useful than _____.

Answer 12

microsatellites - variable number tandem repeats

than SNP’s - single nucleotide polymorphisms