1-18 Linkage and Recombination-Shrimpton Flashcards Preview

MSI Unit I > 1-18 Linkage and Recombination-Shrimpton > Flashcards

Flashcards in 1-18 Linkage and Recombination-Shrimpton Deck (12)

Direct vs indirect testing

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

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


DNA variation, mutation types

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%


informativeness regarding the question being asked

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


linkage? recombination?

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


crossing over

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


double crossing over

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



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


Phase: Cis & Trans haplotypes

2 different genes found on same homologue are in cis.

Two different genes found on different homologs are in trans.

Two linked genes = haplotype


linkage disequilibrium

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


Lod Scores (Z)

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


genetic linkage analysis

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


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

microsatellites - variable number tandem repeats
than SNP's - single nucleotide polymorphisms

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