Chapter 5 Flashcards
_______: genes located on the same chromosome
syntenic genes
_______: genes close enough on the same chromosome that they assort together more often than independently
linked genes
linked genes are _______ syntenic
always
what is another name for parental gametes in genetic linkage?
non-recombinants
what is another name for non-parental gametes in genetic linkage?
recombinants
_______ plots the positions of genes on chromosomes
Genetic linkage mapping
_______ is observed when no crossing over occurs between linked genes; only parental gametes are formed
Complete genetic linkage
The two parental types are approximately _______ in frequency, as are the two recombinant types
equal
What is the formula for recombination frequency?
RF = (#recombinants / total number of progeny) x 100
What is the maximum recombination value?
50%
The probability of a double crossover is the _______ of the probabilities of the single crossovers
product
_______ was the first to demonstrate that genes are on chromosomes
Morgan
Creighton and McClintock (as well as Stern studying Drosophila) showed that crossover is accompanied by chromosome _______ and _______ in plants and animals
breakage and rejoining
_______ used the results of several experiments to create a genetic map for 5 X-linked genes in drosophila
Alfred Sturtevant
Recombination frequencies between two genes can be converted into units of physical distance called _______
map units (m.u.) or centiMorgan (cM)
polymorphic DNA sequences are called _______
genetic markers
_______ are clusters of syntenic genes that are linked to one another
Linkage groups
Genetic markers are typically in _______ regions of the genome
noncoding
What are the 3 different genetic markers?
1) Variable Number Tandem Repeats (VNTRs)
2) Single Nucleotide Polymorphisms (SNPs)
3) Restriction Fragment Length Polymorphisms (RFLPs)
_______ have sequences repeat end-to-end in a chromosomal region
Variable Number Tandem Repeats (VNTRs)
_______ involve variants where one base pair is substituted by another base pair, typically in a noncoding region
Single Nucleotide Polymorphisms (SNPs)
_______ are changes in DNA sequence that are detected using DNA-cutting enzymes called restriction endonucleases (restriction enzymes)
Restriction Fragment Length Polymorphisms (RFLPs)
Pieces of DNA resulting from restriction enzyme cutting are called _______
restriction fragments
The specific array of SNPs in a small region on a single chromosome is called a _______
haplotype
Haplotype SNPs are closely linked variants and will tend to be passed on _______ during _______
together
meiosis
_______: the arrangement of alleles of linked genes on parental chromosomes
allelic phase
When a disease-causing allele is seen to segregate along with a known genetic marker, allelic phase (can / can’t) be determined
can
_______ determines the likelihood of linkage for many recombinant frequencies, called theta (θ) values (essentially map distances)
LOD score
A LOD SCORE OF:
θ=0 means _______
θ=50 means _______
complete linkage
independent assortment
θ = map units ; θ = 0.1 = ____ m.u.
10
While interpreting LOD scores:
- LOD scores of 3.0 or higher hold significant evidence _______ of linkage at the theta value
- LOD scores of less than -2.0 hold significant evidence _______ genetic linkage
1) in favor
2) against
While interpreting LOD scores:
- LOD scores between _______ are inconclusive
- The _______ value indicates the recombination frequency most likely to be correct
1) 3.0 and -2.0
2) Zmax
_______ detects and locates genes that influence traits as a group of multiple genes
Genome-wide association studies (GWAS)
GWAS looks for associations between traits and groups of alleles in _______
populations
GWAS results are represented in the form of a “_______”
- the higher the green bar, the stronger the association
Manhattan plot
linkage disequilibrium reflects the _______ distribution of alleles for linked genes (or linked gene and marker)
nonrandom
When frequencies of haplotypes in a population deviate significantly from what is expected, it is called _______
linkage disequilibrium
