SNP Flashcards
what is SNP?
single nucleotide polymorphisms - a site in a genome where a single nucleotide is polymorphic among different individuals
what does it mean for a single nucleotide to be polymorphic?
it means there is a change in a single nucleotide
SNPs are the smallest kind of change that can occur within a given gene
true
SNPs are the most common genetic change
true
SNPs represent ____ % of all the variation in DNA sequences that occur among different people
90%
how many SNPS would occur in a gene that is about 2000-3000 bp in length?
10 polymorphic sites
The high frequency of SNPs in genes indicate that polymorphism is the norm for most human genes
true
A DNA locus that has two or more sequence variations , each present at the frequency of 1% or more in a population
polymorphism
monomorphic
locus is 99% of individuals in a population
what is a common frequency in most species for polymorphisms?
1 in 700
about how many loci are in humans?
less than 1 million, or around 1 in 3000
what are some types of polymorphisms?
SNPs, VNTR, deletions, duplications
what is VNTR?
veritable number tandem repeats - includes micro satellites (short tandem sequences - STR) and mini satellites (long sequence repeated)
what is the frequency of STR / microsatellites
- repeat is about 1-6 bp long
- the whole tandem repeats is less than a couple bp in length
- found about every 1000 bp in the human genome
why do micro satellites tend to be hotspots for mutation?
alterations in the sequences of micro satellites oftentimes escape proofreading of DNA polymerase, so there could easily be a mutation in the number of repeats
what is the frequency of mini satellite
- repeat is about 6-80 bo long
- size of the micro satellite is about 1-20 kip
why are repetitive sequences useful?
- they are used as molecular markers (especially micro satellites) to map the location of genes
- also useful for studying variation among populations
how does VNTR relate to identification?
VNTRs show variations in length and can be found on many chromosomes, where each variation acts as an inherited alleles allowing use for identification
what are some uses of VNTR?
genetics, biology research, forensics, fingerprinting
when do STRs (short tandem repeats) occur?
when a pattern of two or more nucleotides are repeated and the repeats sequences are next to each other
- pattern ranges from 2-10
where in the genome do STRs occur?
usually in non-coding intron region
what creates a unique genetic profile?
the number of STR repeats at a given locus
what is the prevalent method for determining genetic profiles in forensic cases?
STR
what are some applications of VNTR and STR?
- forensics
- 13 specific STR loci as the standard for CODIS in FBI
- mass disasters
- paternity testing
- military DNA dog tag
- convicted felon database
- genetic testing/gene mapping
- bone marrow transplant follow up
what are some characteristics of polymorphisms?
- usually not on a coding region of genome
- must associate specific fragment with disease or trait
- many times linked to a disease but NOT the cause of the trait
- problem?
Single nucleotide substitution (SNS)
one nucleotides is replaced by another
what are some forms of genetic variations?
SNS
micro/mini sattelties
deletions/insertaions
changes in chromosomes number, segmental rearrangements and deletions
SNPs appear at least once per ____ average intervals
0.3-1-kb average intervals
for it to be an SNP, it must occur in at least ____ % of the population
1%
the total number of SNPs is around ___ to ___ million
5-10
SNPs occur every ___ to ____ bases in human genome
300-1000 bases
two of every three SNPs involve the replacement of ____ with ____
cytosine with thymine
SNPs occur in both coding genes and noncoding regions of the genome
true
many SNPs have no effect on cell function
true
SNPs can still predispose people to disease or influence repose to drugs
true
SNP haplotype
A set of closely linked genetic markers present
on one chromosome which tend to be inherited
together (not easily separable by recombination)
- haplotype has the advantage in carrying more information about gents-phenotype
SNPs in coding regions may ____ the protein structure made by that coding region
alter
DNA Chips Can Detect SNP Genotypes
(Or Haplotypes) Across An Individuals Genome
Millions of DNA sequences are on this chip. Same idea as mapping stars. Pin points/data points, same technology they used.
what are the probes in the DNA chip?
tethered nucleic acids with known sequence
what are the targets in DNA chip?
free nucleic acid sample whose purpose is being detected, where the labeled nucleic acid that is washed over the chip
