Gene Mapping Flashcards
what is the chromosome theory? who proposed it along with genes as the basic unit of inheritance? when?
sutton and boveri in 1902 proposed chromosome is a linkage group of mendelian factors
morgan et al in 1920 proposed genes are in a linear sequence on the chromosomes, they can be mapped
describe Morgan’s contribution to genetics and how his linkage studies worked
reasoned hereditary information must be arranged linearly on chromosomes, one of first nobel prizes in medicine in the field of genetics
measured distance btw 2 genes is measured in centimorgans (cM)
he described linkage concepts
describe what crossover, recombination and linkage are
genes are said to be linked when they occur in close proximity to one another on the same chromosome
crossover = recombination that occurs multiple times at random locations during meiosis
if 2 genes are very close to e/o on a chromosome then they are tightly linked and will be unlikely to crossover
what are the different polymorphic markers and linkage analysis used in genetics?
the first step in gene mapping is to establish linkage with a known polymorphic marker
this can be done by recombination mapping to determine whether the gene is near a particular marker
4 different types of polymorphisms
3 mill found as a result of HGP
examples: southern blot
dzs caused by TEs?
hemophilia A and B, severe combined immunodeficiency, porphyria, predisposition to CA, Duchenne muscular dystrophy
LINE1 TEs that land on factor VIII cause what?
hemophilia
insertion of L1 into APC genes causes what?
colon cancer
what are traditional gene maps?
traditional maps with physical locations of gene based upon sequence of nucleotide base pairs
what are epigenomic maps?
physical locations of genes but “annotations” or marked locations where modifications are made above base pair sequences altering, activating, repressing, winding/unwinding and opening/closing sequences
what are cancer genomic maps?
locations of where “gain-of-function” and possible “loss-of-function” genes or epigenetic elements reside causing oncogenesis
what are cancer genomic maps?
locations of where “gain-of-function” and possible “loss-of-function” genes or epigenetic elements reside causing oncogenesis
3 types of traditional human genome maps?
physical maps - vary in resolution, measured in bps, genome sequence is ultimate physical map
cytogenetic maps - karyotype
linkage maps - distance is measured in the frequency of recombination coupling arrangements of alleles on linked genes
3 types of traditional human genome maps?
physical maps - vary in resolution, measured in bps, genome sequence is ultimate physical map
cytogenetic maps - karyotype
linkage maps - distance is measured in the frequency of recombination coupling arrangements of alleles on linked genes
if the gene of interest and the marker are on different chromosomes the alleles will remain together in an egg or sperm what %age of the time?
50% - thus they are unlinked
if the gene of interest and the marker are on the same chromosomes the alleles will remain together in an egg or sperm what %age of the time?
50% - thus they are unlinked
if the gene of interest and the marker are on the same chromosomes the alleles will remain together in an egg or sperm what %age of the time?
50% - thus they are unlinked
if the gene of interest and the marker are close together on the same chromosomes the alleles will remain together in an egg or sperm what %age of the time?
crossover btw the 2 alleles is much less likely to occur and shows less than 50% recombination - thus said to be linked
if the gene of interest and the marker are close together on the same chromosomes the alleles will remain together in an egg or sperm what %age of the time?
crossover btw the 2 alleles is much less likely to occur and shows less than 50% recombination - thus said to be linked
distance btw genes is expressed how? cM is equal to what recombination frequency?
centimorgans (cM)
the cM is equal to 1% recombination frequency
physically 1 cM is ~equal to 1 million base pairs of DNA
distance btw genes is expressed how? cM is equal to what recombination frequency?
centimorgans (cM)
the cM is equal to 1% recombination frequency
physically 1 cM is ~equal to 1 million base pairs of DNA
what are restriction enzymes or restriction endonuclease? relation to palindromes?
enzymes which recognize a specific sequence of nucleotides and produce a double-stranded cut in the DNA
cuts are made to correspond to 4-8 bps, many of which are palindromic which correspond to nitrogenous base sequences btw complementary strands which when read from the 5’ to 3’ direction are identical
4 different types of DNA polymorphisms?
- RFLP (restriction fragment length polymorphism)
- VNTR (variable number of tandem repeats)
- STR (short tandem repeats)
- SNPs (single nucleotide polymorphism)
what are VNTRs? dzs that are characteristic? when it is used?
variable number of tandem repeats
these polymorphisms are a result of varying numbers of mini-satellite repeats in a specific region of the chromosome
repeat is flanked on both sides by a restriction site
ex: fragile X syndrome, Huntington’s dz
used for parental testing or DNA fingerprinting
what are STRs? can be amplified and visualized how? how are they used?
Short tandem repeat polymorphisms (microsatellites)
specifically repetitive sequences in which the repeated unit is 4-6 bps long
can be amplified with PCR by using products of varying length which can then be visualized on agarose gel electrophoresis
distributed throughout the chromosomes = very useful in mapping genes
used in paternity testing and in forensic cases as well as gene mapping
what are SNPs? occur how often? can be typed/identified how? how many changes caused by SNPs in our genome, how many of these deleteriously impact the gene and how many of these are lethal?
represent nucleotide positions in the human genome where only 2 nucleotides are found
occur about once every 1000 bps
can be typed by pCR amplification and identification by sequencing or through probes on DNA chips
of our 20-25k genes, 2000 have SNPs, of those 200 deleteriously impact the gene, of those 5 are lethal if recessive homozygous
what is DNA profiling? what does it use?
technique employed to assist in the identification of individuals by their respective DNA profiles
it uses repetitive sequences that are highly variable called variable number tandem repeats, specifically identify short tandem repeats
what are DNA profiles?
encrypted sets of numbers that reflect a person’s DNA makeup which can also be used as the person’s identifier
used in parental testing and criminal investigation
