Flashcards
MCDB 101B: Midterm 2 (Lec 11-19)
Cards in this deck (37)
- 1Mendel's Laws violations1) The principle of segregation
Each member of a gene pair (allele) is equally likely to be found in a gamete
2) The principle of independent assortment In the formation of gametes, segregation of any pair of alleles is independent of the segregation of other pairs of alleles
-Linkage is violation of #2 - 2Closely-linkedNO CROSSING OVER
(no indep assortment (violate 2nd law))
Same gametes as parental - 3Completely unlinkedObeys 2nd law
equal distribution of ALL gametes
on different chrom or sufficiently far apart on same chrome so at least one crossover occurs between them in every meiosis - 4Partially linked what causes it?parental gametes are more frequent
recombinant less frequent than parental
Caused by meiotic recombination during meiosis 1 (2 genes on same chrom)
violates 2nd, not 1st law - 5RecombinationCrossing over between chromosomes during meiosis I produces recombinant gametes
Crossing over - exchange of DNA between chromosomes
"cutting and pasting" - 6Parental / recomb gametesparental - same as parents
recomb - not present in parents, alleles swapped - 7Calculate linkage X linked / autosomalanalyze gametes from dihybrid
Cross true breeding P ==> F1 - dihybrid
X-linked:
cross dihybrid with male and examine male offspring
M progeny - see X inherited from F
If crossing over occurs, seen in M b/c get X from F
M parental get doesn't matter b/c M offspring gets Y from M
Autosomal:
perform TESTCROSS with homoz recessive at both genes - 8Syntenictwo genes on same chromosome
- 9Recombination FrequencyMeasure of distance between two genes
RF = # recomb / total progeny
Larger dist = higher chance of recombination during meiosis
max = 50% - 10Three point crossFaster, more accurate than two point cross for mapping genes
make trihybrid
x-linked: cross to male
autosomal: testcross to homoz rec - 11Three point cross steps1) determine parental gen by looking at parental progeny (most frequent)
2) determine gene in middle by looking at DCO (which one changed from parental?)
3) dist = DCO + SCO / total
-for SCO, cross occurred btwn genes in which dist is being analyzed
4) outside dist = SCO(1) + SCO(2) + 2*DCO / total
*w/o correction RF doesn't include DCO - 12Chromosomal interferenceOccurrence of one crossover reduces the likelihood of another crossover nearby
(fewer DCOs than expected)
Recomb in 1 blocks 2nd crossover - 13Expected DCO FrequencyProb of crossover in Region 1 (RF 1) * Prob of crossover in Region 2 (RF 2)
- 14Coefficient of coincidenceobserved DCO frequency / expected DCO frequency
CoC = 1 ==> equal
= 0 ==> no observed DCOs
expected = prob of crossover in region 1 * region 2
observed = # DCO / total - 15Interference1 - Coefficient of Coincidence
Int = 0 ==> expected = observed
Int = 1 ==> no DCOs - 16Correspondence btw genetic and physical map exception?physical map = DNA seq
unit of physical dist = DNA base pair
Approximate linear relationship btw genetic distance (m.u.) and physical distance (bp) btwn any two genes
EXCEPTION: recombination hotspots - 17linkage groupgenes chained together by linkage relationships
ex: chromosome
human chrome - 270 mu - 18Chi Square testsee if genes are linked/unlinked
null hyp - obs and exp data are not different (possible genes are unlinked)
alternate hyp - obs diff from exp (linked)
x^2 = (obs-exp)^2 / exp
**do this for each class and add for x^2
df = n (# categories) - 1
p value - probability that obs data arose by change under null hyp - 19reject / can't reject nullp>0.05 ==> can't reject (possible unlinked)
p<0.05 ==> reject null (linked) - 20ratio of gametic types for chi squareif unlinked, parental = recomb, so all gametic types should be equal
- 21chi square value effect on p value?higher chi square # = lower p value
(if same degrees of freedom) - 22Lecture 13 Human Chromosomes and Organelle InheritanceX
- 23Karyotype def, how are they dividedStained and photographed preparation of METAPHASE chromosomes arranged according to size and position of centromeres
Each chrome divided into two regions (arms) separated by centromere
p - short arm (petit)
q - long arm - 24FISHfind locations of specific DNA seq on chromosomes
Attach fluorescent tag to DNA probe that hybridizes to a specific sequence (probe compl to target seq)
4 spots - undergoing mitosis and divided DNA - 25Change in nucleotidessingle base pair substitution
Frameshift mutation (insertion/deletion) - 26Chromosome abnormalitieschange large sections of DNA (eg millions of nucleotides)
whole genes, sections of chrom, or whole chromosomes are added, deleted, or moved
ex: deletions, inversions, translations, duplications, extra chromosomes - 27Relocation of genetic materialtranslocation
(addn from another chrome)
inversion
(two sections switch around) - 28Loss of genetic materialdeletion
missing chromosome - 29gain of genetic materialduplication
extra chromosome - 30recombination vs chromosomal rearrangementsboth involve cutting and rejoining of DNA
Meiotic recomb - exchange homologous regions of homologous chromosomes
-no loss/gain of DNA
rearrangements - occur in meiosis or mitosis w/in or btwn any chrome
-can lead to loss or gain or reordering of DNA
-triggered by DNA damage - 31gene mapping using deletion analysis1) deletion uncovers a recessive mutation
2) deletions can be used to identify a gene's location - 32Aneupolidyunbalanced set of chromosomes
relative gene dosage upset
(imbalance with one chromosome and all other chromosomes)
monosomy-loss of a single chromosome copy
trisomy-extra copy of one of the chromosomes
pregnancy complications - Aneu in 1/2 cases of spontaneous abortions (miscarriage)
trisomy 13, 18, 21 only viable. rest die - 33euploidbalanced set of chromosomes (2n)
normal - 34nullisomymissing both chromosomes in homologous pair
- 35polyploidymore than two complete sets of chromosomes
duplicated whole genome
ex: Humans - 4n = 92 chromosomes
tetraploid = four sets of chromosomes, 4n
hexaploid = 6n
not necessarily lethal because dosage is "balanced" - 36Lec 16 Modern Experimental Geneticsx
- 37Loss of Function mutationmutant gene product hass less or no function
hypomorphic - less function
null mutation - no function
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- Flashcards on MCDB 101B: Midterm 2 (Lec 11-19), created by Phil Nosrat on 15/02/2016.
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