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42 terms

AT Linkage Recombination

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Genetic Linkage
Genes on the same chromosome are physically linked. The closer genes are the more likely their allele will be transmitted as units
Recombination
____Creates recombinant combination of alleles from different genes on the same chromosome
Distance
Recombination of alleles depends on the________ between genes
Chi Square Test
____________pinpoints the probability that ratios are evidence of linkage
predicted value
The larger your sample, the closer your observed values are expected to match the___________
Chi Square test
measures "goodness of fit" between expected to match the predicted values, accounts for sample, or the size of the experimental population
1:1:1:1
Deviations from___ratios can represent chance events or linkage
Ratios
__will never determine if observed values are expected to match the predicted values
Null Hypothesis
observed values are not different from the expected values ex- no linkage or 1:1:1:1 ratio
Alternative Hypothesis
observed values are different from expected values ex. genes are linked, deviation from 1:1:1:1
Chi Square formula
X² = ∑(observed- expected)²/number expected
linked genes
Recombination results when crossing over during meiosis separates ______
1909 Frans Janssens
observed chiasmata, regions in which nonsister chromatids of homologous chromosomes cross over each other
Thomas Hunt Morgan
Suggested that chiasmata were sites of chromosome breakage and change resulting in genetic recombination
reciprocal exchange
genetic recombination depends on the__ of parts between maternal and paternal chromosomes
Creighton and McClintock
studied corn
Curtis Stern
studied fruit flies
Physical Marker
to keep track of specific chromosome parts
Genetic marker
point of reference to determine if a particular progeny were results of recombination
Alfred Sturtevant
Percent of recombination or recombination frequency reflects the distance separating genes
Recombination frequency
distance between two genes
1RF
= 1 map unit or 1 centiMorgan
Chiasmata
are the visible signs of crossing over
segregate independently
Genes close together on the same chromosome are linked and do not _____
heterozygotes
Linked genes lead to a larger number of parental classes than expected in double______
Mapping
locating genes along a chromosome, genes are arranged in a line alone a chromosome
Limitations of two point crosses
-difficult to determine gene order if close together
-act dist between gene don't always add up
-pairwise crosses time and labor consuming
physical map
Order of genes is correctly predicted by__
Distance and physical markers
-double, triple and more crossovers
- 50% RF observable in a cross
-variation across chromo in rate of recomb
Mapping functions
___ compensate for inaccuracies but are not often imprecise
Linkage groups
Genes chained together by linkage relationship
Terminalization
Shifting of the chiasmata from the original position at the centromere toward the chromosome end or telemore
Autosomal Traits
Traits that reside on autosomal cells and not inherited
Recombination class
reshuffled combination of alleles that were not present in the parental generation
Parental class
combination of alleles present in the original parental generation
Recombinant type
phenotype reflect a new combination of genes that occurs during gamete formation
parental type
phenotype that reflect a previously existing parental combination of genes that is retained during gamete formation
syntenic
relationship of two or more loci found to be located on the same chromosome
chromosomal interference
the phenomenon of crossovers not occurring independently
Tetrad
a pair of synapse homologous chromosome during prophase of meiosis one (bivalent)
centiMorgan
unit of measure for RF or 1 cM is equal to 1% chance that a maker at one genetic locus will be separated due to cross over
Two point cross
comparisons help establish relative gene position