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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

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