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Flashcards in Linkage and genetic mapping Deck (15):
1

Genes on the same chromosome are inherited together (syntenic)

Linkage

2

Set of linked genes
-Genes located on chromosome 4 are in linkage group IV

Linkage group

3

Constructed based on the rate of recombination between linked genes using test crosses
-determine the order/arrangement of genes on a chromosome

Linkage map (genetic map)

4

Place on a homologous pair of chromosomes at which a physical exchange is occurring (site of cross over)

Chiasma

5

-The reciprocal exchange of chromatid segments at corresponding positions along homologous chromosomes (involves breakage and rejoining of 2 chromatids)
-leads to genetic recombination (different combination of alleles in the progeny)

Crossing over

6

Two extreme scenarios

1. Independently assort
2.Genes are very close on the same chromosome

7

Genes are on different chromosomes or far apart on same chromosome

Independently assort

8

No recombination between genes

Genes very close on the same chromosome

9

Distance between genes (or cM for centiMorgan)

Map units (mu)

10

% recombination = #recombinants / Total # progeny

Map units calculation

11

Cross a triple heterozygote with a triple homozygous recessive

Mapping three genes using a three-point testcross

12

Occurs when two chiasmata form and there is a double exchange between two nonsister chromatids

Double Cross Over

13

Important to Remember!

The expected frequency of DCO gametes is much lower than that of either SCO gamete class.
-DCO is less likely to happen than single crossover

14

Important to Remember!

-Progeny in the lowest abundance result from DCO
-Progeny in the highest abundance is parental

15

Limits to Genetic maps

*DCO do not happen as often as predicted
-one chiasma inhibits formation of another nearby chiasma: interference
*Sometimes DCO can restore/maintain the parental phenotype
*Crossing over is not random; there are recombination hot and cold spots