Genetics Chapter 6

Synteny

two or more genes located on the same chromosome that are physically linked

Genetic Linkage

Genes close together on a chromosome tend to be transmitted as a unit

Linkage Groups

A group of genes that are linked together

Two factor cross vs 3 factor

2 vs 3 linked genes

In diploid eukaryotic species, linkage is altered during meiosis as a result of

Crossing over

Replicated sister chromatid homologues associate as

bivalents

Nonparental or recombinant cells 

haploid cells that contain a combination of alleles not found in the original chromosome

Recombinant offspring

Genetically different than either parents (combination of the two)

First evidence of genetic linkage came from

Morgan

Genetic mapping

determining gene locus distances from linked genes

Genes that are far apart result in

many recombinant offspring

Genes that are close result in

Very few recombinant offspring

One map unit is equivilane to

1% recombination frequency

Map Distance Formula

Number of recombinant offspring/Total number of offspring

Interference 

Lower than expected value of genetic crossovers

Interference equation 

I=1-C

Coefficient of coincidence equation

C=Observed # of double crossovers/expected number of double crossovers

Expected ratio of genes in a double cross when 1 parent Is heterozygous and 1 parent is homozygous recessive

1:1:1:1

If I is a positive value it means 

positive interference