Pedigrees & Linkage

Pedigree analysis (humans)

Is used to determine individual genotypes and to predict the mode of transmission of single gene traits

Huntington disease

Autosomal Dominant

Huntington Disease definition

a progressive nerve degeneration, usually beginning about middle age, that results in severe physical and mental disability and ultimately in death

Albinism

autosomal recessive

Albinism definition

absence of pigment in the skin, hair, and iris of the eyes

Locus

physical location of a gene on a chromosome

Alleles

Homologous pairs of chromosomes often contain alternative forms of a given gene

Linkage

Genes on the same chromosome are inherited together

1 map unit

1 cM (centimorgan)

Cis configuration

mutant alleles of both genes are on the same chromosome (ab/AB)

Trans configuration

mutant alleles are on different homologues of the same chromosome (Ab/aB)

Recombination frequencies between genes are inversely proportional to…

their distance apart

Recombination frequencies

Gene mapping methods use _ _ between alleles in order to determine the relative distances between them

1 map unit =

1 percent recombination

Recombination results from…

crossing-over between linked alleles

Genetic map

shows the linear order of the genes along the chromosome spaced so that the distances between genes is proportional to the frequency of recombination between them

Linked

Genes with recombination frequencies less than 50 percent are on the same chromosome

Unlinked

Two genes that undergo independent assortment have recombination frequency of 50 percent and are located on nonhomologous chromosomes or far apart on the same chromosome

The recombination frequency between two genes indicates…

how much recombination is actually observed in a particular experiment; it is a measure of recombination

Genetic Map is also called…

Linkage map, Chromosome map

Polymorphism

The presence in a population of two or more relatively common forms of a gene or a chromosome

simple-nucleotide polymorphism (SNP)

single base pair difference

Restriction fragment length polymorphism (RFLP)

what SNPs in restriction sites yield

Simple sequence repeat (SSR)

Polymorphism resulting from a tandemly repeated short DNA sequence

SNPs are _ in the human genome

abundant

Restriction endonucleases

used to map genes as they produce a unique set of fragments for a gene

Differences in DNA sequence generate…

different DNA cleavage sites for specific restriction enzymes

Restriction enzyme cleavage of polymorphic alleles that are different in RFLP pattern produces….

different size fragments by gel electrophoresis