Chapter 5: Linkage Map Practice Flashcards

A set of vocabulary-style flashcards covering the concepts of gene linkage, recombination, and genetic mapping based on Chapter 5 lecture notes.

Gene Linkage

The occurrence of different alleles of two or more genes on a chromosome being inherited in a manner inconsistent with Mendel's Second law.

Recombination

The process during meiosis where homologous chromosomes exchange segments, resulting in different combinations of alleles for different genes.

Recombinant Gametes

Gametes generated by crossing over between two linked heterozygous loci and independent assortment of two unlinked heterozygous loci.

Crossing Over Mechanics

A process taking place in paired bivalents consisting of $4$ chromatids and involving $2$ of the chromatids.

$50\%$ Recombination Frequency

A result suggesting that two genes are either on different chromosomes or on the same chromosome but located very far apart.

Degrees of Freedom in Genetic Testing

In a $\chi^2$ test to determine if genes $H$ and $I$ are unlinked based on four offspring categories ($HI, Hi, hI, hi$), there are $3$ degrees of freedom.

$50$ Map Units

A measurement in a two-point test cross indicating that two genes are either on different pairs of chromosomes or linked and at least $50$ map units apart.

Middle Gene Determination

In a mapping experiment with genes $px$, $sp$, and $cn$, the gene identified as being in the middle based on progeny data.

Gene Order (Calculated)

The sequence of linked genes based on pairwise distances; for example, distances $A-B = 22\,m.u.$, $B-C = 7\,m.u.$, $C-D = 9\,m.u.$, $B-D = 2\,m.u.$, $A-D = 20\,m.u.$, and $A-C = 29\,m.u.$ indicate the order $ADBC$.

Map Distance Prediction

The principle that if the distance between genes $A$ and $B$ is $10\,m.u.$ and $B$ and $C$ is $25\,m.u.$, the distance between $A$ and $C$ is either $15\,m.u.$ or $35\,m.u.$ depending on the order.

X-linked Recessive Alleles

Alleles located on the $X$ chromosome, such as singed bristles ($sn$) and cut wings ($ct$) in Drosophila, which determine map distance through $F2$ male distribution.