Gene Mapping

Question 1

Linked Genes & Chromosome Maps

Answer 1

Movement of chromosomes follows the pattern that Mendel predicted for genes
This observation led to the Chromosomal Theory of Inheritance - genes are carried on chromosomes, and chromosomes segregate independently into gametes during meiosis
Genes that are found on the same chromosome are sometimes called LINKED GENES
We only have 23 pairs of chromosomes and 1000s of genes
Some genes mus coexist on chromosomes as linked genes

Question 2

Review: Crossing Over

Answer 2

Occurs in Prophase I of meiosis when sister chromatids exchange pieces of chromosomes
Random event and occurs, with equal probability, at nearly any point on the sister chromatids except near the centromere
If genes are located closely on the same chromosomes They are more likely to crossover together
If genes are located further apart, they are more likely to separate during crossover

Question 3

What is the Gene-Chromosome Theory

Answer 3

States that genes exist at specific sites arranged in a linear manner along chromosomes

Question 4

What is Chromosome/Gene Mapping?

Answer 4

The process for determining the relative position of genes on a chromosome
The relative position of the genes on the chromosome can be mapped using the crossover % ( the % of time that genes separate during crossing over
The higher the % = the farther apart he genes
The smaller the % = the closer the genes
1% in crossover = 1 map unit (cm) away from each other
Gene maps can be read in both directions

Question 5

Map Unit

Answer 5

The distance between points on a chromosome where a crossover is likely to occur in 1% of meiotic events

Question 6

Map Distance

Answer 6

The distance between genes on a single chromosome

Question 7

Recombination (Parental Type, Recombinant Type)

Answer 7

Parental Type - Describes offspring that have chromosomes that are identical to those other parents
Recombinant Type - Offspring that have a different combination of alleles than the chromosomes of their parents
Chromosomes of the F1 generation have a different combination of alleles than the parent generation

Question 8

Recombination Frequency stats

Answer 8

The percentage of recombinant types in the F1 generation is directly proportional to the distance between the genes

Recombination Frequency is the percentage of times that a crossover occurred as P gametes were formed

Recombinant Freuency = no. Of recombinant types x 100% / total no. of offspring