Lab 5

Question 1

Two general types of genome mapping….What are they?

Similarity…Difference?

Answer 1

1 * genetic mapping

2 * physical mapping

➢ BOTH: show location of a gene (or section of DNA) on a chromosome

➢ BUT: rely on very different information.

Question 2

What is Genetic Mapping? = 3

Answer 2

1. classical genetics approach
2. locate (map) the gene on its chromosome by crossbreeding with individuals that carry known genetic marker traits and collecting statistics on how
   frequently the mutant and marker traits are inherited together
3. looks at how genetic information is shuffled between chromosomes or
   between different regions in the same chromosome during meiosis via recombination or ‘crossing over’.

Question 3

What is Physical mapping approach?

Answer 3

• looks at the physical distance between known DNA sequences (including genes) by working out the number of base pairs between them

Question 4

Mapping population:

Answer 4

Prepare a mapping population by crossing for example a wt and a mutant or two mutants.

SLIDE 4

Question 5

How do we get from a mutation to the gene?

Answer 5

• Mapping:
  ……* Crossovers produce recombinant chromatids.

……* The frequency of a crossover can be used to map genes on chromosomes

Question 6

Genetic linkage analysis (mapping):

‘If 1, 2, 3 and 4 are genes with known phenotypes
(genetic marker):’

▪ determine the position of a mutation by determining the recombination frequencies between the
mutation and the 4 markers.

▪ In the example, the mutation has a closer link with gene 1 than with genes 2, 3 or 4.

Answer 6

1. The position of the mutation can be determined more and more accurately with an increased number of
   markers in close proximity to the mutation
2. NOTE: Genetic markers can be genes with known
   phenotypes or Restriction Fragment Length
3. Polymorphisms (RFLP),
4. Amplified Fragment Length Polymorphisms ((AFLP),
5. Single Nucleotide
   Polymorphisms (SNP) and many others

Question 7

Recombination Frequency:

Recombination frequency between two genes:

Answer 7

1 ▪ Measures how much recombination is observed in a particular experiment

2. ➢Recombination frequencies < 50 %
   ➔ the two genes are on the same
   chromosome (e.g. 3 and 4) = linked
3. ➢Recombination frequencies = 50 %
   ➔ the two genes are either far apart
   on the same chromosome (e.g. 1 and 2) = unlinked or on nonhomologues chromosomes (e.g. 5 and 6)