Lecture 9- DNA

Question 1

Type II Restriction enzymes

Answer 1

Cleaves DNA at defined points close to or within its recognition sequence

Question 2

Classical Mapping

Answer 2

A method of gene mapping in which we map genes by looking at visible phenotypes and take SCOs and DCOs into account to figure it out.

Question 3

milestones

Answer 3

Sequences of DNA that have shown up enough times in a disease, or phenotypes that we can probabilistically relate to specific genes. This is used in gene mapping that uses DNA markers

Question 4

DNA markers

Answer 4

Used in a technique of gene mapping

Question 5

Microsatellites

Answer 5

Nucleotide repeats of varying length
Typically (for our purposes) two nucleotides that repeat
Ex: CA
These repeats can be from 5-50, so we look at the number of repeats in individuals and see if that is related to a disease or not, or can be used on crime scenes to see if the CA number of a suspect matches up with that of the DNA found
- Are used when there is a disease that is believed to be linked to a gene, but there isn’t anything abnormal or weird about the gene itself, so we look upstream of downstream of it to find microsatellites and then see if the micro satellites have any correlation with the disease

Question 6

Restriction fragment length polymorphism

Answer 6

• Restriction enzymes cut in different locations varying from person to person given genomic differences. This can cause different sized fragments to be produced depending on the person, and/or depending on the allele they have. This can then be used to identify whether someone has a dominant or recessive trait.
• Can also be used for gene mapping
• You can look at the placement of the RFLPs of the parents and then of the offspring, and if you know the parent’s genotypes, from the numbers you can tell which offspring got parental chromosomes and which didn’t, then figure out the distance between genes.

Question 7

SNP

Answer 7

Single nucleotide polymorphism: a change in a single nucleotide. Most SNPs are in the non-coding region of DNA. Most SNPs don’t matter. They can be detected either by sequencing, or by restriction digests, if they change a restriction site.

Question 8

Genomic library

Answer 8

• Take cells (doesn’t matter where they come from as long as they have nuclei) and take out as much genomic DNA as possible and linearize it
• Then use different restriction enzymes on it and use the frequency and place at which they cut to figure out how to solve the genome
• Each fragments is a “book”
• Take a fragment of DNA (a book) and insert it into a plasmid and put the plasmid in the bacteria
• The DNA polymerase in the bacteria will copy the plasmid more times than the genomic DNA b/c it is smaller
• Collect bacteria, store it in the fridge, and this is your genomic library, packaged so you can come back to it later to study it

Question 9

cDNA library

Answer 9

• Depends on which cell you get it from b/c it comes from the mRNA, which is different for every cell type since different cell types transcribe different genes
• These libraries are specific for every cell type
• We use reverse transcriptase, RT, to make cDNA (which is double stranded) from mRNA, giving us this mRNA/DNA hybrid