DB Lecture 31: DNA Recombination

Question 1

What are the two types of crossing over and their outcomes?

Answer 1

equal homologous recombination: between two similar sequences on two chromosomes, normally no consequences (normal diversity)
unequal homologous recombination: when homologous copies of the gene align out of register and undergo recombination, results in two or more copies of the same gene present on the same chromosome

Question 2

What is transposition?

Answer 2

the movement of a transpson (unit of DNA) from one site to a new target site
occurs in the absence of homology
insertion generally occurs at random sites
catalyzed by transposase ( gene for this often found in the transposon)- highly regulated

Question 3

How do bacterial transposons differ from eukaryotic transposons?

Answer 3

bacterial: DNA only mechanism

eukaryotic retrotransposons: move via RNA intermediate

Question 4

What are LINES?

Answer 4

long interspersed elements
L1 elements that code for a protein that has reverse transcriptase activity
retrotransposons by an L1 element can cause disease
provide regions of homology where recombination can take place

Question 5

What are SINES?

Answer 5

AluI element
contain no coding sequence
transposition depends on assistance of L1 elements
movement can cause disruption in gene –> disease

Question 6

What are VNTRs?

Answer 6

variable number of tandem repeats
small DNA sequences (9-80 bps) present in multiple contiguous copies in the same orientation (tandem repeats)
pattern is unique to each person