CH4710 RM27

what are the base pairs

G and C

A and T/U

how many H bonds between G and C

3

how many H bonds between A and T/U

2

Watson and Crick model for DNA components

• double helix

• major and minor grooves

DNA parallel vs antiparallel

parallel: DNA strands both run in same direction

antiparallel: DNA strands run in opposite directions

• xray analysis shows that DNA runs antiparallel

replication of DNA overall (simple)

1. preexisting “parent” strands become separated

2. each “parent” serves as a template for the biosynthesis of a complementary “daughter” strand

replication of DNA detailed

1. DNA polymerase binds to dNTP

2. DNA polymerase brings dNTP to the growing daughter strand

3. the first phosphate (or alpha phosphate) of dNTP makes a covalent bond with the 3rd OH of the ribose of the last nucleotide of the daughter chain

   1. alpha phosphate (dNTP) bonds with OH of nucleotide ribose of daughter strand

4. beta and gamma phosphates and DNA polymerase leave

5. process repeats

palindrome

region of DNA that is identical when read either forward or backward

mirror repeat

looking at a DNA strand, imagine a line cut down the middle. there’s a reflection over the line (mirror image)

hairpin structures

self-complementarity within each strand

cruciform structures

self-complementarity within each strand

transcription

process by which mRNAs are formed on a DNA template

denaturation

“melting” of double helix

caused by pH extremes or high temps

separated the strands, unwinding

annealing

opposite of denaturation

rewinding of strands

spontaneous process

hypochromic effect/hyperchromic effect

hypo: decrease in absorption of UV when DNA is annealed

hyper: increase in absorption of UV when DNA is denatured

deamination

spontaneous loss of exocyclic amino groups

ex. cytosine can be recognized as foreign and is deaminated to uracil

depurination

hydrolysis of the N-beta-glycosyl bond between the base and pentose

• creates “abasic site” or DNA site with no purine/pyrimidine