DNA: discovery and replication Flashcards
What are two things that you need in order to purify a gene?
1) method of isolating cell components
2) assay for genetic materialness
What are the components of nucleotides?
Base, sugar, phosphate
- charged phosphate backbone exposed to water
- bases - hydrophobic planar molecules (important because hydrogen bonds are most stable, and the distance between the two strands stay constant)
What are two things that the DNA strands suggest?
1) sequence of the nucleotides do not affect overall structure so information can be encoded arbitrarily by sequence of base pairs
2) two strands bind complementary base pairing so two new strands contain informaiton
What are three things that could happen to two DNA strands during replication?
1) conservative replication - each make new strand and two old strands re-annealed, and two new ones re-annealed as well
2) semiconservative replication - each old strand made and remained annealed to new strand (DNA IS THIS)
3) dispersive replication: DNA would break apart and rejoin to produce four strands, each mix of old and new DNA
What is critical for DNA replication?
- Ragged end
- DNA synthesis always occurs 5’ to 3’
What are two problems that a live cell has?
1) has to unwind the strands
2) has to create ragged ends
What are the two enzymes that cells have?
1) Helicase: expends energy to unwind DNA
2) Primase: adds short stretch of complementary RNA, primer, acts as ragged end so that DNA polymerase can work
What is origin of replication?
- there are specific spots that initiate replication called origin of replication
- bacteria have one
- eukaryotes have many along the length of the chromosome
What are replication forks?
As helicase unwinds the DNA in each direction from origin of replication, bubble forms w/ so called REPLICATION FORKS on either end to act as template for new strands
What happens when polymerase make mistakes?
1) polymerase proofreads
2) mechanism - mismatch repair (during recombination)
3) excision repair
