2.5 - What can go wrong with DNA?

Question 1

How does DNA replication work?

Answer 1

DNA can copy itself
The DNA helix unzips to form two single strands.
Each strand acts as a template.
Free floating mononucleotides join to each original strand using complementary base pairing by DNA polymerase enzyme.
Hydrogen bonds form between the bases on the original and new strand.
The new DNA molecule has one strand from the original DNA and one new strand. Both strands are identical.
It is semi conservative replication (as one strand is old and one strand is new).

Question 2

What is the name of the enzyme involved in DNA replication?

Answer 2

DNA polymerase

Question 3

When does DNA replication happen?

Answer 3

Interphase

Question 4

Differences between replication of DNA and transcription of DNA

Answer 4

DNA replication involves DNA nucleotides, but transcription involves RNA nucleotides.
DNA replication uses DNA polymerase, whereas transcription uses RNA polymerase
DNA replication produces 2 strands of DNA, however transcription produces a single strand of mRNA
DNA replication produces an identical copy of DNA, whereas transcription produces a complementary copy of the DNA as RNA.

Question 5

Meselson and Stahl showed Evidence for DNA replication being what?

Answer 5

Semi conservative

Question 6

What did Meselson and Stahl do?

Answer 6

They used an experiment with isotopes of nitrogen to show that DNA replication is semi conservative.They grew the bacteria Escherichia coli with different isotopes of Nitrogen. The bacteria was exposed to N15 for several generations until it was exposed to a lighter N14.

Question 7

What did they find?

Answer 7

The 15N strand is heavy so makes a band low down the tube
High density (heavy) sinks further down the tube.

After one generation there was only one band
This was the 14/15 hybrid

After another generation there were 2 bands
A light chain and a 14/15 level