DNA Replication Flashcards
Semi-conservative replication
Ensures genetic continuity between generations of
cells meaning that genetic information is passed on from one generation to the next.
Describe the steps of semi-conservative replication of DNA
- An enzyme, DNA helicase, causes the two
strands of DNA to separate breaking the hydrogen bonds between the complementary bases. - One of the strands is used as the template and
complementary base pairing occurs between
the template strand and free nucleotides. - Once activated nucleotides are bound the
enzyme DNA polymerase joins them together by
forming phosphodiester bonds. The result is that two identical strands of DNA are formed.
DNA replication
DNA is made up of two polynucleotide strands that form a double helix.
During DNA replication, each of the two strands is used as a template from which new strands are copied.
Evaluate the Watson crick model (AO3)
- Watson and Crick were two scientists who worked together to confirm the double-helix structure of DNA in 1953.
- Watson and Crick also came up with a model by which DNA might be replicated:
This theory was called semi-conservative DNA replication
The theory is based upon the specific hydrogen bonding between pairs of nitrogenous bases (A+T and C+G) being used during replication to conserve the genetic sequence
However, this was just a theory, another theory suggested DNA replicated ‘conservatively’ The theory of conservative DNA replication suggested that the strands of the original DNA molecule would stay together, and the new, replicated DNA molecule would be made out of two brand new strands Watson and Crick’s theory of semi-conservative DNA replication was later proved to be correct by the work of two other scientists, Meselson and Stahl.
- They used bacteria and two nitrogen isotopes, a heavy form (15N) and the normal, lighter form (14N), to prove this
What is DNA polymerase? (AO1)
An enzyme that binds primer and begins the synthesis of a new strand.
Responsible for: synthesizing DNA incorporating complementary nucleotides one by one to the growing chain.
semi-conservative replication of DNA (1)
An enzyme, DNA helicase, causes the two
strands of DNA to separate breaking the hydrogen bonds between the complementary bases.
semi-conservative replication of DNA (2)
One of the strands is used as the template and
complementary base pairing occurs between
the template strand and free nucleotides.
semi-conservative replication of DNA (3)
Once activated nucleotides are bound the
enzyme DNA polymerase joins them together by
forming phosphodiester bonds. The result is that two identical strands of DNA are formed.
(which are complementary to the parent.)
What is the name given to the orientation of DNA strands in the double helix?
Antiparallel
What are the two isotopes of nitrogen encorporated into the DNA of E. coli in the experiment by Meselson & Stahl?
‘Heavy’ 15N & ‘Light’ 14N
The stages involved in semi-conservative replication are:
Simple
- The DNA helicase unzips the DNA helix
- Complementary base pairing
- DNA polymerase forms strands
Explain some reasons why there might be DNA from cancer cells in this blood plasma.
When cancer cells die they can break open. This releases DNA into the blood plasma.
Suggest why control groups for cancer treatment are NOT given placebos.
It’s unethical to not treat the cancer
What are some differences between DNA and RNA?
DNA contain deoxyribose and thymine, with RNA it contains ribose and uracil
Which molecule carries information in a form that is inherited from one generation to another?
Hereditary information stored in DNA
