DNA replication and the genetic code 3.9 Flashcards
1
Q
why do cells divide
A
- growth & repair
- to produce gametes
2
Q
what is the products of mitosis
A
- 2 genetically identical daughter cells (genetically identical to parent cells & eachother)
3
Q
What process does DNA need to undergo before cytokinesis can occur in mitosis
A
- DNA replication needs to occur
4
Q
what is the function of DNA helicase
A
- it unwinds and separates the 2 strands of the DNA double helix molecule
- it can be thought of ‘unzipping’ the molecules into 2 separate strands
5
Q
explain how DNA helicase carrys out its function
A
- it travels along the DNA backbone catalysing reactions that break the hydrogen bonds between complementary base pairs as it reaches them
6
Q
what is the function of DNA polymerase
A
- It catalyses the formation of phosphodiester bonds between free nucleotides and original DNA bases as they are exposed during the unzipping process
7
Q
explain the process of how semi-conservative replication occurs
A
8
Q
what is meant continuous & discontinuous replication
A
- DNA only unwinds in one direction
- DNA polymerase has to replicate each of the template strands in opposite directions.
- The strand that is replicated from the opposite end to the unzipping is called the lagging strand and DNA polymerase has to work its way back along the strand (This results in DNA sections being produced (okazaki fragments), which then have to be joined)
- The strand with DNA polymerase going in the same direction as the unzipping is called the leading strand and is produced as one ‘continuous’ strand
9
Q
what is meant by mutation
A
- errors that occur randomly when a sequence of bases are not copied correctly which leads to a change in the sequence of DNA bases
10
Q
what is a codon and what does it do
A
- codes for an amino acid
- made up of 3 DNA bases
11
Q
what is meant by a gene
A
- section of DNA that contains the codons to form a complete protein
12
Q
why is there a specific codon that always comes at the start of a sequence
A
- ensures that codons are read in frame
13
Q
what is meant by degenerate code
A
- one amino acid can be coded for by more than 1 codon so a protein can be formed using different sequences of bases
14
Q
Explain the process of DNA replication
A
- the 2 strands of DNA double helix separate
- ^each strand serves as a template for the creation of a new DNA strand
- complementary base pairing rules ensure that new strands are identical to original
