DNA replication and the genetic code 3.9

Question 1

why do cells divide

Answer 1

• growth & repair
• to produce gametes

Question 2

what is the products of mitosis

Answer 2

• 2 genetically identical daughter cells (genetically identical to parent cells & eachother)

Question 3

What process does DNA need to undergo before cytokinesis can occur in mitosis

Answer 3

• DNA replication needs to occur

Question 4

what is the function of DNA helicase

Answer 4

• 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

Question 5

explain how DNA helicase carrys out its function

Answer 5

• it travels along the DNA backbone catalysing reactions that break the hydrogen bonds between complementary base pairs as it reaches them

Question 6

what is the function of DNA polymerase

Answer 6

• It catalyses the formation of phosphodiester bonds between free nucleotides and original DNA bases as they are exposed during the unzipping process

Question 7

explain the process of how semi-conservative replication occurs

Answer 7

Question 8

what is meant continuous & discontinuous replication

Answer 8

• 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

Question 9

what is meant by mutation

Answer 9

• errors that occur randomly when a sequence of bases are not copied correctly which leads to a change in the sequence of DNA bases

Question 10

what is a codon and what does it do

Answer 10

• codes for an amino acid
• made up of 3 DNA bases

Question 11

what is meant by a gene

Answer 11

• section of DNA that contains the codons to form a complete protein

Question 12

why is there a specific codon that always comes at the start of a sequence

Answer 12

• ensures that codons are read in frame

Question 13

what is meant by degenerate code

Answer 13

• one amino acid can be coded for by more than 1 codon so a protein can be formed using different sequences of bases

Question 14

Explain the process of DNA replication

Answer 14

• 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