DNA

Question 1

Nucleotide

Answer 1

Composed of deoxyribose sugar, phosphate and base

Question 2

Sugar-Phosphate backbone

Answer 2

Connect the sugar (deoxyribose) with the phosphate of two nucleotides together foriming the sugar-phosphate backbone of dna strand

Question 3

Hydrogen Bond

Answer 3

Weak bond that joins complimentary bases on opposite sides of dna

Question 4

3’/5’ end of dna

Answer 4

Marks the end of a dna strand. Has either a deoxyribose sugar (3’) or phosphate (5’) at the end forming a double helix

Question 5

Dna structure summary

Answer 5

Structure of DNA — nucleotides (deoxyribose sugar, phosphate and base), sugar–phosphate backbone, base pairing (adenine–thymine and guanine–cytosine), by hydrogen bonds and double stranded antiparallel structure, with deoxyribose and phosphate at 3’ and 5’ ends of each strand respectively, forming a double helix.

Question 6

Base sequence of dna forms…

Answer 6

The base sequence of DNA forms the genetic code.

Question 7

What happens before cell division and what is needed for DNA replication

Answer 7

Prior to cell division, DNA is replicated by a DNA polymerase. DNA polymerase needs primers to start replication. A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing polymerase to add DNA nucleotides.

Question 8

DNA Polymerase

Answer 8

DNA polymerase adds DNA nucleotides, using complementary base pairing, to the deoxyribose (3’) end of the new DNA strand which is forming, ie in the 5’ to 3’ direction

Question 9

DNA Replication

Answer 9

DNA is unwound and hydrogen bonds between bases are broken to form two template strands.

DNA polymerase can only add DNA nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand replicated in fragments.

Question 10

Ligase

Answer 10

Fragments of DNA are joined together by ligase.

Question 11

Leading Strand (summary)

Answer 11

Strand of dna which is replicated continuously from 3’ to 5’ end

Question 12

Lagging Strand

Answer 12

Strand of dna which is replicated in fragments from 3’ to 5’ end

Question 13

Pcr summary

Answer 13

Polymerase chain reaction (PCR) amplifies DNA using complementary primers for specific target sequences.

Question 14

PCR Stages

Answer 14

1. DNA is heated to between 92 and 98°C to separate the strands.
2. It is then cooled to between 50 and 65°C to allow primers to bind to target sequences.
3. It is then heated to between 70 and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA.

Repeated cycles of heating and cooling amplify the target region of DNA.

Question 15

Practical applications of pcr

Answer 15

PCR can amplify DNA to help solve crimes, settle paternity suits and diagnose genetic disorders.

Question 16

PCR Primers

Answer 16

In PCR, primers are short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified.

Question 17

Primers

Answer 17

A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing polymerase to add DNA nucleotides