UNIT 1 - KA2
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What are the three parts In a nucleotide (DNA)
Phosphate , deoxyribose sugar , base Check jotter for diagram
What is the full name for DNA
Deoxyribonucleic Acid
Sugar phosphate backbone
• a strong chemical bond joins the nucleotides it forms between the deoxyribose sugar for one and the phosphate group of the next
What type of bonds hold the two strands of DNA together
Weak hydrogen bonds between bases hold the two strands of DNA together
Anti parallel strands
• DNA strands have 2 ends • a 3’ end with deoxyribose sugar at the end • a 5’ end with phosphate at the end • the two strands run anti parallel to each other
What is the shape of a DNA molecule
The DNA molecule takes the shape of a twisted double helix with the sugar phosphate backbone (upright on the outside and the base pairs on the inside)
What does the base sequence of DNA do
The base sequence of DNA forms the genetic code
Draw a diagram of the structure of DNA
Check jotter for answer
When does DNA replication take place
DNA replication takes place just prior to cell division
Which enzyme is responsible for DNA replication
DNA polymerase is the enzyme responsible for DNA replication
What does DNA polymerase require to start replication
DNA polymerase needs primers to start replication
What is a primer
A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand
Briefly describe what DNA polymerase does
DNA polymerase adds DNA nucleotides using complementary base pairing to the deoxyribose (3’) end of the new DNA strand which is forming
How should the two new DNA strands be made
The two strands of a DNA molecule run antiparallel to each other. Therefore the two new strands of DNA must be made in different ways
What happens prior to cell division (1st step of DNA replication)
Prior to cell division, DNA is replicated by an enzyme called 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 DNA polymerase to add DNA nucleotides)
How are the two template strands formed (2nd step of DNA replication)
DNA is unwound and hydrogen bonds between bases are broken to form template strands
How does DNA polymerase add DNA nucleotides (3rd step of DNA replication)
DNA polymerase adds DNA nucleotides , using complementary base pairing to the deoxyribose 3’ end of the new DNA strand which is forming
Why are the two strands replicated in different ways (4th step of DNA replication)
DNA polymerase can only add DNA nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand being replicated in fragments
Which enzyme joins DNA on the lagging strand (5th step of DNA replication)
The fragments of DNA on the lagging strand are joined together by an enzyme called ligase
Draw a diagram of the two new template DNA strands
Check jotter
What is the technique polymerase chain reaction
PCR or polymerase chain reaction is a technique used to AMPLIFY DNA outside the body (in vitro)
What are PCR primers (think of stage 2 of PCR)
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
Where does heat tolerant DNA polymerase add nucleotides to
Heat tolerant DNA polymerase adds nucleotides to the primers at the 3’ end of the original strand of DNA , leading to the replication of that region of DNA
What are the three applications of PCR
• forensics / solve crimes • settle paternity suits • diagnose genetic disorders