DNA structure and replication
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DNA is made up of repeating units called...?
What three components make up a nucleotide?
A phosphate, deoxyribose sugar and base molecule
What are the four types of bases?
Adenine, guanine, cytosine and thymine
Adenine pairs with...?
Cytosine pairs with...?
How do nucleotides join up?
The sugar on one nucleotide joins with the phosphate of the next molecule - creating a sugar phosphate backbone
What kind of easily broken bonds join two nucleotide strands between the bases?
DNA is organised into...?
A section of DNA thousands of base paris long is called a...?
Each gene carries the code for how many proteins?
Why is DNA a unique molecule?
As it is able to reproduce itself exactly
What is the name of the process by which DNA copies itself?
What must be present in the nucleus for replication to occur?
DNA, a supply of the four types of nucleotide, the appropriate enzymes and ATP
Describe DNA replication
- The original DNA molecule becomes untwisted through the action of an enzyme
- The weak hydrogen bonds between the bases breaks causing the two strands of DNA to seperate ("unzip") and expose the bases
- The free nucleotides found in the nucleus find their complementary nucleotide on the open chain
- Weak hydrogen bonds form between the bases
- The sugar phosphate bond forms between nucleotides giving each new strand its "backbone"
- A new DNA molecule is finally formed
Why is DNA replication said to be semi-conservative?
As half of the original DNA molecule is kepy by the cell
Why is DNA replication essential for the continuation of life?
It ensures that an exact copy of the genetic information is passed from cell to cell during growth, and from generation to generation during reproduction
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