Unit 1-Structure And Replication Of DNA Flashcards
Unit or molecules that DNA or RNA are made of?
Nucleotides
3 parts of a nucleotide
Phosphate, deoxyribose sugar, and a base
What determines the genetic code?
The base sequence
What holds the nucleotides together in a strand of DNA ?
Strong chemical bonds (covalent)
Which parts of nucleotides are joined together to form a strand?
Phosphate of one nucleotide and the deoxyribose sugar, on another nucleotide.
What holds the bases in adjacent strands together?
Weak hydrogen bonds hold the bases together
What is at the 3’ end of a DNA strand?
A deoxyribose sugar
What is at the 5’ end of a DNA strand?
A phosphate
What end can nucleotides be added to?
The 3’ end.
How many different nucleotides are there?
4 different nucleotides
What are the 4 different bases?
Adenine, Cytosine, Guanine and Thymine
The two strands of DNA are antiparallel.
What does this mean?
One strand runs in a 5’ to 3’ direction and the other runs in a 3’ to 5’ direction.
The distinctive shape of DNA molecules
Double helix
Describe double helix shape of DNA
Two anti-parallel chains of nucleotides
What is DNA arranged in?
Tightly coiled chromosomes.
What is DNA polymerase?
An enzyme that adds new nucleotides to a growing strand of DNA.
What is a primer?
Small sequence of single-stranded DNA required to start DNA replication.
What strand has to be replicated in fragments?
Lagging strand (5’ end)
Which strand is synthesised continuously
Leading strand (3’ end)
Why is the 5’ end called the lagging strand?
Replication happens slower than the 3’ end.
Why is the 3’ end called the leading strand?
Replication happens more quickly
What is DNA ligase?
Ligase is an enzyme that joins all the DNA fragments together once they are all in place.
For DNA replication to occur, what must the nucleus contain?
Primers
DNA (Template)
Enzymes (Ligase and DNA Polyemrase)
Nucleotides (the 4 types)
ATP
Where does DNA replication occur?
In the nucleus.
Steps in DNA replication
- DNA molecule unwinds
- Hydrogen bonds between the adjacent bases are broken
- Free-floating nucleotides in the nucleus join onto their complementary bases.
Which end of the DNA can nucleotides be added to?
The 3’ end.
How can you recognise the 3’ and 5’ ends of a DNA strand?
The 5’ end at the phosphate end
The 3’ end at the deoxyribose end
Why is DNA replication important?
It ensures that when the cell divides, each daughter cell will inherit an identical copy of the DNA.
What does PCR stand for?
Polymerase Chain Reaction
What is the function of the PCR?
PCR amplifies DNA
(Creates many copies of a piece of DNA).
What is the role of primers in PCR?
Complementary primers for specific target DNA sequences are used.
What are the steps involved in PCR?
DNA is heated (92–98°C) to separate/denature the DNA strands.
Cooled (50–65 °C) to allow the primers to bind to the target sequence of DNA.
Heat tolerant DNA polymerase (70-80°C) then adds nucleotides to the primers (at the 3’ end of the original DNA strands).
Repeated cycles of heating and cooling amplify the region of DNA.
What are the practical uses of PCR?
Solve crimes - provide more DNA to analyse.
Diagnosing genetic disorders.
Settling paternity disputes using DNA profiling.
