DNA Replication Flashcards
Explain DNA replication step by step.
1) DNA double helix unwinds by the enzyme DNA helicase.
2) While its unwinding, free floating nucleotides base pair with their complementary bases.
3) When they are lined up, DNA polymerase joins them together.
4) 2 identical strands of DNA are formed.
What is semi-conservative replication?
The two final strands of DNA have one original strand and one new strand.
Which way does the enzyme DNA polymerase move across a DNA strand?
From 3’ to 5’ only.
Which strand of DNA is continuously replicated?
The leading strand that goes from 3’ to 5’
Which strand of DNA is discontinuously replicated?
The lagging strand that goes from 5’ to 3’
How does discontinuous replication work?
DNA polymerase waits for the strands to unzip, then it starts from the middle of the lagging strand and goes 3’ to 5’ making Okazaki fragments. The Okazaki fragments are joined afterwards by an enzyme.
What is a mutation?
A change in the sequence of bases caused by random and spontaneous errors.
What is a triplet code?
A sequence of 3 bases called a codon that codes for 1 amino acid.
What are the 3 main features of the genetic code?
It is degenerate, universal and non overlapping.
Why do cells need to divide to make more cells?
Growth and repair.
The genetic code is universal. What does this mean?
The same codon codes are used for the same amino acids in all organisms.
The genetic code is degenerate. What does this mean?
Most amino acids have more than one codon that codes for that amino acid.
The genetic code is non overlapping. What does this mean?
Each base is only read once and it is read in a sequence pattern that doesn’t overlap. So it is read like 123|456|789
