What are the 4 nitrogenous bases?
Adenine, Thymine, Cytosine, Guanine
What 3 components make up a nucleotide?
deoxyribose sugar, phosphate, nitrogenous base
What is a histone?
A histone is a structural protein that helps bind DNA to form a chromosome in eukaryotes.
What are the 4 main enzymes involved in DNA replication
1. Helicase 2. Primase3. DNA polymerase4. Ligase
What is the first stage of DNA replication?
the enzyme DNA helicase breaks the hydrogen bonds between the 2 nitrogenous bases, 'unwinding' the double helix strands.
What is the second stage of DNA replication?
The enzyme primase adds RNA primers the ends of each strand, acting as a template for the DNA polymerase.
What is the third stage of DNA replication?
DNA polymerase creates complementary base pairs to the single stranded molecule, using the template laid by primase, thus creating a double helix molecule. For example, If the separated strand contained a Adenine base, DNA polymerase would create a thymine base to complement and join it.
What is the fourth and final stage of DNA replication?
The final stage of DNA replication involves the enzyme ligase which 'glues' the broken Okazaki fragments in the lagging strand together.
What protein ensures that DNA strands seperate by helicase do not rejoin?
Single-stranded binding (SSB) proteins
What enzyme stops supercoiling during DNA replication?
Topoisomerase
What is meant by the description "antiparallel" regarding the strands that make up DNA?
The 5' to 3' direction of one strand runs counter to the 3' to 5' direction of the other strand. This is important when considering lagging and leading strands during DNA polymerase.
What is meant by lagging and leading strands?
DNA polymerase works in the 5' to 3' direction, or going off the old template, 3' to 5' direction. This means that the lagging strand must work backwards, this results in incomplete or disconnected fragments (Okazaki fragments). It's the job of ligase to glue these disconnected fragments together. The leading strand does not have this issue.
What is the purpose of supercoiling DNA?
Compacts the DNA and compensates for structural strain caused by DNA strand changes.