7.1.2

What is the structure of nucleosomes?

8 histone protein molecules with a length of DNA wrapped around it.

Another histone protein holds it all together

7.1.3

What is the purpose of nucleosomes?

Help to supercoil chromosomes and to regulate transcription

7.1.4

What is the difference between single copy DNA and highly repetitive sequences in nuclear DNA?

single copy genes are unique to the individual and code for specific characteristics.  They only make up approximately 1.5% of human DNA.

Repetitive sequences, also known as satellite DNA, don't have an apparent function for the individual and are used in DNA profiling and research

7.2.1

What direction does DNA replication occur?

5' to 3'

7.2.3

Where is DNA replication initiated?

7.2.2

What does DNA Helicase do?

Uncoils the DNA double helix and splits it into two template strands.

7.2.2

What does DNA Polymerase do?

DNA polymerase III adds nucleotides in a 5'to3' direction.

DNA Polymerase I removes the RNA primer and replaces it with DNA

7.2.2

What does RNA primase do?

adds a short length of RNA attached by base pairing to the template strand of the DNA this acts as a primer which allows DNA polymerase to bind to to begin replication.

7.2.2

What does DNA Ligase do?

DNA Ligase seals up any nicks where DNA nucleotides are left unconnected.

7.2.2

What are okazaki fragments?

These are short lengths of DNA on the template strand where nucleotides are added in the opposite direction to the uncoiling of the DNA.

7.2.2

What is the purpose of deoxynucleoside triphosphates in DNA replication?

7.3.1

What direction is transcription carried out?

5' to 3'

7.3.2

What is the difference between the sense and antisense strands of DNA?

The antisense strand is the strand which provides a template for transcription.  This means that apart from U/T the sense strand has the same base sequences as the resulting mRNA.