Storing and Using Genetic Information

Question 1

What is the major groove of DNA important for?

Answer 1

The interactions of DNA with protein molecules

Question 2

What does the nucleus contain?

Answer 2

Most of the cell’s DNA.

It is the site of replication of DNA and the first steps in decoding it for protein synthesis

Question 3

What is the nucleolus?

Answer 3

• Can take up to 25% of its volume.

- Site of transcription and assembly of rRNA

Question 4

How much DNA is there in each nucleus

Answer 4

2m of DNA in each nucleus

Question 5

What happens to the DNA in the nucleus?

Answer 5

The DNA molecule is packaged into chromosomes.

Question 6

What are chromosomes?

Answer 6

A single piece of DNA containing many genes, regulatory elements and other nucleotide sequences

Question 7

How is DNA packaged into chromosomes?

Answer 7

DNA is complexed with histones to form nucleosides. Each nucleosome consists of 8 histone proteins of which the DNA wraps around. A chromatosome consists of a nucleosome plus the H1 histone.
The nucleosomes fold up and the 300nm fibres are formed and compressed and folded to produce a 250 nm wide fibre. Tight coiling of the 250nm fibre produces the chromatid of a chromosome.

Question 8

What does DNA transcription and replication require?

Answer 8

The two strands of DNA to be separated temporarily to allow enzymes access to the DNA template

Question 9

What poses as a barrier to the enzymes wanting access to the DNA template?

Answer 9

Nucleosomes and folding of chromatin

Question 10

How is chromatin made more accessible?

Answer 10

• Histones can be enzymatically modified

- Histones can be displaced by chromatin remodelling complexes

Question 11

What two terms could describe DNA replication?

Answer 11

Semi-conservative and bi-directional.
-It is semi-conservative because one half of each new molecule is old, and the other half is new.
Special proteins ‘unzip’ the double helix by breaking the hydrogen bonds. New nucleotide molecules are then paired with the two DNA strands, and it is replicated in 5’ to 3’ direction.

Question 12

What are the main events of metaphase?

Answer 12

Chromosomes are most COMPACTED and visible at this stage.

DNA is packed into cells by repeatedly folding the CHROMATIN fibres into a hierarchy of multiple loops and coils.

Question 13

What are exons and introns?

Answer 13

Exons are the coding regions which code for the protein that has been made from this gene.

Introns are the non-coding regions which get spliced.

Question 14

What does the genetic code describe?

Answer 14

Describes how base sequences are converted into amino acids

Question 15

Each set of 3 bases= ?

Answer 15

Codon, which specifies 1 particularamino acid

Question 16

What is degeneracy?

Answer 16

There are several different options to make an amino acid.
This degeneracy minimises the effect of genetic mutations where alterations to the base sequences are less likely to ALTER the protein being coded for. This prevents any alteration in protein structure and hence function.

Question 17

What can single point mutations cause?

Answer 17

Still can caused dysfunctional proteins.

Eg. a mutated haemoglobin causes Sickle Cell Anaemia

Question 18

What is the main role of RNA?

Answer 18

Protein synthesis

Question 19

____________ is transcribed from DNA and carries information for __________

Answer 19

MESSENGER RNA is transcribed from DNA and carries information for protein synthesis

Question 20

What is alternative splicing?

Answer 20

A process where the exons of the RNA produced by transcription of a gene (primary gene transcript or pre-mRNA) are reconnected in MULTIPLE ways during RNA SPLICING.

Question 21

What does alternative splicing result in?

Answer 21

Different mRNAs, which may be translated into different protein isoforms. Thus a single gene may code for multiple proteins.

Question 22

What is the major role of tRNA?

Answer 22

• It translates mRNA sequence into amino acid sequence.

- It acts as an adapter molecule between the coded amino acid and the mRNA.

Question 23

What are rRNA molecules?

Answer 23

rRNA are produced in the nucleus and then is transported to the cytoplasm, where they combine with PROTEINS to form a RIBOSOME.

Question 24

What is chromatin?

Answer 24

• The name given to the mixture of DNA, proteins and RNA that PACKAGE DNA within the nucleus.
• It is divided between HETEROCHROMATIN (condensed) and EUCHROMATIC (extended) forms.

Question 25

DNA is _____ to produce mRNA, tRNA, rRNA which is then _______ to make the protein.

Answer 25

transcribed

translated

Question 26

What is the role of mRNA?

Answer 26

It is transcribed from DNA and CARRIES information for protein synthesis