Storing and Using Genetic Information Flashcards
What is the major groove of DNA important for?
The interactions of DNA with protein molecules
What does the nucleus contain?
Most of the cell’s DNA.
It is the site of replication of DNA and the first steps in decoding it for protein synthesis
What is the nucleolus?
- Can take up to 25% of its volume.
- Site of transcription and assembly of rRNA
How much DNA is there in each nucleus
2m of DNA in each nucleus
What happens to the DNA in the nucleus?
The DNA molecule is packaged into chromosomes.
What are chromosomes?
A single piece of DNA containing many genes, regulatory elements and other nucleotide sequences
How is DNA packaged into chromosomes?
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.
What does DNA transcription and replication require?
The two strands of DNA to be separated temporarily to allow enzymes access to the DNA template
What poses as a barrier to the enzymes wanting access to the DNA template?
Nucleosomes and folding of chromatin
How is chromatin made more accessible?
- Histones can be enzymatically modified
- Histones can be displaced by chromatin remodelling complexes
What two terms could describe DNA replication?
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.
What are the main events of metaphase?
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.
What are exons and introns?
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.
What does the genetic code describe?
Describes how base sequences are converted into amino acids
Each set of 3 bases= ?
Codon, which specifies 1 particularamino acid
What is degeneracy?
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.
What can single point mutations cause?
Still can caused dysfunctional proteins.
Eg. a mutated haemoglobin causes Sickle Cell Anaemia
What is the main role of RNA?
Protein synthesis
____________ is transcribed from DNA and carries information for __________
MESSENGER RNA is transcribed from DNA and carries information for protein synthesis
What is alternative splicing?
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.
What does alternative splicing result in?
Different mRNAs, which may be translated into different protein isoforms. Thus a single gene may code for multiple proteins.
What is the major role of tRNA?
- It translates mRNA sequence into amino acid sequence.
- It acts as an adapter molecule between the coded amino acid and the mRNA.
What are rRNA molecules?
rRNA are produced in the nucleus and then is transported to the cytoplasm, where they combine with PROTEINS to form a RIBOSOME.
What is chromatin?
- 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.
DNA is _____ to produce mRNA, tRNA, rRNA which is then _______ to make the protein.
transcribed
translated
What is the role of mRNA?
It is transcribed from DNA and CARRIES information for protein synthesis
