Storing and Using genetic information Flashcards
What is the phenotype of an organism?
Outward, physical appearance
What is the genotype of an organism?
Full hereditary information
What is a nucleotide monomer?
Makes up chains for DNA
Made of a sugar, base and phosphate group
How do the molecules bind in DNA?
- Phosphate bind to 5th and 3rd C of sugar
- Base binds to 1st C
How are the bases structured in the double helix?
Bases are in the centre of the helix and bound by the outside to the sugar-phosphate backbone
What is the name of the sugar used in DNA?
2-deoxyribose
What is the name of the sugar in RNA?
Ribose - OH instead of H on 2nd C
How many bases per turn of helix?
10
What is meant by the chains of DNA running antiparallel to each other?
One runs from 5’ to 3’ from the top of the helix whilst the other is the opposite
What structure contains most of the cell’s genetic material (DNA)?
Nucleus
What occurs in the nucleus?
Replication of DNA and first steps in protein synthesis
What are DNA molecules packaged into in the nucleus?
Chromosomes
What are chromosome?
Single piece of DNA containing many genes, regulatory elements and other nucleotide sequences
What is a nucleosome?
Bundles of histones (proteins) with DNA wrapped around it
What is a chromatin?
Mixture of DNA, proteins and RNA that package DNA within the nucleus
Molecules that form a chromosome
What are two types of chromatin?
Heterochromatin (condensed and euchromatin (extended) forms
List stages of DNA packaging from smallest to largest
- Nucleosome
- Coils
- Supercoils
- Chromosome
Why must the double helix strands separate during transcription & replication?
To remove the histones & folding barriers so enzymes have access to DNA
What are two mechanisms which make chromatin maple accessible to enzymes?
- Histones enigmatically modified
- Histones displaced by chromatin remodelling complexes
Both reversibly
What type of chromatin is more favourable for RNA polymerase and why?
Requires looser structure therefore euchromatin
What does semi-conservative replication mean?
It means the 2 new DNA molecules contains 1 stand from the original and one from the new strand
In what direction is the DNA replicated by DNA polymerase?
3’ to 5’ - the antisense strand
What are the coding region in DNA?
Exons
What is telomerase used for?
Replicating DNA strand from the 5’ to 3’ end
What are the non-coding regions in DNA?
Introns
What happens to introns and extols during transcription?
Introns spliced out and ends on exons join
How many codons code for an amino acid?
3 but the number of codons is greater than the number of AA
What are synonyms?
Condons which refer to the same AA
How does degeneracy minimises effect of genetic mutations?
Variation of synonyms at 3rd codon means that changes to codon sequence are less likely to alter coded protein
What is degeneracy?
Amino acids are encoded by more than one codon
Which AA are an exception to degeneracy?
Methionine and tryptophan
What type of mutation of codon sequence who alter the protein?
Codon that encodes for a stop or termination signal
What disorder can single point mutations cause?
Sickle cell anaemia - Glu to Val - clumps haemoglobin together
How can single point mutations cause dysfunctional proteins?
Base change = change in amino acid = change in structure = change in function
mRNA role
Transcribes DNA in nucleus and moves to cytoplasm for protein synthesis
What is the pre-mRNA strand?
Complement strand to DNA template which contains introns and exons
What is alternative splicing?
Process where introns of pre-mRNA are spliced out and exon ends are brought together
What is a strand of codons bound by in RNA?
An initiation codon and a termination codon
Why are reading frames required in translation?
Reading frames required to read RNA strand by tRNA to deliver correct AA
Role of tRNA?
Translate mRNA sequences into AA sequence
Role of rRNA?
transported from nucleus to cytoplasms where they combine the proteins to form a ribosome
