Storage and Retrieval of Genetic Information + The genome and its transmission Flashcards
(45 cards)
What are the similarities between DNA and RNA
Both are polynucleotides
both have a sugar-phosphate backbone formed of phosphodiester bonds
both contain adenine guanine and cytosine nitrogen contain bases
Outline the Structure of DNA
Doubles stranded helix with two antiparallel strands
sugar phosphate backbone
contains deoxyribose H atom of 2’ carbon (more stable than OH on RNA)
Contains Thymine as well as A,C,G
Has H bonding between complimentary base pairs. (A-T=2) (C-G=3) Pyrimidines (1C ring) bind to purines (2 C ring) maintains the diameter and stability of double helix
RNA strucutre
Single stranded
can have sections where the strand folds and forms double stranded segments held in place by H bonds
made up of ribose contains a OH group on 2’ carbon
lot less stable prone to cleavage in aqueous environments
Doesn’t contain thymine instead contains uracil
How much of the human genome is coding vs non coding
Majority of human genome is non coding
genes constitute around 2%
What are Repeat elements?
Non coding DNA
LINE and SINE elements can be used to detect polymorphisms for DNA fingerprinting
What are gene regulatory elements?
premotor and enhancer regions on the DNA
What are promotor regions on the DNA?
found usually immediately upstream of gene this is known as the TATA Box
Specific transcription factors will bind to the specific sequences on the DNA in this region and either augment or suppress gene transcription through activation or deactivation of RNA polymerase II
What are enhancer regions of DNA?
Other regulatory elements than can be found scattered before after or even in the introns of genes
Specific transcription factors bind to these specific regions and together form an committee that ultimately decides whether to augment or suppress transcription of a gene (this is regulated by the environment)
What are the two components of genes
Introns (intervening) non coding sections of DNA
Exons (expressed) coding sections of DNA
What are the other types of repeat sequences that make up the genome?
Satellite DNA –> tandem repeats of neuclotides found in the DNA
mini-satellite = highly polymorphic up to 1000 copies in one block
micro-satellite= small arrays of simple sequence repeats usually in introns
What is the function satellite DNA
has a role in at the telomere helping to prevent enzymatic attack
has a role at the centromere forms the structural non coding scaffolding
What are some issues that occur due to micro and mini satellite DNA repeats
Large scale duplication/deletion between homologous chromosomes
Translocation of DNA between non-homologous chromosomes
Microsatellites in coding regions can cause protein misfolding and aggregations in the cell
What is the process of DNA replication?
Why is it called this?
Semiconservative replication
each polynucleotide strand acts as a template for the synthesis of a complementary template strand
each DNA molecule has one original and one newly synthesised strand
What must be preset for DNA to be able to replicate?
dNTP’s (deoxyribonuclotide triphosphates dATP, dGTP etc)
various enzymes DNA polymerase DNA ligase
Outline the process of Semiconservative replication
Histone coat removed
section of DNA to be synthesised is unwound by DNA helicase (H bonds between complimentary base pears break )
On the leading strand dNTP’s form H bonds with complimentary bases
An RNA primase must first make a short section of RNA that allows the DNA polymerase to attach and start synthesising the new strand.
DNA polymerase moves in the 3’ to 5’ direction and joins adjacent nucleotides together via phosphodiester bonds DNA polymerase is rapid.
DNA polymerase only works in one direction synthesising the new strand in the 5’to 3’ direction (i.e. reads the 3’ to 5’ but makes in the 5’ to 3’) therefore on the lagging strand:
RNA primase (that also works in the 5’ to 3’ direction) initially makes small attachment units
This allows DNA polymerase attachment and synthesis of small sections in the 5’ to 3’ direction this leaves gaps behind it
These fragments are known as Okazaki fragments and have then got to be joined via DNA ligase.
What direction does DNA polymerase work in?
DNA polymerase only works in one direction synthesising the new strand in the 5’to 3’ direction (i.e. reads the 3’ to 5’ but makes in the 5’ to 3’)
What is and why is DNA polymerases proof reading ability essential?
Has a proofreading ability can stop if there is a change in diameter indicting bases haven’t paired correctly can go back and excise the incorrect base and swap it for the right dNTP.
ensures that there are no mutations in the DNA that could lead to the production of faulty proteins
Decreases the risk of deregulated cell proliferation
How are how chromosome replicated?
To initially start SCR must have binding of initiator protein to the DNA this forms a replication bubble allowing replication from the inside out (2 replication forks going in opposite directions from one bubble)
There are multiple of these bubbles making the process rapid
Where does transcription occur and what is required for it to occur
occurs in the nucleoplasm
must have and accessible DNA template strand
must have nucleoside triphosphates NTP’s present (CTP,ATP,GTP,UTP)
RNA polymerase II must also be present
Outline the process of transcription
Gene must be exposed via the binding of initiator proteins for form a replication bubble and expose the template strands
RNA polymerase only works in the 5’ to 3’ direction therefore bind to the leading DNA template strand
NTP’s diffuse and pair with complimentary bases and RNA polymerase II joins adjacent nucleotides synthesising a RNS strand in the 5’ to 3’ direction
co-transcriptional modification of RNA
binding of a splicesome
carriers out RNA splicing takes out the introns and leaves the coding exons
Alternative splicing may occur that allows multiple proteins to produced from one gene through rearrangement of exons
Translation where does it occur what must be present?
mRNA must successfully leave the nucleus
occurs in the cytosol
Ribosomes must be present as well as tRNA
What is tRNA
adaptor molecule
hairpin shaped strand of RNA held in place by hydrogen bonds
has a specific anticodon complimentary to a triplet codon on the mRNA and carriers a specific amino acid on the top of the hairpin molecule
What can stop mRNA leaving the nucleus
has to pass through nuclear pore but this is highly selective
microRNA can be bound to an argonaut protein to from a RNA induced silencing complex that can bind to mRNA and prevent it leaving the nucleus
