Flashcards in Week 7 Deck (85)
Who discovered the structure of DNA ?
Watson and Crick
What are the 2 types of nucleic acid?
DNA and RNA
What are the 2 categories of nitrogenous bases ?
What are purine nitrogenous bases?
They have 2 carbon rings.
What are the Purine nitrogenous bases?
Adenine and Guanine
What type of ring system do during bases have?
Imidazole ring system
What are pyrimidine nitrogenous bases?
They have 1 carbon ring
How many carbon atoms and Nitrogen atoms are present in a pyrimidine nitrogenous bases?
What are the pyrimidine nitrogenous bases?
What type of compounds are the nitrogenous bases of DNA/RNA?
What are heterocyclic compounds?
A cyclic compound that has atoms of at least two different elements in its ring.
Describe the saturation of bonds in Nitrogenous DNA/ RNA bases.
All nitrogenous bases are unsaturated and have conjugated double bonds.
What is meant by the term 'conjugate double bonds'?
Single and double bonds are alternating.
What are the effects to a molecule of having conjugate double bonds?
This allow the electrons to be delocalised over the whole system and to be shared between many atoms.
What feature of nitrogenous bases allows them to absorb UV light?
They are planar molecules
How many hydrogen bonds join Adenine to Thymine?
How many hydrogen bonds join guanine to cytosine?
What are nucleosides?
A compound consisting of a purine or pyrimidine nitrogenous base linked to a sugar.
In a nucleoside, describe the bonding of the sugar to the nitrogenous base.
A Beta-N-glycosidic bond connects the 1' carbon of the sugar to the 1' Nitrogen of a pyrimidine base of the 9' N of a purine base.
What do nucleotides consist of ?
They have a nitrogenous base, a 5 carbon sugar and at least one phosphate group.
What are the 2 possible sugars of a nucleotide?
What are the factors that determine a nucleotide being a ribonucleoside ?
IT will have 3OH groups and be able to be phosphorylated on the 2',3' or 5' carbon.
Why type of bonding joins nucleotides?
3'to5' phosphodiester bonds.
What is meant by DNA being anti-parallel?
One strand runs 3' to 5' and the other runs 5' to 3'.
What type of bonding joins the 2 strands of DNA ?
Is the ladder of DNA 2D or 3D?
What makes a ladder of DNA become 3D ?
The ladder coils to form a 3D helix.
What are desired as the 'rungs' of the DNA ladder?
The paired nitrogenous bases.
What causes DNA to have major and minor grooves?
The way the DNA bases stack on top of each other.
What is the distance of one complete turn of a DNA helix?
What is the distance between nitrogenous base pairs in the DNA helix?
What is the diameter of a DNA helix?
What forces are present in a DNA helix?
VAn der Waals interactions
What are the different possible conformations of DNA ?
When is the A conformation of DNA present?
When DNA is hydrated
Where is the B conformation of DNA found?
When is the Z form of DNA favoured?
When there is alot of G-C in the DNA sequence.
How many base pairs does Beta DNA have per turn of the helix?
When is supercoiling of DNA likely to occur?
In long, linear strands of DNA or in circularised DNA.
What are the different forms of RNA?
Small RNA molecules in cells
What does rRNA stand for?
Ribosomal ribonucleic acid
What is the main purpose of rRNA in the cells?
It is involved in gene expression due to combining RNA and proteins.
What % of total cellular RNA does rRNA make up?
What does tRNA stand for?
Transfer ribonucleic acid
What is the general purpose of tRNA in the cells?
Carries activated amino acids to the ribosome for protein synthesis.
What composition of the cellular RNA is made up by tRNA?
What does mRNA stand for?
What are introns?
Segments of DNA or RNA which do not code for a protein and are therefore removed via spicing.
What are axons?
Segments of DNA or RNA which code for a specific sequence of amino acids.
In what type of mRNA are inions present?
What is chromatin?
A complex of DNA and proteins that forms chromosomes within the nucleus of Eukaryotic cells.
What are the 2 forms of chromatin?
Euchromatin and Heterochromatin
What is Euchromatin?
A large string of DNA wrapped loosely around multiple histone cores and is easily transcribed because is is accessible by translators proteins.
What is Heterochromatin?
A large string of DNA which is tightly wrapped around histones and is difficult to transcribe and translate as there is little room for proteins to reach the DNA.
Which type of chromatin contains alot of satellite DNA ?
What is satellite DNA?
Sequences of DNA that doesn't contain many genes and contain many tandem repeats of introns.
What are the 'beads' on chromatin which is said to look like 'beads on a string'?
What are nucleosomes?
DNA wrapped around 8 histone proteins.
What is a solenoid?
6 nucleosomes joined and wrapped into a 30nm spiral.
What is often used to support the structure of a solenoid?
Additional histone complexes
What is meant by the 'SAR' of solenoids?
The 'scaffold attachment area' - section of DNA where alot of Adenine and Thymine are located.
What causes a super solenoid to form?
When the SAR regions of many solenoids meet and attach.
How many base pairs long is the largest human chromosome?
What are the stages of the cell cycle?
What occurs in G1 of the cell cycle?
Organelles are replicated and protein synthesis occurs. Enzymes and nutrients that are needed later in the cell cycle are produced.
What happens in S of the cell cycle?
Cellular DNA (chromosomes) are replicated.
What happens in G2 of the cell cycle?
Cell growth continues whilst more protein synthesis occurs.
What is G0 of the cell cycle?
A non dividing and non differentiating state.
What are the 3 main stages of DNA replication?
In general , what occur in the initiation phase of DNA replication?
Correct assembly of relevant proteins to the origin site and termination sites.
In general, what occurs in the elongation phase of DNA replication?
DNA replicated by the addition of complimentary nitrogenous bases following base pairing rules.
In general, what happens in the Termination phase of DNA replication?
Replication terminates and protein machinery is disabled. The daughter molecules separate and segregate into new cells.
What is the entire machinery of replication for DNA replication known as?
What is polymerisation?
The addition of successive nucleotides to form DNA catalysed by DNA polymerase.
What is the purpose of DNA polymerase in DNA replication?
Adds nucleotides to a primer until it reaches a stop codon or a section of DNA which has already been replicatied.
Which direction does DNA polymerase work in?
3' to 5'
Describe the replication of DNA on the leading strand.
What direction is the leading strand of DNA replicated in ?
3' to 5'
Describe the replication of the lagging strand of DNA.
Uses Okazaki fragments
What is required for the replication of the lagging strand of DNA?
What are Okazaki fragments?
Short sequences of nucleotides which are discontinuously replicated and later linked to form DNA
What bonds hold nucleic acid chains together?
In a phosphodiester, which regions of nucleotides join?
The hydroxy group of one and the phosphate group of another
When a peptide bonds for, which areas of amino acids bond?
The nitrogen of one amino acid residue and the carbonyl group of another amino acid residue