Nucleic acids Flashcards
What are the full names of the 2 kinds of nucleic acids?
Deoxyribonucleic acid
Ribonucleic acid
What 3 structures make up a nucleotide?
- a five carbon sugar.
- a nitrogenous base.
- a phosphate group
What are the purines? How many rings do they have?
Guanine and adenine
2 rings
What are the pyrimidines? How many rings do they have?
Cytosine and thymine (and uracil)
1 ring
What is a nucleoside composed of?
A nitrogenous base and a sugar - NOT a phosphate group
What are the names of the 4 nucleosides?
Deoxyadenosine
Deoxycitidine
Deoxyguanosine
Deoxythymidine
What are the names of the 4 nucleotides found in DNA?
Deoxyadenosine monophosphate
Deoxycitidine monophosphate
Deoxyguanosine monophosphate
Deoxythymidine monophosphate
What kind of bond are nucleotides joined with?
Phosphodiester bonds
How many hydrogen bonds do cytosine and guanine form?
3
How many hydrogen bonds go adenine and thymine form?
2
What does Chargaff’s rule state?
In double stranded DNA, %A = %T and %G = %C
Is DNA right handed or left handed?
Right handed
State the approximate diameter and height of DNA
Diameter 2 nm
6. Height 3.4 nm per turn
How many base pairs are there per turn of DNA?
10
What are the 3 alternate DNA conformations? Describe them
- B-DNA - the common form
- A-DNA - 11bp/turn, right-handed, slanted base-pairs.
- Z-DNA - 12bp/turn, left-handed. Zig-zag backbone.
Why might Z-DNA form?
If DNA contains long runs of alternating G and C
Why might A-DNA form?
If DNA is dehydrated
What is the most common configuration of DNA?
B-DNA
What does underwinding of DNA form?
Negative supercoils
What does overwinding of DNA form?
Positive supercoils - more turns than in the relaxed state
Unwinding a DNA molecule with fixed ends introduces what kind of supercoils?
Positive
What kind of enzyme manages supercoiling?
Topoisomerases
What is the hyperchromic shift?
The increase in UV absorbance (especially at 260 nm) that occurs when double-stranded DNA is denatured into single strands
How does the OH on C2 change the properties of RNA?
Makes it denser, and more reactive
(less stable) and versatile than DNA
What nucleotide changes in RNA compared to DNA?
RNA has uracil, DNA has thymine
What is the full uracil nucleotide name?
Uridine monophosphate
How does transfer RNA form?
RNA molecules fold back on themselves to form complex secondary structures with intramolecular base-pairing
List the 4 functions of RNA
- Carry information (messenger RNA).
- Act as a transporter (transfer RNA).
- Act structurally or catalytically (e.g. ribosomal RNA).
- Act as a regulator of gene expression (e.g. micro RNAs)
Define genome
The genetic (i.e. hereditary) material (usually
DNA) contained in an organism, cell, virus or organelle
Define chromosome
A single long molecule of DNA that includes numerous genes. The DNA of a chromosome is usually associated with proteins.
Define gene
The entire stretch of DNA necessary for the
production of a particular functional product, which may be a protein or an RNA molecule.
Define chromatin
The DNA-protein complex present in the nuclei of eukaryotic cells during interphase
