Nucleic acids Flashcards
How many DNA Bases code for a single amino acid
3
How many different combinations of amino acids are there
4(3) - 64 combinations
What happens to the remaining combinations of amino acids
- several codons can code for one amino acid
- some used for start/stop/termination
- mutation results in a change in amino acid and a new one can easily be inserted
What is the definition of a gene
a gene is a section of DNA that codes for the production of a polypeptide
What is semi-conservative replication
One strand from original strand and one strand newly formed
Describe the process of transcription briefly
- DNA/ gene copied and transcribed into mRNA
- free activated (RNA) nucleotides
- line up by complimentary base pairing
- Catalysed by RNA polymerase
Describe briefly process of translation
- Mrna moves to ribosomes
- tRNA binds to mRNA
- anticodons bind to codons
- complimentary amino acid attaches to tRNA
- formation of peptide bond between amino acids
What is the importance of complimentary base pairing
- DNA can be replicated without error / same sequence of amino acids produced
- reduces occurrence of mutation
- allows formation of hydrogen bonds
How is the glucose molecule well suited to its function
- soluble so can easily be transported around the organism
- small - can easily diffuse across cell membranes
- easily broken down to release energy
- molecules can join alpha glucose molecules to form maltose (named disaccharides)
Describe the structural relationship between deoxyribose and the other components of the
DNA molecule.
- part of a nucleotide
- bonded to base and phosphate
- phosphate joined to C5/C3 base at C1
- part of backbone of DNA
- links to next phosphate on adjacent nucleotide
- nucleotide is a monomer of DNA
How does a DNA molecule replicate
- semi-conservative replication
- double helix unwinds
- hydrogen bonds between bases break
- each strand acts as a template for the formation of a new molecule
- free nucleotides align with exposed bases
- complimentary base pairing/ purine to pyrimidine
- hydrogen bonds reform
- sugar phosphate reforms /adjacent nucleotides join
- DNA polymerase joins backbone/strands
- each new molecule has one old strand and one new
How is information coded on genes is used to synthesis a polypeptide
- synthesis
- DNA, copied into /, mRNA or described ;
- transcription / transcribed ;
- one strand copied ;
- complementary base-pairing ;
- triplet code / code read in threes / codon is 3 bases ;
- base sequence determines amino acid sequence ;
- translation ;
- ribosomes ;
- role of tRNA described
How do polypeptides control the physical development of an organism
- haemoglobin e.g
- enzyme reactions/metabolism
- hormones
- receptors
- turning genes on/off
How does the structure of DNA allow it to function
-double stranded
-each strand acts as a template
-hydrogen binds easily break/form between bases
-complimentary base pairs
- purines can only pair with pyrimidines due to diff sizes giving equal sized rungs on the ladder
-Hydrogen bonding A-T = 2
C-G=3
What happens if the sequence of nucleotides change
- there is a different combination of amino acids
- different tertiary structure
- cant perform specific function
What supplies the energy for phosphodiester bonds
hydrolysis of activated nucleotides in the nucleoplasm
How to prokaryotes/mitochondria/chloroplasts replicate
- bubble sprouts
- unwinds/unzips
- complimentary bases join to exposed nucleotides
- eventually whole loop is copied
What is the complimentary base pairs
purines always pair with pyrimidines so rungs on the ladder are always the same length
Purines and pyrimidines
-purines - double ringed A+G
-Pyrimidines - single ringed - C+T
contains nitrogen
What is the difference between ribose and deoxyribose
deoxyribose contains an H instead of an OH
What is the meslston and Stahl experiement
proof of semi - conservative replication
1st - heavy as old DNA
2nd - 1X heavy 1x light
3rd- 1x hevay 2x light
semi conservative replication (in detail)
- DNA starts as a double helix, DNA gyrase - untwists
- DNA helicase unzips - breaks hydrogen bonds
- single stranded binding proteins attach to prevent reanneling (binding back together)
- DNA polymerase binds to the leadign strand and forms covalent phosphodiester bonds at the start of the replication fork
- moves in a 5’ 3’ direction
- free nucleotides in nucleoplasm fly in and attach via complimentary base pairs
- lagging strand synthesised discontinuously
- DNA ligase closes the gaps in the backbone
- each new strand consists of one old strand and one new
What does mRNA consist of
- contains ribose
- contains uracil
process of transcription (detail)
- gene unwinds/unzips
- hydrogen bonds break
- DNA polymerase catalyses the formation of temp hydrogen bonds between RNA and DNA bases on template strand
- coding strand produced complimentray to template strand
