D1 Continuity and Change : Molecules Flashcards
DNA replication, protein synthesis and mutations
histones
Proteins around which eukaryotic DNA is wrapped, forming structures called nucleosomes. This organisation helps to regulate gene expression and protect the structural integrity of DNA.
nucleosomes
A structural unit of eukaryotic chromatin, consisting of DNA wrapped around a core of histone proteins.§
helicase
An enzyme that unwinds and separates the DNA double helix during DNA replication.
polymerase chain reaction (PCR)
A laboratory technique used to amplify a specific DNA sequence, producing multiple copies of it.
primers
A short DNA or RNA sequence that serves as a starting point for DNA synthesis by DNA polymerase.
taq polymerase
A heat-stable DNA polymerase commonly used in PCR reactions.
3 phases of taq polymerase
- denaturation = DNA heated + strands separate
- annealing = temp lowered so primers can bind to complementary sequences on DNA template
- extension = DNA polymerase extends the primers by synthesising new DNA strands
gel electrophoresis
A technique used to separate and analyse DNA fragments based on their size and charge using an electric field and a gel matrix.
phosphodeister bonds
The covalent bond that forms between the phosphate group of one nucleotide and the sugar of the adjacent nucleotide in a DNA or RNA strand.
replication fork
The Y-shaped structure formed during DNA replication where the DNA double helix is unwound and new strands are synthesised.
leading strand
The DNA strand that is synthesised continuously in the 5ʹ to 3ʹ direction during DNA replication.
lagging strand
The DNA strand that is synthesised discontinuously in short fragments called Okazaki fragments during DNA replication.
okazaki fragments
Short DNA fragments that are synthesised on the lagging strand during DNA replication and later joined together.
DNA primase
An enzyme that synthesises short RNA primers needed for DNA replication.
DNA Polymerase I
An enzyme involved in DNA repair that removes RNA primers and replaces them with DNA.
DNA polymerase III
The primary DNA polymerase responsible for DNA synthesis during replication in prokaryotic cells.
DNA ligase
An enzyme that catalyses the joining of DNA fragments by forming phosphodiester bonds between them.
single strand binding proteins
Proteins that bind to and stabilise single-stranded DNA during DNA replication or repair.
gyrase
An enzyme involved in DNA replication that helps relieve the tension and supercoiling generated ahead of the replication fork.
transcription
Process by which the genetic information encoded in DNA is copied into RNA.
mRNA§
Messenger RNA, a type of RNA that carries the genetic information from DNA in the nucleus to ribosomes in the cytoplasm, where it is used as a template to synthesise proteins.
translation
Process by which ribosomes use the genetic information carried by mRNA to synthesise proteins.
tRNA
A type of RNA molecule that acts as an adaptor during translation, bringing amino acids to the ribosome and aligning them in the correct order based on the mRNA sequence.
codon
A set of three adjacent nucleotides in DNA or mRNA that code for a particular amino acid.
anticodon
A sequence of three nucleotides in tRNA that is complementary to a specific codon in mRNA, allowing the tRNA to recognise and bind to the corresponding codon.
degeneracy
Refers to the redundancy in the genetic code, which allows for multiple codons to code for the same amino acid.
3 types of mutations
frameshift
- insertion
- deletion
substitution
introns
Non-coding regions or intervening sequences within a gene that are transcribed into RNA but are removed during post-transcriptional processing.
telomere
Repeated nucleotide sequences located at the ends of chromosomes that protect the genetic information from degradation and maintain chromosome stability during DNA replication.
exons
Coding regions within a gene that contain the instructions for synthesising a protein and are retained in the mature RNA molecule.
pre-mRNA
The initial RNA molecule transcribed from DNA, which contains both introns and exons.
a 5’ cap
A modified guanine nucleotide added to the 5’ end of pre-mRNA during post-transcriptional modification, providing stability and assisting in mRNA processing and transport.
poly-A tail
Multiple adenine nucleotides added to the 3´ end of a mRNA transcript to protect and stabilise the molecule.
splicing
The process of removing introns from pre-mRNA and joining the exons together to produce mature mRNA that can be translated into a protein.
3 stages of translation
- initiation = ribosome assembles and starts new chain
- elongation = adding amino acids
- termination = ribosome recognises a stop codon and releases chain
single nucleotide polymorphisms (SNPs)
Replacement of a single nucleotide with another, producing variation within a species. These are often found in non-coding regions of DNA
synonymous substitutions
A neutral mutation that does not change the amino acid sequence due to the degeneracy of the genetic code.
non-synonymous substitutions
A mutation that causes a change in the amino acid sequence.
mutagens
Agents that can cause mutations.
3 chemical mutagens
- mustard gas
- nitrous acid
- formaldehyde
3 effects of mutations
- beneficial
- harmful
- silent
genetic engineering
The process of altering the DNA of an organism in order to introduce new characteristics, remove unwanted traits or modify existing ones.
gene knockout
A technique in which a specific gene is intentionally made inoperative to study its function.
CRISPR
A specific region of DNA that is found in bacteria that contains short, repeated sequences and unique spacer sequences that are incorporated from foreign DNA encountered by the bacteria.
cas9
An endonuclease enzyme that can be used to cut DNA at specific target sites on a chromosome.
