D1 Continuity and Change : Molecules

Question 1

histones

Answer 1

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.

Question 2

nucleosomes

Answer 2

A structural unit of eukaryotic chromatin, consisting of DNA wrapped around a core of histone proteins.§

Question 3

helicase

Answer 3

An enzyme that unwinds and separates the DNA double helix during DNA replication.

Question 4

polymerase chain reaction (PCR)

Answer 4

A laboratory technique used to amplify a specific DNA sequence, producing multiple copies of it.

Question 5

primers

Answer 5

A short DNA or RNA sequence that serves as a starting point for DNA synthesis by DNA polymerase.

Question 6

taq polymerase

Answer 6

A heat-stable DNA polymerase commonly used in PCR reactions.

Question 7

3 phases of taq polymerase

Answer 7

• 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

Question 8

gel electrophoresis

Answer 8

A technique used to separate and analyse DNA fragments based on their size and charge using an electric field and a gel matrix.

Question 9

phosphodeister bonds

Answer 9

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.

Question 10

replication fork

Answer 10

The Y-shaped structure formed during DNA replication where the DNA double helix is unwound and new strands are synthesised.

Question 11

leading strand

Answer 11

The DNA strand that is synthesised continuously in the 5ʹ to 3ʹ direction during DNA replication.

Question 12

lagging strand

Answer 12

The DNA strand that is synthesised discontinuously in short fragments called Okazaki fragments during DNA replication.

Question 13

okazaki fragments

Answer 13

Short DNA fragments that are synthesised on the lagging strand during DNA replication and later joined together.

Question 14

DNA primase

Answer 14

An enzyme that synthesises short RNA primers needed for DNA replication.

Question 15

DNA Polymerase I

Answer 15

An enzyme involved in DNA repair that removes RNA primers and replaces them with DNA.

Question 16

DNA polymerase III

Answer 16

The primary DNA polymerase responsible for DNA synthesis during replication in prokaryotic cells.

Question 17

DNA ligase

Answer 17

An enzyme that catalyses the joining of DNA fragments by forming phosphodiester bonds between them.

Question 18

single strand binding proteins

Answer 18

Proteins that bind to and stabilise single-stranded DNA during DNA replication or repair.

Question 19

gyrase

Answer 19

An enzyme involved in DNA replication that helps relieve the tension and supercoiling generated ahead of the replication fork.

Question 20

transcription

Answer 20

Process by which the genetic information encoded in DNA is copied into RNA.

Question 21

mRNA§

Answer 21

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.

Question 22

translation

Answer 22

Process by which ribosomes use the genetic information carried by mRNA to synthesise proteins.

Question 23

tRNA

Answer 23

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.

Question 24

codon

Answer 24

A set of three adjacent nucleotides in DNA or mRNA that code for a particular amino acid.

Question 25

anticodon

Answer 25

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.

Question 26

degeneracy

Answer 26

Refers to the redundancy in the genetic code, which allows for multiple codons to code for the same amino acid.

Question 27

3 types of mutations

Answer 27

frameshift - insertion - deletion substitution

Question 28

introns

Answer 28

Non-coding regions or intervening sequences within a gene that are transcribed into RNA but are removed during post-transcriptional processing.

Question 29

telomere

Answer 29

Repeated nucleotide sequences located at the ends of chromosomes that protect the genetic information from degradation and maintain chromosome stability during DNA replication.

Question 30

exons

Answer 30

Coding regions within a gene that contain the instructions for synthesising a protein and are retained in the mature RNA molecule.

Question 31

pre-mRNA

Answer 31

The initial RNA molecule transcribed from DNA, which contains both introns and exons.

Question 32

a 5' cap

Answer 32

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.

Question 33

poly-A tail

Answer 33

Multiple adenine nucleotides added to the 3´ end of a mRNA transcript to protect and stabilise the molecule.

Question 34

splicing

Answer 34

The process of removing introns from pre-mRNA and joining the exons together to produce mature mRNA that can be translated into a protein.

Question 35

3 stages of translation

Answer 35

- initiation = ribosome assembles and starts new chain - elongation = adding amino acids - termination = ribosome recognises a stop codon and releases chain

Question 36

single nucleotide polymorphisms (SNPs)

Answer 36

Replacement of a single nucleotide with another, producing variation within a species. These are often found in non-coding regions of DNA

Question 37

synonymous substitutions

Answer 37

A neutral mutation that does not change the amino acid sequence due to the degeneracy of the genetic code.

Question 38

non-synonymous substitutions

Answer 38

A mutation that causes a change in the amino acid sequence.

Question 39

mutagens

Answer 39

Agents that can cause mutations.

Question 40

3 chemical mutagens

Answer 40

- mustard gas - nitrous acid - formaldehyde

Question 41

3 effects of mutations

Answer 41

- beneficial - harmful - silent

Question 42

genetic engineering

Answer 42

The process of altering the DNA of an organism in order to introduce new characteristics, remove unwanted traits or modify existing ones.

Question 43

gene knockout

Answer 43

A technique in which a specific gene is intentionally made inoperative to study its function.

Question 44

CRISPR

Answer 44

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.

Question 45

cas9

Answer 45

An endonuclease enzyme that can be used to cut DNA at specific target sites on a chromosome.