Bio HL Unit 4

DNA polymerase

An enzyme responsible for synthesising DNA molecules during DNA replication

purine

nitrogenous DNA bases consisting of two rings of atoms; adenine and guanine

pyrimidine

nitrogenous DNA bases consisting of one ring of atoms; cytosine and thymine (and uracil in RNA)

nucleosome

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

linker DNA

A section of variable length of DNA between nucleosomes

chromatin

The complex of DNA and proteins that make up chromosomes in their relaxed form in eukaryotic cells

Hershey-Chase experiment

A crucial experiment in determining that DNA was the genetic material of inheritance

Chargaff's data

A crucial experiment that determined the relative amounts of pyrimidine and purine bases indicating complementary base pairing, and these ratios varied between species

directionality (of DNA)

The orientation or polarity of a DNA strand, referring to the 5ʹ (phosphate) to 3ʹ (hydroxyl) directionality of nucleotide addition during DNA synthesis

phosphodiester 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 III

The primary DNA polymerase responsible for DNA synthesis during replication in prokaryotic cells as well as proofreading the newly synthesised strand

DNA polymerase I

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

DNA ligase

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

promoter

A non-coding region of DNA to which RNA polymerase binds to initiate transcription

transcription factors

A group of proteins that impact gene expression

non-coding

Areas of the genome that do not encode proteins

introns

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

exons

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

telomeres

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

post-transcriptional modification

Changes to mRNA after transcription, including removal of pieces of the mRNA and other modifications that are necessary for a working protein to be produced

post-translational modification

The process of modifying a protein after it has been synthesised, which may involve the addition of chemical groups, such as phosphates or sugars, or cleavage of specific peptide bonds

pre-mRNA

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

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

alternative splicing

A mechanism by which different combinations of exons within a gene can be spliced together to generate multiple mRNA isoforms and increase protein diversity

termination

The final stage of translation, where the ribosome recognises a stop codon on the mRNA and releases the newly synthesised polypeptide chain

pre-proinsulin

The initial form of insulin synthesised in pancreatic cells, consisting of a signal peptide, proinsulin, and additional amino acid sequences

proinsulin

The intermediate form of insulin that is processed from preproinsulin by removing the signal peptide, and later converted into mature insulin by further enzymatic cleavage

proteasome

Protein complexes that degrade and recycle damaged or unwanted proteins

gene knockout

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

genetic engineering

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

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

(single) guide RNAs (sgRNA)

A synthetic RNA molecule that is used in the CRISPR-Cas9 gene editing system

conserved sequences

Sequences that remain identical or similar across a species or group of species over evolutionary time

highly conserved sequences

Regions of DNA or RNA that exhibit an exceptionally high level of similarity across different species

proliferation

increase in the number of cells as a result of cell growth and cell division

meristem

Regions of undifferentiated cells at the tips of roots and shoots, in plants, that have the potential to become any cell type in the plant

epithelium

A thin tissue layer that covers the surfaces of organs, body cavities and the skin, providing protection and serving as a barrier

cell cycle

The sequence of events that a cell undergoes, including growth, DNA replication, nuclear and cytoplasmic division

interphase

The phase of the cell cycle where a cell grows, carries out its normal functions, and prepares for cell division

Gap 1 (G1)

The first stage of interphase, involves cell growth and normal metabolic functions

Synthesis (S)

The second stage of interphase in which DNA replication occurs

Gap 2 (G2)

The third stage of interphase, involving cell growth and preparation for nuclear division

cyclins

A family of proteins that regulate the cell cycle by activating cyclin-dependent kinases

cyclin-dependent kinases (CDKs)

A group of enzymes that are activated by cyclins and act to phosphorylate specific proteins to drive the cell cycle forward

proto-oncogene

Genes that code for proteins that help promote cell growth and division

tumour suppressor genes

Genes that code for proteins that normally slow down or prevent cell division

tumour

An abnormal mass or growth of cells

benign

A non-cancerous tumour that does not invade nearby tissues or spread to other parts of the body

malignant

A cancerous tumour that is capable of invading nearby tissues and spreading to other parts of the body

metastasis

The spread of cancer cells from the original site of the tumour to other parts of the body, forming secondary tumours

primary tumour

The original site where abnormal cell growth occurs before cancer cells spread to other parts of the body

secondary tumour

A tumour formed by the spread of cancer cells from a primary tumour to other parts of the body

mitotic index

A measure of the proportion of actively dividing cells in a population

phenotypic plasticity

The ability of an organism to exhibit variations in its physical characteristics or traits in response to environmental influences

genotype

The specific set of DNA that an organism possesses

enhancer

A non-coding region of DNA to which activator proteins bind, facilitating the binding of RNA polymerase to a promoter

activator proteins

Specific types of regulatory proteins that bind enhancers to activating the transcription of nearby genes

operon

A group of genes that share a promoter

repressor proteins

Transcription factors that can block the binding of RNA polymerase or other transcription factors to a promoter, downregulating gene expression

nucleases

Enzymes that break down nucleic acids such as DNA and mRNA

epigenesis

The process by which cells and organisms differentiate through the interaction between DNA and environmental factors

epigenetic

Heritable changes in gene expression or cell characteristics that do not involve changes to the underlying DNA sequence

DNA methylation

Addition of a methyl group to DNA

transcriptomes

Entire set of mRNA transcripts within a cell or organism

heterochromatin

The highly condensed and transcriptionally inactive form of chromatin

euchromatin

The less condensed and transcriptionally active form of chromatin

acetylation

The addition of an acetyl group to a molecule

germline

The cells that give rise to sperm and egg cells

monozygotic twins

Twins produced from a single fertilised egg

dizygotic twins

Twins who develop from two different, separate eggs, which are each fertilised by a different sperm

inflammation

The body's immune response to infection, injury, or irritants, characterised by redness, swelling, pain and heat

oxidative stress

A condition whereby there are too many unstable free molecules that can cause cellular damage

imprinted genes

Genes that retain their epigenetic tags

oestradiol

A steroid hormone, a form of oestrogen, responsible for a range of reproductive and physiological processes

tryptophan

tryptophan operon is a cluster of five genes found in bacterial DNA that are necessary for the synthesis of the amino acid

lac operon

A cluster of three genes found in bacterial DNA that code for proteins involved in the digestion of lactose, a disaccharide found in milk