Molecular Biology and Hereditary Principles

Molecular Biology

The study of the molecules of biology, including understanding biological systems, molecular biology techniques for diagnosis, and research.

Molecule of Hereditary

what characteristics make something a living organism and which molecules produce these characteristics

GENE

a specific functional segment of DNA that codes for specific proteins or RNA

Genome

The entire genetic makeup of an organism.

Locus

The specific point on a chromosome where a gene is located.

Nucleotide

A molecular subunit consisting of a base, a sugar, and a phosphate group.

Phosphodiester bonds

Bonds that join nucleotides together to form single-stranded DNA ($ssDNA$) with a sugar phosphate backbone.

Complementary base pairing (DNA)

Adenine pairs with Thymine via $2$ hydrogen bonds, and Guanine pairs with Cytosine via $3$ hydrogen bonds.

Semiconservative replication

A model of DNA replication where the resulting double-stranded DNA contains one original template strand and one newly synthesized strand.

DNA Polymerase

An enzyme often referred to as a "photocopier" that adds $dNTPs$ (e.g., $dATP$, $dCTP$, $dGTP$, $dTTP$) to the $3'$ end of a growing strand.

Introns

Non-coding sections of a gene that are spliced out and not expressed in the final protein.

Exons

The portions of a gene that are expressed and kept in the processed mRNA.

PolyA tail

A string of A's added to the tail end of eukaryotic mRNA before it is exported for translation.

Alternate splicing

A process where mRNA is processed differently to produce more than one type of protein from a single gene.

Triplet codon

A set of $3$ bases read by the ribosome; there are $61$ codons specifying $20$ amino acids and $3$ stop codons.

Release factor

A protein complementary to stop codons that triggers the release of the polypeptide chain during translation.

Restriction Enzyme

Often called "molecular scissors," these are tools used by genetic engineers to cut DNA.

DNA Ligase

Often called "molecular glue," this enzyme is used to join DNA fragments together.

Denaturation (PCR Step 1)

Occurs at $95^{\circ}\text{C}$; the double strand of DNA is broken into two single strands as hydrogen bonds are broken.

Annealing (PCR Step 2)

Occurs at $50-75^{\circ}\text{C}$; complementary mini strands (primers) join to the template as hydrogen bonds form.

Extension (PCR Step 3)

Occurs at $72^{\circ}\text{C}$; bases are added onto the $3'$ end after the primer using Taq polymerase.

VNTRs (Variable Number Tandem Repeats)

Scattered randomly throughout the genome, these are $2-3$ base pair repeats (e.g., $(AC)_n$ where $n = 20-200$) used in DNA profiling.

Recombinant DNA

DNA created by combining genetic material from more than one organism.

Why are cloning factors needed during recombinant DNA?

To act as carriers, foreign DNA is lost quickly as cells are not cultured

Plasmids

Small, double-stranded circles of DNA that replicate autonomously and are used as cloning vectors.

Why are expression factors needed during recombinant DNA

to control ‘turning on’ gene

cDNA (complementary DNA)

DNA synthesized from human mRNA (with introns already removed), used when putting eukaryotic DNA into prokaryotes to ensure correct translation.

Agarose

A linear polysaccharide used in electrophoresis gels to separate larger molecules.

Polyacrylamide

a gel used in electrophoresis for smaller molecules or proteins

Use of electrophoresis

analyse and purify proteins, DNA or RNA. Separation based on size, charge or both via migration of electric field

IsoElectric Focussing (IEF)

A technique that separates proteins in a pH gradient until they reach their $pI$ (isoelectric point) where the net charge is zero.

Zwitterions

Dipolar ions that predominate at $pH\ 7$.