Grade 12 Biology- Molecular Genetics

DNA

The hereditary material that carries genetic information.

Genetic Mutation

A change in the DNA sequence that can lead to variations in organisms.

Transcription

The process of copying a segment of DNA into RNA.

Translation

The process of synthesizing proteins from mRNA.

Template Strand

The DNA strand that is read by RNA polymerase during transcription.

Adenine

A nitrogenous base that pairs with thymine in DNA.

Thymine

A nitrogenous base that pairs with adenine in DNA.

Guanine

A nitrogenous base that pairs with cytosine in DNA.

Cytosine

A nitrogenous base that pairs with guanine in DNA.

Double Helix

The structure of DNA, consisting of two intertwined strands.

Phosphodiester Bond

The bond linking nucleotides in a DNA strand.

Nucleotide

The building block of DNA, composed of a sugar, phosphate, and a nitrogenous base.

Replication Fork

The Y-shaped region where DNA strands are separated during replication.

Semi-Conservative Replication

The replication model where each daughter DNA molecule contains one parental DNA strand.

RNA Polymerase

An enzyme that synthesizes RNA from a DNA template.

Operon

A group of genes regulated as a unit, controlling gene expression in prokaryotes.

Lac Operon

An operon that regulates the metabolism of lactose in bacteria.

Transcription Initiation Site

The specific location on the DNA where RNA polymerase begins transcription.

Elongation

The phase in transcription where RNA is synthesized from the DNA template.

Termination

The end of transcription, marked by RNA polymerase reaching a stop signal.

Alternative Splicing

The process of producing different mRNA variants from the same gene.

Post-Transcriptional Modification

Changes to mRNA after transcription, such as the addition of a 5' cap and a poly-A tail.

Ribosome

The cellular structure where protein synthesis occurs.

Codon

A sequence of three nucleotides on mRNA that codes for an amino acid.

Polysome

A complex of multiple ribosomes translating the same mRNA molecule.

E site

The exit site on a ribosome where discharged tRNAs leave.

P site

The peptidyl site on a ribosome where the growing polypeptide chain is held.

A site

The aminoacyl site on a ribosome where new tRNA molecules bind.

Hayflick Limit

The number of times a normal somatic human cell can divide before cell division stops.

Telomeres

Repeating sequences at the ends of chromosomes that protect them from degradation.

Central Dogma of Molecular Genetics

The framework describing the flow of genetic information from DNA to RNA to protein.

Enzyme helicase

The enzyme that unwinds the DNA double helix during replication.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand during replication.

Proofreading

The process by which DNA polymerase checks and corrects errors during DNA replication.

Exonucleases

Enzymes that remove damaged sections of DNA for repair.

Frederick Meischer

The scientist who first isolated nuclein from white blood cells.