Grade 12 Biology: Molecular Genetics, Gene Expression, and Development

A complete set of vocabulary flashcards covering the grade 12 biology concepts from the notes, including nucleic acid structure, replication, transcription, translation, prokaryotic and eukaryotic gene regulation, and cellular development.

DNA

The molecule that stores genetic information.

RNA

A molecule that helps use genetic information to make proteins.

Nucleotide

The basic building block of DNA and RNA.

Three parts of a nucleotide

A phosphate group, a pentose sugar, and a nitrogenous base.

Nitrogenous bases in DNA

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

Nitrogenous bases in RNA

Adenine (A), Uracil (U), Cytosine (C), and Guanine (G).

Complementary base pairing

A pairs with T in DNA, and C pairs with G.

Hydrogen bonds in DNA

A–T forms 2 hydrogen bonds; G–C forms 3.

Deoxyribose

The five-carbon sugar found in DNA.

Ribose

The five-carbon sugar found in RNA.

Nuclear DNA

DNA found inside the nucleus, organized into linear chromosomes.

Mitochondrial DNA

DNA found inside mitochondria.

Chloroplast DNA

DNA found inside chloroplasts in plant cells.

Plasmid DNA

Small, usually circular DNA found outside the main chromosome, especially in bacteria.

Prokaryotic DNA

Usually circular DNA located in the nucleoid region, which is not surrounded by a membrane.

Eukaryotic DNA

Linear nuclear DNA organized into chromosomes and associated with histone proteins.

Endosymbiotic theory

The theory that mitochondria and chloroplasts evolved from ancient bacteria.

DNA replication

The process of copying DNA to produce two DNA molecules.

Semiconservative replication

Each new DNA molecule contains one original strand and one new strand.

Helicase

The enzyme that separates the two DNA strands.

DNA polymerase

The enzyme that builds new DNA strands by adding complementary nucleotides.

DNA ligase

The enzyme that joins DNA fragments together.

Template strand

The original DNA strand used to guide the formation of a new complementary strand.

Purpose of DNA replication

To copy genetic information before cell division.

Gene expression

The process of using information in a gene to produce a functional product.

Central dogma

The usual flow of genetic information: DNA → RNA → Protein.

Transcription

The process of making RNA from a DNA template.

RNA polymerase

The enzyme that makes RNA during transcription.

Promoter

A DNA sequence where RNA polymerase binds to begin transcription.

mRNA (messenger RNA)

Carries genetic instructions from DNA to the ribosome.

RNA processing

Changes made to eukaryotic RNA before it becomes mature mRNA.

5′ cap

A protective structure added to the beginning of eukaryotic mRNA.

Poly-A tail

A series of adenine nucleotides added to the end of eukaryotic mRNA.

RNA splicing

The removal of introns and joining of exons.

Introns

RNA sequences removed during splicing.

Exons

RNA sequences retained and joined together in mature mRNA.

Translation

The process of using mRNA instructions to assemble a chain of amino acids.

Ribosome

The structure where translation occurs and amino acids are joined together.

tRNA (transfer RNA)

Carries specific amino acids to the ribosome.

rRNA (ribosomal RNA)

Forms part of the ribosome and helps catalyze peptide-bond formation.

Codon

A sequence of three mRNA nucleotides that specifies an amino acid or stop signal.

Anticodon

A sequence of three tRNA nucleotides that pairs with an mRNA codon.

Start codon

AUG; the usual signal to begin translation.

Stop codons

UAA, UAG, and UGA; signal the end of translation.

Amino acids

The building blocks of proteins.

Peptide bond

The bond that joins amino acids together.

Polypeptide

A chain of amino acids that can fold to form part or all of a protein.

Protein synthesis

The process of making proteins through transcription and translation.

Replication vs. transcription

Replication copies DNA; transcription makes RNA from DNA.

Transcription vs. translation

Transcription makes RNA; translation uses mRNA to make a polypeptide.

Gene regulation

The control of when and how much a gene is expressed.

Operon in E. coli

A group of related bacterial genes controlled together as one unit.

Promoter in an operon

The DNA region where RNA polymerase binds to begin transcription.

Operator

A DNA control sequence where a repressor can bind.

Structural genes

Genes that encode proteins needed for a particular function.

Repressor

A protein that blocks or reduces transcription by binding to a regulatory DNA sequence.

Inducible operon

An operon that is normally OFF but can be switched ON by an inducer.

Repressible operon

An operon that is normally ON but can be switched OFF.

Inducer

A molecule that inactivates a repressor, allowing transcription.

Corepressor

A molecule that binds to and activates a repressor, allowing it to block transcription.

lac operon

An inducible operon in E. coli that contains genes needed for lactose use.

Allolactose

A molecule derived from lactose that inactivates the lac repressor.

lac operon when lactose is absent

The active repressor binds the operator, blocking transcription.

lac operon when lactose is present

Allolactose inactivates the repressor, allowing transcription.

trp operon

A repressible operon in E. coli that contains genes needed to synthesize tryptophan.

trp operon when tryptophan is low

The repressor remains inactive, allowing transcription.

trp operon when tryptophan is high

Tryptophan activates the repressor, which blocks transcription.

Negative feedback in the trp operon

Tryptophan inhibits the process that produces more tryptophan when enough is available.

Chromatin

DNA packaged with proteins, including histones.

Histone acetylation

A modification that generally loosens chromatin and promotes transcription.

DNA methylation

The addition of methyl groups to DNA; it often reduces gene expression.

Histone methylation

The addition of methyl groups to histones; its effect depends on the modification site.

Heterochromatin

A tightly packed form of chromatin that is generally less transcriptionally active.

Transcription factors

Proteins that help regulate transcription.

Activators

Proteins that increase gene expression.

Repressors in eukaryotes

Proteins that reduce or silence gene expression.

Post-transcriptional control

Regulation of gene expression after RNA has been produced.

Alternative splicing

Joining different combinations of exons to produce different mRNAs from one gene.

MicroRNAs (miRNAs)

Small RNA molecules that can degrade mRNA or block its translation.

Cell differentiation

The process by which cells become specialized for particular functions.

Cell specialization

The development of structures and functions suited to a cell's role.

Cytoplasmic determinants

Unevenly distributed molecules in an egg that influence early development.

Cell signaling

Communication between cells that helps coordinate their activities and development.

Homeotic genes

Genes that help determine the identity and organization of body structures.

Apoptosis

Programmed cell death that removes unnecessary cells and helps shape tissues.

Why cells with the same DNA have different functions

They express different sets of genes.