Nucleic Acid

Nucleic acid

Large biological polymer essential to life and composed of nucleotide monomers. Function is Storage and transfer of genetic information and, in the case of ATP, cellular energy transfer. Two main nucleic acids are DNA and RNA.

Nucleotide

Monomer consisting of a five-carbon sugar, phosphate group and nitrogenous base.

DNA

Deoxyribonucleic acid; biomolecule containing biological instructions needed for development, survival and reproduction. Found in nucleus and mitochondria in eukaryotes. Found in nucleoid and plasmids in prokaryotes.

DNA nitrogenous bases

Adenine (A), thymine(T), guanine(G) and cytosine(C).

Genome

The complete genetic information/base sequence of an organism.

Deoxyribose

Five-carbon sugar lacking an oxygen on its 2′ carbon. DNA nucleotide sugar.

DNA phosphate group

Negatively charged component forming part of the sugar-phosphate backbone and allowing nucleotides to link together.

Nitrogenous base

Nitrogen-containing organic component of a nucleotide involved in complementary base pairing.

Purine

Large double-ring nitrogenous base. Adenine and guanine.

Pyrimidine

Smaller single-ring nitrogenous base. Cytosine and thymine.

DNA double helix

Two DNA strands wound around one another in a helical structure.

Sugar-phosphate backbone

Alternating sugar and phosphate components forming the outside of each DNA strand.

Complementary base pairing

Specific pairing in which adenine binds thymine and cytosine binds guanine.

A–T bonding

Adenine and thymine are held together by two hydrogen bonds.

C–G bonding

Cytosine and guanine are held together by three hydrogen bonds.

Complementary DNA strands

Knowledge of the sequence of one DNA strand allows the sequence of the other to be determined.

RNA

Ribonucleic acid; nucleic acid involved in using the biological information encoded in DNA to produce proteins. Three major RNA types

mRNA

Messenger RNA carrying genetic information used to determine a protein's amino-acid sequence.

rRNA

Ribosomal RNA; structural and catalytic component of ribosomes.

tRNA

Transfer RNA that brings the appropriate amino acids to the ribosome during translation.

RNA sugar

Ribose.

Uracil

Nitrogenous base used in RNA instead of thymine.

DNA vs RNA strand number

DNA is normally double-stranded; RNA is normally single-stranded.

DNA replication

Production of two identical copies of DNA from one original DNA molecule. Allows cells to proliferate and organisms to reproduce. Requires enzymes, energy in the form of ATP and free nucleotides. Occurs during interphase of the cell cycle.

Template strand

Existing DNA strand used to guide construction of a complementary new strand.

Basis of accurate DNA replication

Complementary base pairing between A–T and C–G.

Helicase

Enzyme involved in separating DNA strands.

DNA polymerase

Enzyme involved in producing new DNA strands.

Chromosomes and reproduction

Chromosome

DNA-containing structure carrying genetic information.

Gamete

Reproductive cell containing one copy of each chromosome.

Haploid cell (n)

Cell containing one copy of each chromosome.

Fertilisation

Fusion of the nuclei of two gametes.

Zygote

Cell formed following fertilisation and containing genetic information from both parents.

Protein synthesis

Production of proteins using genetic information encoded in DNA.

Codon

Sequence of three nucleotides that specifies a particular amino acid or signal.

Genetic code

Rules linking nucleotide codons to amino acids.

Number of possible codons

64.

Amino-acid coding codons

61 codons encode amino acids.

Stop codons

Three codons signal termination rather than specifying an amino acid.

Degeneracy of the genetic code

Some amino acids are specified by more than one codon.

Specificity of a codon

Each individual codon corresponds to only one amino acid or stop signal.

Universality of the genetic code

The genetic code is broadly shared across living organisms.

Transcription

Process in which a DNA gene sequence is copied to produce an RNA molecule. Occurs in nucleus for eukaryotes, occurs in cytoplasm for prokaryotes.

RNA polymerase

Enzyme that moves along DNA and creates a complementary RNA strand.

Product of transcription for protein synthesis

mRNA.

Translation

Process in which the nucleotide sequence of mRNA is converted into an amino-acid sequence. Site of translation

Role of the ribosome in translation

Binds mRNA and assembles amino acids into a protein.

Role of tRNA in translation

Delivers the appropriate amino acid according to the genetic sequence.

Relationship between gene and protein

The DNA sequence of a gene determines the amino-acid sequence of the protein it encodes.

DNA profiling

Technique in which DNA is cut into fragments and separated to produce a characteristic pattern of bands.

Gel electrophoresis principle

An electric field causes DNA fragments to move through a gel, producing bands based on how far they travel.

ATP

Adenosine triphosphate; a single nucleotide functioning as the cell's major energy currency. Stores energy obtained from cellular processes and transfers that energy to processes that require it. Made up of adenine + ribose + three phosphate groups.

Why ATP is high energy

The terminal phosphate interactions are unstable and can be broken to release usable energy.