2.8-2.14 : nucleotides and nucleic acids unit 1

anti sense strand

the strand of DNA which is used as a complementary template and is used for complementary mRNA synthesis

anticodon

a sequence of three nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon

coding DNA

the sections of DNA which code for proteins

codon

a nucleotide base tripled on messenger RNA that encodes a single amino acid

complementary base pairing

describes how hydrogen bonds form between complementary purine and pyrimidine bases, two bonds form between A and T in DNA or U in RNA, three bonds form between G and C

degenerate (genetic code)

a feature of the genetic code; more than one triplet can code for a particular amino acid

deletion mutation

a type of mutation where nucleotide(s) are not incorporated into the chain and are lost which results in a frameshift mutation

deoxyribonucleic acid (DNA)

a double stranded polynucleotide that contains the genetic material of an organism and is made up of deoxyribonucleotide monomers joined together by phosphodiester bonds

deoxyribose

a modified sugar, lacking one oxygen atom

DNA nucleotide

the monomer that makes up DNA and consists of a deoxyribose, a nitrogenous base and a phosphate group

DNA polymerase

an enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new DNA strand

gene mutation

a change to a least one nucleotide base in DNA or the arrangement of bases, gene mutations occur spontaneously and may result in a harmful or beneficial changes to the genotype

gene

a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain

genetic code

the rules by which triplets in a DNA base sequence code for the sequence of amino acids in a polypeptide chain, the genetic code is degenerate, universal and non-overlapping

helicase

an enzyme that catalyses the unwinding and unzipping of DNA in many processes like replication and transcription

hydrogen bond

a type of intermolecular bond between a partial positive charge hydrogen and a partial negative charge atom such as oxygen or nitrogen which is used to hold together the secondary, tertiary and quaternary structures of proteins

insertion mutation

a type of mutation where extra nucleotide(s) are incorporated into the growing DNA chain which results in a frameshift mutation

messenger RNA (mRNA)

a type of RNA carries genetic information from the DNA in the nucleus to the ribosomes for translation

mononucleotide

a nucleotide consisting of one molecule each of a phosphoric acid, a sugar, and either a purine or a pyrimidine base

mononucleotide

a nucleotide consisting of one molecule each of a phosphoric acid, a sugar, and either a purine or a pyrimidine base

non-overlapping (genetic code)

a feature of the genetic code; each base in a sequence is read once and is only part of one triplet

nucleotides

the individual monomers that make up polynucleotides which are composed of a phosphate group, pentose sugar and a nitrogenous base

phosphate

a group of molecules composed of one phosphate atom bound to multiple oxygen atoms

phosphodiester bond

a type of bond that joins nucleotides together to create polynucleotides

polynucleotide

a biopolymer composed of 13 or more nucleotide monomers covalently bonded in a chain

purines

a class of nitrogenous bases which are made up of two rings that adenine and guanine are members of

ribose

a ‘normal’ sugar, with one oxygen atom attached to each carbon atom

ribosomal RNA (rRNA)

a type of RNA that makes up ribosomes

RNA polymerase

an enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new RNA strand

semi conservative replication

the replication of DNA to produce two new DNA molecules which both contain one new strand and one old strand from the original DNA molecule

sickle cell amaemia

a disease characterised by hook shaped red blood cells, a missense point mutation of GAG to GTG in the HbA (normal) allele for the beta-globin polypeptide results in the HbS (sickle cell) allele of the gene

start codon

a genetic codon in messenger RNA that stimulates the binding of a transfer RNA which starts protein synthesis

stop codon

a genetic codon in messenger RNA that signals the termination of protein synthesis during translation

substitution mutation

a type of mutation where the incorrect nucleotide is incorporated into the growing DNA chain

thymine

a pyrimidine nucleobase, which pairs with adenine (A), a purine nucleobase

transcription

the process of synthesising a new mRNA strand from a molecule of DNA

transfer RNA (tRNA)

a type of RNA that has three hairpin loops, an anticodon for attachment to the mRNA codon and an amino acid binding site and is used to carry amino acids to the ribosome

translation

the process of protein synthesis where complementary rRNAs carrying amino acids are brought to each codon in an mRNA molecule as it moves through a ribosome

triplet (genetic code)

a specific sequence of three nucleotides on a molecule of DNA or RNA codes for a particular amino acid in protein synthesis

universal (genetic code)

a term used to describe the fact that the same codons code for the same amino acids in all organisms