Unit 1 KA3 Flashcards
Gene
A section of DNA that carries the code for the production of protein molecules.
Genotype
The genetic composition of a cell, which is determined by the sequence of bases.
Phenotype
The characteristics of an organism, which are determined by the proteins produced as a result of gene expression.
Phenotype can also be affected by environmental factors.
RNA
Ribonucleic acid - another type of nucleic acid.
It is single stranded, and is made of nucleotides that contain ribose sugar instead of deoxyribose, and one different base (uracil instead of thymine).
Ribose
5 carbon sugar found in RNA nucleotides (ribonucleotides).
Uracil
One of the 4 bases found in RNA (replaces thymine).
Pairs with adenine : A - U
mRNA
Messenger RNA.
Carries a copy of the DNA code for a specific protein from the nucleus to ribosomes in the cytoplasm.
The code is transcribed in the nucleus, to form mRNA.
Transcription
Synthesis of mRNA.
The base sequence of a gene is copied onto a messenger molecule known as mRNA.
Transcription happens in the nucleus.
Codon
A triplet of 3 bases on mRNA or DNA that corresponds to a specific amino acid.
tRNA
A type of RNA that collects specific amino acids which are joined on at an attachment site.
It transports the amino acids to the ribosome for translation.
Anti-codon
A triplet of bases on the tRNA molecule which lines up with the mRNA codon by complementary base pairing inside the ribosome.
This ensures that amino acids are joined together in the correct sequence.
Translation
The mRNA base sequence (which was transcribed from DNA) is converted into an amino acid sequence.
Translation happens inside ribosomes in the cytoplasm.
rRNA
Ribosomal RNA.
Combines with protein to form the structure of a ribosome.
Polypeptide
A chain of amino acids joined by peptide bonds.
Formed at the ribosome.
Only becomes a protein when folded.
RNA polymerase
The enzyme responsible for mRNA synthesis.
It unwinds and separates the DNA strand, then synthesises an mRNA strand by joining free ribonucleotides which line up along the gene by complementary base pairing.
Primary transcript
A piece of mRNA which is an exact complementary copy of the DNA base sequence in the gene.
It includes introns.
RNA splicing
Introns are removed from the primary transcript and exons are spliced together to create the mature transcript of mRNA.
This is the version that is translated.
Mature transcript
The piece of mRNA formed by RNA splicing.
It contains exons spliced together.
Introns
Non-coding sections of a gene.
They need to be removed during RNA splicing.
Exons
The coding regions of genes.
They are spliced together to form the mature transcript of mRNA
Promoter region
The section of a gene where transcription begins.
Transcription is controlled by transcription factors.
Alternative mRNA splicing
Different mature transcripts can be made from the same primary transcript, by splicing different exons together.
This produces different proteins.
Protein
Many amino acids join together to form a polypeptide chain, which is then coiled and folded to form a protein.
There are 20 different types of amino acid, resulting in a huge variety of proteins.
The sequence of amino acids is known as the primary structure
Structural proteins
These are made of alpha helices (spirals), arranged in parallel and bonded together with hydrogen bonds to form strong fibres for building cell structures.
Examples include collagen and keratin.
Globular proteins
The alpha helices (spirals) are folded into 3D shapes, maintained by hydrogen and other bonds.
Examples of globular proteins are enzymes, receptors and antibodies.
Their function depends on their precise shape, as they are able to bind to specific molecules.
