Gene expression

change in the quantity or structure of DNA in an organism

change or rearrangement of nucleotide bases in DNA

-Different amino acid results in different tertiary structure -This means that the shape of the protein changes due to the different bonds forming -This change in shape will affect the functionality of the protein, especially if an enzyme (active site no longer complementary to substrate)

-The change in base may result in the same amino acid being produced -Due to the degenerate code -Tertiary structure of the protein will not change

-Reading frame for the codons has been shifted by one base. -The wrong 3 bases are now read as a triplet -Codes for a different amino acid from that point forward -Tertiary structure of protein different and protein likely to be dysfunctional -Mutation near the start of the base sequence results in a more drastically altered protein

-Arise spontaneously during DNA replication -High energy ionising radiation -Chemicals

Substitution: one nucleotide is replaced by another with different base

-formation of one the three stop codons that marks of the end of a polypeptide. The production of the polypeptide coded for is stopped prematurely and the protein would be different and not function normally -The formation of a codon for a different amino acid meaning that the structure of the polypeptide would be different -The formation of a different codon but one that produces a codon for the same amino acid as before

-Natural mutation rate (spontaneous mutation) is 1 mutation per 100 000 genes per generation. Mutagenic agents increase this rate: -High energy ionising radiation: eg alpha and beta radiation, x rays, UV light. -Chemicals: eg nitrogen dioxide alters DNA structure of interferes with transcription

loss of a nucleotide base from the DNA sequence, causes a frameshift

causes a frameshift. All bases following the substitution shifted to the left causing remaining to codons to be different and potentially code for different amino acids

addition of a nucleotide base in a sequence, causes a frameshift

causes a frameshift. All bases following the substitution shifted to the right causing remaining to codons to be different and potentially code for different amino acids

one or more bases repeated, causes a frame shift

causes a frameshift. All bases following the substitution shifted to the right causing remaining to codons to be different and potentially code for different amino acids

sequence of bases separated from the DNA sequence and then reattach in the same place but the opposite order

amino acid sequence in the area of inversion affected

group of bases separated from the DNA sequence on one chromosome and inserted into the DNA sequence on a different chromosome

process by which cells develop into specicalised cells. No one cell can provide the best conditions for all functions. More efficient if they are adapted to their function

the only cell that can differentiate and divide into identical copies through a process of self renewal

Totipotent cells can develop into any types of cell, eg fertilised egg

Certain parts of the DNA are selectively translated so that only some genes are switched on in order to differentiate the cell into a specific type and form the tissues that make up the foetus

During specialisation only some genes are expressed so the cell only makes the proteins it needs to carry out its specialised function. A variety of stimuli ensure that the genes that are not needed stay switched off.

-preventing transcription and so preventing the production of mRNA -prevening translation