Genes Flashcards
Heterochromatin
DNA tightly packaged & genes not expressed
Euchromatin
DNA loosely packaged & genes expressed
Gene
Sequence of nucleotides which determines the order of monomers in a polypeptide or nucleic acid molecule which a cell (or virus) may synthesise
Genome
The entire DNA sequence (human genome is 24 chromosomes)
Promoter
region of DNA that initiates transcription of a particular gene
Transcription reading & synthesis
- DNA read 3’ to 5’
- mRNA synthesis 5’ to 3’
Translation reading & synthesis
- mRNA read 5’ to 3’
- Polypeptide synthesis N to C
Mutation
A heritable alteration in a gene or chromosome and the process that produces the alteration
Small scale DNA changes
- Base substitutions
- Base additions & deletions
Large scale DNA changes
- Chromosome rearrangements
- Transposable element insertions
Transition base substitution
Change to same type of base
Transversion base substitution
Change to different type of base
Phenotype
The form (trait) that you will see
Genotype
The genetic make up
Mutation causing sickle cell anaemia
Base substitution mutation (missense)
Glu6 -> Val
How mutations change the amount of gene product
- Alter promoter activity
- Alter translation initiation at AUG
- Prevent mRNA splicing
- Reduce mRNA stability
How mutations change the polypeptide length
Deletion & additions
- Change ‘sense’ codon into stopcodon (nonsense mutation)
- Deletion of stopcodon
Mutations that cause large scale changes (chromosome rearrangement)
- Insertion
- Deletion
- Inversion
- Translocation
Mutations that cause large scale changes (transposable element insertions)
- Movement of discrete DNA elements
- Gene inactivity by insertion
Transposable elements
Sequences of DNA that move from one location in the genome to another
