Genetics Flashcards
What is the central dogma of molecular biology
The flow of genetic information from DNA to RNA to proteins
Describe the structure of a gene
Polymer molecule made up of a string of deoxyribonucleic acids, the sequence contains information to generate a new organism.
DNA is always read from 5’ to 3’ and DNA has a antiparallel double helix structure
describe the process of transcription
mRNA is catalysed by RNA polymerases.
Initiation: RNA polymerase II binds to the strat of a gene, DNA strands separate
Elongation: RNA strand grows
Termination: RNA polymerase II dissociates
Function of 5’ cap and 3’ polyA tail
stop the proteins from degrading and signal for the export out of the nucleus after the mRNA is fully processed.
Describe splicing
Occurs through use of the spliceosome, process which removes introns from the primary mRNA transcript to form the mature mRNA transcript.
What is the transciptome
The set of all RNA transcripts, both coding and non-coding regions. Different cells transcribe different sets of genes (gene signature)
What is the proteome
The complete set of proteins expressed by an organism.
Cells produce different proteins from the same pre-RNA transcript.
What is a gene
The unit of inheritance. They encode the info for making proteins
What is the genome
Sequence of all the DNA in an organism (genes and non protein coding regions)
Describe transcription factors
TFs are proteins that bind to short but VERY specific sequences of DNA (TATA box).
They affect the rate of transcription positively or negatively.
Mutations to TF binding sites or TFs themselves underlie many diseases.
Effects can be prevented by a silencer or boosted by an enhancer.
Describe epigenetics
Epigenetic changes are genetic modifications that impact gene activity without changing the DNA sequence. Such as enhancers and silencers.
Genes often have several enhancers
Describe closed and open DNA
Closed: Heterochromatin. DNA not always accesible to TFs. Histones bind DNA and form larger nucleasomes (wrapped up DNA/closed)
Open: euchromatin
chromatin is DNA, RNA and protein
What is constitutive gene expression
genes which are expressed in all cells at the same time and to the same level.
They have a constituative promoter
Examples include beta-actin, GAPDH, and basal transcription factors
What is inducible gene expression
Genes only expressed in certain tissues at certain times
Examples include: collagen, globin, cyclins and melatonin
What is the locus control region
Open chromatin spanning several genes
Example: globin genes
TFs bind to globin LCR and opens DNA for all globin genes making expression possible.
If there is a mutration in the LCR, then the locus stays closed, the DNA is tightly wrapped and TFs cant access it = low flobin expresssion
4 types of protein structure
Primary: AA sequence
secondary: alpha-helix or beta-pleated sheet
Tertiary: 3D folding of the polypeptide (held by H bonds)
Quaternary: Polypeptide subunits assemble to form overall functional protein
Describe proteolysis
The cleavage (cutting) of a protein, often used to activate an inactive protein.
Clotting cascade involves several serine proteases that become sequentially activated.
Cleavage of a zymogen (inactive protein) is often used to control protein activated in a time and tissue sensitive manner.
Examples of gene mutation diseases
Sickle cell anaemia: beta-globin gene mutation
Cystic fibrosis: mutation in CFTR
