27. DNA, RNA and polypeptide Flashcards
Where does the variability in the human genome come from?
- Gene content (density and number) in each chromosome differs
- Gene sizes differ
- Genes can encode proteins
- Genes can encode other RNA
How does gene expression generate diversity of cells/organs?
220 cell types in humans forming distance organs
- Differential gene expression
How does open/condensed dna regulate gene expression?
- Dna has various levels of organisation and gene expression controlled by physical properties
- More open it is, the more it is expressed
What does each nucleotide consist of?
- A phosphate group
- A sugar
- A nitrogenous base
What sort of secondary structures can RNA form?
- Rna is mainly single stranded but can also form secondary structures
- Hairpins are double stranded regions formed by complementary sections on the single stranded RNA
What are the three types of RNA involved in translation?
- Messenger RNA=mRNA
- Transfer RNA=tRNA
- Ribosomal RNA=rRNA
What are the two types of regulatory RNAs?
- Micro RNA=miRNA
- Small interfering RNA= siRNA
What does messenger RNA do?
- It carries the coding message of the DNA
- Formed by transcription, template used during protein synthesis
What does ribosomal RNA do?
- It formed part of the ribosome
- Each ribosome is made of a large and small subunit
- Both rRNA and ribosomal proteins make up these subunits
What are the two key structural elements in transfer RNA?
- The 3’ end is the CCA sequence where a specific amino acid will attach
- The anticodon is when he tRNA matches to the mRNA template
What is the process of ‘charging’?
Where a specific amino acid is added to the 3’ CCA of the tRNA
What is the enzyme that facilitates this charging?
Amino-acyl-tRNA-synthase
- There are different versions of amino-acyl-tRNA syntheses that can only bind specific tRNAs and their matching amino acids
What does microRNA (miRNA) do?
- It is an endogenous type of RNA interference
- Transcribed from DNA and requires processing to become single stranded
- Binds imperfectly to mRNA and blocks translation/marking mRNA for degradation
What does small interfering RNA do? siRNA
- These are synthetic and double stranded types of RNA interferences
- Require unwinding
- Perfectly bind mRNA transcribed from DNA to degrade siRNA-mRNA complexes
How does RNA interference affect X inactivation?
- The Xist gene is on the X chromosome
- Transcription of the Xist gene makes an interference RNA
- The RNA binds to the X chromosome from which it was transcribed
- Methylation and histone deacetylation attract chromosomal proteins that form heterochromatin, inactivating the chromosome
What is the secondary structure of the protein?
- Folding due to amino acid interactions
- The carboxyl and amino groups can form bonds to give rise to alpha helices and beta sheets
What is the tertiary structure of the protein?
3D packaging due to amino acid interaction
