nucleic acids; transcription and translation Flashcards
what is DNA?
- ultimate potential of a cell
what is mRNA?
- current direction of a cell
what are proteins?
- functional capabilities of a cell e.g. acts as signalling molecules/ enzymes
what does mRNA allow?
- conversion of DNA into proteins
what are the building blocks of nucleic acids? what do they contain?
- nucleotides
- sugar, bases and phosphoryl group
describe the sugars in nucleotide
- 5 carbon pentose sugar
- ribose in RNA
- deoxyribose in DNA (no OH group on carbon2)
describe the bases in nucleotides
- in DNA= adenine, thymine, cytosine and guanine
- in RNA= adenine, uracil, cytosine and guanine
what are the bases that contain one ring called? what bases does this include?
- pyrimidines
- thymine, cytosine and uracil
what are the bases that contain two rings called? what bases does this include?
- purines
- adenine and guanine
what does nitrogen 9 of the base bond with?
- carbon one of the sugar
describe the phosphoryl group in nucleotides
- oxygen of the phosphate binds to carbon 5 of sugar
what is the primary structure of nucleic acids
- DNA/RNA are biopolymers of nucleotides
- nucleotides are joined by phosphodiester bonds between adjacent carbons of deoxyribose sugars (3’ and 5’)
why are nucleic acids slightly acidic?
- due to deprotonation of hydroxyl group at physiological pH
what is the difference between DNA and RNA
DNA= double helix; RNA= single strand
DNA= deoxyribose; RNA= ribose
DNA= thymine; RNA= uracil
what are the complementary base pairings identified by Watson and Crick?
- A-T ( 2 hydrogen bonds)
- C-G (3 hydrogen bonds)
what are the roles of histone proteins?
- anchor and support DNA to allow dense packaging within cells of chromosomes
- transference via unzipping both strands and making copies to ensure accurate translation
what is DNA replication?
- important part of the cell cycle that enables division and duplication of genetic material
what is the first step of DNA replication?
- separation of strands via helicase that breaks hydrogen bonds
- unzip DNA molecule
what is the second step of DNA replication?
- primer binding; small strip of RNA primer kick starts replication process
what is the third step of DNA replication?
- elongation
- DNA polymerase adds complementary base pairs in the 5’ to 3’ direction to build a new DNA molecule that wraps around parental strand
what is the fourth step of DNA replication?
- termination involves exonucleases removing the original primers and the bases
- re-adding them to complete a new DNA double helix
how much of the genome is identical? what is the percentage of variation and why?
- 99.9% of genome in humans is identical
- 0.1% variation due to gradual appearance of mutations
what are the two types of mutations?
- bases can be inserted or deleted incorrectly resulting in a changed protein
describe Darwin’s theory of evolution
- advantageous mutation forms the basis of this theory as a more efficient property was introduced
- increased chance of survival
what are the three types of RNA and what do they do?
- messenger RNA decodes DNA
- ribosomal RNA decodes mRNA
- transfer RNA facilitates protein formation
what does transcription involve?
- conversion of DNA into mRNA
- DNA unwinds and RNA polymerase replicates DNA template to form mRNA primary transcript (3’ -5’)
what are promoters?
- DNA region next to transcription site that aids RNA polymerase
what are enhancers?
- DNA regions that attract the transcription factor complex proteins
what are transcription factors?
- TF complex involves proteins that regulate the rate of mRNA formation
- (+/-) stimulate
how can gene expression be regulated?
- exercise
- amount and/ or types of cell signals modulates number of mRNA copies
what are the three ways the type of cell signals modulate mRNA copies are made?
- regulating promoter and enhancer activity
-alerting transcription factor activity - controlling access of RNA polymerase to the gene
what is gene expression governed by?
- signals sent to cells after exercise as he signals produced will result in different regions of the gene being copied hence different mRNA
what are examples of how proteins are adapted for different types of exercise?
- PGC- 1alpha4 activated following strength training
- PGC- 1alpha1 activated following endurance training
what does mRNA splicing involve?
- primary mRNA transcript isn’t final mature mRNA as introns need to be spliced in the nucleus
- remaining exons form mature mRNA
what are introns?
- non- coding regions of mRNA
how can mRNA transcripts lead to translation of more proteins?
- due to alternate mRNA splicing
- accounts for different isoforms of proteins e.g. tropomyosin have many diff spliced areas= diff areas spliced in skeletal muscle compared to smooth
what does translation involve?
- occurs in ribosomes or endoplasmic reticulum
- formation of a polypeptide chain from a mature mRNA transcript
what does mRNA bind to?
- small subunit of rRNA where it is decoded and a signal sent by ribosomal proteins to the large subunit where translation then begins
what is the 3 base sequence on mRNA known as and what is it complementary to?
- codon is complementary to 3 base sequence on tRNA known as anti- codon which binds to large subunit of rRNA holding an amino acid
how does the interaction of codon and anti- codon facilitate the polypeptide chain?
- facilitate the formation of a new polypeptide chain via peptide linkages C-N
how does the ribosome move along the mRNA transcriptase?
- in the 5’ to 3’ direction
- forms multiple codon and anti- codon pairings with ‘ charged’ tRNA molecules
what bond is formed between each amino acid?
- peptide bond formed between each amino acid carried by tRNA
- results in a polypeptide chain being formed in opposite direction to mRNA movement
how many combinations can be formed?
- 4 base pairs alone could not directly encode 20 amino acids
- 3 bases on tRNA correspond to a specific amino acid
- codon sequence on mRNA that attracts anti codon with specific aa
= 64 combos
what happens to the polypeptide chain once it is formed?
- chain formed in cytosol is modified
- endoplasmic reticulum contains various proteins that fold the protein to form its tertiary structure
what happens in the Golgi apparatus?
- govern post- traditional modifications e.g., glycosylation, phosphorylation
what does the specific peptide sequence guide them to?
- specific locations
- cell release e.g. insulin, adrenaline
- traffic to a specific organelle e.g. nucleus, mitochondria or cell membrane
