DNA, RNA and Protein

base and 5 carbon sugar

nucleoside and phosphate group

Adenine and guanine are the two nucleotides that are purines.

<p>cytosine, thymine, uracil are the nucleotide bases that are pyrimidines</p> Signup and view all the answers

<p>They are bonds that form between 3’ OH group and 5’ triphosphate and they link nucleotides.</p> Signup and view all the answers

<p>1)Anti-parallel double helix - One strand 5’ to 3’, other strand 3’ to 5’ 2) Sugar-phosphate backbone 3) Base pairs in the inside, held together with H bonds</p> Signup and view all the answers

<ol> <li>RNA primer (short strand of RNA) required to start DNA replication</li> <li>Helix unwound by helicase</li> <li>Replication fork with leading and lagging strand</li> <li>Leading synthesized in 5’→ 3’ direction - catalyzed by DNA polymerase</li> <li>Lagging is synthesized in Okazaki fragments which are then joined by DNA ligase</li> </ol> Signup and view all the answers

<p>After one round of replication, every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA.</p> Signup and view all the answers

<p>Eukaryotic genomes have many origins of replication. It starts simultaneously at several points in the genome which means that:-</p> <ol> <li>It is bidirectional</li> <li>It ensures that replication can be finished in a reasonable time.</li> </ol> Signup and view all the answers

<p>Nucleotides can only be added to free 3' ends.</p> <ol> <li>Leading strand- always has a free 3' end and it keeps extending until it meets another fork within the replication framework.</li> <li>Lagging strand consists of short fragments called the Okazaki fragments. Short RNA primer degrades and Okazaki fragments are joined together.</li> </ol> Signup and view all the answers

<p>When the primase attaches to the bottom strand, it creates the RNA primers for strand replication. Then the DNA polymerase attaches to the RNA primer to build the new strands.</p> Signup and view all the answers

<p>DNA helices unwinds the DNA strands by breaking the bonds for the strands to extend.</p> Signup and view all the answers

<ol> <li>rRNA- combines with proteins to form ribosomes</li> <li>tRNA- carries amino acids to be incorporated into protein</li> <li>mRNA- carries genetic information for protein synthesis</li> </ol> Signup and view all the answers

<p>They are single stranded and contain local stretches of intramolecular base pairing because of proximity of bases H bases are formed.</p> Signup and view all the answers

<ol> <li>DNA information is transcribed into mRNA to make protein.</li> <li>mRNA goes into ribosome made of rRNA and proteins</li> <li>tRNA brings amino acids and allows ribosomes to synthesise a new protein.</li> </ol> Signup and view all the answers

<p>It is a bridge between mRNA and the monomers and brings the monomers to mRNA for translation from one polymer to another.</p> Signup and view all the answers

<p>tRNA molecules have a distinct three dimensional structure and when it is flattened into two dimensions, it resembles a cloverleaf structure.</p> Signup and view all the answers

<p>Prokaryotic cells have one type of RNA polymerase. Eukaryotic cells have three types of RNA polymerase:-</p> <ol> <li>Pol I</li> <li>Pol II</li> <li>Pol III</li> </ol> Signup and view all the answers

<p>It can be distinguished by their sensitivity to toxins like alpha amanitin and Pol II synthesised all mRNA.</p> Signup and view all the answers

<ol> <li>RNA polymerase binding</li> <li>DNA chain separation</li> <li>Transcription initiation</li> <li>Elongation</li> <li>Termination</li> </ol> Signup and view all the answers

<ol> <li>Detection initiation sites (promoters) on DNA</li> <li>Requires transcription factors- TFIID - first general transcription factor to bind to the promotor, binds to TATA box through TBP (TATA box binding protein). General transcription factor required for all Pol II transcribed genes</li> </ol> Signup and view all the answers

<ol> <li>Selection of first nucleotide of growing RNA.</li> <li>It requires additional general transcription factors.</li> <li>Pol II and TFIIF extend transcript on their own. TFIID remains at promoter, a new initiation complex can assemble.</li> </ol> Signup and view all the answers

<ol> <li>A transcription bubble moves in one direction along the DNA</li> <li>DNA is unwound in front of the polymerase and rewound behind it.</li> <li>RNA chain is synthesised in a 5' to 3' direction. It is transcribed in 5'-3' direction and polymerase thus moves in a 3'-5' direction.</li> <li>The new RNA sequence is complementary to the template strand.</li> <li>It is identical to the coding strand.</li> </ol> Signup and view all the answers

<ol> <li>Newly synthesised RNA makes a stem loop structure.</li> <li>A specific enzyme cleave the new RNA.</li> <li>The RNA gets released and the polymerase dissociates.</li> </ol> Signup and view all the answers

<p>It requires specific transcription factors</p> <ol> <li>DNA binding proteins</li> <li>DNA binding domain</li> <li>Transcriptional activation domain This regulates transcription positively or negatively.</li> </ol> Signup and view all the answers

<ol> <li>Splice out introns (exons = coding, intron = non-coding)</li> <li>Add poly-adenosine tail- marks the end of coding mRNA</li> <li>Add 5’ cap</li> </ol> Signup and view all the answers

<p>Features of the genetic code</p> <ol> <li>Degenerate- many amino acids have more than one codon</li> <li>Unambiguous- each codon codes for only one amino acids or a Stop codon.</li> <li>Near universal</li> </ol> Signup and view all the answers

<ol> <li>Initiation - formation of initiation complex, energy provided by GTP</li> <li>Elongation - anticodons of tRNA form base pairs with codons on mRNA, aminoacyl-tRNA synthetases catalyse the covalent attachment of amino acids to their corresponding tRNA molecules</li> <li>Peptide bond formation and translocation- peptidyl transferase catalyzes peptide bond formation between amino acids in P and A sites, EF-2 moves ribosome along mRNA</li> <li>Termination - A site encounters stop codon, termination protein binds to the codon and the ribosome dissociates, leads to a change in peptidyl transferase activity which results in the release of the protein from the last tRNA to which it was attached</li> </ol> Signup and view all the answers

<p>A codon is a sequence of three nucleotides in messenger RNA that determines the position of amino acids when a cell starts making proteins. An anticodon is a sequence of three nucleotides in transfer RNA that binds to a corresponding codon and designates a specific amino acid.</p> Signup and view all the answers

<ol> <li>Targeting- moving a protein to its final cellular destination- many possible locations within a cell depending on the presence of specific amino acid sequences within the translated protein.</li> <li>Modification- addition of further functional chemical groups</li> <li>Degradation- unwanted or damaged proteins have to be removed.</li> </ol> Signup and view all the answers

<ol> <li>Free ribosomes in the cytosol make proteins destined for the cytosol, nucleus. mitochondria and they are translocated post translationally.</li> <li>Bound ribosomes on the rough endoplasmic reticulum make proteins destined for the plasma membrane, ER, Golgi apparatus, secretion and they are translocated co translationally.</li> </ol> Signup and view all the answers

<p>3 tRNA binding sires - P, E, A - P (peptidyl site) → A (acceptor site) → E (exit site)</p> Signup and view all the answers

<ol> <li>Glycolsylation- Addition an processing of carbohydrates in the ER and the Golgi</li> <li>Formation of disulphide bonds in the ER</li> <li>Folding and assembly of multi subunit proteins in the ER.</li> <li>Specific proteolytic cleavage (cleavage of polypeptide allowing it to fold into different shapes) in the ER, Golgi and secretory vesicles.</li> </ol> Signup and view all the answers

<ol> <li>Point mutation</li> <li>Missense mutation</li> <li>Nonsense mutation</li> <li>Silent mutation</li> <li>Framework mutation</li> </ol> Signup and view all the answers

<p>change in single base in DNA</p> Signup and view all the answers

<p>results in change of amino acid sequence</p> Signup and view all the answers

<p>creates new termination codon</p> Signup and view all the answers

<p>no change of amino acid sequence and no observable difference in phenotype</p> Signup and view all the answers

<p>addition or deletion of 1 or 2 bases which changes the reading frame of translation</p> Signup and view all the answers