Ribonucleic acids molecular structures and functions.pptx

This presentation gives details on ribonucleic acid molecules. And their detailed structures.
Structure of mRNA, tRNA and rRNA.
Elaborates codones and anticodones which code for a specific protein.
The 3 molecules interact.
mRNA is a Templet containing condones, the tRNA Carrie's a specific amino acid by attaching its end containing anticodones to complementary condones on mRNA. The rRNA is responsible for picking the the amino acid from tRNA and formulates a growing poly peptide chain via peptide bonding

1. The versatility of RNA

2. RNA: types & structure Polymer of nucleotides What is the difference? Five RNA types: rRNA mRNA tRNA snRNA snoRNA

3. Components of RNA

4. The versatility of RNA RNA folds into unique 3-D structures which act similarly to globular proteins; “ tRNA looks like natures attempt to make RNA do the job of a protein” -Francis Crick Generally the pathway of gene expression from DNA to functional product via an RNA intermediate overemphasizes proteins as the ultimate goal; However, RNAs are involved in a variety of cellular processes along the pathway of gene expression including; DNA replication; RNA processing; mRNA turnover; protein synthesis; protein targeting RNA catalyzes chemical reactions in living cells (ribozymes)

5. Relationship between the 5 RNA types during gene expression

6. tRNA Adaptor like molecule that decodes mRNA codons into amino acids Brings amino acid corresponding to the appropriate mRNA codon Each amino acid has unique tRNA T-loop D -loop Anticodon-loop

7. tRNA structure The three tRNA loops form the cloverleaf secondary structure; each loop has a specific function The T-loop ; involved in recognition by the ribosomes The D-loop ; associated with recognition by the aminoacyl tRNA synthatase The Anticodon loop ; base pairs with the codon in mRNA Every tRNA has the sequence ACC on the 3’-End to which the amino acid is attached The anticodon loop in all tRNAs is bounded by U on the 5’-side and a modified purine on the 3’-side

8. tRNA : secondary and tertiary structures

9. rRNA Type Size Large subunit Small subunit Prokaryotic 70S 50S   ( 5S rRNA ,   23S rRNA ) 30S   ( 16S rRNA ) Eukaryotic 80S 60S   ( 5S rRNA ,   5.8S rRNA ,   28S rRNA ) 40S ( 18S rRNA ) Component of the ribosome, the site of protein synthesis in all living cells Provides a mechanism for decoding mRNA into amino acids and interacts with  tRNAs  during translation by providing  peptidyltransferase   activity RNAs are in parenthesis - Sites of attack for several antimicrobials, especially TB drugs -16S RNA used to classify microorganisms; the Microbiome / Metagenomics

10. Ribonucleoproteins (RNPs) Most RNAs are associated with proteins as RNA-protein complexes called ribonucleotpoteins One important RNP is the ribosome RNA-based catalytic reactions occur in conjunction with proteins Catalytic RNAs are called ribozymes ; they catalyze a number of reactions in cells ranging from cleavage of phosphodiester bonds to peptide formation

11. RNPs are involved in a wide range of cellular processes

12. Types of naturally occurring ribozymes

13. mRNA Information in DNA is copied ( transcribed ) into mRNA, which goes to ribosome for translation mRNA is; -unstable in cells ( why ? ) -< 5% total RNA -Methylated heads (CH3 cup) - Polyadenylated tails: utilized in biotech - Represents expressed genes in cells Template DNA strand; Antisense, Non-coding strand Reverse Primer Sense; Non-template DNA strand; Coding strand Forward Primer

14. 2 . Fundamental Molecular Biology II The processes governing flow of genetic info -DNA replication -Transcription -Translation

15. DNA replication

16. Re-cap; the dogma of biology Each process governing the flow of genetic info is given a specific name; Replication; the process of making an exact copy of DNA from the original DNA Transcription; the process of being copied to generate a ssRNA identical in sequence to one strand in dsDNA The info is rewritten (transcribed), but in basically the same language of nucleotides Translation; the process in which the RNA nucleotide sequence is converted into the amino acid sequence of a protein The term denotes that the info in the language of nucleotides is copied (translated) into another language of amino acids

17. DNA replication The regulation of DNA replication is fundamental to understanding of the continuity of life As cells multiply and give rise to new cells, the genome must be accurately duplicated so that information is passed on to each new generation with minimal error Understanding DNA replication helps to understand molecular tests e.g. PCR, Sequencing

18. DNA polymerases Polymerize nucleotides into growing DNA strands Bacteria have 5 DNA pols, mammals 14 Eukaryotes have 3 DNA pols for chromosomal DNA replication; DNA polymerase α DNA polymerase δ DNA polymerase ε DNA polymerase γ : mtDNA replication The above 4 are called replicative DNA pols ; other types of DNA pols are used in DNA repair processes (e.g. Klenow , etc.; have 3’ – 5’ activity) Chromosomal

19. All DNA pols add nucleotides in the 5’-3 ’ direction DNA pol catalyzes formation of phosphodiester bond between the 5’C-PO4 of a new dNTP and the 3’C-OH of the last nucleotide in the newly synthesized strand DNA pol cannot initiate DNA synthesis de novo Except for DNA pol α that’s involved in primer synthesis, all DNA pols require a primer DNA pol recognize and bind the free 3’-OH at the end of the primer Once primed, the pol extends pre-existing chains rapidly

20. DNA polymerase works in 5’ – 3’ direction

21. DNA polymerase works in 5 ’ – 3’ direction

22. 22

23. Semi-conservative nature of DNA r eplication: gives two daughter duplex DNAs, each with one original strand and one new strand

24. Transcription

25. Transcription The copying of the sequence of the template strand of the gene into a complementary RNA transcript (mRNA) The beginning of gene expression Transcription and translation are coupled in bacteria In eukaryotes, mRNA and protein synthesis are separated between two cellular compartments

26. Transcription and translation coupled in prokaryotes

27. Transcription and translation uncoupled in eukaryotes Regulation at each level

28. Sense and Antisense strands A DNA sequence is read in triplets using the antisense ( non-coding ) strand; Called the template strand , directs the synthesis of RNA via complementary base-pairing The other non-template strand is the sense ( coding ) strand; Bears the same sequence as the mRNA (except for possessing U instead of T)

29. Sense and antisense strands

30. Promoters: in bacteria they have two distinct “Consensus” Sequences A promoters is a sequence to which RNA polymerase b inds to begin transcription

31. Structure of bacterial RNA pol Comprised of; Core Enzyme , and A transcription factor called the Sigma factor, δ Together, the core enzyme and δ form a functional enzyme complex called the “ Holoenzyme ”

32. The core enzyme, cont’d The core enzyme catalyzes polymerization It is conserved from bacteria to humans Has high affinity for most DNA; in absence of δ it initiates synthesis anywhere on a DNA template in vitro The δ is responsible for decreasing the non-specific binding affinity of RNA pol

33. The sigma factor ( δ ) Recognizes the promoter The -35 and -10 sequences are required for recognition -10 region is responsible for initial melting of the template strand There several δ per species

34. E. coli sigma factors

35. Types of DNA-dependent RNA polymerases RNA polymerases catalyze RNA synthesis using DNA as a Template; they initiate RNA synthesis de novo (in contrast to DNA pol) Sites for antibiotic attack (RIF, etc.)

36. The mechanism of transcription Occurs in three stages Initiation Elongation Termination

37. Initiation Further divided into three stages; Formation of a closed promoter complex The DNA remains DS and the complex is reversible Formation of an open promoter complex Melting occurs to expose the template strand AT rich -10 region and negative supercoiling helps Irreversible; polymerization is initiated Promoter clearance There is a staged disruption of δ -core enzyme interaction

38. Elongation Transcription bubble is formed as RNA pol winds and unwinds strands The catalytic site of the RNA pol has both; A Substrate Binding Sub-site at which the incoming NTP is bound to the pol and to the complementary nt residue of the template And a Product Binding Sub-site , at which the 3’-terminus of the growing RNA chain is positioned NTP and a phosphodiester bond forms with the 3’-OH of the last nt in the RNA chain Transcription also proceeds in 5’ – 3’

39. Transcription elongation