FUNBIO 12 2024 Genetic Information Flow PDF

Genetic information flow: From DNA to RNA (Transcription, RNA polymerases, RNA processing) Class Foundation Year Course Fundamentals of Human Biology Code FUNBIO.12 Lecturers Prof Michael Keogh  Learning Objectives 1.Explain the concept of gene expression 2.Discuss in...

Genetic information flow: From DNA to RNA (Transcription, RNA polymerases, RNA processing) Class Foundation Year Course Fundamentals of Human Biology Code FUNBIO.12 Lecturers Prof Michael Keogh  Learning Objectives 1.Explain the concept of gene expression 2.Discuss in detail how DNA is transcribed into RNA 3.Describe the structure of RNA, the different types of RNA present in a cell 4.Differentiate between coding and non-coding RNA 5.Explain the role of specialized enzymes in the transcription process. 6.Discuss transcriptional RNA modifications: polyadenylation, capping, splicing 7.Explain the role of exons and introns in gene expression  All cells in your body possess the same DNA over 200 cell types. (Q) ‘What makes a muscle cell different to a neuron?’ (A) Different cells express different proteins Muscle cells will produce motor proteins to allow for movement Neurons will produce proteins involved in conduction of electrical impulses  Explain the concept of gene expression 1. What is a gene? 2. What is the gene expression?  What is a gene? HUGO: The Human Genome Project estimated that humans have between 20,000 and 25,000 genes. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. DNA Genes are made up of sequences of DNA the basic physical and functional unit of heredity Many genes code to make proteins  (ALO 1&2) Gene [+1 : Transcription Coding region Rho-dependent/ start – initiation site] +1 Terminator independent terminators DNA Promoter TATA(AT) box 5’ RNA 3’ Not all DNA codes for protein; only genes do (gene expression) RNA Polymerase unwinds DNA and begins initiation at the site of the promoter. RNA nucleotides are inserted complimentary to the template strand. mRNA moves from the nucleus to the cytoplasm via nuclear pores.  Gene expression is the process by which Transcription the inheritable information in a gene, such as the DNA sequence, is made into a functional gene product, such as a protein Translation Gene expression can be promoted or impeded at each stage Chemical and structural modification of DNA or chromatin Transcription & Post-transcriptional modification RNA transport & mRNA degradation Translation & Post-translational modifications  Gene expression detection: Gene expression can be detected by many molecular techniques e.g. -PCR &Real Time PCR -Gel Electrophoresis and southern blotting -Microarrays (as shown) -FISH in situ hybridization (functional expression) Curr Protoc Mol Biol. 2013 January ; 0 22: Unit–22.1 doi:10.1002/0471142727.mb2201s101  Transcription is controlled separately for each gene in your genome (like dials on a digital sound board) Number of RNA molecules Gene 1 Gene 2 Gene 3 Gene 4 Gene 5 (ALO 1&2) Gene Gene expression (transcription) Figure 13-11 p281 Solomon (ALO 1& 2) towards the 3’ end towards the 5’ end ⇒⇒⇒⇒⇒⇒⇒⇒⇒ (ALO 2) Messenger RNA transcription Three stages in the transcription process: A primer is NOT required for 1. Initiation RNA, Mg2+ ions act as a 2. Elongation catalyst 3. Termination Step 1. Initiation RNA Pol (RNAP below) binds to DNA and unwinds a 17-18 bp segment of the promoter. Step 2: Elongation – The RNAP moves along the template strand synthesizing RNA until it reaches the terminator region Step 3: Termination The transcribed terminator sequence causes the RNAP to pause and thus to dissociate. (ALO 2) DNA transcription to RNA NTPs (A, G, C & U) !! A primer is NOT required !! 5’ (ALO 2) Template - DNA Coding strand – sense strand 5’ ⇒ ⇒ ⇒ ⇒ ⇒ 3’ 3’ ⇐ ⇐ ⇐ ⇐ ⇐ 5’ Template strand – antisense strand 5’ ⇒ ⇒ ⇒ ⇒ ⇒ 3’ (ALO 2) Coding DNA strand – sense strand 5’ ⇒ ⇒ ⇒ ⇒ ⇒ 3’ 5’ OLGA 3’ 3’ ⇐ ⇐ ⇐ ⇐ ⇐ 5’ 3’ AGLO 5’ Template DNA strand – antisense strand [mRNA] 5’ OLGA 3’  (ALO 1&2) Prokaryotes VS Eukaryotes mRNA transcript is mature, and mRNA transcript is not mature (pre-mRNA) used directly for translation and must be modified by processing. without modification. Transcription and translation are not coupled Since prokaryotes lack a (mRNA must first be exported to the nucleus, mRNA also is cytoplasm before translation occurs). translated on ribosomes before it is transcribed completely (i.e., transcription and translation are Eukaryote mRNAs are coupled). monocistronic, they contain amino acid Prokaryote mRNAs are coding information for just polycistronic, they contain amino one gene. acid coding information for more than one gene. Half-life of a few mins to 24 hours. Half life