RNA and Gene Expression How does DNA determine our traits? By - PowerPoint PPT Presentation

RNA and Gene Expression

How does DNA determine our traits? • By directing the synthesis of proteins • Proteins represent functional genes • Molecular flow of information is: DNA RNA Protein

Gene Expression 1. Transcription – Genetic information is transferred from DNA to mRNA 2. RNA Processing – enzyme-regulated modifications to the mRNA transcript (eukaryotes only) 3. Translation – mRNA information is decoded to synthesize proteins

• Histone acetylation ( unpack DNA )

RNA (Ribonucleic acid) • A nucleic acid composed of ribose sugars, phosphates, and nitrogenous bases • How does RNA differ from DNA?

DNA RNA • Double stranded • Single stranded • Deoxyribose sugar • Ribose sugar • Adenine, Cytosine, • Adenine, Cytosine, Guanine, and Thymine Guanine and Uracil • Nucleus only • Nucleus, cytoplasm, and ribosomes

What molecules are required for gene expression?

Gene Expression Molecules 1. mRNA 2. tRNA 3. rRNA 4. amino acids 5. ribosomes

mRNA (messenger) • linear RNA that transfers genetic information from DNA to ribosomes

tRNA (transfer) • RNA (~80 nucleotides in length) twisted in hairpin shape • supplies the amino acids to ribosomes for translation

rRNA (ribosomal) • globular RNA that composes ribosomes, forms the peptide bond between amino acids during protein synthesis

Amino Acids • monomers of proteins • linked together to form proteins during translation

Ribosomes • site of translation (third step of gene expression)

Gene Expression Animation Overview of Gene Expression

Eukaryotic Gene Structure • Promoter • Exon • Intron • Terminator

Gene Expression 1. Transcription 2. RNA Processing (eukaryotes only) 3. Translation

Transcription and RNA Processing

Transcription

Transcription Animations Transcription – Virtual Cell HHMI Transcription

RNA Processing • Enzyme-mediated modifications to the mRNA transcript 1. Addition of a GTP cap to 5’ end (protection, bind to ribosome) 2. Addition of a poly- A tail to 3’ end (protection) 3. Excision (removal) of introns: non-coding segments of DNA ( RNA splicing ) • mRNA then exits the nucleus

RNA Processing

Translation (Gene to Protein) • Genetic information from a sequence of nucleotides in a gene is used to produce a sequence of amino acids in a protein • Occurs on ribosomes in the cytoplasm

Translation • Initiation • Elongation • Termination

Translation Terminology • Codon • Start codon • Ribosome • Stop codon • Anti-codon • mRNA • tRNA • rRNA

Translation- Virtual Cell (Animation)

Genetic Code

Translation Animation HHMI Translation Animation

RNA interference (RNAi) • Regulates gene expression at the level of mRNA transcription • Example of an RNAi molecule is microRNA ( miRNA ) – Degrades the target mRNA OR – Blocks translation of the mRNA

Phenotypes Are Determined Through Protein Activities • Post translation protein modifications determine the function of proteins: – Transport proteins – Catalytic proteins – Structural proteins