Nucleic Acids:

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Nucleic Acids:. The Molecules of Life. DNA and RNA. Both are polymers. They are made up of monomers called ______________. Nucleotides have three parts to them: a _____________ b _____________ c _____________. _____________ bonding…. Joins nucleotides together ____________ reaction - PowerPoint PPT Presentation

Transcript of Nucleic Acids:

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Nucleic Acids:The Molecules of Life

DNA and RNABoth are polymers.They are made up of monomers called ______________

Nucleotides have three parts to them: a _____________b _____________c _____________ _____________ bondingJoins nucleotides together____________ reactionEliminates ____ molecule

PBASESugarPBASESugarPBASESugarPBASESugarPBASESugarAdenine Guanine Cytosine Thymine BASEBASEThymine Adenine Thymine BASECytosine BASEGuanine BASEAdenine The Bases________:thyminecytosine


RNA has URACIL instead of thymine

Base pairingComplementary base pairing

DNA ReplicationWhen cells divide, you need to have 2 copies of the DNA in the cellDNA ReplicationMost important feature of DNA is its ability to replicate itself, (almost) exactly

The double helix is unzipped during replication

New nucleotides are aligned along the DNA strands (built by DNA polymerase)

The new helix contains one original strand and one new strand

1234Semi - conservative replication Meselson & Stahl

Ribonucleic Acid (RNA) & its role in Protein synthesisThe structure of ribonucleic acidLearning Objectives:Describe the structure of ribonucleic acid (RNA)Describe the structure and role of messenger RNA (mRNA)Describe the structure and role of transfer RNA (tRNA)RNARNA = ribonucleic acidRNA is a single -stranded polymerEach RNA nucleotide consists of:A pentose sugar (ribose)A phosphate groupA base adenine, cytosine, guanine, uracil (instead of thymine)RNA used in protein synthesis is messenger RNA (mRNA) or transfer RNA (tRNA).

RNADNARNA contains the pentose sugar ribose.DNA contains the pentose sugar deoxyribose.Messenger RNA (mRNA)mRNA is used to transfer the DNA code from the nucleus to the cytoplasm.mRNA is complementary to the DNA code.mRNA is small enough to leave the nuclear pores.Once in the cytoplasm, mRNA associates with the ribosomes.mRNA is used to determine the sequence of amino acids during protein synthesis.mRNA is easily broken down and only exists whilst it is needed to manufacture a protein.The sequence of nucleotides in the mRNA is referred to as the genetic code.

Transcription (forming mRNA)

The Genetic Code (recap of unit 1)3 nucleotide bases on mRNA (a codon) codes for each amino acid in a protein.A few amino acids have a single codon.The code is degenerate most amino acids have more than one codon.3 codons code for no amino acids they are stop codons and mark the end of the polypeptide chain.Non-overlapping each nucleotide is read only once.Universal same codon codes for the same amino acid in all organisms (few minor exceptions).Transfer RNA (tRNA)tRNA is a small molecule (~80 nucleotides).Single stranded and folded into a clover leaf shape with one end of the chain slightly longer.This longer section is attached to an amino acid.Each tRNA can carry a different amino acid.3 bases at the opposite end of the tRNA are called an anticodon.Each amino acid has a different anticodon.The anticodon pairs with the complementary codon on the mRNA.

Amino acid joins hereAnticodonComparison of DNA, mRNA and tRNAFeatureDNAmRNAtRNADouble/SingleSizeShapeSugarBasesQuantity in cellsStabilityComparison of DNA, mRNA and tRNAFeatureDNAmRNAtRNADouble/SingleDoubleSingleSingleSizeLargestVariableSmallerShapeDouble helixSingle helixClover shapeSugarDeoxyriboseRiboseRiboseBasesA, G, T, CA, G, U, CA, G, U, CQuantity in cellsConstant (gametes)VariesVariesStabilityVery stableUnstableMore stable than mRNA, less than DNAPolypeptide synthesis transcription and splicingLearning Objectives:How is pre-mRNA produced from DNA in the process called transcription?

How is pre-mRNA modified to form mRNA?The process by which DNA is read to produce a strand of mRNAA G T C G T C A A T G C T A T G C A T T C C G T A C

T C A G C A G T T A C G A T A C G T A A G G C A T GDNAmRNAA G U C G U C A A U G C U A U G C A U U C C G U A CRNA polymeraseCoding StrandTemplate Strand555333TRANSCRIPTION

24TranscriptionHelicase (enzyme) acts on a region of DNA to break the hydrogen bonds between the bases.RNA polymerase moves along one of the two DNA strands template strandRNA polymerase matches up complementary RNA nucleotides.C matches G and G matches CU matches A and A matches TAs the RNA nucleotides join together the pre-mRNA is formed.The DNA behind the RNA polymerase rejoins into a double helix.When the RNA polymerase reaches a stop codon, the chain is terminated and the pre-mRNA detaches.

Splicing of mRNA to form mRNAOnce the introns (non-functional DNA) have been removed, the remaining exon sections join together.

RNA Splicing

snRNPsSpliceosomeFun fact of the dayIntrons figured prominently in Star Trek: The Next Generation, Season 7, Episode 271, entitled "Genesis."

In this episode, a synthetic T-cell inadvertently activated the crewmembers' introns, resulting in de-evolution and the expression of ancient physiological traits

Transcription Animation

mRNA splicing

Polypeptide synthesis translationLearning Objectives:How is a polypeptide synthesised during the process of translation?

What are the roles of mRNA and tRNA in translation?A G U C G U C A A U G C U A U G C A U U C C G U A C GRemember our strand of mRNA from before?

U C AG C AG U UA C GA U AC G UA A GG C AU G CSERSERALAALAVALTHRILEARGLYSTRANSLATIONSynthesising the polypeptide (translation)mRNA attaches to the ribosome at the start codon AUG.tRNA with a complementary anticodon attaches to the mRNA UAC.This tRNA is attached to an amino acid methionineThe ribosome moves along the mRNA bringing in 2 tRNA molecules at any one time.An enzyme and ATP are used to join the amino acids with a peptide bond.The first tRNA is released and can collect another amino acid.The process is repeated until a stop codon is reached.Many ribosomes can travel along the mRNA at the same time polysome.

Translation Animation


Using PCs log

Enter sequence of 22 bases from an imaginary DNA coding strand

Try several different strands with same software.

Who can get the most matches to the human genome?


Create a model of either TRANSLATION or TRANSCRIPTION

Can be any format e.g.: PowerPoint, Poster, 3D Model