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Structure of DNA Nucleic acid Subunits = nucleotides In DNA

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Presentation on theme: "Structure of DNA Nucleic acid Subunits = nucleotides In DNA"— Presentation transcript:

1 Structure of DNA Nucleic acid Subunits = nucleotides In DNA
5 carbon sugar = deoxyribose Phosphate group Nitrogenous base Adenine, guanine, cytosine, thymine Bonds between sugar and phosphate group - backbone

2 Double-helix model Antiparallel strands Run in opposite directions Allows bases to touch Hydrogen bonds Weak Between specific bases Base pairing Only certain bases bond A to T C to G Together 2 bases = base pair

3 What does DNA do? Makes more DNA Makes RNA Makes proteins
Building blocks of life

4 RNA DNA 5-carbon sugar – ribose 5-carbon sugar – deoxyribose
Phosphate group Bases: A, C, G, U Single-stranded “Blueprints” Made in nucleus, but used in cytoplasm DNA 5-carbon sugar – deoxyribose Phosphate group Bases: A, C, G, T Double-stranded “Master plan” Stays in nucleus

5 Role of RNA Disposable copy of DNA Makes proteins from amino acids
Types Messenger (mRNA) Instructions for assembly Brings info. from nucleus to rest of cell Ribosomal (rRNA) Several with proteins make ribosomes Where proteins are assembled Transfer (tRNA) Carries amino acids to ribosomes Specific for an amino acid

6 RNA Synthesis Transcription DNA made into RNA Occurs in nucleus
RNA polymerase Binds to a promotor region Specific base sequence on DNA Separates DNA strands Uses one strand as a template Attaches complementary bases Except no T Until it reaches a “stop” sequence Creates pre-mRNA

7 RNA Editing A lot of “useless” bases in our DNA that ends up in the RNA Introns Enzymes cut these sections out Recent research Leaves exons Information used Creates mRNA Leaves the nucleus

8 Genetic Code Bases are read in sets of 3 = codon
Represents a specific amino acid Some amino acids have more than one codon Start and stop codons “Punctuation” Start = AUG = methionine 3 different stop codons No amino acid, just stops


10 Translation mRNA leaves nucleus Attaches to a ribosome “Reads” codons
tRNA Has anticodon sequence Complementary to codon sequence Brings in specific amino acid Ribosome moves to next codon New tRNA comes in Amino acids bond Old tRNA leaves Ribosome moves to next codon….

11 Keeps adding amino acids
Forming polypeptide bonds Reaches stop codon No amino acid added Translation stops Polypeptide chain released Further folding to form protein Other products recycled and reused



14 Central Dogma – How do Genes Work?
DNA (genes)  RNA  proteins Viruses different RNA  DNA Genetic code is universal Same bases Read as codons Codons = same amino acids

15 Mutations Mistakes Often caught/fixed by enzymes
Occasionally “slip” through Passed on to offspring of that cell Point mutations Substitution Frameshift mutations Insertion Deletion THE FAT CAT ATE HIS HAT THE SFA TCA TAT EHI SHA THE FAT ATA THE ISH

16 Chromosomal Mutations
Change number of structure of chromosomes More DNA/genes involved Deletion Duplication Inversion Translocation

17 Cause Mutations Random Accumulate over time Mutagens Chemical Physical
Interfere with base-pairing Weaken DNA

18 Helpful vs. Harmful Most are neutral Create genetic variation Harmful
Change protein structure Change gene activity Disrupt normal activities Examples Cancers Sickle cell disease Beneficial New trait is helpful for survival Pesticide resistance Increase human bone strength and density Resistance to HIV Polyploidy Larger, stronger, seedless plants

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