DNA Basics

The Structure of DNA A VERY long polymer of repeating units called nucleotides A VERY long polymer of repeating units called nucleotides Double-stranded helix Double-stranded helix Sugar-phosphate backbone Sugar-phosphate backbone sugar is Deoxyribose sugar is Deoxyribose Four bases hang off the backbone Four bases hang off the backbone Adenine, Thymine, Guanine, Cytosine Adenine, Thymine, Guanine, Cytosine Order of the bases is key to genetic function Order of the bases is key to genetic function

The DNA Double Helix

Terminology Chromosomes contain genes which are made up of DNA and protein Chromosomes contain genes which are made up of DNA and protein Humans have 46 chromosomes (23 pairs) Humans have 46 chromosomes (23 pairs) 23 from mother, 23 from father 23 from mother, 23 from father DNA = long string of A,T,G,C’s DNA = long string of A,T,G,C’s Gene = short section of DNA Gene = short section of DNA contains recipe for one protein contains recipe for one protein less than 10% of DNA is genes, 90% “junk” less than 10% of DNA is genes, 90% “junk” approx 25,000 genes in humans approx 25,000 genes in humans

Base Pairing Everything about the function of DNA is due to base pairing Everything about the function of DNA is due to base pairing Nitrogen bases from one strand of DNA form weak hydrogen bonds with complementary bases of other strand Nitrogen bases from one strand of DNA form weak hydrogen bonds with complementary bases of other strand A always bonds to T, G always bonds to C A always bonds to T, G always bonds to C

A to T Base Pairing

C to G Base Pairing

DNA Replication DNA is double-stranded DNA is double-stranded Strands are connected by the bases Strands are connected by the bases A on one strand double hydrogen bonds to T on the other strand A on one strand double hydrogen bonds to T on the other strand C on one strand triple hydrogen bonds to G on the other strand C on one strand triple hydrogen bonds to G on the other strand Strands are coiled in a double helix Strands are coiled in a double helix Strands are unzipped by enzyme helicase Strands are unzipped by enzyme helicase New bases hydrogen bond to exposed bases on parent strands, creating 2 new double helixes New bases hydrogen bond to exposed bases on parent strands, creating 2 new double helixes

DNA Replication Before a cell divides: Before a cell divides:

The Central Dogma of Biology DNA makes RNA makes Protein DNA makes RNA makes Protein Proteins make you what you are Proteins make you what you are eye color, diabetic, etc… eye color, diabetic, etc… DNA is sacred, can’t leave nucleus (too big) DNA is sacred, can’t leave nucleus (too big) Cell makes messenger RNA copy of DNA’s instructions that can leave the nucleus Cell makes messenger RNA copy of DNA’s instructions that can leave the nucleus Copying mRNA from DNA is called Transcription Copying mRNA from DNA is called Transcription

The Central Dogma DNA  RNA  Protein DNA  RNA  Protein

Transcription Animations “DNA makes RNA” Animation Animation Animation

Differences between DNA and RNA DNA is double stranded; RNA is single stranded – relevance? DNA is double stranded; RNA is single stranded – relevance? DNA has deoxyribose; RNA has ribose sugar DNA has deoxyribose; RNA has ribose sugar DNA has bases adenine, thymine, guanine, and cytosine; RNA has bases adenine, URACIL, guanine, and cytosine DNA has bases adenine, thymine, guanine, and cytosine; RNA has bases adenine, URACIL, guanine, and cytosine Many types of RNA – main ones are: Many types of RNA – main ones are: rRNA, tRNA, and mRNA rRNA, tRNA, and mRNA

RNA makes Protein mRNA codes for protein in a process called Translation mRNA codes for protein in a process called Translation Occurs at the cell’s ribosomes Occurs at the cell’s ribosomes Proteins are long strings of amino acids Proteins are long strings of amino acids tRNA molecules bring amino acids to the mRNA molecule and link up by base pairing tRNA molecules bring amino acids to the mRNA molecule and link up by base pairing

Translation Practice Use the table of Codon Triplets to translate this bit of mRNA Use the table of Codon Triplets to translate this bit of mRNA

Translation Practice mRNA codons (a codon is a set of three mRNA bases mRNA codons (a codon is a set of three mRNA bases GCU ACG GAG CUU CGG AGC UAG GCU ACG GAG CUU CGG AGC UAG Order of amino acids according to sequence above Order of amino acids according to sequence above _____ ____________________________ _____ ____________________________

When The Process Goes Wrong Genetic disease – Sickle Cell Anemia Genetic disease – Sickle Cell Anemia A single base is wrong in the DNA A single base is wrong in the DNA There is an A where a T belongs There is an A where a T belongs This causes a single amino acid to be wrong in the hemoglobin protein (452 amino acids big) This causes a single amino acid to be wrong in the hemoglobin protein (452 amino acids big) Valine goes where glutamate belongs Valine goes where glutamate belongs Hemoglobin is slightly mis-shapen as a result Hemoglobin is slightly mis-shapen as a result

Applications of DNA Technology Recombinant DNA - inserting genes into DNA strands Recombinant DNA - inserting genes into DNA strands Transgenics – a genetically altered organism (bacteria producing human insulin) Transgenics – a genetically altered organism (bacteria producing human insulin) Gene therapy Gene therapy DNA fingerprinting DNA fingerprinting

Complete the following w/s Complete the following w/s Quick review Quick review DNA basics DNA basics DNA technology DNA technology Practice transcription and translation Practice transcription and translation