Chapter 4 DNA & RNA The Nucleic Acids Remember: Each chromosome is a very long DNA molecule that contains many genes. Gene: A segment of DNA that is part of a chromosome that is responsible for inherited traits such as eye color, hair color, skin color, etc. It directs the protein production that controls the cell.

Chapter 4 DNA & RNA The Nucleic Acids DNA: (Deoxyribonucleic Acid): Is an organic molecule composed of nucleotides. Is a molecule that is common to all living things, from bacteria to humans. It is the blueprint of an organism, containing the genetic instructions for building proteins. A DNA molecule canNOT be viewed with a compound light microscope. The composition of DNA was first described correctly in 1953 by two scientists, Watson and Crick. They discovered that it was formed from two long chains of nucleotides shaped much like a spiraling ladder, and they called it a double helix.

Chapter 4 DNA & RNA The Nucleic Acids Structure of DNA: (DNA is composed of nucleotides.) Nucleotides of DNA have three Parts: 1.Deoxyribose (a five carbon sugar) 2.Phosphate group (these two bond together to make up the sides of the ladder) 3.1 of 4 Nitrogen Bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

Chapter 4 DNA & RNA The Nucleic Acids

Chapter 4 DNA & RNA The Nucleic Acids

Chapter 4 DNA & RNA The Nucleic Acids

Chapter 4 DNA & RNA The Nucleic Acids The nitrogen bases adenine and guanine are called purines which have a double ring of carbon and nitrogen. The nitrogen bases cytosine and thymine are called pyrmidines, which have a single ring of carbon and nitrogen.

Chapter 4 DNA & RNA The Nucleic Acids The 2 chains of nucleotides in a DNA molecule are held together by hydrogen bonds between the nitrogen bases.

Chapter 4 DNA & RNA The Nucleic Acids The 2 chains of nucleotides in a DNA molecule are held together by hydrogen bonds between the nitrogen bases. The 2 bases on the same rung of the DNA ladder are referred to as a base pair. In DNA Cytosine always bonds with guanine, and Thymine always bonds with adenine! C=GG=C T=AA=T

Chapter 4 DNA & RNA The Nucleic Acids Base Pairing Rules. The strictness of base-pairing results in 2 strands that are complementary, which means the sequence of bases on one strand determines the sequence of bases on the other strand. Example: 1 st strand of DNA has T C G A A T T The other strand must haveA C T A

Chapter 4 DNA & RNA The Nucleic Acids Base Pairing Rules. The strictness of base-pairing results in 2 strands that are complementary, which means the sequence of bases on one strand determines the sequence of bases on the other strand. Example: 1 st strand of DNA has T C G A A T T The other strand must haveA G C T T A A

Chapter 4 DNA & RNA The Nucleic Acids All organisms contain the same DNA (made up of nucleotides with adenine, thymine, guanine, and cytosine) The reason organisms can be different from each other is because the order of nucleotides in two different organisms are different (sequence of bases) Example: A squirrel differs from a rosebush because the order of nucleotides in its DNA is different.

Chapter 4 DNA & RNA The Nucleic Acids Replication: During mitosis and meiosis the cells divide. Each time a cell divides it must make a copy of its DNA. Replication is the process by which DNA is duplicated, forming two identical copies from one original.

Chapter 4 DNA & RNA The Nucleic Acids These are the steps of replication: 1. The enzyme DNA helicase breaks the hydrogen bonds between the nitrogen bases that hold the two strands together, unzipping the DNA molecule. 2. As the DNA continues to unzip, free nucleotides from the surroundings in the nucleus bond to the single strands base pairing. 3. The enzyme DNA polymerase forms the sugar-to- phosphate bonds that connect nucleotides on each strand of DNA.

Chapter 4 DNA & RNA The Nucleic Acids Replication of DNA doesn’t begin at one end of the molecule and end at the other, rather it occurs simultaneously at many points on the molecule, speeding up to process. Replication is completed when the entire molecule has been unzipped and replicated.

Chapter 4 DNA & RNA The Nucleic Acids

Chapter 4 DNA & RNA The Nucleic Acids Each new DNA molecule has one nucleotide strand from the original DNA molecule and one nucleotide strand that has been newly synthesized from free nucleotides in the cell.

Chapter 4 DNA & RNA The Nucleic Acids Gene Expression is the use of genetic information in DNA to make proteins.

Chapter 4 DNA & RNA The Nucleic Acids Gene Expression is the use of genetic information in DNA to make proteins. Gene Expression takes place in 2 stages:

Chapter 4 DNA & RNA The Nucleic Acids Gene Expression is the use of genetic information in DNA to make proteins. Gene Expression takes place in 2 stages: 1.Transcription is when the RNA copy of a gene is made.

Chapter 4 DNA & RNA The Nucleic Acids Gene Expression is the use of genetic information in DNA to make proteins. Gene Expression takes place in 2 stages: 1.Transcription is when the RNA copy of a gene is made.

Chapter 4 DNA & RNA The Nucleic Acids Gene Expression is the use of genetic information in DNA to make proteins. Gene Expression takes place in 2 stages: Transcription is when the RNA copy of a gene is made. Translation is the 2 nd stage of gene expression where 3 different kinds of RNA work together to assemble amino acids into a protein molecule.

Chapter 4 DNA & RNA The Nucleic Acids Gene Expression is the use of genetic information in DNA to make proteins. Gene Expression takes place in 2 stages: 1.Transcription is when the RNA copy of a gene is made. 2.Translation is the 2 nd stage of gene expression where 3 different kinds of RNA work together to assemble amino acids into a protein molecule. Those 3 different kinds of RNA that work together are mRNA, tRNA, rRNA.

Chapter 4 DNA & RNA The Nucleic Acids Transcription Transcription is the process of producing RNA (Ribonucleic Acid) from DNA. RNA is the form in which information moves from DNA in the nucleus to the ribosomes in the cytoplasm.

Chapter 4 DNA & RNA The Nucleic Acids Transcription The process of transcription is similar to the process of replication, but RNA differs from DNA in 3 ways: 1. RNA is single stranded (DNA is double stranded) 2. RNA has ribose as the sugar (DNA has deoxyribose as the sugar 3. RNA has four nitrogen bases, but Thymine is replaced with Uracil

Chapter 4 DNA & RNA The Nucleic Acids There are 3 Types of RNA: 1. mRNA-messenger RNA: It carries the information from DNA (in the nucleus) out into the cytoplasm 2. tRNA-transfer RNA: It brings amino acids to the ribosomes so they can be assembled into proteins. 3. rRNA-ribosomal RNA: It makes up the ribosomes, the site of protein synthesis

Chapter 4 DNA & RNA Cytosine Guanine Adenine Uracil Thymine

Chapter 4 DNA & RNA The Nucleic Acids The Genetic Code Remember that DNA’s purpose is to provide a blueprint for making proteins.

Chapter 4 DNA & RNA The Nucleic Acids The Genetic Code Remember that DNA’s purpose is to provide a blueprint for making proteins. Proteins are built from chains of smaller molecules called amino acids, and there are 20 of them.

Chapter 4 DNA & RNA The Nucleic Acids The Genetic Code Remember that DNA’s purpose is to provide a blueprint for making proteins. Proteins are built from chains of smaller molecules called amino acids, and there are 20 of them. Recall that there are only four nitrogen bases. So how can four bases code for 20 amino acids?

Chapter 4 DNA & RNA The Nucleic Acids The Genetic Code The answer is that each strand of DNA is read in sets of three nitrogen bases, called a codon.

Chapter 4 DNA & RNA The Nucleic Acids The Genetic Code The answer is that each strand of DNA is read in sets of three nitrogen bases, called a codon. By reading in groups of three bases there are 64 combinations possible. Of these 61 code for amino acids, and there is a START codon (AUG) and 2 STOP codons (UAA & UAG)

Chapter 4 DNA & RNA The Nucleic Acids

Chapter 4 DNA & RNA The Nucleic Acids Protein Synthesis Equation: DNA mRNA Protein

Chapter 4 DNA & RNA The Nucleic Acids Protein Synthesis Equation: DNA mRNA Protein transcription translation

Chapter 4 DNA & RNA The Nucleic Acids Translation Translation (or protein synthesis, gene expression) is the process of converting the information in a sequence of nitrogen bases in mRNA into a sequence of amino acids that make up a protein.

Chapter 4 DNA & RNA The Nucleic Acids Translation The steps of translation are:

Chapter 4 DNA & RNA The Nucleic Acids Translation The steps of translation are: 1.The first codon of the mRNA strand attaches to a ribosome (rRNA).

Chapter 4 DNA & RNA The Nucleic Acids Translation The steps of translation are: 1. The first codon of the mRNA strand attaches to a ribosome (rRNA). 2. Then a tRNA molecule has a special section called an anti codon that is complementary to the codon on the mRNA molecule. The first codon is methionine. AUG signals the start of protein synthesis.

Chapter 4 DNA & RNA The Nucleic Acids Translation The steps of translation are: 3. Next the ribosome slides down the mRNA strand to the next codon. 4. When the first and second amino acids are in place, an enzyme joins them by a peptide bond.

Chapter 4 DNA & RNA The Nucleic Acids Translation The steps of translation are: 5.This process continues until it reaches a stop codon. The chain of amino acids are now considered a protein.

Chapter 4 DNA & RNA The Nucleic Acids The order of events that leads to genetic expression: Protein synthesis DNA to RNA to amino acids to protein

Chapter 4 DNA & RNA The Nucleic Acids

Chapter 4 DNA & RNA The Nucleic Acids Mutations: Mutation is any mistake or change in the DNA sequence. Mutations in gametes can be passed on to offspring of the affected individual, but mutations in body cells affect only the individual in which they occur.

Chapter 4 DNA & RNA The Nucleic Acids Mutations: 1. Chromosome mutation –involves a change in the structure or number of chromosomes. One example is nondisjunction (when one or more pairs of homologous chromosomes fail to separate during meiosis.) Down Syndrome in humans is caused by the presence of an extra 21 st chromosome. Other chromosome mutations may be caused by deletion, translocation, inversion, and duplication of parts of the whole chromosome.

Chapter 4 DNA & RNA The Nucleic Acids Four Types of Mutations: 1.Deletion mutation- a piece of chromosome breaks off completely. The new cell will lack a certain set of genes. Often this is fatal to the zygote. 2.Duplication mutation- a chromosome fragment attaches to its homologous chromosome, which then carry two copies of a certain set of genes.

Chapter 4 Deletion MutationDuplication Mutation

Chapter 4 3.Inversion mutation- the chromosome piece reattaches to the original chromosome but in a reverse position. 4.If the piece reattaches to a nonhomologous chromosome a translocation mutation results.

Chapter 4 Translocation Mutation Inverse Mutation

Chapter 4 DNA & RNA The Nucleic Acids Mutations: Gene mutation—involves a change in the chemical makeup of the DNA. This is where one or more DNA nucleotides are deleted or substituted with others. These are called point mutations. Frame shift—are mutations that change one or just a few nucleotides in a gene on a chromosome. Example: sickle cell anemia and cystic fibrosis

Chapter 4 Occasionally random gene mutations produce changes that make the individual better adapted to the environment. Such mutated genes tend to increase in frequency with in a population.

Chapter 4 DNA & RNA The Nucleic Acids Mutations: 3. Mutagens increase the incidence of mutation.

Chapter 4 DNA & RNA The Nucleic Acids Mutations: 1.Mutagen mutation increase the incidence of mutation. Examples of these: Xrays Ultraviolet rays Radioactive substances Chemicals Nicotine Alcohol