Chapter 12 Notes DNA and RNA

12-1 DNA In 1928 Fredrick Griffith was studying the bacteria that cause pneumonia. - smooth  mouse dies - rough  mouse lives - heat killed smooth  mouse lives - above + rough  mouse dies Griffith experiment movie

Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia 12-1 DNA

Griffith called this process transformation: one type of bacteria turned into another ex. rough turns into smooth Griffith named this transformation because the bad bacteria had transferred their disease causing abilities to the harmless bacteria.

Oswald Avery: 1944 Avery destroyed bacteria’s proteins/lipids/ carbohydrates: transformation still occurred! Avery destroyed DNA: Transformation did not occur! Avery and other scientists found that DNA is the nucleic acid that stores and transmits the genetic information from one generation to the next

12-1 DNA Scientists were still undetermined if the cell’s genetic material was DNA or proteins Bacteriophage: virus that infects bacteria, composed of a protein coat and a DNA core Alfred Hershey and Martha Chase worked together in 1952 to study DNA in viruses. They studied one particular type of virus called a bacteriophage.

Hershey & Chase They reasoned that if they could determine if the protein or DNA core entered the bacteria, they would learn whether genes were made of DNA or protein. They used radioactive markers (S and P) to test this. Grew viruses with radioactive P-32 in DNA, let viruses infect bacteria, found radioactivity in bacteria 1952: Hershey and Chase concluded that the genetic material of the bacteriophage they infected with bacteria was DNA, not protein

Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

12-1 DNA Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

DNA’s Job Scientists knew that DNA has 3 functions: 1. Genes had to carry info from one generation to the next. 2. Genes put information to work by determining the inheritable characteristics of an organism. 3. Genes have to be easily copied because genes are replicated every time a cell divides

12-1 DNA DNA is made up of single units called nucleotides Each nucleotide of DNA consists of three parts: a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogen base The difference in nucleotides is in the nitrogen base

12-1 DNA The two categories of nitrogenous bases are purines and pyrimidines Purines: double ring structure - adenine and guanine Pyrimidines: single ring structure - cytosine and thymine

12-1 DNA DNA is like a ladder - the rungs are made of the nitrogenous bases - the backbone is formed by the sugar and phosphate groups Chargaff’s rule: [A] = [T]; [C] = [G] Percent of G and C equal, percent of A and T equal!

12-1 DNA PurinesPyrimidines AdenineGuanine CytosineThymine Phosphate group Deoxyribose

The Components and Structure of DNA Four types of nitrogenous bases: Guanine Purines Pyrimidines Adenine Cytosine Thymine Purines: Double-ring structure Adenine and Guanine Pyrimidines: Single ring Cytosine and Thymine Backbone of DNA: Sugar-Phosphate Adenine Phosphate group Guanine Deoxyribose CytosineThymine

12-1 DNA Watson and Crick discovered that the DNA molecule took the shape of a double helix In a double helix A binds to T, and C binds to G - explains Chargaff’s rule

X-ray Evidence Around this same time (late 1940’s – early 1950’s), Rosalind Franklin discovered that DNA was a double helix. She used a process called X-ray Diffraction. She shot X-rays at the DNA and recorded where the X-rays reflected. Her x-ray pattern did not reveal the exact structure, but it did paint the picture.

How many hydrogen bonds for A-T? C-G? Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Section Quiz Avery and other scientists discovered that DNA is found in a protein coat. DNA stores and transmits genetic information from one generation to the next. transformation does not affect bacteria. proteins transmit genetic information from one generation to the next.

Section Quiz DNA is a long molecule made of monomers called nucleotides. purines. pyrimidines. sugars.

Section Quiz Chargaff's rules state that the number of guanine nucleotides must equal the number of cytosine nucleotides. adenine nucleotides. thymine nucleotides. thymine plus adenine nucleotides.

Section Quiz In DNA, the following base pairs occur: A with C, and G with T. A with T, and C with G. A with G, and C with T. A with T, and C with T.

12-2 Chromosomes and DNA Replication Prokaryotes have a single strand of DNA that forms a circle - found in the cytoplasm The DNA of eukaryotes is linear and forms many strands - found in the nucleus Eukaryotes: much more complicated because there is about 1000x more DNA than a prokaryote. The number of chromosomes varies between organisms.

12-2 Chromosomes and DNA Replication Chromosome E. Coli Bacterium Bases on the Chromosomes

12-2 Chromosome Structure Eukaryotic DNA is tightly packed to form chromosomes - each chromosome contains both DNA and protein, packed together to form chromatin. DNA is tightly wrapped around proteins called histones to form a beadlike nucleosome. Nucleosomes function to fold enormous lengths of DNA into the tiny space of the nucleus. During cell division, the chromatin condenses to form a tightly packed structure called a chromosome.

12-2 Chromosomes and DNA Replication Chromosome Supercoils Coils Nucleosome Histones DNA double helix

The Double Helix Watson and Crick’s model of DNA revealed the mechanism by which DNA can copy itself. Each strand of DNA can be used to make another strand. Because of this we say that DNA is “complementary”. Replication: the process of duplicating DNA How DNA replicates: 1. DNA separates into two strands 2. Two new complementary strands are produced using the base pairing rules 3. Each original strand serves as a template

12-2 Chromosomes and DNA Replication DNA Replication: the copying of DNA before a cell divides DNA polymerase: the enzyme used in replication DNA polymerase joins individual nucleotides, proofreads to make sure bases paired correctly DNA replication animation

12-2 Chromosomes and DNA Replication Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Replication fork Original strand New strand

Section Quiz In prokaryotic cells, DNA is found in the cytoplasm. nucleus. ribosome. cell membrane.

Section Quiz The first step in DNA replication is producing two new strands. separating the strands. producing DNA polymerase. correctly pairing bases.

Section Quiz A DNA molecule separates, and the sequence GCGAATTCG occurs in one strand. What is the base sequence on the other strand? GCGAATTCG CGCTTAAGC TATCCGGAT GATGGCCAG

Section Quiz In addition to carrying out the replication of DNA, the enzyme DNA polymerase also functions to unzip the DNA molecule. regulate the time copying occurs in the cell cycle. “proofread” the new copies to minimize the number of mistakes. wrap the new strands onto histone proteins.

12-3 RNA and Protein Synthesis RNA, like DNA, consists of long chains of nucleotides. Three differences between DNA and RNA - the sugar is ribose - single stranded - contains uracil instead of thymine

12-3 RNA and Protein Synthesis

Genes are coded DNA instructions that control the production of proteins. - each gene controls the production of a specific protein - DNA (gene)  specific RNA sequence  specific amino acid sequence

12-3 RNA and Protein Synthesis There are 3 types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA), all involved in building proteins mRNA: carries copies of instructions from DNA to the rest of the cell rRNA: along with proteins, makes ribosomes

12-3 RNA and Protein Synthesis

Ribosome Ribosomal RNA

12-3 RNA and Protein Synthesis Amino acid Transfer RNA

12-3 RNA and Protein Synthesis tRNA: during protein construction, transfers each amino acid to the ribosome as specified by mRNA Transcription: the copying of the DNA into a complementary strand of RNA - uses the enzyme RNA polymerase

12-3 RNA and Protein Synthesis During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA. The enzyme binds to the regions of DNA known as promoters. Transcription Movie

12-3 RNA and Protein Synthesis RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only)

12-3 RNA and Protein Synthesis RNA Editing Before it leaves the nucleus, RNA is edited. Splicing occurs by removing introns and fusing exons together. Introns & exons – sequences of DNA Introns are CUT OUT while still in nucleus! EXons are kept (Expressed in mRNA)

12-3 RNA and Protein Synthesis Exon Intron DNA Pre-mRNA mRNA Cap Tail

12-3 RNA and Protein Synthesis The Genetic Code The genetic code is read in three letter segments called codons. There are 64 different codon possibilities -there are only 20 different amino acids that they code for -AUG is the start codon - there are 3 stop codons

12-3 RNA and Protein Synthesis

12-3 Amino Acids: p. 303

Another version: mRNA coding chart

12-3 RNA and Protein Synthesis Translation: the decoding of mRNA into an amino acid sequence During translation, the cell uses information from messenger RNA to produce proteins Proteins are joined in a chain of animo acids called a polypeptide chain - anticodon: the three letter sequence on tRNA that binds with mRNA

12-3 RNA and Protein Synthesis Nucleus mRNA

12-3 RNA and Protein Synthesis Lysine tRNA Phenylalanine Methionine Ribosome mRNA Start codon

12-3 RNA and Protein Synthesis tRNA Ribosome mRNA Lysine Translation direction

12-3 RNA and Protein Synthesis Polypeptide Ribosome tRNA mRNA

Section Quiz The role of a master plan in a building is similar to the role of which molecule? messenger RNA DNA transfer RNA ribosomal RNA

Section Quiz A base that is present in RNA but NOT in DNA is thymine. uracil. cytosine. adenine.

Section Quiz The nucleic acid responsible for bringing individual amino acids to the ribosome is transfer RNA. DNA. messenger RNA. ribosomal RNA.

Section Quiz A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the intron. exon. promoter. codon.

Concept Map fromtoto make up Section 12-3 also calledwhich functions toalso called which functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNACarry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNARibosomeRibosomes

Section 12.4: Mutations Vocabulary: 1. mutation4. chromosome mutations 2. point mutation 5. polyploidy 3. frameshift mutation Sometimes there are mistakes in copying DNA. Mutations: changes in the genetic material

Types of Mutations Gene Mutations - Changes in a single gene. Chromosome Mutations - Changes in whole chromosomes.

Point Mutations Point mutations – a change in one or a few nucleotides Substitution Insertion Deletion Insertion and deletion mutations can be more dangerous than a simple change in one amino acid (substitution). The code is still read in groups of three. Inserting an extra nitrogen base will throw off the entire “reading” of the code.

Gene Mutations Substitution Insertion Deletion

Frameshift Mutations Frameshift Mutations – shift the “reading frame” of the genetic message These can lead to a completely different protein!

Chromosome Mutations This involves a change in an entire chromosome, not just one or a few bases. 4 types: Deletion Duplication Inversion Translocation Video Clip

Chromosomal Mutations Deletion Duplication Inversion Translocation

Significance of Mutations Many mutations are neutral and have no effect on the expression of genes (making of proteins). Some have very harmful effects (defective proteins). Others are beneficial. Ex. Polyploidy – the condition of having an extra set of chromosomes (good for plants, often larger and stronger than diploid plants) Mutations are a source of genetic variation, and variation can be beneficial.