DNA and RNA Chapter 12 Hereditary Material Genes are protein codes.
Our genes are on our chromosomes. Chromosomes are made up of DNA. Genes are composed DNA! {Ask students where the chromosomes are in this picture.Or ask them where the DNA is.Remind them that the mitochondria also have DNA.} Chromosome Structure Chromatin is tightly coiled around proteins called histones. DNA and histone molecules form a beadlike structure: nucleosome Nucleosomes create the supercoils of DNA in a chromosome. Chromosome Structure of Eukaryotes
Nucleosome Chromosome DNA double helix Coils Supercoils Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only m. Histones Structure of DNA In eukaryotes, DNA is found in the NUCLEUS of cells.
DNA is made up of a series of monomers called nucleotides. Nucleotide structure: 1. 5carbon sugar: Deoxyribose 2. Phosphate group 3. Nitrogenous base DNA is a twisted-ladder called a DOUBLE HELIX! DNA Nucleotide O O=P-O N CH2 O C1 C4 C3 C2 Phosphate Group
Nitrogenous base (A, G, C, or T) CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose) Nitrogenous Bases Double ring PURINES Adenine (A) Guanine (G)
Single ring PYRIMIDINES Thymine (T) Cytosine (C) A or G T or C Chargaffs (Base Pairing) Rule
Adenine must pair with Thymine Guanine must pair with Cytosine The bases form weak hydrogen bonds Why do they pair together this way? T A G C DNA Double Helix Rungs of ladder Nitrogenous Base (A,T,G or C)
Legs of ladder Phosphate & Sugar Backbone DNA Structure Nucleotide Hydrogen bonds Sugar-phosphate backbone Key
Adenine (A) Thymine (T) Cytosine (C) Guanine (G) DNA Replication Occurs during cell division.
Helicase enzyme unzips the molecule of DNA, breaking the hydrogen bonds. Free-nucleotides in the nucleus will be bonded with its complementary base. DNA polymerase helps to bond the nucleotides together and check for errors. DNA Replication Section 12-2 Original strand DNA polymerase New strand
Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand DNA Replication The Scientists Griffith one strain of bacteria was transformed into another strain. Avery found that DNA was the transforming factor. Hershey and Chase DNA is the genetic material. Watson and Crick discovered the molecular structure of DNA. Griffiths Transformation Experiment Averys experiment isolated the element that caused the bacterial to become lethalDNA Hershey-Chase Experiment
Section 12-1 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 Chargaff and Franklin Chargaff Rosalind Franklin
Percentages of guanine and cytosine bases are almost equal in any sample of DNA Same is true of adenine and thymine DNA in all instances and from all organisms followed this rule Rosalind Franklin X-Ray diffraction showed that DNA was twisted into a double helix. RNA and Protein Synthesis
Section 12-3 RNA Long, single strand of nucleotides.
Nitrogen bases: A,U,G,Cno Thymine! Sugar: Ribose Found in cytoplasm and nucleus Types: messenger, transfer, ribosomal Function: Involved in the synthesis of protein molecules. Protein Synthesis occurs in two phases:
TRANSCRIPTION TRANSLATION Transcription Location where it occurs: Nucleus
RNA polymerase will unwind DNA at the region to be transcribed. It locates and binds at the promoter. mRNA is then made by base-pairing: A-U, G-C, T-A, C-G
If DNA sequence is:GATTACA Then mRNA sequence is: CUAAUGU When finished, mRNA leaves the nucleus and goes to the cytoplasm. Transcription Section 12-3 RNA polymerase DNA RNA
Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA Translation Location: Cytoplasm mRNA finds a ribosome
Ribosome reads strand for the start codon A codon is a mRNA triplet.Ex: AUG, UUC, etc Start codon is: AUG Transfer RNAs bring amino acids to ribosome. Translation continued
tRNAs anticodon bonds with mRNA codon. mRNA codons AUG UAA CGC tRNA anticodons UAC AUU GCG Amino acids connected with peptide bonds. When a Stop codon is reached.Protein is released from ribosome. Translation Section 12-3 Animation How to Interpret m-RNAs Code:
Each 3 nitrogen base sequence is called a CODON. Each codon specifies for a particular amino acid. AUG codon starts the initiation of the protein and codes for the amino acid methionine. Stop codons do not code for any amino acids ending the protein chain. A polypeptide is a chain of amino acids joined with peptide bonds aka a PROTEIN! Codon Chart #1 Section 12-3 Codon Chart #2 Methionine, Asparagine, Leucine
Lets Practice! DNA: TACTTGGAT mRNA:AUGAACCUA tRNA:UACUUGGAU Amino Acid squence: Methionine, Asparagine, Leucine Mutations Section 12-4 Mutations Changes that occur in the DNA Two types: 1. Gene mutations
2. Chromosomal mutations Many mutations are harmless Pros: increase adaptation or survival Cons: some can be lethal or debilitating Gene Mutations Changes that occur in a single gene.
Point mutations: one nucleotide that affects one amino acid. (substitutions produce point mutations) Frameshift mutations: involve the reading of the DNA or m-RNA strand; many amino acids are affected. (insertion or deletions produce frameshift mutations) Gene Mutations Frameshift mutations Point mutation: Substitution
Insertion Deletion Chromosomal Mutations
Whole chromosome is affected. Four types: 1. Deletion loss of material 2. Duplication addition of material 3. Inversion rearrangement of material 4. Translocation switching material with another chromosome Chromosomal Mutations
Deletion Duplication Inversion Translocation