DNA and the Language of Life Chapter 12 DNA and the Language of Life

DNA: The Genetic Material

How do we know that DNA is the genetic material? Essential Question How do we know that DNA is the genetic material?

1928 - Key Player Identified the “Transforming Factor” Frederick Griffith

Griffith's "Transforming Factor" Is the Genetic Material

1944 DNA Identified as “The Transforming Factor” Oswald Avery Colin MacLeod Maclyn McCarty

Isolated genetic material in vitro. DNA from S strain causes R strain to be transformed Proteases cannot prevent transformation RNase cannot prevent transformation Molecular weight is large DNase destroyed all transforming activity

1950 - Erwin Chargaff Chargaff’s Rules Proportion of A = that of T and G=C Equal proportions of A and G and C and T

1952 More Evidence of DNA & Heredity Martha Chase & Alfred Hershey

Virus Experiments of Hershey & Chase Provide More Evidence

1953 - DNA Structure Determined James Watson & Francis Crick

Structure of DNA

Key Players Rosalind Franklin Maurice Wilkins

X-ray Crystallography of DNA Photo 51

Nucleic Acids Store Information

Nucleotide

The DNA Molecule is antiparallel.

Nucleotide monomers join together by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone.

DNA contains four different nitrogenous bases DNA contains four different nitrogenous bases. Thymine and cytosine have single-ring structures. Adenine and guanine have double-ring structures.                                                                                                                                                                                                                           

Remembering which are which! Angels of God are PURe. A(ngels) = Adenine G(od) = Guanine PUR(e) = Pur(ines)

Numbers of Hydrogen Bonds A-T have two but G-C have three

Section 12.2 DNA Replication The Molecular Mechanism of Inheritance

DNA Replication Occurs before cell division (S-phase) Each daughter molecule has one old strand (derived or “conserved” from the parent molecule) and one newly made strand.

DNA Replication is Semiconservative G T A A T G C Parent molecule Figure 16.9 A model for DNA replication: the basic concept

DNA Replication is Semiconservative G C G T A T A A T A T G C G C Parent molecule Separation of strands Figure 16.9 A model for DNA replication: the basic concept

DNA Replication is Semiconservative G C G C G C G T A T A T A T A A T A T A T A T G C G C G C G C Parent molecule Separation of strands “Daughter” DNA molecules, each consisting of one parental strand and one new strand Figure 16.9 A model for DNA replication: the basic concept

Molecular Genetics DNA Replication

Section 12.3 DNA, RNA and Protein

Key Terms RNA Transcription Translation codon

DNA is the universal language of life. Translate the following statement: DNA is the universal language of life.

Genetic makeup – the sequence of nucleotide bases in DNA. Genotype Genetic makeup – the sequence of nucleotide bases in DNA.

The Relationship Between Genes and Proteins 1 gene = 1 polypeptide.

DNA vs. RNA Double stranded Thymine is one of the bases Deoxyribose sugar Single stranded Uracil instead of Thymine Ribose sugar

From gene to polypeptide.

Transcription/Translation Analogy DNA  RNA (Transcription) Like transcribing a speech Language is the same Form changes (spoken to written) RNA  Protein (Translation) Converts nucleic acid language into amino acid language. Based on codons (3 base word)

Molecular Genetics

Triplet Code Shared by almost all organisms 61 of the triplets code for amino acids Some amino acids are coded for by more than 1 codon. No codon represents more than 1 amino acid. 3 STOP codons come at end of gene sequence.

Triplet Code

Triplet Code Inner circle signifies first nucleotide in codon, second circle signifies second nucleotide in codon, outer circle.

Concept 12.5 There are Two Main Steps From Gene to Protein DNA  RNA RNA  Protein

Key Terms Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA) Codon anticodon

Transcription (DNA  RNA) RNA nucleotides base-pair one by one with DNA nucleotides on one of the DNA strands (called the template strand). RNA polymerase links the RNA nucleotides together.

In eukaryotes, the RNA transcript is edited before it leaves the nucleus. Introns are removed and the exons are spliced together before the "final draft" transcript moves into the cytoplasm where it gets translated.

Translation (RNA  Protein)

tRNAs transport and match amino acids to their appropriate codons on the mRNA transcript. One end of the tRNA attaches to an amino acid. At the other end, a triplet of bases called the anticodon matches to the complementary mRNA codon.

Ribosomes bring mRNA and tRNAs together during translation Ribosomes bring mRNA and tRNAs together during translation. Each ribosome has an attachment site for an mRNA transcript, and two sites for tRNAs.

Ribosomes

Adding Amino Acids to a Polypeptide chain

Translation begins with the attachment of a ribosome and the first tRNA to a "start" (AUG) codon. The ribosome then moves along the mRNA transcript. The polypeptide elongates as an amino acid is added for each codon. When the ribosome arrives at a "stop" codon, the completed polypeptide is released.

Molecular Genetics

Section 12.4 Gene Mutation

Key Terms Mutation - any change in the nucleotide sequence of DNA. mutagen - Physical or chemical agents that cause mutations.

Body-cell v. Sex-cell Mutation Somatic cell mutations are not passed on to the next generation. Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.

DNA Mutations Substitutions Insertions Deletions

DNA Mutations Insertion or deletion of one or more nucleotides in a gene is usually more disastrous than the effects of a base substitution.

Types of DNA Mutations There are three general categories of gene mutation: base substitutions, insertions, or deletions.

THE BIG FAT CAT ATE THE WET RAT DNA Mutations THE BIG FAT CAT ATE THE WET RAT Normal THE BIG FAT CAT ATE THE WET RAT

THE BIZ FAT CAT ATE THE WET RAT DNA Mutations THE BIG FAT CAT ATE THE WET RAT Substitution THE BIZ FAT CAT ATE THE WET RAT

DNA Mutations THE BIG FAT CAT ATE THE WET RAT Insertion (causing frameshift) THE BIG ZFA TCA TAT ETH EWE TRA

THB IGF ATC ATA TET HEW ETR AT DNA Mutations THE BIG FAT CAT ATE THE WET RAT Deletion (causing frameshift) THB IGF ATC ATA TET HEW ETR AT

THE BIG FAT FAT ATE THE WET RAT DNA Mutations THE BIG FAT CAT ATE THE WET RAT Duplication THE BIG FAT FAT ATE THE WET RAT Fragile X Syndrome

Common Mutagens Most common: high-energy radiation (X-rays and ultraviolet light) Chemical mutagen: chemicals that are similar to normal DNA bases but cause incorrect base-pairing when incorporated into DNA. A mutation present in a gamete can be passed on to its offspring.