Chapter 12DNA and RNA
transformation, bacteriophage, nucleotide, base pairing, chromatin, histone, replication, DNA polymerase, gene,
messenger RNA, ribosomal RNA, Transfer RNA, transcription, RNA polymerase, promoter, intron, exon, codon, translation, anticodon, mutation, point mutation,
frameshift mutation, polyploidy, adenine, cytosine, deletion, guanine, nitrogen base, purine, pyrimidine, thymine, uracil
12-1 DNAFrederick Griffith – 1928 – looking at how mice
react to two
related pneumonia bacteria
• Experiment
- Rough bacteria – mice live
- Smooth bacteria – mice got pneumonia & die
- Heat-killed smooth bacteria – mice live
- Heat killed smooth + rough bacteria – mice got pneumonia & die
Figure 12–2 Griffith’s Experiment
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 pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)
Dies of pneumonia
• Results = heat killed smooth bacteria could pass on their trait to harmless strain… called transformation
Oswald Avery – 1944 – repeated Griffith’s exp. and found thatDNA was the transforming factor
Alfred Hershey & Martha Chase – 1952 – worked with bacteria and virus to find out if protein or DNA held genes
• Virus = DNA/RNA surrounded by a protein coat
• Bacteriophage = a virus that infects bacteria
• Experiment
- Radioactive marker attached to protein part of bacteriophage… infects bacteria… marker was seen outside of bacteria
- Radioactive marker to DNA…infection… marker was seen inside bacteria
Figure 12–4 Hershey-Chase Experiment
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
• Results = genetic material of bacteriophage was DNA
Components and Structure of DNANucleotides = units (monomers) that make up
DNA molecule
• Made of 3 parts:
- deoxyribose – a 5-carbon sugar
- a phosphate group
- a nitrogenous base
• 4 possible nitrogenous bases
- purines: adenine or quinine
- pyrimidines: cytosine or thymine
Purines Pyrimidines
Adenine Guanine Cytosine Thymine
Phosphate group Deoxyribose
Erwin Chargaff – studied amounts of nitrogenous bases in DNA
• % guanine equal to % cytosine
• % adenine equal to % thymine
• also known as base pairing rule: A=T and C=G
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Rosalind Franklin – 1952 – X-ray diffraction to get pattern from structure of DNA
James Watson & Francis Crick – 1953 – published model and paper on DNA structure as a double helix
• double helix is similar to a twisted ladder or spiral staircase
- deoxyribose and phosphate make up sides/backbone
- nitrogenous base makes up stairs/rungs
12-2 – Chromosomes and DNA Replication
Prokaryotes = generally circular strand of DNA in cytoplasm
Eukaryotes = multiple molecules of DNA in nucleus
Chromosome
E. coli bacterium
Bases on the chromosome
Chromosome structure
• Chromatin = DNA that is tightly packed around proteins called histones
- during cell division, chromatin form packed chromosomes
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNA
double
helix
DNA Replication
• Replication = process of copying DNA
- occurs during S phase of Interphase
- process:
1. DNA is separated into two strands by an enzyme
2. free nucleotides are added by DNA polymerase according to base pairing rule
DNA Replication
Nitrogenous bases
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Replication fork
Original strand
New strand
DNA Replication
12-3 RNA and Protein Synthesis
RNA structure
• Has ribose as a sugar instead of deoxyribose
• Is generally single-stranded
• Has uracil instead of thymine
Types of RNA
• All types control protein synthesis in a cell
• 3 main types
- mRNA = messenger RNA – copies of instructions from DNA
- rRNA = ribosomal RNA – part of ribosomes
- tRNA = transfer RNA – transfers amino acids to ribosome
from to to make up
also called which functions to also called also called which functions towhich functions to
can be
RNA
Messenger RNA Ribosomal RNA Transfer RNA
mRNA Carry instructions rRNACombine
with proteins tRNABring
amino acids toribosome
DNA Ribosome Ribosomes
RNA Decoding Chart
Figure 12–14 Transcription
• Transcription = process of copying part of nucleotide Sequence of DNA into a complementary strand of RNA
• run by enzyme called RNA polymerase
RNADNA
RNApolymerase
Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
Transcription
The Genetic Code
• Proteins are chains of amino acids
- 20 different amino acids
- the order or sequence of amino acids determines properties of the protein
- codon = 3 consecutive nucleotides that specify a single amino acid
- one amino acid can have multiple codons
A U G G G C U C C A U C G G C G C A U A AmRNAmRNA
startcodon
codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1
Translation• Translation = the decoding of an mRNA
message into a polypeptide chain (protein)
• Occurs on ribosomes
Translation
• Process:
- mRNA binds to ribosome
- tRNA brings appropriate amino acid to ribosome – tRNA has anticodon that is complementary to codon on mRNA; begins with specific start codon - AUG
- peptide bonds are made between amino acids
- assembly line continues until a stop codon
Why bother?
• Transcription and translation keep master plans (DNA) safe in the nucleus, while blueprints (RNA) are sent to the worksite (ribosomes)
• Proteins are needed to act as enzymes that produces the color of your skin, the type of blood cell, the rate of growth
12-4 Mutations• Mutation = a change in the genetic
material
• Point mutations = change in one or a few nucleotides
• Frameshift mutations = adding or deleting a nucleotide… very disruptive
Chromosomal Mutations
Deletion
Duplication
• Chromosomal mutations = change in the number or structure of chromosomes.
- Deletion = loss of all or part of a chromosome
- Duplication = produce extra copies of parts of chromosome
Deletion & Duplication
- Inversion = reverse direction of parts of chromosome
- Translocation = part of one chromosome breaks and attaches to another
- Polyploidy = an organism has an extra sets of chromosomes
Inversion
Translocation
Translocation & Inversion