Chapter 12 DNA and RNA transformation, bacteriophage, nucleotide, base pairing, chromatin, histone,...

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