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chapter 12 dna and rna

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 dna
12-1 DNA

Frederick 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

Heat-killed, disease-causing bacteria (smooth colonies)

Harmless bacteria (rough colonies)

Harmless bacteria (rough colonies)

Control(no growth)

Heat-killed, disease-causing bacteria (smooth colonies)

Disease-causing bacteria (smooth colonies)

Dies of pneumonia

Dies of pneumonia

Lives

Lives

Live, disease-causingbacteria (smooth colonies)

Figure 12–2 Griffith’s Experiment
slide4
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

slide5
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

Figure 12–4 Hershey-Chase Experiment
  • Results = genetic material of bacteriophage was DNA
components and structure of dna
Components and Structure of DNA

Nucleotides = units (monomers) that make up DNA molecule

  • Made of 3 parts:

- deoxyribose – a 5-carbon sugar

- a phosphate group

- a nitrogenous base

slide8

Purines

Pyrimidines

Adenine

Guanine

Cytosine

Thymine

Phosphate group

Deoxyribose

  • 4 possible nitrogenous bases

- purines: adenine or quinine

- pyrimidines: cytosine or thymine

slide9

Nucleotide

Hydrogen bonds

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

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
slide10
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
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

slide12

Nucleosome

Chromosome

DNA

double

helix

Coils

Supercoils

Histones

Chromosome structure

  • Chromatin = DNA that is tightly packed around proteins called histones

- during cell division, chromatin form packed chromosomes

dna replication
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 replication1

Original strand

DNA polymerase

New strand

Growth

DNA polymerase

Growth

Replication fork

Replication fork

New strand

Original strand

DNA Replication

Nitrogenous bases

12 3 rna and protein synthesis
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
slide17
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

slide18

Messenger RNA

Ribosomal RNA

Transfer RNA

Bringamino acids toribosome

Combine

with proteins

tRNA

mRNA

Carry instructions

rRNA

DNA

Ribosome

Ribosomes

RNA

can be

also called

which functions to

also called

which functions to

also called

which functions to

from

to

to make up

figure 12 14 transcription

Adenine (DNA and RNA)

Cystosine (DNA and RNA)

Guanine(DNA and RNA)

Thymine (DNA only)

Uracil (RNA only)

RNApolymerase

DNA

RNA

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
slide22

start

codon

A

U

G

G

G

C

U

C

C

A

U

C

G

G

C

G

C

A

U

A

A

mRNA

codon1

codon 2

codon 3

codon 4

codon 5

codon 6

codon 7

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

translation
Translation
  • Translation = the decoding of an mRNA message into a polypeptide chain (protein)
  • Occurs on ribosomes
slide25
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

slide26
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
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
  • 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

slide30

Inversion

Translocation

- 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