Download DNA makes up chromosomes!

Chapter 12
DNA and RNA
There are four
kinds of
bases in
DNA:
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adenine
guanine
cytosine
thymine
DNA Double Helix
Chapter 12-2
Chromosomes and DNA Replication
DNA makes up chromosomes!
DNA and Chromosomes
• DNA and Chromosomes
• In prokaryotic cells, DNA is located in the
cytoplasm.
• Most prokaryotes have a single DNA molecule
containing nearly all of the cell’s genetic
information.
DNA and Chromosomes
Chromosome
E. Coli Bacterium
Bases on the
Chromosomes
DNA and Chromosomes
• Many eukaryotes have 1000 times the
amount of DNA as prokaryotes.
• Eukaryotic DNA is located in the cell
nucleus inside chromosomes.
• The number of chromosomes varies
widely from one species to the next.
DNA and Chromosomes
• Chromosome Structure
– Eukaryotic chromosomes contain DNA and protein, tightly
packed together to form chromatin.
– Chromatin consists of DNA tightly coiled around proteins called
histones.
– DNA and histone molecules form nucleosomes.
– Nucleosomes pack together, forming a thick fiber.
DNA and Chromosomes
• Chromosomes in Prokaryotic Cells (bacteria)
– One circular chromosome
– Found in cytoplasm
• Chromosomes in Eukaryotic Cells
– Found in nucleus
– DNA found in several chromosomes
– Number of chromosomes will vary with species
DNA Replication
• Each strand of DNA has all the information
needed to reconstruct the other half
• Strands are complementary and can be
used to make the other strand
A
T
C
G
T
A
C
G
G
C
T
A
A
T
DNA Replication
• During DNA replication
– The DNA molecule separates into two
strands.
– Produces two new complementary strands
following the rules of base pairing.
– Each strand of the double helix of DNA serves
as a template for the new strand.
DNA Replication
New Strand
Original strand
Nitrogen Bases
Growth
Growth
Replication Fork
Replication Fork
DNA Polymerase
\\loyola2\bschuller$\Biology PresentationExpress\Chapter12\Section02\Resources\ActiveArt\index.html
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http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html
http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf
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http://www.youtube.com/watch?v=hfZ8o9D1tus
http://www.youtube.com/watch?v=4jtmOZaIvS0
DNA Replication
1. Enzymes unzips DNA by breaking
hydrogen bonds. Strands separate at the
replication fork.
Replication Fork
DNA Replication
2. New complementary nucleotides are
added to make a new strand
3. The enzyme DNA polymerase attaches
nucleotides to produce new strands. DNA
polymerase proofreads each strand.
12-3 RNA and Protein Synthesis
Genes are coded DNA instructions that
control the production of PROTEINS.
Genetic messages can be decoded by
copying part of the nucleotide sequence
from DNA into RNA.
RNA contains coded information for making
proteins.
Central Idea of Genetics!
DNA
RNA
Transcription
PROTEIN
Translation
RNA
• RNA – Ribonucleic Acid
– Composed of a long strain of nucleotides
– Contains sugar, phosphate group, and nitrogen
base
RNA
DNA
Ribose sugar
Deoxyribose sugar
Singe-stranded
Doubled-stranded
Uricil
Thymine
RNA
• Types:
– Messenger RNA (mRNA) – messenger from
DNA to the rest of the cell
– Ribosomal RNA (rRNA) – make up ribosomes
– Transfer RNA (tRNA) – transfer amino acids
to the ribosomes
Transcription
• The process of
making RNA by
copying part of the
DNA sequence into a
complementary RNA
sequence
Transcription
•
Requires enzyme RNA polymerase
1. RNA Polymerase binds to DNA and
separates strands
2. RNA Polymerase uses DNA as template
and assembles complementary RNA
strands
Transcription
Transcription Animations
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http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html
http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf
RNA Editing
• RNA Editing
– The DNA of eukaryotic genes contains
sequences of nucleotides, called introns, that
are not involved in coding for proteins.
– The DNA sequences that code for proteins
are called exons.
– When RNA molecules are formed, introns and
exons are copied from DNA.
RNA Editing
Exon Intron
• The introns are
cut out of RNA
molecules.
• The exons are
the spliced
together to form
mRNA.
DNA
Pre-mRNA
mRNA
Cap
Tail
Protein Review
• Proteins are made by joining
– AMINO ACIDS
• Each protein contains a combination of the
20 amino acids
• The function of the protein is determined
by number and sequence of amino acids
• (A polypeptide is a protein!)
Protein 1
Protein 2
Genetic Code
• The genetic code is the “language” of mRNA
instructions.
• A codon consists of three consecutive nucleotides on
mRNA that specify a particular amino acid.
Each codon specifies a particular amino acid
that is to be placed on the polypeptide chain.
Genetic Code
RNA Sequence UCGCACGGU
Codon Sequence –
UCG–CAC–GGU
Use the Amino Acid
Guide to determine
amino acid –
UCG–CAC–GGU
Amino acid sequence –
UCG–CAC–GGU
Serine – Histidine – Glycine
Translation
• Translation is the decoding of an mRNA
message into a polypeptide chain
(protein).
• Translation takes place on ribosomes.
• During translation, the cell uses
information from messenger RNA to
produce proteins.
Translation
1. Messenger RNA is transcribed in the
nucleus, and then enters the cytoplasm
where it attaches to a ribosome.
Translation
2. The ribosome “reads” the mRNA codon
and the corresponding amino acid is
brought to the ribosome by the tRNA
Amino Acid
Amino Acid
codon
Translation
3. The ribosome forms bonds between the
amino acids to form the protein
Bond formed
Translation
4. Translation
continues until
the ribosome
reaches a stop
codon on the
mRNA and
releases the
protein
(polypeptide)
The BIG Picture!
Translation Animation
• http://wwwclass.unl.edu/biochem/gp2/m_biology/animation/gene/ge
ne_a3.html
• http://www.stolaf.edu/people/giannini/flashanimat/molgen
etics/translation.swf