Download DNA- The Genetic Material

CHAPTER 13:
DNA, RNA, and Proteins
FIZZ 1
Essential Questions:
1.
What is the Central
Dogma of Biology?
CHAPTER 13:
DNA, RNA, and Proteins
FIZZ 1
Essential Questions:
2. What is DNA?
CHAPTER 13:
DNA, RNA, and Proteins
FIZZ 1
Essential Questions:
3. How is DNA related to
traits?
CHAPTER 13:
DNA, RNA, and Proteins
FIZZ 1
Essential Questions:
4. What is the Genetic
Code?
DNA- The Genetic Material
• Why should I care about DNA?
• DNA stores the information that tells cells which proteins to make
• Your proteins give you your physical/chemical/ identity
• Your DNA is different from everyone else’s DNA on earth
Does DNA have anything to do with why I am
so special?
• Yes, it’s the variability of DNA that makes us
all different!
The Central Dogma of Biology
DNA
RNA
PROTEINS
DNA is transcribed into RNA
RNA is translated into Proteins
Proteins give you your traits or Phenotype
Searching for the Genetic Material
• Griffith - Discovered the
transformation of harmless R
strain Bacteria by heat killed S
bacteria
• Avery – Identified DNA as the
transformative agent
• Hershey & Chase –Studied
bacteriophages and proved
DNA was the source of
hereditary information
Who Discovered the Structure of DNA?
 James Watson & Francis Crick discovered the
structure of DNA after observing an X-ray
picture of it taken by Rosalind Franklin
The Structure of DNA
The Structure of DNA is both complex and
simply elegant
DNA is a polymer of Nucleotidesremember a polymer is like a chain of
beads- DNA is made of 2 chains
There are 4 different Nucleotides (beads)
abbreviated as A, T G, or C
The Base on one chain “complements” and
makes a bond with the base on the opposite
chain
The bases are bound together by hydrogen
bonds.
The two strands are twisted together
DNA Structure
DNA is a polymer of nucleotides (the beads on the chain)
Each Nucleotide contains
1 Nitrogenous base + 1 phosphate group + 1 sugar
In DNA the sugar is deoxyribose
Nucleotide
Nitrogenous Bases
The Structure of DNA
There are 4 different Nucleotides
identified by their Nitrogenous
Bases:
Adenine Guanine (the pyrimidines)
Cytosine Thymine (the purines)
The Bases are said to “complement”
one another - A bonds to T, G bonds
to C according to the base pairing
rules(also called Chargraffs Rules)
The bases are bound to each other by
hydrogen bonds.
The Structure of DNA
The DNA Double Helix is
composed of 2 interconnected
nucleotide chains
The nucleotide chains are
composed of a Sugar-Phosphate
backbone, with bases in the
middle
The Nucleotides are joined by
Phosphodiester bonds
The two strands are twisted
together and joined by Hydrogen
bonds between he bases
Structure of DNA
DNA Replication
Why does DNA replicate?
Cells get worn out, new cells must be made
New cells must make exact copies of themselves
Copies of replicated genes can be passed on to
offspring
How is DNA Replicated?
1.
Helicase breaks hydrogen bonds in the middle of the strand,
creating a replication fork
2.
Unpaired bases form new bonds with free nucleotides in the cell
How is DNA Replicated?
3.
New strand is rewound together by
DNA Polymerase, creating 2
identical DNA molecules
4.
Sometimes replication errors make
a mistake (A bonds to a G);
5.
There are 3 x 109 bases in the
average cell
6.
Takes about 4 hours for a cell to
replicate its DNA
3.
The process is SEMIConservative, ie each new DNA
molecule has one old strand
Transcription
DNA is located in the
nucleus of the cell
DNA CANNOT leave the
nucleus of the cell
because it is double
stranded
So How does it get out?
http://www.dnalc.org/resources/3d/12-transcription-basic.html
Transcription
Mr. Dougherty! I am afraid for the DNA, it can’t get to the ribosome!
What will it do?
Relax, RNA is the key!
What is RNA?
•A nucleic acid that is similar to DNA
•Ribose is the sugar
•Instead of thymine, Uracil
•Single stranded
Steps of Transcription
1. DNA strand unwinds via RNAPolymerase (not helicase)
2. Free nucleotides bond to bases, except U in RNA bonds to A
from DNA
3. RNA polymerase joins single stranded RNA together
4.Messenger RNA (mRNA) moves to the ribosome in the cytoplasm
(or on the Rough ER)
Transcription
Animation of Transcription!
http://www.johnkyrk.com/DNAtranscription.html
Translation (Protein Synthesis)
What is protein synthesis?
The Conversion of RNA to
Amino Acids which make up
proteins
Why is it called translation?
The genetic code (ATCG) is
translated into a protein
Where does it occur?
At the ribosome in the cytoplasm
Globular Protein found in Human Blood
(serum albumin)
Translation and the Genetic Code
RNA is composed of 3 letter
“words” called CODONS
Each codon of RNA represents
a specific Amino Acid
For instance AUG is the start
codon, and UUU represents
the amino acid Phe
(phenylalanine)
Why is it called translation?
The genetic code (ATCG) is
translated
into a protein
Translation and the Genetic Code
RNA is composed of 3 letter
“words” called CODONS
Each codon of RNA represents a
specific Amino Acid
For instance AUG is the start
codon, and UUU represents the
amino acid Phe (phenylalanine)
Why is it called translation?
The genetic code (ATCG) is
translated
into a protein
Genetic Code
Problem
If the DNA code is
AAT GCG TTT CGC ATA TAT
Then the RNA compliment is
___ ___ ___ ___ ___ ___
and the Amino Acid sequence that
results is
____ ____ ____ ____ ____ ____
How Does Translation Occur?
The 3 Steps of Translation
1. Initiation
A. Ribosome attaches to mRNA (each 3 bases is called a
codon)
B. tRNA brings anticodon and AA to ribosome
2. Elongation
A. More tRNA’s bring more AA’s to ribosome
B. AA’s connected together to make polypeptides (by
peptide bonds)
3. Termination
A. Ribosome reaches a STOP signal on mRNA
B. Polypeptide (protein) is broken off and becomes part of
the human body
C. Golgi apparatus modifies completed protein; ER
transports it in/out of cell
Translation- The Movie
Translation Animation Part 2!
Translation Animation
Scary Translation
Scary Animation of Translation!
http://www.youtube.com/watch?v=983lhh2
0rGY
The processes of transcription and
translation are the same in all living
organisms!
Blue Whale
Tarantula
CHAPTER 14:
Genes in Action
Essential Questions:
What is DNA?
What is the Central
Dogma of Biology?
What is the Genetic
Code?
How is DNA related to
traits?
Control of Gene Expression in
Eukaryotes
In eukaryotes, cells differ in which genes are being expressed
based on cell function – ex. nerve vs. muscle.
•Genes in eukaryotic cells are turned on and off like a light
switch. The genes that are turned on in a muscle cell are
different than the genes that are turned on in a nerve cell.
•Gene expression is what makes cells different in a
multicellular organism
Nerve Cell vs.
Muscle Cell
Gene Mutations
A Mutation is a change in the sequence of bases within
a gene
Causes:
• Mutations can be spontaneous or caused by
environmental influences called mutagens.
• Mutagens include radiation (X-rays, UV
radiation), and organic chemicals (in cigarette
smoke and pesticides).
Types of Mutations
Frameshift mutations –
• one or more bases are inserted or deleted from a
sequence of DNA
• can result in nonfunctional proteins
• can result in no protein at all – stop codon where there
shouldn’t be one
Point mutations (3 Types) –
• One base is substituted for another
• May result in change of amino acid sequence
• May not affect protein at all
Types of point mutations
• 1. Silent mutation - the change in the codon results in
the same amino acid
• Ex: UAU  UAC both code for tyrosine
• 2. Nonsense mutation - a codon is changed to a stop
codon; resulting protein may be too short to function
–
Ex: UAC  UAG (a stop codon)
• 3. Missense mutation - involves the substitution of a
different amino acid, the result may be a protein that
cannot reach its final shape
– Ex: Hbs which causes sickle-cell disease
Repair of Mutations
• DNA polymerase proofreads the new strand
against the old strand and detects mismatched
pairs, reducing mistakes to one in a billion
nucleotide pairs replicated.
• If errors occur in sex cells – mutation may be
passed onto offspring
• If errors occur in body cells - cancer may
result
Genetic Diseases
Autosomal dominant disease  Presence of dominant allele means
that individual will have the disease
Autosomal recessive disease  Disease only present when BOTH
recessive alleles are present
Sex-linked Dominant  Disease present when dominant allele is
present on either sex chromosome
Sex-linked Recessive  Disease present when recessive allele is
present on either sex chromosome
Common Genetic Diseases
Huntington’s Disease Autosomal dominant ;
Neuromuscular disease; degeneration of muscle tissue; onset in early 30’s.
Folk Singer Woody Guthrie had the disease
Cystic Fibrosis Autosomal Recessive; Defective Protein is made that creates excess
mucus; clogs lungs.
Color Blindness Sex-linked recessive
Inablity to distinguish colors (8% of male population)
Some Genetics Diseases
Hemophilia Sex-linked recessive
Inablity of blood to clot
Nicholas, Czar of Russia (Mid 1800’s) child was hemophiliac
Muscular Dystrophy Sex-linked recessive
Tay-Sach’s Disease  Autosomal Recessive
Degeneration of Central Nervous System; infant mortality
Changes in Chromosome Number
• Nondisjunction – occurs when:
– In meiosis I, homologous pair both go into the same
daughter cell or
– In meiosis II, the sister chromatids both go into the same
gamete.
• The result:
– Trisomy (3 copies of a single chromosome) or
– Monosomy (1 copy of a single chromosome)
Nondisjunction in Meiosis I
Changes in Chromosome Structure
• Mutation - a permanent genetic change.
• Chromosome mutation - a change in chromosome
structure
• Radiation, organic chemicals, or even viruses may
cause chromosomes to break, leading to
mutations.
• Types of chromosomal mutations: inversion,
translocation, deletion, and duplication.
Deletions
• Deletions occur when a single break causes a lost
end piece, or two breaks result in a loss in the
interior.
• An individual inherits a normal chromosome from
one parent and a chromosome with a deletion
from the other parent
• No longer has a pair of alleles for each trait
• A syndrome can result – type depends on
chromosome(s) affected.
Williams Syndrome
• Chromosome 7 loses an end piece
• Children have a pixie look (turned-up noses, wide mouth,
small chin, large ears)
• Poor academic skills, good verbal and musical abilities
• Skin ages prematurely from lack of the gene that controls
the production of elastin (also affects cardiovascular
health).
Duplication
• Duplication results in a chromosome segment being repeated
in the same chromosome
– Produces extra alleles for a trait.
• Ex: An inverted duplication in chromosome 15 causes inv dup
15 syndrome
– Poor muscle tone, mental retardation, seizures, curved
spine, and autistic characteristics
Duplication
Translocation
• Translocation is exchange of chromosomal segments between
two, non-homologous chromosomes.
– Ex: Alagille syndrome results from a deletion of
chromosome 20 or a translocation that disrupts an allele on
chromosome 20.
– Distinctive face, abnormalities of eyes & internal organs,
and severe itching.
Translocation: Alagille Syndrome
Inversion
• Inversion involves a segment of a chromosome being turned
180 degrees
• The reverse sequence of alleles can alter gene activity.
• Crossing-over between inverted and normal chromosomes
can cause duplications and deletions in resulting
chromosomes.
Inversion