Download DNA, RNA, Protein synthesis, and Mutations

DNA, RNA, Protein
synthesis, and
Mutations
Chapters 12-13.3
1A)Identify the components of DNA
and explain its role in heredity.
• DNA’s
•
Role in heredity:
Contains the genetic information of a cell
that can be:
• Stored
• Ion
transport
• movement
• Cell growth
• Respiration
• Copied
• Copy
genetic information before a cell divides
• Transmitted
• After
cell division-each cell has a identical copy of
information
1A)Identify the components of DNA
and explain its role in heredity.
DNA (Deoxyribonucleic
acid)Structure of DNA
1.
polymer made of nucleotides
(Monomer)
• deoxyribose
sugar
• phosphate group
• nitrogen-containing base
• Nucleotides join by covalent bonds
•
Nitrogen bases: make one
nucleotide different from another
•1A)Identify the components of DNA
and explain its role in heredity.
2. Bases
 purines
 2 Nitrogen rings

adenine (A)
guanine (G)

IN DNA:



pyrimidines
1Nitrogen ring


in
cytosine (C)
thymine (T)
RNA
cytosine
(C)
Uracil (U)
1B)What is the importance of
hydrogen bonds?
3. complementary base
pairing
C-G
and A-T
connected by hydrogen
bonds
weak
bonds
C and G have 3
A and T have 2
1C) Describe the discoveries that
led to the modeling of DNA.
• Chargaff’s
Rule
Discovered that the % of A and T were
almost the same
• Same as C & G
• Therefore he concluded that:
•
•A
pairs with T
• C pairs with G
1C) Describe the discoveries that led
to the modeling of DNA.
Double helix model
• Watson and Crick proposed by double helix
model- 1953
• 2 nucleotide chains that wrap around each
other (like a spiral staircase)
• inspired by x-ray photograph of DNA crystals
by Rosalind Franklin
Shows twisted DNA-Helix
• sugar on outside
• N-bases in the center
• http://www.pbs.org/wnet/dna/episode1/#
•
1C) Describe the discoveries that led
to the modeling of DNA.
Ladder model:
sides –
•
alternating deoxyribose sugar and
phosphate
rungs –
• nitrogen bases attached to deoxyribose
sugar
•
•
hydrogen bonds hold two half ladders
together
•
•
•
purine always attached to a pyrimidine
between H and an O or an N atom
nucleotide sequence of one half is exact
complement of other half (Anti-parallel)
http://www.youtube.com/watch?v=qy8dk5
iS1f0&feature=related
1D) Explain the events of DNA replication.
occurs in the Nucleus
1.
process of copying DNA in a cell
2.
enzymes called helicases break H bonds and 2 sides separate
3.
DNA polymerase enzyme assembles new DNA half using
nucleotides found in nucleus
4.
each half serves as a template (pattern) to make a new half
5.
two exact copies of original DNA produced (due to
complementary nature of nucleotides)
•
•
•
DNA polymerase also “proofreads” each new DNA strand, ensuring that
each molecule is a perfect copy of the original
each has one old and one new half
2A.) Compare and contrast DNA and RNA.
DNA
RNA
•
•
•
•
Ribonucleic acid
Ribose sugar
Bases: A,U,C,G
• uracil replaces
thymine
Single strand
•
•
•
•
Deoxyribonucleic acid
Deoxyribose sugar
Bases: A,T,C,G
Double Strand
2B.) What is the role of the three
types of RNA?
messenger RNA
(mRNA)
•
carries genetic Ribosomal
information from
RNA (rRNA)
DNA to
•
makes up
cytoplasm
ribosomes
(ribosome)
transfer RNA
(tRNA)•
binds to
specific
amino
acids
•
Cloverleaf
shape
2C)Explain the steps of transcription.
1. process where genetic info. is copied
from DNA to RNA
•
•
•
DNA is blueprint for all proteins
proteins made at ribosomes
DNA can’t leave nucleus
RNA polymerase (transcription enzyme)
binds to promoter (beginning of a
single gene)
•
Gene- small section of a chromosome
that determines a specific trait)
2. DNA section (gene) separates
3. RNA polymerase attaches to DNA
nucleotide and adds complementary
RNA nucleotide
4. continues till RNA reaches termination
signal (marks end of gene)
5. mRNA leaves nucleus
3A) Explain the steps of protein
synthesis.
Proteins
• 1. polymers made of polypeptides
Polypeptides made of amino acids
(monomers)
• Amino acids are connected by peptide
bonds (C-N bond)
•
• 2.
20 amino acids
3B)Analyze the genetic code to determine
codon and anticodon relationships.
The Genetic Code
1. sequence of 3 mRNA nucleotides that
code for an amino acid
2. codon - sequence of 3 mRNA bases
that code for a specific amino acid
•
start codon
• AUG(methionine)
•
stop codon –
• UAA,
- starts translation
UAG, UGA- cause translation to stop
3A) Explain the steps of protein synthesis.
Translation:
• assembling amino acids from mRNA code
• tRNA transports amino acids to ribosome
•
•
opposite to the amino acid attachment site is
sequence of 3 bases complementary to a specific
codon called the ANTICODON
•
•
•
region that binds to specific amino acid
insures that amino acids added in order prescribed by
mRNA
ribosomes (free and attached) have one binding
site for mRNA and two for tRNA
ribosome attaches to start codon and moves along to
each codon until stop codon reached
•
•
matching of anticodon and codon causes amino acids
to join previous one and form peptide bond
several ribosomes may translate same mRNA
3A) Explain the steps of protein synthesis.
Translation:
4A) What is a mutation?
• mutation
a change in the nucleotide sequence
• Latin word mutare, meaning “to change.”
•
4B) Explain the difference between
gene mutations and chromosomal
mutations.
Two basic categories of mutations:
1. gene mutations
•
produce changes in a single gene
2. chromosomal mutations.
•
produce changes in whole chromosomes
4C) Explain the different gene mutations.
Point Mutations:
Mutations that involve changes in one or a few
nucleotides
• occur at a single point in the DNA sequence
• generally occur during replication.
• If a gene in one cell is altered
•
• the
alteration can be passed on to every cell that
develops from the original one
•
3 types:
• Substitution
• Insertion
• Deletion
4C) Explain the different gene mutations
Substitutions:
•one
base is changed to a different base.
•usually affects no more than a single amino
acid, and sometimes they have no effect at all
4C) Explain the different gene mutations
Insertion
• A nucleotide is
added to DNA
sequence
Frameshift mutations:
• shifts the “reading frame”
of the genetic message
• can change every amino
acid that follows the point
of the mutation
• can alter a protein so it is
unable to perform its
normal functions.
• Both insertion and
deletions are framshift
Deletions
• A nucleotide is
deleted to DNA
sequence
4D) Describe the different chromosomal
mutations.
Deletion
involves the loss of all or part of
a chromosome.
Duplication
produces an extra copy of all or
part of a chromosome
Inversion
reverses the direction of parts of
a chromosome
Translocation
occurs when part of one
chromosome breaks off and
attaches to another.
4E) Explain 3 effects mutations can
have on genes.
Mutagens
• chemical or physical agents in the
environment that cause mutations.
• Chemical mutagens:
•
certain pesticides, a few natural plant alkaloids,
tobacco smoke, and environmental pollutants.
• Physical
•
mutagens:
some forms of electromagnetic radiation, such as
X-rays and ultraviolet light.
4E) Explain 3 effects mutations can
have on genes.
If these mutagens interact with DNA, they can
produce mutations at high rates:
Some compounds interfere with base-pairing,
increasing the error rate of DNA replication.
• Others weaken the DNA strand, causing breaks
and inversions that produce chromosomal
mutations.
• Cells can sometimes repair the damage; but when
they cannot, the DNA base sequence changes
permanently.
•
4F) Why are mutations important?
HARMFUL
•
•
•
Can create defective proteins that
disrupt normal biological activities
(genetic disorders).
Causes some cancers due to
uncontrolled growth of cells.
Example of point mutation:
• Sickle cell disease
• is a disorder associated with
changes in the shape of red
blood cells.
• Normal red blood cells are
round.
• Sickle cells appear long and
pointed.
• Causes anemia, severe pain,
frequent infections, and
stunted growth.
BENEFICAL
•
•
•
•
helped many insects resist
chemical pesticides.
enabled microorganisms to adapt
to new chemicals in the
environment.
Polyploidy
• an organism has extra sets of
chromosomes
Polyploidy plants are often larger
and stronger than diploid plants.
• bananas and limes
• naturally in citrus plants, often
spontaneous mutations.