Download Nucleic Acids and Protein Synthesis Modern Biology Chapter 10

Modern Biology
Chapter 10
Nucleic Acids
and Protein
Synthesis
10-1
DNA
full name is
DeoxyriboNucleicAcid
A Nucleotide
The monomer of
nucleic acids…
Structure of DNA
•
Basic Structure
 three basic components
 deoxyribose: 5 C sugar
Structure of DNA
•
Basic Structure

three basic components
 phosphate group (PO4)3-
Structure of DNA
Basic Structure
three basic components
nitrogenous base
adenine (A)
guanine (G)
thymine (T)
cytosine (C)
Structure of DNA
•
The double helix

many scientists worked to solve the structure of
DNA
Chargaff
•
Concluded that A must bond with T
and C with G
Structure of DNA
•
The double helix

many scientists worked to solve the structure
of DNA
 Rosalind Franklin


took X-ray photographs of DNA
died in 1958 without recognition for her enormous
contribution
X-ray crystallography
Rosiland Franklin
Structure of DNA
•
The double helix

many scientists worked to solve the structure of
DNA
 Wilkins

received Nobel prize with Watson and Crick
Structure of DNA
•
The double helix

many scientists worked to solve the structure of
DNA
 Watson and Crick



first to construct a model of DNA molecule
received Nobel prize for their work in 1962
Primarily piggy-backed on others’ work, but were the first
to put the pieces together correctly
Watson and Crick
Structure of DNA
The double helix
two nucleotide
chains that wrap
around each other
base-pairs form the
rungs of the ladder
Structure of DNA
•
The double helix

alternating chains of phosphate groups and
deoxyribose molecules form the backbone of
the structure
 all rungs are of equal length
 approx. 10 base pairs per turn of DNA molecule
Structure of DNA
•
Complementary base pairing


to ensure that the rungs are of equal length
nucleic acids pair up
base-pairing rules
 cytosine bonds with guanine (C-G)
 adenine bonds with thymine (A-T)
Structure
of DNA
connected by
hydrogen bonds
 C and G share
3 H-bonds
 A and T share
2 H-bonds
Replication of DNA
•
replication: process of copying DNA

the steps:
 double chains must separate between the nucleic acids


replication fork: point at which the chains separate
helicase: enzyme that breaks apart DNA molecule
 nucleotide bases match up with their compliments

DNA polymerase: enzyme that assembles new bases to
original strand
Replication of DNA
•
replication: process of copying DNA


complimentary bases allow for accurate
replication
new strands of DNA actually contain one old
strand and one new strand
Types of
replication
possible with
a double
strand
•DNA is semiconservative
A movie for your viewing
enjoyment
Animation Illustrating DNA Replication by
Complementary Base Pairing
•
More complex view
Replication of DNA
•
Accuracy and Repair


highly accurate with only 1 error per 10,000
pairs
mutation: change in a nucleotide sequence
Mutation
Replication of DNA
•
Accuracy and Repair

proofreading and repair reduce error rate to
1 error per 1,000,000,000 base pairings
 enzymes proofread and repair any errors that are
identified
 Equivalent to 1,488,095 copies of Huckleberry
Finn
Fixing the errors
Replication of DNA
•
Accuracy and Repair

some factors increase the rate at which DNA
mutates
 radiation
 certain chemicals
 sun light
Radiation
Excited electrons run
around uncontrollably
and cause problems.
We use this trait for
helping patients battle
cancer- chemo therapy.
Solar Radiation
Modern Biology
Chapter 10
RNA
Structure of RNA
•
full name is RiboNucleic Acid
Structure of RNA
basic structure



backbone of
phosphate
groups and
ribose
single stranded
uracil (U)
replaces
thymine in
pairing with
adenine
TYPES OF RNA
Types of RNA
•
mRNA: messenger RNA


carries copy of DNA strand from nucleus to
ribosome
single, uncoiled chain
Types of RNA
•
tRNA: transfer RNA


carries specific amino acids
to ribosomes to pair with
mRNA
single chain (about 80 base
pairs long) folded into a
hairpin like shape
Types of RNA
rRNA: ribosomal RNA


Along with proteins
rRNA forms ribosomes
globular form
Transcription
•
•
process where genetic information is
copied from DNA to RNA
ANIMATION OF THE PROCESS OF
TRANSCRIPTION
Transcription
•
steps of transcription



•
•
RNA polymerase binds to DNA in specific
sites called promoter regions
DNA unzips and nucleic bases follow
complementary base-pairing rules
Termination sequence marks end of
transcription
products of transcription are all forms of
RNA
Movie Time
• DNA unzips
• RNA polymerase does it’s thing
• RNA is formed
Comparing
DNA and
RNA
Section 12-3
RNA Concept Map
RNA
can be
Messenger
RNA
Ribosomal
RNA
also called
which functions to
mRNA
Carry
instructions
also called
which functions to
rRNA
Combine
with proteins
from
to
to make up
DNA
Ribosome
Ribosomes
Transfer
RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome
Protein structure and
composition
•
•
•
•
proteins are polymers
made up of long chains of amino acids
20 different amino acids
proteins fold into specific shapes based on
the sequence of amino acids
The amino acids
The genetic code
•genetic code
determines
sequence of
amino acids
in proteins
nucleolus
mRNA
DNA
•genetic code determines sequence of amino
acids in proteins
The genetic code
•
codon: each triad (group of three bases)
on mRNA




each codon codes for a specific amino acid
many codons may code for the same amino
acid
start codon (AUG) codes for methionine
stop codons (UAA, UAG, UGA) cause the
ribosomes to disengage
Translation
• process of assembling amino acids to form
proteins
• tRNA and anticodons


amino acids are transported to ribosomes on
tRNAs
tRNAs have anticodons which match up with
codons on mRNA
Translation
•
ribosomes


site of protein synthesis
three binding sites
 mRNA binds to one
 two tRNAs with anticodons complementing the
codons on mRNA bind to other two
Translation
•
protein assembly

ribosome attaches to start codon (AUG)
 first amino acid in every polypeptide is methionine




ribosome moves along mRNA matching
complementary tRNAs with the amino acids
along the way
amino acids form peptide bonds to form
polypeptide chains
ribosomes move 3 base pairs at a time (1 codon)
stop codon ends process
Videos
•
•
Raven's
Test your “mad DNA” skills
Explain this to your neighbor!
Videos
•
•
ANIMATION OF THE PROCESS OF
TRANSLATION
Animation of Protein Folding
INFORMATION PROCESSING &
THE CENTRAL DOGMA
•the letters of the genetic alphabet are the
nucleotides A, T, G, & C
•unit of information is CODON = genetic 'word'
 a triplet sequence of nucleotides CAT in a
polynucleotide
 3 nucleotides = 1 codon (word) = 1 amino acid
the definition of (codon) word = amino acid
Size of Human Genome
≈ 3,000,000,000 base pairs or 1.5b in single
strand genes
≈ 500,000,000 possible codons (words or
amino acids)
Size of Human Genome
to put it in perspective…
average page your textbook = approx 850
words thus, the human genome is equal to
590,000 pages or 470 copies of bio text book
reading at 3 bases/sec it would take you about
47.6 years @ 8h/d - 7d/w
Size of Human Genome
Mice & humans (indeed, most or all
mammals including dogs, cats, rabbits,
monkeys, & apes)
have roughly the same number of
nucleotides in their genomes -- about 3
billion bp.