Transcript AP Biology - ReicheltScience.com

AP Biology
 Tests
back today
 Curve was 12 points
 Grades on test haven’t had 12 points
added (they are correct in ps)
 Study guide changes rip out page 7 (that
is a different chapter)
 Test is December 20
History of DNA
Thomas
Morgan
1900
Frederick
Griffith
1928
Oswald
Avery 1940
Hershey
and Chase
1952
Erwin
Chargaff
1950
Rosalind
Franklin
1950
Watson
and Crick
1953
Griffith
Conclusion:
Phage
Hershey/Chase
Hershey/Chase
Hershey/Chase
Conclusion:
Franklin
Franklin
Watson/Crick
AP Biology
 Review
from last class
 Continue
DNA talk
 Replication
today
Watson/Crick
DNA Replication
Semiconservative: when a double helix replicates,
each of the daughter molecules has one old strand
and one new
Replication
Vocab on Replication
 Origin
of replication- special sites where
replication begins
 Replication fork- a “bubble” where parental
strands are unwound
 Helicase- unzips parent strand
 Single-stranded binding protein- binds to
unpaired DNA to stabilize them
 Topoisomerase- relieves strain from twisting
Replication
Vocab contd.
 Primer-
initial nucleotide is a short stretch
of RNA
 Primase- an enzyme that synthesizes the
primer
 DNA polymerase- catalyzes the synthesis
of new DNA by adding nucleotides to a
preexisting chain
DNA
3’ vs 5’
The 5’
3’ runs in
the opposite
direction as the:
3’
5’
Antiparallel- the two
strands of DNA are
oriented in opposite
directions to each
other.
DNA
 DNA
can ONLY add nucleotides from the 3’
side on parent Strand
 DNA daughters are “built” from 5’
3’
DNA
 Leading
strand- the continuous strand
 Lagging strand- the strand that is copied away
from the fork
 Lagging strands called- Okazaki fragments.
DNA
Chapter 17
 Gene
 Test
expression and protein synthesis
next Thursday 
Proteins
 Proteins
are link between genotype and
phenotype
 Gene
expression- process by which DNA
directs protein synthesis, includes two
stages called transcription and translation
DNA
DNA
RNA
Protein
Protein Review
 Amino
acids - building blocks of protein
 Polymer
bonded
- many building blocks covalently
 Peptide
bonds- covalent bond between
amino acids
 20
total amino acids
DNA/RNA
DNA
RNA
Double helix
Single strand
A,T,C,G
A,U,C,G
Deoxyribose sugar
Ribose sugar
mRNA
rRNA
tRNA
Protein Synthesis
Codons
 How
be if:
many nucleotides could there
1.
Each kind of nucleotide base were
translated into an amino acid?
2.
If a two-letter sequence was in place?
3.
If there were triplet bases?
Codons
 Codons
– the mRNA
nucleotide triplets,
written normally in
the 5’ 3’ direction
 CCU
 AUG
 AGC
 AGG
Transcription
Vocabulary:
 RNA
polymerase- separates DNA and joins
RNA nucleotides together, nucleotide
bases assemble in a 5’ 3’ direction (no
primer required)
 Promoter- When RNA polymerase initiates
transcription sequence
 Terminator- when RNA polymerase signals
the end of transcription
Transcription
Steps of Transcription
1.
2.
3.
Initiation- RNA synthesis begins
Elongation- the RNA strand gets bigger
Termination- the RNA transcript is released
Transcription
RNA Processing
Pre-mRNA must be altered before it travels
outside of the nucleus
 Alternation of mRNA ends
1. 5’ cap – a modified guanine added to
the 5’ end
2. Poly-A tail- 50-250 adenine nucleotides
are added to the 3’ side
RNA Processing
Pre-mRNA must be altered before it travels
outside of the nucleus
 RNA splicing- removal of large portions of
the RNA molecule (cut-and-paste)
 This means that there are long noncoding
portions of DNA are not coding for
anything.


Introns - noncoding regions
Exons – coding regions
Translation
Vocabulary:
 Anticodon-
attached to tRNA molecules,
a nucleotide triplet. Complementary to
the mRNA codon
 Wobble – the flexible base pairing at the
third nucleotide position.
Translation
Translation
Translation
Translation
Translation
Steps of Translation
1.
2.
3.
Initiation- brings together mRNA and
tRNA to begin synthesizing proteins
Elongation – Amino acids are added
Termination – A stop codon reaches A
site, and the amino acids (polypeptide)
is released
Translation