Download II. Replication - Fort Thomas Independent Schools

II.
Replication
- The process of DNA making a
copy of itself
Steps for Replication
 1. DNA helicase (enzyme) – breaks hydrogen bonds


between bases separating the 2 strands
2. The complimentary bases are brought to the single
strand
3. DNA polymerase connects the new DNA strand with
the old and rezips the molecule
DNA Replication
new
T -A -G -A -G -C -T -T --
old
old
A–T
T–A
C–G
T–A
C–G
G–C
A–T
A–T
new
-- A
-- T
-- C
-- T
-- C
-- G
-- A
-- A
DNA helicase
DNA polymerase
DNA polymerase
Review
1.The making of more DNA is called ?
2. Which enzyme is used first in the making of more DNA – DNA polymerase
or DNA helicase ?
3. This enzyme is like a glue – putting the base pairs back together.
4. Replicate this strand of DNA
G–C
A–T
C–G
T–A
T–A
5. How would you describe the shape of DNA ?
III. RNA
ribonucleic acid
- function : makes proteins
A. Differences between DNA and RNA
DNA
RNA
2 strands
1 strand
deoxyribose sugar
ribose sugar
thymine base
uracil base
B. 3 types of RNA
1. messenger RNA (mRNA)
- straight strand
- takes information from DNA in nucleus to the ribosome to make
proteins
2. transfer RNA (tRNA)
- folded strand
- 20 different kinds
- brings amino acid to ribosome to make proteins
3. ribosomal RNA (rRNA)
- round
- makes ribosomes
-
C. Transcription –making of RNA from
DNA
• Done in the nucleus then travels to ribosomes in
•
cytoplasm
Uses RNA polymerase (enzyme) to break bonds between
bases separating the 2 strands of DNA
DNA strand
G
mRNA
C–G
C
A
T–A
U
U
A–T
A
A
T–A
U
A
T–A
U
C
G–C
G
U
A-T
A
mRNA
Review
1. What are the 3 types of RNA.
2. Give 3 differences between RNA and DNA.
3. The process of making more DNA is called ________ while the
making of RNA is __________.
4. How does a cell know it is making RNA from DNA instead of making
more DNA from DNA ?
5. Change the following DNA strand into mRNA
T-T-A-A-G-C-G-A-T-C
6. RNA is used in the making of ___________.
7. There are 20 different kinds of this type of RNA.
III. Protein Synthesis
the making of proteins using information coded from DNA and carried
out by RNA.
• A. Amino Acids
- basic building blocks of proteins
- 20 different ones
- joined together by peptide bonds
- carried by tRNA
• B. Codon – 3 bases in a row within a mRNA strand
that call for a specific anticodon that
codes for a specific amino acid.
*** AUG is the universal start codon for all
organisms.
C. Translation – process of making proteins by
using mRNA
Start
alanine
stop
arginine
amino acids
tRNA
U A C
mRNA
AU G
codon
C G
G C
C
G
A U C
U A G
C G A
GCU
anticodon
occurs in
ribosomes
Review
1. Change the following DNA strand into mRNA.
2.
G-C-G-T-T-A-G-C-T
Assemble the protein from the mRNA
sequence from your answer to #1.
A-T-C-
**errors do occur but rarely – about 1 per
billion nucleotides
• Factors that damage DNA
a. excessive body heat (fever)
b. radiation (UV & X-rays)
c. chemicals (carcinogens)
-- DNA has proofreading enzymes that
constantly try and repair mistakes in base
pairing.
• Human Genome Project
- project with scientist all over the world
to map out the sequence and location of
all traits (genes) on all human
chromosomes. Humans have 3.5 billion
base pairs per sex cell.