II. RNA
-Ribonucleic Acid
-Function – makes proteins
A. Differences between
RNA and DNA
DNA
-- 2 strands
-- deoxyribose
-- thymine
--
RNA
1 strand
ribose sugar
uracil
B. 3 types of RNA
1. Messenger RNA (mRNA)
- straight strand
- transmit information from nucleus to
ribosomes on how to make protein
2. Transfer RNA (tRNA)
- folded strand
- 20 types – each type is an amino acid
- brings amino acid to ribosome to make
protein
3. Ribosomal RNA (rRNA)
- globular (round)
- makes ribosomes
C. Transcription
• The making of RNA from DNA
• Done in the nucleus
• Uses RNA polymerase instead
of DNA helicase to break Hbonds between DNA strands.
RNA polymerase attaches to a
section of DNA called a
promoter. Will stop transcribing
when a termination signal is
reached.
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
• Introns – sections of DNA that
will not be read (“junk DNA”)
• Exons – sections of DNA that
will be read
• mRNA goes from nucleus to
cytoplasm to ribosomes to
make proteins.
D. Factors that damage
DNA
• Excessive body heat (fever)
• Radiation (UV and X-rays)
• Chemicals (carcinogens)
**** errors do occur but rarely – about 1 per billion
nucleotides
**** DNA is constantly trying to repair itself, has
proofreading enzymes
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
alanine
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
Human Genome Project
• 15 year project with scientist all
over the world. Mapped out the
sequence and location of all
traits (genes) on all
chromosomes of a human.
• Humans have 3,200,000,000
base pairs per sex cell. (It
would take about 10yrs. to read
each base.)
Transcription Model
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.
Review
1.
2.
Change the following DNA strand into
mRNA. A-T-C-G-C-G-T-T-A-G-C-T
Assemble the protein from the mRNA
sequence from your answer to #1.
IV. Mutations
- change in DNA
- germ cell mutations – mutations
in sex cells – affect offspring
- somatic cell mutations – occur in body
cells . Ex. Skin cancer, leukemia
• A. Chromosome Mutations
1. Deletion – piece of chromosome
breaks off. Ex. Fragile X syndrome
2. Inversion – piece breaks off and
reattaches upside down.
A
A
B
C
C
B
3. translocation – inversion with a
non homologous chromosome. Piece
breaks off and attaches to different #
chromosome upside down.
A
A
A
A
B
B
B
B
C
C
C
D
D
D
D
21
C
19
4. Nondisjunction- when chromosome pairs
fail to separate so there are multiple copies.
Ex. Down Syndome Ex. 21st chromosome
B. Gene Mutations
- occur within a specific gene
or piece of a gene
1. Point mutation –
substitution, addition, or
deletion of a nitrogen base. Ex.
Sickle cell anemia
-- frameshift mutation - type of point
mutation that involves the addition or
deletion of a nitrogen base.
• Ex. ATTCGCGGT
•
ATTTCGCGGT
•
ATCGCGGT
-- additions and deletions have
a greater effect than
substitutions.