Download Replication Transcription Translation

Replication
Transcription
Translation
DNA
1. Double Stranded Helix
2. Hydrogen Bonds between
Nitrogenous Base Pairs
3. Adenine-Thymine and
Guanine-Cytosine
Adenine
shares 2
hydrogen
bonds with
Thymine
Guanine
shares 3
hydrogen
bonds with
Cytosine
Gene
• A gene is a segment of DNA
• A gene is a sequence of nucleotides that
codes for a functional product (usually a
protein)
• 1 gene = 1000’s of base pairs
• 41000 possibilities of combinations
A Gene is a Segment of DNA
When a gene is expressed, DNA is transcribed to produce
RNA and RNA is then translated to produce proteins.
Replication
• The duplication of DNA which occurs
during the S phase of Interphase.
• 1 Strand  2 Complementary Strands
• Where? In the nucleus
Hydrogen bond
(H-bonds)
thymine
adenine
cytosine
guanine
phosphate
deoxyribose sugar
Sugar / phosphate “strand”
Nitrogenous base “rung”
DNA nucleotide
Deoxyribose sugar
phosphate
RNA nucleotide
ribose sugar
Nitrogenous base
(guanine)
phosphate
Nitrogenous base
(uracil)
Step 1: Hydrogen bonds
between complementary
bases break
DNA “unzips”
DNA strands
pull apart from each other
Step 2: DNA nucleotides in the cell
match up with each side of the
“unzipped” DNA
each “unzipped’ strands forms a
template for a new strand
Step 3: Each “old’ strand
forms a template for a
“new” strand
two identical DNA
molecules form
“new” strand, identical
sequence to the original
“old” (original) strand
RNA Review
• Like DNA, RNA is a chain of
nucleotides.
• RNA contains the base
Uracil, instead of Thymine.
• RNA is small enough to exit
through nuclear pores,
unlike DNA.
• RNA can be found in the
nucleus, in the cytoplasm, or
in the ribosomes (rRNA).
Transcription
• The process by which a gene found in DNA
is copied into a complementary strand of
RNA.
• 1 Strand DNA  2 Strands RNA
• Where? In the nucleus
DNA
RNA
Label the Following
Step 1: Hydrogen bonds
between complimentary
bases break
DNA “unzips” as the strands
pull apart from each other
Step 2:
RNA nucleotides
in the cell match
up with only one
side of the
“unzipped” DNA
each “unzipped’
strands forms a
template for a
mRNA strand
RNA nucleotide
mRNA strand
Step 3:
mRNA strand
breaks off
from the DNA
strand
One side of DNA strand
Step 4:
mRNA strand
leaves the
nucleus for
the ribosome
Step 5: Once the mRNA
leaves, the DNA “zips”
back together
• Transcription is different from DNA replication
– during the process of transcription, only a
segment of DNA, or gene, is transferred into an
RNA message (whereas replication copies the
whole chromosome).
• mRNA then takes the gene’s coded message to
the ribosome for protein synthesis.
• Transcription not only produces mRNA – tRNA
and rRNA are also made through the process of
transcription.
Translation
• The process that converts, or translates, an
mRNA message into the amino acid sequence of
a protein.
• 1 Strand RNA  Amino Acid Chain  Protein
• Where? Cytoplasm or Rough E.R. – at the
ribosomes
Definitions
Codon
• Three-base segment of mRNA that code for amino
acids.
Anticodon
• Three-base segment of tRNA that is complementary
to an mRNA codon.
• Pairing results in deposition of amino acid.
Amino Acid
• Monomer of protein
The problem: How does a
particular sequence of
nucleotides specify a particular
sequence of amino acids?
By means of transfer RNA
(tRNA) molecules, each specific
for one amino acid and for a
particular triplet of nucleotides
in mRNA called a codon. The
family of tRNA molecules
enables the codons in a mRNA
molecule to be translated into
the sequence of amino acids in
the protein.
Step 1 – The mRNA
codon attracts and pairs
up with a complementary
tRNA anticodon
Step 2 – The ribosome
helps forms a peptide
bond between the two
amino acids carried by
the tRNA molecules
Step 3 – The ribosome
pulls the mRNA strand to
expose the next codon,
and the steps repeat until
the protein is complete
RNA and Protein Synthesis
• RNA is a singlestranded nucleic acid
• RNA acts as a
messenger between
DNA and ribosomes
• The process of
translation takes
amino acids and forms
proteins
Why Is It Necessary?
• DNA in the Nucleus
• Ribosomes in the Cytoplasm
• Need a Messenger
Protein Synthesis
• Proteins are coded directly from the mRNA
with 3 bases (one codon) for each amino
acid. What’s up with that?
Mutation
• A change in the nitrogenous base sequence
of DNA; that change causes a change in the
product coded for by the mutated gene.
Mutations
What happens when you get insertions or deletions of bases in
the DNA sequence?
Usually you end up with a mess.
THE BIG FAT CAT ATE THE RAT AND GOT ILL
Deletion of one base
THE IGF ATC ATA TET HER ATA NDG OTI LL
And its all pops and buzzes.
Sickle-Cell
Anemia
Definitions
• Carcinogens
Substances and preparations which, if they are
inhaled or ingested or if they penetrate the skin;
may induce cancer or increase its incidence and
can affect any cells or tissues
• Mutagens
may induce hereditary genetic defects or increase
their incidence and effect the germ cells (gonads)
• Teratogens
may induce non-hereditary congenital
malformations or increase their incidence and
effect the growing fetus
Mutagens
•
•
•
•
•
•
•
Tobacco products
Nitrous Acid
Mold Toxins
X-rays
Gamma Rays
UV Radiation
Some Artificial Sweeteners