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DNA REPLICATION(Use you notes and pages 444-445)
The process by which DNA makes copies of itself is called DNA _______________________.
The following are the steps for DNA Replication:
1. The double helix _________________________.
2. The hydrogen bonds that hold the base pairs together are broken by _______________________.
This separates the two strands of the molecule, somewhat like unzipping a zipper.
Each single strand of parent DNA serves as a pattern, or _______________________, for a new
complementary strand.
3. The new strands are assembled from free floating nucleotides that have been made earlier in the nucleus.
What are the 3 parts of a nucleotide???
________________________________________________________________________An enzyme called
DNA _____________________________ moves along the separated parent DNA strands, matching the
nitrogen bases on each __________________, or original strand to new ___________________ bases on the
free nucleotides.
Along each strand, adenine bonds to ____________________________ and cytosine bonds to
_____________________________________.
Eventually because the parent DNA has two strands, two new ___________________double helixes are formed.
When we make new chromosomes, its very, very important that the new chromosomes are exactly like the old ones.
Otherwise, you might have your nose coming out of your ear!
Draw the 2 new DNA double helixes below:
The Making of RNA (RNA SYNTHESIS): TRANSCRIPTION
Each of the 100,000 or so proteins in the human body is synthesized from a different message that has been
transcribed from a specific ______________ on DNA.
What is the relationship between
DNA and genes???? ______________________________________________________________________
A gene can not be taken outside the nucleus to where proteins are made. It’s information must be copied into a
message called _______________(Messenger RNA).
The process of making mRNA
is called ______________________________________
"Why do we need mRNA if DNA holds all the genetic information, the instructions or blueprints for the proteins the
cell is supposed to produce?"
DNA is kept safe inside the nucleus and proteins are made on ______________________ which are found in the
cytoplasm or on Rough ER. If the DNA were to venture out of the nucleus into the
_____________________________ where the ribosomes are in order to give them the instructions for which proteins
were to be made, then it would be more vulnerable to damage from:
chemicals
, UV light
, or other agents
. If DNA is damaged in any way, then the coding sequence is
changed and a _______________________could result which could greatly affect the cell or even the whole organism!
DNA should be protected as much as possible.
How is the DNA supposed to get the information it encodes out to the ribosomes make the
______________________________?
The answer is that there must be a MESSENGER. This messenger is _______________
RNA is made up of a_________________________ sugar, a phosphate group, and nitrogen bases The RNA nitrogen
bases are ________________________adenine, cytosine, and guanine. Uracil is used instead of thymine as the
matching base to __________________________.
Unlike DNA RNA is only single stranded. The RNA bases are matches to the DNA they from which they are
“transcribed”. The mRNA is a message made from the DNA information.
So, how is mRNA made?
Messenger RNA is synthesized (made) in the nucleus of a cell by the ___________________________ of DNA, a
process similar to DNA replication.
In Transcription:
1. A small section of the DNA double helix unzips,
2. RNA _____________________ (ribonucleotides) must match up in the proper order by hydrogen-bonding to their
complementary bases on DNA,
This time the nucleotides are joined together by a different enzyme called
RNA
________________________ and piece of _____________________ results.
UNLIKE DNA replication where both strands are copied
only ONE of the two DNA strands is transcribed into mRNA.
RNA is a
_________________________molecule. The DNA strand that is transcribed is called the ________________________
strand
But how do the RNA polymerase enzymes know where to begin?
Where does one ________________ start and stop and the next one begin?
The starting point of a gene is marked by a certain 3 base sequence (called a codon) which is known as a
_________________________________site.
Once the RNA polymerase has been directed to the start point, promoter site, of the gene it carries out the process of
transcription.
These promoter sites act as a "start sign"
. Similarly, there are other 3 base sequences (codons) at the end of a
gene that signal a gene to
____. When the end of the gene is near, the STOP codon is read by RNA Polymerase
and the enzyme “falls off”the DNA template strand, thus stopping transcription!
The sequence of RNA nitrogen bases determine the sequence of the ___________________ to be assembled into
polypetptides which make up a _________________.
1. The code word for each amino acid is _______bases long. A three base code in DNA
or mRNA is called a __________________________.
2. Since codons are three bases long, there can be 64 different codons, which code _________ amino acids.
All the codons have a purpose. Some of the codons are signals that start or stop the process of
__________________________: protein synthesis.
Some are simply two or more different codons for the same amino acid.
What are the codons used for the amino acid Lysine? ____________________________
What is the only “start” codon? ____________________
What are the stop codons? ________________________
Protein synthesis (translation): Read 448-452 then copy table 21.3 below
Complete the following protein synthesis chart (use pg. 448 figure 21.7 to help indentify amino acids):