DNA Replication Notes
•
Base-pairing rules – In DNA, adenine always pairs with thymine. Also cytosine always pairs
with guanine.
•
3 basic steps for DNA replication
1) DNA helicase (an enzyme) unwinds the DNA by breaking the hydrogen bonds that link the
complementary nitrogen bases between the two strands.
2) DNA polymerase (an enzyme) move along each of the DNA strands and add nucleotides to the
exposed nitrogen bases (according to base-pairing rules).
3) Process continues until all DNA is copied and polymerases are signaled to detach.
From Genes to Proteins
•
Base-pairing rules for RNA, same as in DNA but Uracil replaces thymine. Uracil (like
Thymine) is complementary to adenine
•
Transcription – the process in which instructions for making a protein are transferred from a
gene to an RNA molecule. Transcription in the nucleus.
•
3 basic steps for Transcription (the making of an mRNA molecule)
1) RNA polymerase (an enzyme) binds to gene's promoter (this is the start signal)
2) RNA polymerase unwinds and separates the double helix
3) RNA polymerase adds and links RNA nucleotides as it “reads” the gene until it reaches a “stop”
signal
•
RNA instructions are written as a series of three-nucleotide sequences on the mRNA called
codons.
•
Each codon along the mRNA strand corresponds to an amino acid or signifies a start or stop
signal for translation.
•
Translation- (process in which protein is made) takes place at the ribosome. During this
process the mRNA molecule is read and amino acids are put together in the order specified by the
mRNA. Transfer RNA (tRNA) brings the corresponding amino acids (that match the mRNA code) to
the ribosome.
Study Guide Questions
1.
What nitrogen base does adenine always bond to in DNA?
2.
What nitrogen base does guanine always bond to in DNA?
3.
What is the complementary strand of DNA to the following sequence?
ATCGGTTAACCGAGC
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
What is the role of DNA helicase in DNA replication?
What is the role of DNA polymerase in DNA replication?
What is made during transcription?
Where does transcription take place?
What are the three basic steps of transcription?
What is a codon?
What does a codon correspond to?
What is made during translation?
Where does translation take place?
What is the job of the tRNA during translation?
Answers
1.
thymine
2.
cytosine
3.
TAGCCAATTGGCTCG
4.
DNA helicase (an enzyme) unwinds the DNA by breaking the hydrogen bonds that link the
complementary nitrogen bases between the two strands.
5.
DNA polymerase (an enzyme) move along each of the DNA strands and add nucleotides to the
exposed nitrogen bases (according to base-pairing rules).
6.
A mRNA (messenger RNA) molecule
7.
Nucleus
8.
3 basic steps for Transcription (the making of an mRNA molecule)
1) RNA polymerase (an enzyme) binds to gene's promoter (this is the start signal)
2) RNA polymerase unwinds and separates the double helix
3) RNA polymerase adds and links RNA nucleotides as it “reads” the gene until it reaches a
“stop” signal
9.
RNA instructions are written as a series of three-nucleotide sequences on the mRNA called
codons.
10.
Each codon along the mRNA strand corresponds to an amino acid or signifies a start or stop
signal for translation.
11.
Protein
12.
Ribosome
13.
Transfer RNA (tRNA) brings the corresponding amino acids (that match the mRNA code) to
the ribosome.