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Name: ________________________________________________ Date: __________________________ Period: _____
Unit 6, Notes Packet 2 – DNA Replication and Protein Synthesis
DNA Replication
32. Cells must copy their DNA before they do what? Explain why?
33. DNA is copied during the S or ______________ phase of ________________.
34. Where does DNA replication take place in eukaryotes?
35. Replication of DNA begins at points called ____________________________.
36. The two strands open at origins of replication forming Y-shaped areas called
___________________________________. New strands of DNA grow here.
37. Label the replication fork and the 5’ and 3’ ends of each parent strand on the picture below.
38. As the two strands open at the origins of replication, replication ____________ form.
________________(bacteria) have a single bubble.
________________ chromosomes have many bubbles.
39. Steps of DNA Replication
1) The enzyme ________________ unwinds and separates the 2 DNA strands by
breaking the weak ________________ bonds between bases.
It “unzips” the double helix.
2) ________________ gathers _______________ and brings them
into the replication fork.
A ________________ is created to start the new strand.
3) The enzyme _______________ matches free nucleotides with the
correct base pairs on the ________________ (parent) strands.
4) The enzyme ____________ connects any “breaks” in the new
strands, and the 2 identical strands ___________ back together.
40. The Big Question: Why are their breaks in the new strands at all?
DNA polymerase can only add nucleotides to the ________ end of the DNA.
This causes the _________ to be built in a ______ to ______ direction.
The _________________ is built into the replication fork.
The _________________ is built in short sections in the ________________direction (out of the fork). This
causes the _________ in the strand.
41. Label the leading strand, lagging strand, DNA polymerase, helicase, and primer in the picture below.
42. Label the enzyme ligase, which joins the sections of DNA in the lagging strand.
43. Proofreading New DNA:
DNA polymerase makes about ________________________ base pairing errors.
_______________ proofread and correct these mistakes  new error rate of __________________________.
43. How does the DNA get damaged? ________________ and ______ radiation damage the DNA in our body
cells.
44. Types of DNA repair
1) ____________________ - when a repair enzyme removes damaged DNA.
2) _____________________ and ___________________ work together to replace and bond new
nucleotides together.
Protein Synthesis
What are Proteins?
1. Hershey and Chase’s virus experiment (see notes packet #1) showed that ___________ was the genetic material
of the cell.
2. _________________ are the workhorses of the cell…they do a lot of different jobs!
A)_____________________- immune system/defense
B) ____________________- hair/nails
C) ____________________ - enzymes
D) ____________________ - hemoglobin (carries oxygen in blood!)
E) ____________________ - muscle
How do our Cells Make Proteins?
3. DNA contains ___________________, sections of nucleotide chains.
Genes code for________________ (proteins).
Polypeptides are ________________________ chains.
4. The Dilemma: DNA is found in the _____________________, but proteins are made in the
_________________________.How do we get the message from one place in the cell to another?
5. The Solution: A molecule called ___________ carries the message. It’s small enough to fit through the
_______________ in the nuclear membrane.
DNA vs. RNA
6. Roles of DNA and RNA: DNA is the _________________. RNA is the _________.
7. Differences between RNA and DNA
DNA
RNA
A. Number of Strands
B. Nitrogen Bases
C. Sugars
Related Question: What base does Uracil pair with?
8. 3 Types of RNA
A. Messenger RNA (mRNA): copies DNA’s code and carries it to the _______________.
B. Transfer RNA (tRNA): takes _________________ to the ribosome, where they can be joined into a chain.
C. Ribosomal RNA (rRNA): makes up the ribosomes
Identify each type of RNA by its picture, shape, and location.
What are the Steps of Protein Synthesis?
9. The two parts of protein synthesis are called _____________ and ______________.
10. Transcription: ___________ picks up the code from the ________ template strand and takes it from the
__________ to the __________.
Steps
1) DNA __________.
2) RNA polymerase (an enzyme) matches ______ bases with the DNA template to make a strand
3) _________ is released and leaves through the nuclear pore.
Label mRNA, DNA, RNA polymerase, and free nucleotides in the picture below.
Let’s Transcribe!: Transcribe an mRNA molecule from the DNA template given below.
DNA
A C
T G G C A A T C G C
mRNA
11. Translation: The instructions (mRNA) are read by __________, and tRNA joins _________________________in
the right order in the ribosome.
Steps
1)
2)
3)
4)
mRNA goes to the __________________.
_____________ brings _______________________ to the ribosome.
tRNA “reads” the mRNA instructions and puts the amino acids in __________________.
Amino acids link together by _____________ bonds to make a _____________________ (protein).
How does tRNA “read” the mRNA instructions?
3
3
bases on mRNA strand  codon
bases at the bottom of each tRNA  anticodon
Only the tRNA with the right anticodon can match up with a particular codon… label the
ribosome, mRNA, codon, tRNA, anticodon, and amino acid in the picture below
Let’s Translate! Translate the mRNA sequences below the two types of codon
(polypeptides)
mRNA
AUG
UCC
CAG
GCU
AAC
GAG
UAG
AUG
GCA
AAA
UUC
CGA
AUU
UGA
Polypeptide
mRNA
Polypeptide
Summing it all Up
12. Create a flowchart showing the processes of transcription and translation.
13. Draw out a summary diagram of protein synthesis.
tables into amino acid sequences