Download Section 1 Workbook Unit 2 ANSWERS File

Complete the following table:
Section 1 Workbook (unit 2) ANSWERS RN nucleotide
DNA
Name: ____________ B5. Describe DNA replication
1)
Label each base given in the diagram below and describe the 4 primary characteristics of DNA.
-­‐Deoxyribose s ugar, phosphate group and one of nitrogen bases making up a nucleotide. -­‐Double helix shape -­‐Two strands held together by hydrogen bonds between the nitrogen bases Sugar phosphate backbone A G T C 2)
Identify the site of DNA replication within the cell.
Nucleus
3)
Explain the three major steps, and all of the enzymes involved, in semi-conservative
replication of DNA. What is meant by semi-conservative replication?
1. Helicase “unzips” DNA strand
2. DNA polymerase joins DNA bases that are complementary to the template strand. One
strand is the original / old one while the other strand is new. = semiconservative replication.
Covalent bonds between the backbone and H-bonds between strands are added
3. Proof reading enzyme checks for mistakes
•
4)
semiconservative replication means that there is one new and one original strand of
DNA
Describe the purpose of DNA replication.
To make a copy of the DNA for the new cell during cell division
Page 1 of 10 5)
If a cell is exposed to acidic conditions during cell division, how would this affect the cell’s
ability to divide? Why?
Enzymes are proteins so a specific shape is needed in order to function. The change in pH
would cause the enzymes, such as helicase and polymerase to denature. When these enzymes
denature, they change shape and therefore, will not function anymore so cell division cannot
occur.
6)
How does the amount of:
a. Adenine compare to the amount of thymine in DNA? Same amount, A pairs with T
b. Guanine compare to the amount of cytosine in DNA? Same amount, G pairs with C
c. Purines compared to the number of pyrimidines? Same amount
7)
How are DNA and RNA chemically similar? Different?
Similar: polymers of nucleotides, phosphate groups, nitrogen bases AGC, & pentose sugar
Different: DNA has thymine while RNA has uracil. RNA single stranded while DNA double
stranded with hydrogen bonds, DNA – deoxyribose sugar, RNA – ribose sugar.
B6. Describe recombinant DNA (rDNA)
8)
Describe recombinant DNA. Include the enzymes required for the formation of rDNA. Use a
diagram to help your explanation.
1. DNA from human – gene of interest is isolated and removed with restriction enzyme (cuts
DNA)
2. Plasmid from bacteria removed and cut with same restriction enzyme
3. Gene put into plasmid = recombined into a single DNA strand = rDNA
4. Put into bacteria – bacteria divide & give off product such as insulin.
9)
Describe at least three uses for recombinant DNA.
•
•
•
Make insulin, human growth hormone, TPA
Create disease resistant plants
Add nutrient to food crop (Golden rice)
Page 2 of 10 B7. Demonstrate an understanding of the process of protein synthesis
10)
Complete the following table:
Describe both processes. Use diagrams to help in your explanation
Transcription
Translation
11)
1. Helicase opens DNA where gene located
2. RNA polymerase adds complementary RNA bases to create mRNA
molecule – from initiation site to termination site. (DNA serves as
template for mRNA)
3. mRNA molecule leaves through nuclear pores to cytoplasm – linear
so it fits through the nuclear pores.
1. Initiation – 2 halves of ribosome (large & small subunits) come around the
mRNA molecule and the start codon (AUG) turns on translation
2. Elongation – tRNA brings AA to ribosome. Codon on mRNA matches
with anticodon on tRNA (A with U & G with C) and AA left to be added to
the polypeptide chain with peptide bonds.
3. Termination - elongation continues until a stop codon is reached (3 of
these) which turns off translation. Ribosome separates releasing mRNA
& primary protein structure to be bent and folded into its functional shape
Which process, transcription or translation, is depicted here? Label the molecules.
ribosome Translation is shown here Amino acids mRNA 12)
tRNA Complete the following table:
Describe each molecules’ role in Protein Synthesis
DNA
Has instructions on how to make a protein = code
mRNA
Copies instructions and takes them to ribosome
tRNA
Brings AA to ribosome to be added to polypeptide chain
ribosomes
Builds polypeptide chain – site for codons & anticodons to meet
Page 3 of 10 13) Of the 5 nitrogen bases, which one is X in the below diagram? How do you know (support your
answer)?
Adenine has 2 hydrogen bonds and is a purine (double ring) Since molecule X is on an mRNA molecule, and RNA does not have thymine, the pyrimidine molecule is uracil. Adenine 14) Label the following in the diagram below: mRNA (3 times), ribosome, anticodon, tRNA, DNA,
amino acid, codon, primary protein, nucleus, cytoplasm.
cytoplasm Nucleus DNA mRNA Amino acid tRNA Primary protein anticodon codon ribosome Page 4 of 10 15) Use the aa codon chart to determine the amino acid sequence produced by the section of
an mRNA molecule below and determine the DNA strand that provided the instructions.
mRNA=
CGC – UAU - UGG
DNA= __ GCG – ATA - ACC__
Amino Acids:
16)
= Arg – Tyr - Try
Use the aa codon chart to predict the amino acid sequence produced by this sequence of bases
on a DNA molecule and label transcription and translation
DNA=
mRNA=
TAC-GAA-CTT-GGG-TCC
AUG -CUU-GAA-CCC-AGG
Amino Acids = ___ Met – Leu – Glu – Pro - Arg
17)
What anti-codon would be present on the tRNA that is complementary to the mRNA codons
given? Anti-codon on tRNA always complements mRNA codon
AUG _UAC_
UAA _AUU__
AGA UCU__
CGU GCA___
Page 5 of 10 18)
Explain what would occur during translation of the following DNA sequence if ACG
underwent a mutation and was converted to ACT.
Unmutated DNA:
GCA
CCT
ACG
GGA
ACC
DNA mutation:
GCA
CCT
ACT
GGA
ACC
mRNA:
CGU
GGA
UGA
CCU
UGG
AA sequence:
Arg –
Gly -
stop
Explanation:
The mutation causes a stop codon to occur early in the synthesis of the protein. Therefore, the
protein will be incomplete and not be able to function.
19)
Production of mRNA is called ______transcription_____
20)
Production of a protein is called ____translation_________
21)
Given the following tRNA sequence, find the DNA strand and polypeptide chain created:
tRNA:
UAC
ACC
GCC
CUA
CCC
AAA
mRNA: AUG UGG CGG GAU GGG UUU
DNA: TAC ACC GCC CTA CCC AAA
AA:
Met
trp arg
asp gly phe
22)
In an experiment conducted to study proteins synthesis, radioactive thymine and
radioactive uracil were added to a culture of human cells. A few hours later, the culture was
analyzed and radioactive mRNA was found.
a. Explain how an mRNA molecule is produced: TRANSCRIPTION
• Helicase opens DNA where gene located
• RNA polymerase adds complementary RNA bases to create mRNA molecule – from
initiation site to termination site. (DNA serves as template for mRNA)
• mRNA molecule leaves through nuclear pores to cytoplasm – linear so it fits
through the nuclear pores.
b. Explain why the mRNA produced is radioactive
Because uracil was incorporated into the mRNA molecule causing it to be radioactive.
c. In a different experiment, radioactive uracil was added to a culture of human cells undergoing
DNA replication. What will be the characteristic of the resulting DNA in terms of radioactivity?
Explain.
DNA does not have uracil therefore it would not be incorporated into the DNA molecule. So
the DNA would NOT be radioactive
Page 6 of 10 B8. Explain how mutations in DNA affect protein synthesis
23) Give examples of two environmental mutagens that can cause mutations in humans. How do
they cause a mutation?
•
•
•
Biological: viruses and bacteria that increase the chance of a mutation
Chemical: food additives, hallucinogenic drugs, asbestos, DDT, pesticides, manufactured
chemicals…. affect enzymes of DNA replication, increasing the chance of mutation
Radiation: UV & cosmic rays - increasing the chance of mutation
24) Define transgenic organisms. Give an example.
An organism that has the DNA of another organism inserted into it is called a transgenic
organism. Example: bacteria with the human insulin gene
25)
Use the examples to explain how mutations in DNA change the sequence of amino
acids in a polypeptide chain, and as a result, may lead to genetic disorders.
a. point mutations, sickle cell anemia
Changes the amino acid glutamate into valine. This results in abnormal hemoglobin molecule
that causes the red blood cell to have a sickle shape that can clog blood vessels and lead to
pain.
b. gene mutation, hemophilia / cystic fibrosis
A gene mutation that causes a lack of or minimal amount of clotting factors to be produced
resulting in excessive bleeding.
c. chromosomal mutation, Trisomy 21
An extra chromosome #21 results in Down’s syndrome.
This causes high levels of purines in the blood which leads to mental deficiencies.
26)
Define gene therapy. What is its purpose?
= alteration of afflicted individuals’ genes (of the same species)
• could help with genetic diseases like cystic fibrosis, Alzheimer’s, some cancers, AIDS
Page 7 of 10 Types of gene mutations Here is a section of DNA before a mutation.
mRNA:
TAC GGG CTC TAG CGA GAT ATT
AUG CCC GAG AUC GCU CUA UAA
AA’s:
Met
DNA:
27)
Pro Glu
Ile Ala Leu stop
Insertion mutation - What would happen to the AA sequence above if one extra base (a G
at the start of the 3rd codon) were added to the original DNA sequence?
Inserted DNA
TAC GGG GCT CTA GCG AGA TAT
Resultant mRNA
AUG CCC CGA GAU CGC UCU AUA
Mutated AA
Met Pro
Arg
Asp
Arg
Ser
T
Ile
a. What conclusions can you draw regarding the effect of insertion mutations on the polypeptide
chain that would be produced?
They cause an incomplete protein to be made – there is an extra base that does not make
up a codon. Frameshift mutation compared to the original strand, every aa after the
insertion changes.
b. Do you think that insertion mutations would likely improve or negatively impact the intended
function of the protein produced?
Negative impact
28) Deletion mutation - What would happen to the AA sequence if one base (the 1st G in the 2nd
codon) were deleted from the original DNA sequence?
DNA
TAC
GGC TCT
AGC
GAG
ATA
TT
mRNA
AUG
CCG
AGA
UCG
CUC
UAU
AA
AA
Met
Pro
Arg
Ser
Leu
Tyr
a. What conclusions can you draw regarding the effect of deletion mutations on the polypeptide
chain that would be produced?
There is an incomplete codon because only 2 bases at the end. Frameshift mutation compared
to the original strand, every aa after the deletion changes.
b. Do you think that deletion would likely improve or negatively impact the intended function of the
protein produced?
Negative impact
29) Substitution mutation - What would happen to the AA produced if a base were substituted
for another base in the original DNA strand? (The substituted bases are highlighted below)
DNA
TAC CGG CTC TAG CGG GAT ATT
mRNA
AUG GCC
GAG
AUC
GCC
CUA
UAA
AA
Met
Glu
Ile
Ala
Leu
Stop
Ala
Page 8 of 10 a. What can you conclude about the effect of substitution mutations on the polypeptide produced
from a strand of DNA?
You can get a complete protein made unlike the other types of point mutations. The amino
acid may not even change so the same protein could still be made – having no affect on the
organism.
b. Would substitutions improve or negatively impact the intended function of the protein produced?
Why?
They could negatively impact the function of the protein by changing the amino acid,
thereby changing the protein.
They could have no impact because the amino acid does not change resulting in the
same protein
Page 9 of 10 Page 10 of 10