REMEDIAL DNA ASSIGNMENT
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DNA AND PROTEIN SYNTHESIS
o The chemical and structural properties of DNA and its role in specifying
the characteristics of an organism (e.g., DNA is a large polymer formed
from four kinds of subunits; genetic information is encoded in genes as
a string of these subunits)
o The structures of proteins (e.g., long, usually folded chain molecules
made of specific sequences of amino acids coded by DNA) and the
role of proteins in cell function)
o Cell functions are regulated through changes in the activity of the
functions performed by proteins and through the selective expression
of individual genes
Genetic Control of Phenotypes
DNA to Protein: View Scenes 1 – 5 and complete the exercise below.
Study the early ideas about how genes control physical features.
Multimedia
Presentation
Scene 1
1a. What do genes determine?
Genes determine physical traits (including characteristic behavior)
1b.
What happens when a gene is expressed?
The information encoded in the DNA of the gene is used to build proteins.
1c.
What is the importance of DNA?
It is the heredity substance of life, passed on from one generation to the next.
Scene 2
2.
Fur, Feathers and Phenotypes: these pictures
from the lesson show the similar phenotypes of
San Joaquin kit foxes from the same clan and
the distinctly different phenotype of a male
Mandarin Duck in mating plumage. (Both are
endangered species.) Define phenotype.
An organism’s physical traits make up its
phenotype, determined by genes.
Scene 3
3.
Urine, You’re Out: The scientist portrayed in this picture is Sir
Archibald Garrod. What specific problem did he study and what
was his resulting hypothesis?
Garrod studied a hereditary disease that causes black urine, due
to the presence of a chemical that normally is broken down by an
enzyme. He thought the absence of the enzyme was the result of
a defective gene. More generally, he suggested that genes
determine phenotypes through enzymes.
Scenes 4 – 5
4a. What was the experimental finding of Beadle and Tatum?
Beadle and Tatum confirmed that one gene controls the production of one enzyme
4b.
Enzymes are proteins. Describe the structure of a protein.
Proteins are made of folded polypeptides. Polypeptides are long chains of amino
acids.
4c.
What exactly does a gene control in protein structure?
Each gene controls a specific polypeptide in a protein, in other words, one gene,
one polypeptide.
DNA to Protein: Complete Interactive Tutorial #1
This interactive tutorial will review various genetic disorders.
Interactive
Tutorial
DNA and RNA Structure
DNA to Protein: View Scenes 6 – 10 and complete the exercise
below.
Examine the similarities and differences between DNA and RNA molecules.
Multimedia
Presentation
Scenes 6 – 7
1.
Twisted Ladder: this image
shows the structural elements of
DNA.
1a.
Give a concise description of
DNA structure.
The DNA double helix spirals
from end to end like a twisted
ladder. Two chains of sugarphosphate groups make up the
sides of the ladder. Pairs of
nitrogenous bases form the rungs.
1b.
Name the nitrogenous bases (upper
boxes), their classification, and how
they combine.
Adenine and guanine are purines; cytosine and
thymine are pyrimidines. Adenine and thymine pair up
only with each other, cytosine and guanine pair up only with each other.
1c.
What is a nucleotide (lower boxes) and what is its structure?
A nucleotide is the basic unit of DNA, made up of a phosphate group and
deoxyribose, plus one of the four possible nitrogenous bases.
1d.
How long is a gene, measured in nucleotides?
A gene can be hundreds or thousands of nucleotides long.
Scene 8
2.
Codon Coding: this illustration shows the relationship between DNA nucleotide
sequences and polypeptide amino acid sequences.
Define codon.
Codon: the sequence of
3 adjacent nucleotides
that specifies the
addition of a particular
amino acid to a
polypeptide chain.
Scenes 9 – 10
3.
Half Related: this diagram shows the chemical and structural differences between
DNA and RNA.
3a.
Ribonucleic acid molecules convey
information between what two
separate locations in a cell? Explain.
RNA conveys information from the
genes of nuclear DNA to the protein
polypeptide assembly process that takes
place in the cytoplasm surrounding the
nucleus.
3b.
How is RNA different from DNA? Complete the table.
Type of sugar
Unique nitrogenous base
Number of nucleotide strands
DNA Deoxyribose Thymine
Double stranded
RNA Ribose
Single stranded
Uracil
DNA to Protein: Complete Interactive Tutorial #2
Review the structure and composition of DNA..
Interactive
Tutorial
RNA Polymerase and Messenger RNA
DNA to Protein: View Scenes 11 – 14 and complete the exercise
below.
Learn how mRNA transcribes the DNA code.
Multimedia
Presentation
Scene 11
1.
Read and Write: Complete the table.
What happens during transcription?
RNA copies (transcribes) the DNA code
for a polypeptide.
What happens during translation?
The code transcribed by RNA is converted
(translated) into a polypeptide.
Scenes 12 – 13
2.
The Un-Zip Code: this diagram shows RNA polymerase at work.
2a.
What kind of molecule is RNA polymerase and
what does it do?
RNA polymerase is an enzyme that unzips
the two strands of DNA, separating them so
that one strand with unpaired nucleotides
can serve as a template for RNA.
2b.
Describe how RNA takes form
along DNA.
RNA nucleotides match up
with complementary bases
on the exposed DNA
nucleotides. The assembly
continues until reaching a
stop code on the DNA, and then the RNA
breaks away from the DNA strand.
Scene 14
3.
Code Courier: this illustration labels essential features of messenger RNA.
3a.
What is the message conveyed
by mRNA?
The message is a copy of the
DNA code for a polypeptide.
3b.
Describe how the nucleotide
sequence on mRNA specifies
amino acids.
Each group of 3 nucleotides, a
codon, specifies a specific amino
acid. The sequence of codons is
the code for a sequence of amino
acids in a polypeptide chain.
3c.
In the table, describe what each
lettered label in the graphic points out.
a.
The nitrogenous bases of RNA
b. A codon specifying a particular amino acid
c.
Individual amino acids bonded together
d. The polypeptide chain of amino acids
Varieties of RNA and their Functions
DNA to Protein: View Scenes 15 – 21 and complete the exercise
below.
Examine mRNA, tRNA, and rRNA.
Multimedia
Presentation
Scenes 15 – 17
1.
Edited Message:
sequenced from bottom
to top, this diagram
illustrates alterations
to mRNA.
1a.
In eukaryotic cells, where and when is mRNA altered?
After transcription while still in the nucleus, before traveling to the cytoplasm
1b.
Describe the features at labels A and C, and their function.
Label C is the cap at one end of the mRNA and label A is the poly-A tail at the
other end. The cap and tail prevent enzymes from breaking down the mRNA.
1c.
Describe the features labeled i and what happens to them.
The introns are DNA segments that do not code for protein assembly. They are cut
out of the mRNA.
1d.
Describe the features labeled E and e, and what happens to them.
The exons, or coding segments, are spliced together after intron removal.
1e.
Describe the features labeled sc and E, and their function.
The codon labeled E is the start codon, where the cap attaches (and where the
translation process initiates). The codon labeled sc is the stop codon where the
poly-A tail attaches (and where the translation process terminates).
1f.
What happens to the mRNA when editing is complete?
It moves to the cytoplasm for translation into a polypeptide.
Scenes 18 – 20
2.
Match Maker: these graphics show transfer RNA. On the left is a diagrammatic
view and on the right a 3D view.
2a.
What is the feature at a1 and a2?
The amino acid attachment site
2b.
What is the feature at b1 and b2,
and how does it work?
An anticodon is the complement
of an mRNA codon. Each
anticodon corresponds to a
specific attached amino acid.
2c.
How large is tRNA, measured in
nucleotides?
Only 80 nucleotides, compared
to thousands in mRNA
2d.
What is the function of tRNA?
Transfer RNA molecules deliver a sequence of certain amino acids as specified by
a sequence of mRNA codons.
Scene 21
3.
Micro Mechanic: this graphic shows the general shape of an
animal cell ribosome and its place of origin in the cell.
3a.
What substances comprise a ribosome?
Ribosomal RNA and various proteins
3b.
Where are ribosomes manufactured?
Inside the nucleolus, a structure within
the nucleus of a cell
3c.
What are the two structural parts of a
ribosome?
A smaller subunit and a larger subunit
3d.
What is the function of a ribosome?
It is the site of the translation process and polypeptide synthesis.
4.
Would all forms of life have ribosomes? Explain.
Yes. As the cell is the basic unit of life, and as cell structures are made of proteins,
ribosomes would be essential to the synthesis of proteins in all forms of life.
(Ribosome structure does vary somewhat by species. Mammals have the largest
ribosomes.)
DNA to Protein: Complete Interactive Tutorial #3
Review the basics of protein synthesis.
Interactive
Tutorial
DNA to Protein: Complete Interactive Tutorial #4
Review transcription.
Interactive
Tutorial
Translation
DNA to Protein: View Scenes 22 – 28 and complete the exercise
below.
In these scenes you will study how the genetic code is used to make proteins.
Multimedia
Presentation
Scenes 22 – 23
1.
Describe the mix of ingredients that must be present in the cytoplasm for
translation to take place.
The RNA molecules mRNA and tRNA and the ribosomes containing rRNA must all
be present. The 20 amino acids must also be present, all of them attached to their
matching tRNA molecules.
Scenes 24 –27
2.
Start Up: this illustration
shows the beginning of
the translation process.
2a.
In the table describe the
sequential steps
indicated by the letter
labels.
a.
The small ribosomal subunit attaches to the mRNA strand. Simultaneously, a tRNA
with a UAC anticodon attaches to mRNA at the site of the complementary initiator
codon AUG.
b. The large ribosomal subunit joins the complex so that the initiator tRNA fits into the
P site, leaving the A site free for the next amino acid-carrying tRNA molecule.
c.
2b.
A tRNA molecule with an anticodon complementary to the next codon on the mRNA
strand moves into the vacant A site. A peptide bond links the amino acid of the A
site tRNA to the amino acid of the P site tRNA.
What is this part of translation called?
Initiation
Scenes 27 – 28
3.
Assembly Line: this
graphic shows the
translation process
underway.
3a.
In the table describe the
sequential steps indicated
by the lettered labels.
d. Once the peptide bond is formed, the tRNA in the P site separates from its amino
acid and departs, ready to pick up another amino acid.
e.
The ribosome moves down one codon so that the tRNA previously in the A site now
occupies the P site.
f.
The tRNA with an anticodon complementary to the next codon moves into the A site
and delivers its amino acid to the growing chain.
g. The translation process continues, following the sequence of codons, until reaching
a stop codon.
3b.
What is this part of translation called?
Elongation
Scene 28
4.
End of the Line: this illustration
shows the completion of the
translation process.
4a.
In the table describe the
sequential steps indicated by
the lettered labels
h. At the stop codon UAA, the ribosome A site accepts a release factor protein instead
of a tRNA.
i.
The release factor causes the tRNA in the P site to break its bond with its amino
acid and exit the ribosome. Also, the ribosomal subunits detach from the mRNA.
j.
The polypeptide of amino acids subsequently coils and folds into a protein.
4b.
What is this part of translation called?
Termination
DNA to Protein: Complete Interactive Tutorial #5
Review translation.
Turning Genes On and Off
DNA to Protein: View Scenes 29 – 30 and complete the exercise
below.
You will learn in these scenes that genes are activated or deactivated by means that
are not yet fully understood.
Multimedia
Presentation
Scene 29
1.
Special Effect: the image on the right side is a digital composite. Why won’t you
ever see a caterfly in nature?
The genes for making wings
cannot switch on before
their time (metamorphosis).
2.
Given what you have learned in this lesson, what processes could a genetic switch
turn on or off?
Either transcription or translation might be turned on or off.
Test: DNA to Protein Comprehensive Exam
You are now ready to take the DNA to Protein comprehensive exam.
Test