Essential Biology 3.3-3.5 – DNA Structure, Replication, transcription and translation (Core)
Topic 3.3 – DNA Structure
1. Draw and label the structure of a simplified single nucleotide, including sugar, phosphate and
base.
2. Complete the table below to show the pairings of the bases in DNA:
Purine
Pyrimidine
3. Where would one find the base uracil?
4. In the space below, draw a single strand of three nucleotides, naming the bonds between them
and showing the correct relative position of these bonds.
5. Define the term double helix.
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Essential Biology 3.3-3.5 – DNA Structure, Replication, transcription and translation (Core)
Topic 3.4 DNA Replication
1. State during which phase of the cell cycle DNA replication occurs.
2. State the function of DNA replication.
3. Which of the following is the end product of DNA replication in a human somatic cell?
A. 23 chromosomes
B. 46 chromosomes
C. 23 pairs of chromosomes
D. 23 pairs of sister chromatids
4. Describe how mitosis ensures that each new daughter cell is identical (mitosis review).
5. Explain the roles of helicase and DNA polymerase in DNA replication.
6.
Explain why DNA replication is considered ‘semi-conservative’.
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Essential Biology 3.3-3.5 – DNA Structure, Replication, transcription and translation (Core)
Topic 3.5 Trascription/Translation
State the central dogma of genetics.
1.
Transcription and translation is also known as protein synthesis, and is the expression of genes.
The genetic code determines the amino acid sequence of a polypeptide, and the properties of
the amino acids give the final structure and function of the protein. Other than membrane
proteins, state four functions of proteins in the cell.
2.
Protein synthesis relies on RNA as a messenger and translating molecule.
Compare the structures of DNA and RNA.
3.
Compare transcription and translation.
Transcription
Begins with…
Translation
mRNA
Ends with…
Location
Uses…
4.
RNA polymerase
Outline the process of transcription in the nucleus, including the roles of RNA polymerase and
complementary base pairing.
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Essential Biology 3.3-3.5 – DNA Structure, Replication, transcription and translation (Core)
5.
Describe the genetic code:
-
Molecule = sequence of bases on mRNA
-
Function= tells ribosome what aa to use
-
Codon = set of three bases on mRNA, recognized by anticodon on tRNA
-
Start codon = three letter code for the first aa – same for nearly all polypeptides always
AUG, translates to methionine/MET
-
Stop codon = three letter code that follows the last aa – says “put no aa here”
6.
Distinguish between triplets and codons.
7.
Explain the significance of the following:
The genetic code is universal.
The genetic code is degenerate.
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Essential Biology 3.3-3.5 – DNA Structure, Replication, transcription and translation (Core)
8.
Deduce the amino acids translated from these
mRNA codons, using the table. Start in the
middle.
AUG
CAG
UCA
GAC
AAA
UGA/UAG
9.
Distinguish between mRNA and tRNA.
10. Explain the process of translation, including mRNA, tRNA, codons, anticodons, ribosomes and
amino acids.
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Essential Biology 3.3-3.5 – DNA Structure, Replication, transcription and translation (Core)
11. Transcribe and translate this DNA sequence.
DNA:
T A C G G G C C C G T G A C A G C C A C T
mRNA:
Am. Acid:
12. Quick mathematical questions:
a. An mRNA strand has 76 codons. How many amino acids will be in the polypeptide?
b. A polypeptide contains 103 amino acids. What is the length of the gene (unit = base pairs)?
c. A gene is 105kbp. How many amino acids are in the polypeptide?
13. Outline the reaction used to join amino acids into a polypeptide (revision).
14. Discuss the one gene, one polypetpide hypothesis in terms of paradigm shifts (how scientific
thinking changes as the result of new discoveries – TOK link).
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