Download SBI4U: Molecular Genetics Unit Review

DNA and DNA replication
1. What is the difference between a nucleotide and a nucleic acid?
Nucleic acids are made up of nucleotide subunits
2. What are the three components of nucleotides?
Sugar (ribose or deoxyribose), phosphate, nitrogenous base (A,T,C,G)
3. What is the difference between the 5’ end of nucleic acids and the 3’ end? Draw a diagram to
show this.
See nucleic acid note
4. When new DNA or RNA is synthesized, in which direction does it grow?
5’ -> 3’ because polymerases can only add nucleotides onto the 3’ end
5. What are two different kinds of bonds that hold nucleic acids together?
Hydrogen bonds (between nitrogenous bases) and phosphodiester bonds (between
nucleotide backbones)
6. Write the complementary DNA strand:
5’- A A T G G C T -3’
3’- U U A C C G A -5'
7. What is the difference between purines and pyrimidines?
Purines have 2 rings, pyrimidines have 1 ring
8. Draw the structure of a double stranded DNA molecule with 3 basepairs
See nucleic acid note
DNA replication
9. Name and describe the three possible models of DNA replication.
Conservative, semi conservative, dispersive
10. Describe the Meselson-Stahl experiment and its results
See DNA replication I note
11. Differentiate between a leading strand and a lagging strand
Leading strand is made continuously, lagging strand is made in small segments called
okazaki fragments behind the leading strand
12. What are Okazaki fragments?
See above
13. Describe the roles of the following enzymes/proteins in DNA replication:
a. DNA helicase – unwinds DNA
b. DNA gyrase – Relieves tension due to unwinding of DNA
c. DNA polymerase – adds DNA nucleotides to form new DNA molecule, also replaces RNA
primers with DNA
d. Single-stranded binding proteins – stabilizes DNA molecule
e. DNA ligase – joins DNA fragments together
f. RNA primase – creates RNA primer
14. Why is it beneficial to have multiple replication bubbles at the same time?
Faster replication
Protein Synthesis
15. What is the central dogma of molecular biology? What is transcription? Translation?
DNA is transcribed into mRNA. mRNA takes the DNA information to ribosomes to be
translated into proteins
16. How does RNA differ from DNA? Name 3 ways.
RNA is smaller, single stranded, uses ribose, uses uracil
17. Describe what happens in initiation, elongation, and termination of:
18.
19.
20.
21.
22.
23.
24.
25.
26.
a. transcription
b. translation
see notes on translation and transcription
What can be found in the promoter region of DNA?
TATA box: where transcription factors bind, so RNA polymerase can bind
What post-transcriptional modifications occur to an mRNA before it leaves the nucleus?
5’ cap, 3’ poly-A tail, RNA splicing
What are the three kinds of RNA, and what are their purposes?
mRNA: carries DNA code to be translated into proteins
rRNA: makes up a part of ribosomes
tRNA: carries amino acids to ribosomes for protein synthesis
What is aminoacl tRNA synthetase?
An enzyme that links tRNAs to their corresponding amino acids
What is a stop codon?
RNA segment that signals the end of translation
When talking about the DNA code, what does the wobble feature mean?
Several different codons can code for the same amino acid
How is translation different in prokaryotes compared to eukaryotes?
Prokaryotes: transcription+translation happen at the same time; ribosomes are
different; RNA polymerase is different
If a DNA template strand reads like this: 5’-ATGATTTCGGGACGA-3’
a. What would the coding strand look like?
3’-TACTAAAGCCCTGCT-3’
b. What would the complementary mRNA strand look like?
3’-UACUAAAGCCCUGCU-3’
c. What amino acid sequence would it produce?
Tyr-STOP
An RNA strand has 4 exons and 3 introns. How many different ways are there to splice this RNA
strand?
4 ways