Download 1. Fill in the blanks regarding the Lac Operon: binds to the

1. Fill in the blanks regarding the Lac Operon:
__________________ binds to the repressor, changes its shape so that the repressor__________
(does/does not) bind the operator.
For lac operon expression, the __________________can’t be bound to the operator and
___________(glucose/lactose) can not be present.
Low levels of glucose result in __________(high/low) levels of cyclic AMP.
In the lac operon, the repressor binding to the operator is an example of negative gene
regulation, while_______________is an example of positive gene regulation.
The lac operon is an example of a(n) _______________(repressible/inducible) operon. In other
words, gene expression is_____________(repressed/induced) when the effecter (lactose) is
bound to the repressor.
2. Match the following with their role in translation.
a. 30S or 40S ribosomal subunit (small subunit)
b. ribosome binding site
c. initiation complex
d. 50S or 60S ribosomal subunit
e. tRNA
f. aminoacyl-tRNA
g. anticodon
h. P-site of ribosome
i. A-site of ribosome
j. peptidyl transferase
k. stop codon
l. release factors
m. start codon
_____ A series of three tRNA bases complementary to a mRNA codon.
_____ The enzyme that forms peptide bonds between amino acids during translation.
_____ The ribosomal subunit that binds to mRNA to form the initiation complex.
_____ The ribosomal site where an aminoacyl-tRNA first attaches during translation.
_____ The ribosomal site where the growing amino acid chain is temporarily being held by a tRNA
as the next codon in the mRNA is being read.
_____ A complex of an amino acid and a tRNA molecule.
_____ The sequence of bases on mRNA to which a 30S or 40S ribosomal subunit first attach.
_____ A series of three mRNA bases coding for no amino acid and thus terminates the protein
chain: UAA, UAG, UGA.
_____ A complex consisting of a 30S or 40S ribosomal subunit, a tRNA having the anticodon UAC
and carrying an altered form of the amino acid methionine (N-formylmethionine or f-Met), and
proteins called initiation factors.
_____ A folded RNA molecule with secondary structure that base pairs with mRNA and carries an
amino acid at its 3’ end.
3. How can one gene encode different forms of a polypeptide?
4. When a ribosome encounters a stop codon, which terminus of the polypeptide has it just finished
making?
5. These cause the termination of translation.
MULTIPLE CHOICE: Select the best answer from the answers provided. Choose only one
answer. 2 pts
6. What is the product of the lacI gene?
a. lactose
b. tryptophan
c. B-galactosidase
d. repressor
e. CAP protein
7. Your bone cells, muscle cells, and skin cells perform different functions because
a. each cell contains different kinds of genes.
b. they are present in different organs.
c. different genes are active in each kind of cell.
d. they contain different numbers of genes.
e. each cell has different mutations.
8. Under normal conditions in wild type E. coli, the lac operon is under ________ control.
a. positive
b. negative
c. inducible
d. both B and C
e. all of the above
9. Which of the following is an example of positive control?
a. lactose inducing the lac operon
b. CAP-cAMP binding to the lac promoter
c. trp binding to the trp repressor
d. lac repressor binding to the lac operator
10. A point mutation may be insignificant because:
a. a new amino acid is coded at an unimportant location.
b. it creates a frameshift
c. a new amino acid may not be encoded.
d. point mutations are neutral
e. a and b
f. a and c
g. a and d
11. Which of the following pairs of codons might you expect to be read by the same tRNA as a
result of wobble? Assume codons are read in a 5’ to 3’ direction.
a. CCC/CCG
b. CCA/CCC
c. CCU/CCC
d. CCG/CCC
12. Based on your knowledge of the lac operon, predict how the following mutations would affect
the function of the operon in both the presence and absence of lactose:
a. Mutation of promoter; CAP protein does not bind to promoter. 3 pts
b. Mutation of operator; repressor will not bind to operator. 3 pts
13. These are involved in the packaging of DNA and organizing DNA into a very small nucleus.
______________
14. What is the charge of the answer of the question above and why is this charge important?
15. This level of DNA packaging involves a core of 8 histones with about 200 base pairs of DNA
wrapped around this core.
16. This level of DNA packaging is basically 2 nucleosome chains stacked on top of each other and
production of this is facilitated by H1, found in linker DNA.
17. Heterochromatin is relatively loosely packed and is transcriptionally active, true or false.
18. Acetylation is done by these, which add acetyl groups to ends of histones.
19. _______________ binding enhancers, cause chromatin modification (loosening), which leads to
expression.