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Due Wednesday 5/12/10
Ch 11 homework
1. The term "gene expression" refers to the (.5)
A) fact that each individual of a species has a unique set of genes.
B) fact that individuals of the same species have different phenotypes.
C) process by which genetic information flows from genes to proteins.
D) fact that certain genes are visible as dark stripes on a chromosome.
E) flow of information from parent to offspring.
2. Outline the function of the lac operon when no lactose is present. (1)
Repressor is expressed from the regulatory gene, it binds to the operator ceasing gene
expression in the lac operon.
3. What is differentiation? At what stage of life does most cellular differentiation occur?
(1)
Differentiation is the specialized structure and function of a cell. It occurs very early
during embryonic development
4. Explain alternate RNA splicing. How does it enable a single gene to encode more than
one kind of polypeptide? (1)
Alternate RNA splicing is when exons of the RNA are recombined in more than 1 way,
resulting in more than one mRNA from a single RNA transcripta
5. What are oncogenes, proto-oncogenes, and tumor-suppressor genes? (1)
Oncogenes are genes that, when present in a single copy, can cause cancer. Protooncogenes are genes that have the potential to become oncogenes. Tumor suppressor
genes are genes that prevent uncontrolled cellular growth
6. Explain how DNA is packaged into chromosomes in Eukaryotes (1).
Histones associate with the DNA to begin coiling and folding of the chromosome. The
histones are then further associated into nucleosomes, which are a complex of 8 histones
and DNA. This allows the DNA to be supercoiled into a chromosome.
7. Enhancers are (.5)
A) adjacent to the gene that they regulate.
B) required to turn on gene expression when transcription factors are in short supply.
C) the site on DNA to which activators bind.
D) required to facilitate the binding of DNA polymerases.
E) the products of transcription factors.
8. Outline the 4 ways genes expression can be regulated after mRNA has been processed
and transported to the cytoplasm. (2)
Breakdown of mRNA- mRNA digested when no longer needed so no longer usable
Initiation of translation- translation of the mRNA into a protein
Protein activation- protein may need further alteration to be functional
Protein breakdown- selective breakdown of proteins
9. Outline how a signal transduction pathway works to control gene expression (1).
Series of molecular changes beginning with the signal molecule that binds to a receptor
protein in the plasma membrane. This message is passed into the nucleus via relay
proteins until a transcription factor is activated, which binds to the DNA, generating a
response.
10. Compare and contrast reproductive and therapeutic cloning (1).
Reproductive cloning is when a new individual is cloned. The new individual will have
identical genetic material to the donor, but may not act or look identical.
Therapeutic cloning is when stem cells are used to grow new tissues. A new individual is
not created, only specific tissues and organs.
Both are the result of nuclear transplantation.
Ch 12 Questions
1. When DNA from two sources is combined into one single piece of DNA, it is known
as (1)
A) cloned DNA.
B) recombinant DNA.
C) a vector.
D) a plasmid.
E) a DNA library.
2. DNA ligase binds (1)
A) exons together.
B) polymerase to the promotor.
C) nucleotides together.
D) introns together.
E) an intron to an exon.
3. Outline how PCR works (2)
DNA is heated to unwind double helix, DNA is cooled and primers bind to target
sequence of DNA at ends. DNA polymerase adds nucleotides to the 3’ end of the primer,
creating two new double strands.
4. What are restriction enzymes and how do they work?(1)
Restriction enzymes are enzymes that cut the DNA at a specific site. They work by
recognizing specific nucleotide sequences on the DNA and cutting only at that site in a
staggered fashion. This creates “sticky ends” for where another piece of DNA that has
been cut with the same restriction enzyme can bind.
5. When performing electrophoresis, which end of the gel (positive or negative) will long
fragments “run” to? What about short segments? What causes this difference? (2)
The DNA fragments “run” from negative to positive. The long fragments will end up
towards the negative end while the shorter ones will run further towards the positive. This
difference is caused by size differences in the fragments.
6. The feature of "sticky ends" that makes them especially useful in DNA recombination
is their ability to (1)
A) bind to DNA and thereby activate transcription.
B) bind to ribosomes and thereby activate translation.
C) form hydrogen-bonded base pairs with complementary single-stranded stretches
of DNA.
D) allow plasmids to attach to the main bacterial chromosome.
E) insert a segment of RNA into a bacterial chromosome.
7. What is recombinant DNA? (1)
Recombinant DNA is DNA that has been created artificially from 2 or more sources.
8. How do you make cDNA from mRNA? Outline the process. (1)
mRNA is isolated and reverse transcriptase is added. The reverse transcriptase
synthesized complimentary single stranded DNA from the mRNA transcript. This new
strand is called cDNA. The mRNA is then digested and polymerases create a
complimentary strand of the DNA resulting in double stranded DNA.