Question

Pick the correcty answer If a mutation that inactivated telomerase occurred in a cell (telomerase activity in the cell = zero), what do you expect the outcome to be?

The position of the centromere would shift at each replication cycle, eventually leading to mutations in the genetic information and cell death. The number of tandem repeats would increase with each replication cycle, eventually leading to a large unstable chromosome and cell death. The telomeres would shorten at each replication cycle, eventually leading to loss of essential genetic information and cell death. DNA primase would be unable to bind to the 5 end of the template strand, eventually causing a reduction in chromosome size and cell death.

	Somatic or body cells have very little telomerase. As a result, the telomeres within these (proliferating) cells _____ with each cell division.
	shorten lengthen remain constant in size can either shorten or lengthen None of the answers is correct.

A researcher is studying telomerase in four types of mouse cells: brain cells, skin cells, blood cells, and gametes (sperm/eggs). What do you suspect she will find?

telomerase activity/amount will be highest in skin cells telomerase activity/amount will be highest in brain cells telomerase activity/amount will be highest in blood cells telomerase activity/amount will be highest in gametes (sperm/eggs) telomerase activity/amount will be the same in all of the cell types Examples of hybridization of single-stranded DNAs used in Chapter 10 include: primers used in DNA sequencing and in PCR sticky-end cloning probes used in Southern and Northern blotting and in diagnosis of mutations All of the answer options are correct. Examples of proteins that bind to DNA and then act on it, found in Chapter 10, include: restriction enzymes Taq DNA polymerase DNA ligase All of the answer options are correct. Why is ligase needed to make recombinant DNA? It enables the donor fragments and the vector DNA molecules to initially hybridize. It is responsible for forming the complementary sticky ends of the donor fragments and the vector DNA. It is only used when blunt-ended vectors are used to form recombinant plasmids. It creates phosphodiester bonds at the sites where inserted DNA and vector have attached by complementary base pairing. It is used in the isolation of recombinant plasmids from those plasmid vectors that did not take up donor DNA. What would be the immediate consequence in the cloning process if someone forgot to add ligase? There would be no hybridization between the vectors and the donor DNA fragments. No complementary sticky ends would form in either the vectors or the donor DNA molecules. Blunt-ended vectors would be able to form covalent bonds with donor DNA. The inserted DNA and the vector would be held together only by hydrogen bonds, so recombinant plasmids would lose the inserted DNA. Recombinant plasmids could not be separated from nonrecombinant plasmids. In the PCR process, if we assume that each cycle takes five minutes, how many-fold amplifications would be accomplished in one hour? 12-fold 32-fold 512-fold 4096-fold The position of the gene for the protein actin in the haploid fungus Neurospora is known from the complete genome sequence. If you had a slow-growing strain that you suspected of being an actin mutant and you wanted to verify that it was one, would you (1) clone the mutant by using convenient restriction sites flanking the actin gene and then sequence it, or (2) amplify the mutant sequence by using PCR and then sequence it? The better choice is to clone and sequence the actin gene to confirm that it has mutated. This is a dependable method provided that suitable restriction sites are available. The better choice is to amplify the actin gene sequence from the mutant and sequence it to confirm that it has mutated. PCR requires fewer steps, and it can be completed more quickly. However, it requires the production of suitable primers. Why is it necessary to use a special DNA polymerase (Taq polymerase) in PCR? because the reaction starts with very small amounts of DNA template because the polymerase has to be able to remain active after heating to 95 degrees Celsius because the reaction uses primers which are not usually required for DNA replication because the amount of template increases with each cycle One feature that virtually all plasmid vectors have in common is the polylinker (also called a multiple cloning site). This is important because it helps select transformants from nontransformants. it carries convenient restriction enzyme sites into which the DNA to be cloned may be inserted. it allows the vector to replicate independent of host. All of the answer options are correct. Virtually all plasmid vectors have a selectable marker. This is important because it helps select transformants from nontransformants. it carries convenient restriction enzyme sites into which the DNA to be cloned may be inserted. it allows the vector to replicate independent of host. All of the answer options are correct. Prototrophy is often the phenotype selected to detect transformants. Prototrophic cells are used for donor DNA extraction; then this DNA is cloned and the clones are added to an auxotrophic recipient culture. Successful transformants are identified by plating the recipient culture on minimal medium and looking for colonies. What experimental design would you use to make sure that a colony that you hope is a transformant is not, in fact, a revertant (mutation back to prototrophy by a second mutation in the originally mutated gene) of the auxotrophic mutation? Use an auxotroph that cannot revert as the recipient, such as one that contains a deletion. Include a selectable marker on the vector that is added to the auxotrophic recipients. Then use the selection conditions to confirm that the colony is a transformant. Sequence the gene of interest isolated from a putative transformant to determine if additional mutations have occurred. All of the answer options are correct.

Answer 1

If a mutation that inactivated telomerase occurred in a cell (telomerase activity in the cell = zero), what do you expect the outcome to be?

The answer is - The telomeres would shorten at each replication cycle, eventually leading to loss of essential genetic information and cell death.

All eukaryotic chromosomes end in telomeres. The terminal that is extreme 5 prime end of each strand fails to replicate. This occurs because DNA polymerase fails to bind to this terminal ends, actually it slips. So a special enyme called telomerase is employed to catalyze the replication at telomere.

So if there is no telomerase activity then in each cycle of replication few terminal sequences would be lost eventually genetic information would be lost.

Somatic or body cells have very little telomerase. As a result, the telomeres within these (proliferating) cells _____ with each cell division.

The answer is - shorten.

A researcher is studying telomerase in four types of mouse cells: brain cells, skin cells, blood cells, and gametes (sperm/eggs). What do you suspect she will find?

The answer is - telomerase activity/amount will be highest in gametes (sperm/eggs).

In normal somatic cells telomerase activity is not observed. So they can replicate a definite number of time after that they will under go apoptosis. But germ cells that is sperm or egg shows telomerase activity.