Exam 222222 Flashcards

Question

What are mitochondria?

Answer 1

Mitochondria produce energy by respiration: glucose + oxygen -> carbon dioxide + ATP. We can think of ATP as energy in storage (a bit like a battery). Useable energy is released when ATP -> ADP (i.e., when ATP loses one of its phosphate groups – triphosphate becomes diphosphate)

Answer 2

Chloroplasts (in plants only) produce sugars by photosynthesis: carbon dioxide + water + sunlight -> sugars + oxygen.

Answer 3

Cells with a distinct nucleus and organelles surrounded by membranes are called eukaryotes. Cells without, such as bacteria, are called prokaryotes. Eukaryotes and prokaryotes differ in many aspects of how they “earn a living.” Eukaryotes are like slow, fancy cadillacs whereas prokaryotes are more like speedy, stripped-down race cars.

Answer 4

With the exception of cells that produce sperm and eggs (sex cells, or gametes), all cells divide by mitosis.

Answer 5

Mitosis is part of the cell cycle, the stages of which are labeled as G1, S, G2 and mitosis. A cell grows and does its jobs (G1), copies its DNA (S) and then gets ready to divide (G2)

Answer 6

The cell cycle is controlled by genes – lots of genes. Two kinds of genes are particularly important (but I stress they aren’t the only genes involved). Genes called oncogenes promote mitosis, whereas tumor-suppressor genes inhibit mitosis.

Answer 7

Cancer arises when regulation of the cell cycle fails and mitosis becomes uncontrolled. For example, genes that either promote or inhibit mitosis may suffer mutations and so not function properly. In an imperfect analogy to traffic signals, it is as if the green light is always on and/or the red light is always off. Cancer is a variable disease with variable causes, including exposure to environmental carcinogens such as tobacco smoke and the rays coming from tanning beds. Not too many cancers are caused by genetic changes that can be inherited, but more may be caused by infectious agents (such as viruses) than we once thought.

Answer 8

Cancer is harder to treat when secondary tumors have arisen through metastasis, but new treatments for cancer at all stages are under constant development. Standard therapies involve surgery and/or the use of radiation and/or drugs (chemotherapies) to slow or halt cell division. For example, the drug Taxol disrupts the little spindles that move chromosomes during mitosis. Newer therapies are more targeted. For example, the drug Avastin blocks angiogenesis, starving tumor cells and making metastasis less likely. Another approach is to block the responses of cancer cells to molecules that occur naturally in the body and which stimulate cell division. And a lot of research is being devoted to ways in which the body’s own defense cells can be stimulated to attack cancer cells. Perhaps most exciting are developments in which the mutations in an individual’s tumor are identified and then a mutation-specific therapy is given – we might call this individualized therapy.

Answer 9

Despite progress with particular kinds of cancer, the disease overall remains the second leading cause of death in the U.S. (heart disease is number one, but not by much of a lead), and the most common kind of cancer is that of the skin followed by the lung. About one out of every three Americans will develop cancer if they live long enough. Of course, developing cancer isn’t the same as dying from cancer.

Answer 10

The basic strategy underlying applied genetics is what we’ll call ISICU – Identify, Sequence, Isolate, Copy, Use. Identify and sequence the bases in genes of interest. Isolate the gene of interest – restriction enzymes (think of them as “DNA scissors”) recognize particular sequences of bases (A, C, T and G) and cut the DNA where those sequences occur. Thus, a gene can be removed from its chromosome. With a gene isolated from its chromosome by cutting it free with restriction enzymes, we can use the polymerase chain reaction (or PCR) to produce millions of copies accurately, quickly and cheaply. PCR basically mimics in a machine the natural process by which DNA is replicated in cells. Now we are ready to use that gene.

Answer 11

DNA that carries a gene from a different species is said to be recombinant.

Answer 12

An individual carrying a gene from a different species is said to be transgenic

Answer 13

With a gene isolated, we can use PCR to produce millions of copies accurately, quickly and cheaply. Heres an example: Using restriction enzymes, a copy of a gene of interest is spliced into a plasmid, which is a bacterial mini-chromosome. The plasmid is then put into a bacterial cell. That recipient cell, and all of its descendants (produced by mitosis), will copy the foreign gene and then can be made to manufacture the protein for which it codes. In this way, we can generate transgenic bacteria with recombinant DNA that produce, say, human insulin, which can be used to treat Type I diabetes (also called juvenile or early-onset diabetes). This process is the core of our current biotech industry.

Answer 14

It relies on a mechanism evolved by bacteria to help them fend of attacks by viruses (a mechanism that is different from the one that involves restriction enzymes and that we discussed earlier). This mechanism, called CRISPR-Cas9, is already being used in research, but what about the possibility of using it to, say, fix malfunctioning genes in humans? There’s a lot of excitement about using CRISPR-Cas9 to fix wonky genes in human eggs, although pretty much all scientists agree that it is far too early to do this clinically. But research is being conducted.

Answer 15

Repetitive sequences of bases that don’t code for proteins (called tandem repeat units) can be cut out of their chromosomes, separated and stained to make them visible. They can then be used as DNA fingerprints because they are so incredibly variable among individuals in how many repeating units they possess. I stress that only stretches of DNA that do not code for proteins can be used in this way. By comparing DNA fingerprints among defendants in a criminal case, we can exclude those for whom we obtain no genetic match. Wrongly imprisoned people have been released from jail thanks to such exclusion. When we find a match, statistical methods can be used to estimate how likely that match may be due to chance. The smaller that estimate, the more certain we can be that the match is real.

Answer 16

The Supreme Court ruled recently that taking such samples is consistent with the U.S. Constitution and the Bill of Rights.