Bio Topic 19 SQ

Which of the following is characteristic of the product of the p53 gene?

It is a transcriptional activator for other genes.

Some genes that encode polypeptides that decrease the rate of cell division are known as

tumor-suppressor genes

Some genes that encode polypeptides that function in DNA repair are known as

tumor-suppressor genes

Which of the following mutations would be likely to increase the chances of a cell becoming cancerous?

A mutation that decreases the expression of a gene that is needed for efficient repair of DNA mutations. All of these answers are correct. A mutation that decreases the expression of a gene that increases the rate of cell division. A mutation that increases the expression of a gene that decreases the rate of cell division.

Why are most cancers more frequent among older people?

A single mutation is usually not sufficient for cancer to develop. Cancer cells typically have at least one oncogene and several mutated tumor-suppressor genes. Because mutations are acquired slowly over time, the cells of younger people are less likely to have acquired enough mutations for their cells to become cancerous.

Tumor-suppressor genes may encode polypeptides that

All of these answers are correct. function in DNA repair. function in cell adhesion. decrease the rate of cell division.

Flies with mutant bicoid genes develop posterior structures at both ends. The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end of a normal (i.e. unmutated) fly embryo, which of the following would occur?

Anterior structures would form in both sides of the embryo.

Which of the following statements regarding cytoplasmic determinants is FALSE?

Cytoplasmic determinants are evenly distributed when the zygote divides to produce two daughter cells. Cytoplasmic determinants are unevenly distributed in fertilized egg cells. Cytoplasmic determinants are unevenly distributed in unfertilized egg cells. The cytoplasmic determinants that are more abundant in a cell help determine which subset of genes is expressed in that cell.

Which of the following statements regarding cytoplasmic determinants is FALSE?

Cytoplasmic determinants are evenly distributed within egg cells prior to fertilization, and then become unevenly distributed immediately after fertilization.

Which of the following statements about how cytoplasmic determinants and induction help control which transcriptional activators are expressed by different cell types is TRUE?

Cytoplasmic determinants are unevenly distributed in egg cells. Induction causes the cells near the cell producing the inductive agent to express some of the same transcriptional activators. Cytoplasmic determinants are unevenly distributed during cell division, causing the resulting daughter cells to express different combinations of transcriptional activators. All of these statements are true.

Different genes are expressed in different cells of our bodies because

Different cells have different combinations of activators

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your heart cells.

Which of the following statements regarding transcriptional activators is TRUE?

Most genes are regulated by several different transcriptional activators.

Which of the following statements comparing gene expression in skin versus muscle cells is TRUE?

Some genes are only expressed in skin cells. Some genes are only expressed in muscle cells. Some genes are expressed at higher levels in skin cells. Other genes are expressed at higher levels in muscle cells. All of these statements are true.

Which of the following statements describes proto-oncogenes?

They can code for proteins associated with cell growth and/or division.

A colleague of yours is asked to develop a strain of mutant mice that will be extremely likely to develop cancer so that these mice can be used to study cancer treatments. Your colleague causes a mutation in a mouse that causes the mouse to express a proto-oncogene at greatly increased levels. However, your colleague is disappointed to find the mouse does not have cancer and asks your advice on what he should do next. What should you tell your colleague?

You remind your colleague that a mutation that increases the expression of a single proto-oncogene is generally not sufficient to cause cells to become cancerous. He should also cause some mutations in the mouse's DNA that cause decreased expression of some of the mouse's tumor-suppressor genes.

An oncogene is formed by

a mutation in a proto-oncogene that causes increased expression of the proto-oncogene.

Proto-oncogenes

are normal genes found in all human cells encode polypeptides that help increase rates of cell division. All of these answers are correct. can become oncogenes when they become mutated in such a way that their expression level increases.

Tumor-suppressor genes

can encode proteins that promote DNA repair or cell-cell adhesion.

Altering expression of a single transcriptional activator

can have a huge effect on organismal development, even causing one body part to develop in place of another.

Certain molecules (polypeptides, mRNAs and other molecules) become unevenly distributed in egg cells and, consequently, in the two daughter cells formed by division of an egg cell. Some of these molecules then lead to expression of different sets of transcriptional activators in the daughter cells. These molecules are known as

cytoplasmic determinants

Different cells may have different combinations of transcriptional activators because

cytoplasmic determinants may not be equally distributed within egg cells during cell division cytoplasmic determinants may not be evenly distributed to the two daughter cells some cells may produce chemicals that turn off expression of transcriptional activators in nearby cells All of these answers are correct

The chances that a cell will become cancerous can be increased by

decreased expression of genes that inhibit cell division All of these answers are correct. increased expression of genes that promote cell division decreased expression of genes that act in DNA repair

The fact that plants can be cloned from many different types of cells demonstrates that

differentiated cells retain all the genes of the zygote.

Muscle cells differ from nerve cells mainly because they

express different genes.

In colorectal cancer, several genes must be mutated in order to make a cell a cancer cell. Which of the following kinds of genes would you expect to be mutated?

genes involved in control of the cell cycle

Some cells produce molecules that are transported either to the surface of the cell or are secreted by the cell. When some of these molecules come into contact with neighboring cells, they trigger expression of specific sets of transcriptional activators within those neighboring cells. This process is known as

induction

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior (e.g. head) larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene

normally leads to formation of head structures.

Cell differentiation always involves

the production of tissue-specific proteins, such as muscle actin.

BRCA1 and BRCA2 are considered to be tumor-suppressor genes because

their normal products participate in repair of DNA damage.