(4) Chapter 18 Flashcards
If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then
the amino acid acts as a corepressor.
For a repressible operon to be transcribed, which of the following conditions must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
Which of the following results is most likely to occur if acetylation of histone tails in the chromatin of embryonic cells is increased?
decreased chromatin condensation
If the DNA of a mammalian promoter region experiences increased methylation on cytosine (C) which of the following results is most likely to occur?
inactivation of the gene
It is possible for a cell to make proteins that last for months, hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?
short-lived proteins enable the cells to control their activities precisely and efficiently
Muscle cells differ from nerve cells mainly because they
express different genes.
The functioning of enhancers is an example of
transcriptional control of gene expression.
Within a cell, the amount of protein made using a given mRNA molecule depends partly on
the rate at which the mRNA is degraded.
Which of the following is the most likely phenotypes of a yeast mutant that contains histones that are resistant to acetylation?
The mutant will show decreased levels of gene expression.
Which of the following statements correctly describes the primary difference between enhancers and proximal control elements?
Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter.
Tests (assays) analyzing transcriptional control of gene expression focus on which of the following characteristics?
amount of the mRNA generated
How are genes coordinately controlled in eukaryotic cells?
Coordinately controlled genes in eukaryotic cells share a set of control elements and are activated by the same chemical signals.
A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____.
two-headed fly
The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.
the establishment of the anterior-posterior axis
The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the _____.
head
What triggers the translation of bicoid mRNA?
fertilization of the egg
The bicoid gene is a type of _____ gene.
egg-polarity
What process produces the gradient of bicoid protein in a fertilized egg?
diffusion
Bicoid mRNA is translated in _____.
the fertilized egg
The bicoid gene is transcribed by _____.
nurse cells
In wildtype Drosophila embryos, the bicoid mRNA is localized to the anterior end of the embryo. If bicoid mRNA was injected into the embryo’s posterior end as well, which of the following developmental events would occur?
The embryo would show anterior structures at both ends of the embryo.
Which of the following is true of the cytoplasm of an unfertilized egg?
It is an unevenly distributed (gradients) mixture of mRNA, proteins, organelles, and other substances. Many proteins are found concentrated at one end of the cell or another and provide positional information to the developing embryo.
How do cells become differentiated?
different genes are expressed so that different proteins are produced. (Cell differentiation results from changes in gene expression)
Cytoplasmic determinants are best described as having which of the following characteristics?
They are maternal substances in the egg that influence the course of early development.
Which of the following describes the normal function of the p53 gene product?
It inhibits the cell cycle.
Two main types of genes involved in cancer development are
proto-oncogenes and tumor-suppressor genes
Which of the following would be most likely to lead to cancer?
amplification of a proto-oncogene and inactivation of a tumor-suppressor gene
All your cells contain proto-oncogenes, which can change into cancer-causing genes. Why do cells possess such potential time bombs?
proto-oncogenes are necessary for the normal control of cell growth and division
Which of the following statements correctly describes a characteristic of tumor-suppressor genes?
They encode proteins that help prevent uncontrolled cell growth.
