- Viruses _____.
use the host cell to copy themselves and make viral proteins
- Which of the following supports the argument that viruses are nonliving?
They are not cellular.
- Which of the following is characteristic of the lytic cycle?
A large number of phages are released at a time.
- Which of the following is a protein produced by a regulatory gene?
- The role of a metabolite that controls a repressible operon is to:
Bind to the repressor protein and activate it.
- What is meant by the description "antiparallel" regarding the strands that make up DNA?
The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
- Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?
- Pattern formation
- One of the human leukemias, CML (chronic myelogenous leukemia), is associated with a chromosomal translocation between chromosomes 9 and 22 in somatic cells of bone marrow. Which of the following allows CML to provide further evidence of this multistep nature of cancer?
The translocation requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces.
- Fertilization normally:
- From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?
Cleavage → gastrulation → organogenesis
- Which of the following correctly displays the sequence of developmental milestones?
Cleavage → morula → blastula → gastrula
- During fertilization, the acrosomal contents:
Digest the protective jelly coat on the surface of the egg.
- The formation of the fertilization membrane requires an increase in the availability of:
- Genomic imprinting, DNA methylation, and histone acetylation are all examples of:
- In a newly fertilized egg, the vitelline layer:
Hardens to form a protective cover.
- Human trophoblasts:
Are of embryonic origin and function in embryo nutrition.
- Transcription of structural genes in an inducible operon _____.
starts when the pathway's substrate is present
- One hereditary disease in humans, xeroderma pigmentosum (XP), makes homozygous individuals exceptionally susceptible to UV-induced mutation damage in the cells of exposed tissue, especially skin. Without extraordinary avoidance of sunlight exposure, patients soon succumb to numerous skin cancers. Which of the following best describes this phenomenon?
Inherited inability to repair UV-induced mutation.
- The vegetal pole of the zygote differs from the animal pole in that:
The vegetal pole has a higher concentration of yolk.
- A human blastomere is:
An embryonic cell that is much smaller than the ovum.
- Gases are exchanged in a mammalian embryo in the:
- At the moment of sperm penetration, human eggs:
Are still surrounded by follicular cells.
- Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator?
- In all vertebrate animals, development requires:
An aqueous environment
- For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
Amino acids (and thus proteins), also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
- If a Drosophila female has a homozygous mutation for a maternal effect gene, _____.
all of her offspring will show the mutant phenotype, regardless of their genotype
- The tryptophan operon is a repressible operon that is:
Turned off whenever tryptophan is added to the growth medium.
- There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that
The rules for base pairing between the third base of a codon and trna are flexible.
- In placental mammals, the yolk sac:
Produces blood cells that then migrate into the embryo.
- For a repressible operon to be transcribed, which of the following must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
- Allolactose, an isomer of lactose, is formed in small amounts from lactose. AnE. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?
Allolactose binds to the repressor protein.
- A human zygote undergoes its first cell division:
24 hours after fertilization
- Cells move to new positions as an embryo establishes its three germ tissue layers during:
- In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP?
Decrease in glucose and increase in camp
- Embryonic lethal mutations result in:
Phenotypes that are never born/hatched.
- Steroid hormones produce their effects in cells by _____.
binding to intracellular receptors and promoting transcription of specific genes
- The migratory neural crest cells:
Form neural and non-neural structures in the periphery.
- In eukaryotes, general transcription factors:
Bind to other proteins or to a sequence element within the promoter called the TATA box.
- A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
An accumulation of A and no production of B and C.
- At the time of implantation, the human embryo is called a:
- The product of the bicoid gene in Drosophila provides essential information about:
The anterior-posterior axis
- The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is:
Ectoderm → mesoderm → endoderm
- In animals, embryonic stem cells differ from adult stem cells in that:
Embryonic stem cells are totipotent, and adult stem cells are pluripotent.