148 terms


Prokaryotes are classified as belonging to two different domains. What are they?
bacteria and archea
What is true of natural selection?
It requires different genetic variation, resulting in decent with modification
A controlled experiment is one that which
There is at least 2 groups, one is a control
What is the sequence of life's hierarchy, proceeding downward
Nervous system, brain, nervous tissue, nerve cell
What four elements make up 96% of living matter
carbon, hydrogen, nitrogen and oxygen
A nitrogen has 7 neutrons and 7 protons what's the mass number and atomic number?
The mass number is 14 and the atomic number is 7
What happens when an atoms absorbs sufficient energy
an electron may move to n electron shell farther away from the nuclues
A covalent chemical bond is one in which...
outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both
Pertaining to electronegativity, N>H, how would NH3 react?
Each H atom has a partial positive charge with the N having a partial negative charge
What are the bonds in a water molecule?
polar covalent
Why does liquid have a high specific heat?
absorption and release of heat when hydrogen bonds break and form
A solution contains 0.00000001 (10^-7) of (OH-), describe it.
What is the pH of a solution with a (OH-) concentration of 10^12 M?
pH 2
Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+), what would happen if the pH in the blood drops.
the HCO3- to act as a base and remove excess H+ with the formation of H2CO3
What type of molecule is soluble in water?
What two functional groups is always found in amino acids?
carboxyl and amino
Which chemical group can act as an acid?
Molecules with which functional groups may form polymers via dehydration reactions?
either hydroxyl or carboxyl groups
Summarize the relationship between dehyration reactions and hydrolysis?
Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers
A molecule with the formula C18H36O2 is...
fatty acid
Which bonds are created during the formation of the primary sturcture of a protein?
peptide bonds
Which level of protein structure are interactions between the side chains most important?
If cells are grown in a medium contain 35S what molecules will be labeled?
DNAase is an enzyme that catalyzes the hyrolysis of the covalent bonds that join nucleotides together. What would happen to DNA first?
the phosphodiester bonds b/w deoxyribose sugars would be broken
One of the primary functions of RNA molecules is to...
function in the synthesis of proteins
Which nitrogenous bases are of the pyrimidine type?
cytosine and uracil
What is the difference between DNA and RNA?
DNA nucleotides contain a different sugar than RNA nucleotides
Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids and steroids?
smooth ER
Which plant cell organelle contains it's own DNA and ribosomes?
A cell with: enzymes, DNA, ribosomes, plasma membrane, and mitochondria would be a...
mostly all eukaryotic cell
The presence of cholesterol in the plasma membranes of some animals
enables the membrane to stay fluid more easily as the temperature drops
In order for a protein to be an integral membrane protein it would have to be
The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is
to mediate cell-to-cell recognition
Water passes quickly through cell membranes because
it moves through aquaporins in the membrane
The nucleus and most of the organelles in a neuron are located in the
cell body
The point of connection between two communicating neurons is called
The operation of the sodium-potassium "pump" moves
sodium ions out of the cell and potassium ions into the cell
The "threshold" potential of a membrane
is the minimum depolarization needed to operate the voltage-gated sodium and potassium channels
Action potentials move along axons
more rapidly in the myelinated than non-myelinated axons
Neurotransmitters are released from axon terminals via
An example of ligand-gated ion channels is
acetylcholine receptors at the neuromuscular junction
The lumen of the transverse tubules of skeletal muscles contains
extracellular fluid
What are the components of water potential?
pressure potential and solute potential
The host range of a virus is determined by
the proteins on its surface and that of the host
Which of the following is characteristic of the lytic cycle?
a large number of phages are released at a time
The difference between vertical and horizontal transmission of plant viruses is that
vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant
What are prions?
misfolded versions of normal brain protein
Emerging viruses arise by
mutation of existing viruses, the spread of existing viruses to a new host species, and the spread of existing viruses more widely within their host species
Engulfing phagocytic cells of innate immunity DO NOT include...
natural killer cells
Histamines trigger dilation of nearby blood vessels as well as an increase in their permeability producing
redness heat and swelling
Adaptive immunity depends on
pathogen-specific recognition
An epitope is
that part of an antigen that actually binds to an antigen receptor
The rearrangement of DNA sequences between variable regions and joining regions is accomplished by...
What does the thymus do relating to the nervous system?
differentiate and produce mature T cells
The MHC is important in a T cell's ability to
distinguish self from nonself
The activation of helper T cells is likely
when an antigen is displayed by a dendritic cell
The function of antibodies is to
mark pathogenic cells for destruction
Yearly vaccination of humans for influenza is necessary because
rapid mutation in flu viruses alters the surface proteins in infected host cells
The cell-mediated immunity that destroys virally infected cells involves
cytotoxic T cells
CD4 and CD8 are
molecules present on the surface of T cells where they interact with MHC molecules
Which statement best describes the difference in responses of effector B cells and cytotoxic T cells?
B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen0infected host cells
A student analyzed a viral genome and found that the genome had the following nucleotide composition: 28% adenine, 20% thymine, 35% cytosine, and 17% guanine. What is the structure of the viral genome?
Single-stranded DNA
In his transformation experiments, what did Griffith observe?
mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form
/in trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of what fact?
DNA contains phosphorus, whereas protein does not
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
sequence of bases
Replication in prokaryotes differs from replication in eukaryotes for what reason?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes do not
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
How does the enzyme telomerase meet the challenge of replicating the end of linear chromosomes?
It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication
What is the function of the DNA polymerase III?
to add nucleotides to the 3' end of a growing DNA strand
The leading and the lagging strands differ in that
the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction
A new DNA strand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end
Which of the following helps to hold the DNA strands apart while they are being replicated
single-strand binding proteins
What enzyme seperates the DNA strands during replication?
What enzyme covalently connects segments of DNA?
What enzyme synthesizes short segments of RNA?
Why do histones bind tightly to DNA?
histones are positively charged, and DNA is negatively charged
What occurs in eukaryotic gene expression but not prokaryotic?
a poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end
alternative RNA splicing?
can allow the production of proteins of different sizes from a single mRNA
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs, this is explained by...
the rules for bases pairing between the third base of a codon and tRNA are flexible
Which of the following is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
Which of the following is a function of a signal peptide?
to translocates polypeptides across the ER membrane
When the ribosome reaches a stop codon on the mRNA, what would happen if translation was stopped here? What would you be able to isolate?
an assembled ribosome with a polypeptide attached to the tRNA in the P site
Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
a deletion of two nucleotides
What is the effect of a nonsense mutation in a gene?
it introduces a premature stop codon into the mRNA
A frameshift mutation could result from
either an insertion or a deletion of a base
Which of the following statements is true about protein synthesis in prokaryotes
translation can begin while transcription is still in progress
Describe a gene?
a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
The anticodon of a particular tRNA molecule is
complementary to the corresponding mRNA codon
Testosterone function inside a cell by
binding with a receptor protein that enters the nucleus and activates specific genes
What do transcription factors do?
control gene expression
What category of receptors forms dimers, adds phosphate groups and activates relay proteins
receptor tyrosine kinases
An inhibitor of phosphodiesterase activity would have which of the following effects?
prolong the effect of epinepherine by maintaining elevated cAMP levels in the cytoplasm
Why do most transduction pathways have multiple steps?
Multiple steps provide for greater possible amplification of a signal
The termination phase of cell signaling requires what?
dissociation of the singaling moleculemfrom the receptor
The tryptophan operon is a repressible operon that is
turned off whenever tryptophan is added to the growth meduim
What protein is produced by a regulatory gene?
What repressor proteins binds with the repressor to alter the conformation?
The lactose operon is likely to be transcribed when...
the cyclic AMP and lactose levels are both high within the cell
What must occur for a repressible operon to be transcribed?
RNA polymerase must bind to the promoter and the repressor must be inactive
Altering gene expression in prokaryotes would most likely serve he organisms survival in which of the following ways?
allowing the organism to adjust to changes in the enviornmental conditions
If you were to observe the activity of the methylated DNA, you would expect it to..
have turned off or slowed down the process
Steroid hormones produce their effects in cells by
binding to intracellular receptors and promoting transcription of specific genes
Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because...
eukaryotic exons may be spliced in alternative patterns
What will have a small protein called ubiquitin attached to it?
a cyclin that usually acts in G1 now that the cell is in G2
The phenomenon in which RNA molecule in a cell are destroyed if they have a sequence complementary to an introduced double-stranded DNA is called
RNA interference
The cancer-causing forms of the Ras protein are involved in which of the following processes?
relaying a signal from a growth factor receptor
A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type of cancer?
colorectal only
Muscle cells differ from nerve cells mainly because they
express different genes
What are primarily responsible for cytokinesis in plant cells but NOT animal cells?
Golgi-derived vesicles
What triggers the cell's passage past the G2 checkpoint and into mitosis?
Why do neurons and some other specialized cells divide infrequently?
the have been shunted into G0
Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. What is the cell most likely doing?
a plant cell in cytokinesis
Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life cycles have in common?
I. Alternation of Generations
II. Meiosis
III. Fertilization
IV. Gametes
V. Spores
II, III, and IV
If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following is an appropriate description of it's contents?
It has half the amount of DNA as the cell that began mitosis
In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?
Length, centromere position, staining pattern, and traits coded for by their genes.
What occurs in meiosis but not mitosis?
synapsis of chromosomes
Homologous chromosomes are aligned at the equator of the spindle during what key event of meiosis
Metaphase 1
Independent assortment of chromosomes is a result of
the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis 1
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase I would be
Black fur in mice ( B ) is dominant to brown fur ( b ). Short tails ( T ) are dominant to long tails ( t ). What fraction of the progeny of crosses BbTt * BBtt will be expected to have black fur and long tails?
Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. Explain this
environmental factors such as soil pH
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
X^CX^c and X^CY
What is true of linkage?
The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
Recombination between linked genes comes about for what reason?
Crossovers between these genes result in chromosomal exchange.
What is most similar to a receptor protein in a membrane that recognizes a chemical signal?
the active site of an allosteric enzyme that binds to a specific substrate
Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP?
It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane
Testosterone functions inside a cell by
binding with a receptor protein that enters the nucleus and activates specific genes
What is true of the transcription factors?
they control gene expression
One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?
receptor tyrosine kinases
Natural selection is based on what?
*genetic variation exists within populations
*populations tend to produce more individuals than the environment can support
*the best-adapted individuals tend to leave the most offspring
What must exist in a population before natural selection can act upon that population?
genetic variation among individuals
The role that humans play in artificial selection is to
choose which organisms breed, and which do not
What evidence strongly supports the common origin of all life on Earth?
all organisms use essentially the same genetic code
What is the correct sequence of events in the origin of life?
I. formation of protobionts
II. synthesis of organic monomers
III. synthesis of organic polymers
IV. formation of DNA-based genetic systems
II, III, I, and IV
The first genes on Earth were probably
auto-catalytic RNA molecules
Approximately how far back in time does the fossil record extend?
3.5 billion years
Which of the following statements provides the best evidence that prokaryotes evolved before eukaryotes?
the oldest fossilized cells resemble prokayrotes
The oxygen revolution changed Earth's environment dramatically. Which of the following took advantage of the presence of free oxygen in the oceans and atmosphere?
the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules
Although each of the following has a better chance of influencing gene frequencies in small populations, which one most consistently requires a small population as a precondition for its occurrence?
genetic drift
In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of ( q ) for this population?
Summarize evolution as it is viewed today.
it is the differential survival and reproduction of the most-fit phenotypes
Two species of frogs belonging to the same genus occasionally mate, but the offspring fail to develop and hatch. What is the mechanism for keeping the two frog species separate?
the postzygotic barrier called hybrid inviability
According to the concept of punctuated equilibrium, the "sudden" appearance of a new species in the fossil record means that...
speciation occurred rapidly in geologic time
Which of the following factors would not contribute to allopatric speciation?
gene flow between the two populations is extensive
If organisms A. B. and C belong to the same class but to different orders and if organisms D, E, and F belong to the same order but to different families, which of the following pairs of organisms would be expected to show the greatest degree of structural homology?
D and F
Some molecular data place the giant panda in the bear family ( Ursidae ) but place the lesser panda in the raccoon family ( Procyonidae ). Consequently, the morphological similarities of these two species are probably due to
possession of analogous structures
When using a cladistic approach ti systematics, which of the following is considered most important for classification?
shared derived characters
Which statement represents the best explanation for the observation that the nuclear DNA of wolves and domestic dogs has a very high degree of sequence homology?
dogs and wolves shared a common ancestor very recently