DAT Booster Biology Practice Exam 8 Flashcards
Which of the following is most likely to be associated with the hydrophobic area of the cell membrane?
integrin
Integrins
transmembrane proteins that join the cytoskeleton to the extracellular matrix or ECM. In order to secure itself in the cell membrane yet physically link these extracellular and intracellular structures, integrin must have a hydrophobic component that associates with the hydrophobic interior of the cell membrane
A cell is lysed and centrifuged to separate all of its organelles, which are then placed back into a new cell. The process of centrifugation was too aggressive and destroyed the membrane of the organelles. Which of the following organelles would still remain functional?
ribosome
ribosome
one of the major non-membrane-bound organelles and plays a role in protein synthesis.
important organelles found in both prokaryotes AND eukaryotes. Both the large and small subunits shown below consist of ribosomal RNA (rRNA) and proteins.
endosymbiotic theory
suggests that at some point in history, an aerobic or photosynthetic bacterium entered into some other cell to form mitochondria and chloroplasts respectively. This is suggested by the fact that chloroplasts and mitochondria have certain features characteristic of bacteria including division by binary fission, their own ribosomes that are similar in structure to those of bacteria, and circular DNA. In particular, eukaryotes have a ribosome with a 60S and 40S subunit. Like prokaryotes, mitochondria and chloroplasts have smaller 50S and 30S subunits and function in a very similar manner
Which of the following best describes how enzymes can catalyze reactions?
Provides a more efficient reaction mechanism
Enzymes are
biological catalysts that provide an alternative reaction mechanism that has lower activation energy than the original mechanism or by stabilizing the transition state.
Reducing the activation energy allows reactions to proceed at a greater speed. Many biological reactions, would otherwise be extremely slow to proceed despite being spontaneous.
A geneticist is investigating several genes of interest. At the end of the experiment, she concludes that two of the genes
Different genes on the same chromosomes
Epigenetics
involves heritable phenotypes that result from changes to the genome without modifying the nucleotide sequence.
DNA Methylation:
Addition of methyl groups that silences genes, leading to lower expression.
Histone Acetylation:
Addition of acetyl groups that promote gene expression.
Histone Deacetylation:
Removal of acetyl groups that reduces gene expression.
Histone Methylation:
Addition of methyl groups that may increase or decrease expression depending on methylation site and quantity.
DNA’s sugar-phosphate backbone has a negative charge due to the phosphate groups. Histone’s positive charge causes electrostatic attraction that allows DNA to wind around histones. Acetylation of these histones removes this
positive charge which removes electrostatic attraction and lets DNA unwind, promoting expression.
The survival of some bacteria even in harsh and extreme environmental conditions is facilitated by which structure?
endospore
Which of the following does NOT affect allele frequencies in a population?
Random mating
Which of the following prevents acetylcholine from remaining for too long in the synapse?
Acetylcholinesterase
Four different nerve fibers are tested to determine which transmits signal the fastest. Which nerve fiber would be expected to have the fastest conduction impulse?
Thick and myelinated
What is the earliest stage seen during embryonic development?
Zygote
The immediately fertilized egg is known as the zygote and is a single cell that then undergoes cleavage. This rapid cleavage without an increase in the size of the overall mass of cells produces cells called blastomeres. At the 16-cell stage, the solid, ball-like morula is formed. Further division produces a hollow, 128-cell blastula. Further division of the blastula produces the blastocyst that consists of an outermost trophoblast that forms the extraembryonic membranes and the inner cell mass that develops into the embryo
A chicken egg is fertilized in a lab to become a zygote. The zygote undergoes 4 cycles of replication. Identify the number of cells present after these 4 cycles and the size of the cytoplasm in each cell.
2^4, smaller size
Therefore, the number of cells is equal to 2n where n is the original number of cells prior to cleavage and n is the number of replication or division cycles.
A virus was placed in culture with isolated cells. The virus was observed to replicate in all of the following cells EXCEPT one. Which one is the EXCEPTION?
ERYTHROCYTES
1,2,4,3
A point mutation in the shell of a turtle results from a nucleotide change due to radiation. Which of the following best describes the likelihood of the turtle’s progeny inheriting the mutation?
0%
Which of these is involved in the polyspermy blocks?
RELEASE OF CORTICAL GRANULES
fast block of polyspermy
results from the rapid influx of extracellular Na+ following the binding of a sperm with the ZP3 protein. This Na+ influx causes depolarization of the egg that repels additional sperm. This fast block is very rapid because it only involves opening Na+ ion channels. However, the diffusion of Na+ from the egg’s cytoplasm means the depolarization is relatively short-lived.
slow block of polyspermy
creates are more long-lasting effect and is stimulated by the depolarization of the fast block. This depolarization causes the release of intracellular stores of Ca2+ into the cytoplasm which then leads to the exocytosis of the enzymes of the cortical granules into the space between the plasma membrane and zona pellucida. These enzymes digest proteins that hold the two together and inactivates ZP3 proteins. The separated zona pellucida develops into the sperm-impermeable fertilization envelope
A palindromic sequence
one in which the nucleic acid sequence of a given strand and its complementary strand is the same when both are read in the 3’-5’ direction or 5’-3’ direction. An example is given below.
Which of the following is the product of spermatogenesis?
spermatozoa
Spermatids are then nourished by Sertoli cells and they develop into
spermatozoa
Non-stem cells have a limit to the number of rounds of cell division they can go through due to which of the following?
telomere shortening
Hayflick limit
pertains to the limited number of times a cell can undergo division until it has to stop and undergo apoptosis.
This arises from the concept of telomere shortening, which is the shortening of DNA with each round of replication. This is due to the way that the lagging strand works in which DNA polymerase needs 3’-OH to start replicating, and after all RNA primers are removed, there is always an un-replicated region at the end of the strand. This is genetic information that is lost and is the reason why telomeres shorten.
tRNA is necessary to link together __________.
amino acids
Which of the following scientists proposed the theory of trait inheritance through use and disuse?
lamarck
Darwin –
due to competition for limited resources, traits that enabled a species to produce more viable offspring were passed down.
Cuvier –
proposed catastrophism where major natural disasters would devastate the population in an area. The alleles that managed to survive extinction would reproduce. Therefore, the particular traits depend on what traits are randomly driven to extinction and what traits are spared by the catastrophe.
This was disproven because research such as those by Darwin proved that evolution was not by pure chance.
mendel
studied peas to explore the nature of inheritance. From this research, he put forth the laws of inheritance that described how alleles were inherited.
Wallace –
co-authored research with Darwin regarding evolution and natural selection.
A honeybee secretes a trail of a chemical factor after locating a source of food, allowing it to communicate the location of the food to other bees. This form of communication is accomplished using which type of compound?
pheromone
A researcher introduces a chemical into a tumor cell that has begun to replicate out of control. After introducing the chemical, the formation of microtubules is stabilized and they are no longer able to shorten. What phase of the cell cycle has been disrupted?
M Phase
Which of the following best describes the actions of ADH?
Acts on collecting duct by increasing permeability to water
jejunum and the ileum
primary sites of nutrient absorption. Some water absorption occurs here but mineral absorption does not.
duodenum
site of continuing digestion by pancreatic digestive enzymes and bile from the liver. Very little if any absorption occurs here.
