DAT Booster Biology Practice Exam 5 Flashcards
In contrast to a prokaryotic organism, which of the following is unique to eukaryotic gene expression?
A. Presence of a promoter region
B. Use of RNA polymerase
C. Polyadenylation of RNA
D. Presence of nucleotides
E. Simultaneous transcription and translation
C
Generally speaking, prokaryotes do not perform post-transcriptional modification, including the addition of a 5′ cap or a polyA tail to their RNA transcript. Furthermore, prokaryotes do not contain introns in their mRNA. Eukaryotic pre-mRNA must undergo several modifications before leaving the nucleus. To stabilize their mRNA, eukaryotes add a 5′ GTP cap and also perform polyadenylation to add a series of Adenine nucleotides to the end of the RNA transcript. Further, splicing is an mRNA processing event unique to eukaryotes and their subsequent gene expression. Splicing is a process in which the spliceosome removes introns from pre-mRNA and splices the exons, resulting in an mRNA that is ready to leave the nucleus – this process is visualized below.
do prokaryotes perform post-transcriptional modification
generally speaking, they do not.
prokaryotes do not contain
introns in their mRNA
eukaryotic pre-mRNA must undergo
several modifications before leaving the nucleus.
To stabilize their mRNA, eukaryotes add a
5’ GTP cap and perform polyadenylation
polyadenylation
add a series of adenine nucleotides to the end of RNA transcript
splicing
an mRNA processing event unique to eukaryotes and their gene expression
spliceosome removes introns from pre-mRNA and splices the exons, resulting in an mRNA that is ready to leave the nucleus
promoter region
eukaryotes and prokaryotes both have this for transcription
In prokaryotes = Pribnow box
In eukaryotes = TATA box
nucleotides are common to both
prokaryotes and eukaryotes as their form of genetic material.
simultaneous transcription and translation are a characteristic unique to
prokaryotes
LH stimulates
Leydig cells to produce testosterone. In turn, testosterone, but not LH directly, helps promote spermatogenesis.
estrogen is involved in the menstrual cycle and in the development of
secondary sex characteristics in females.
triiodothyronine (T3) is one of the thyroid hormones responsible for the
growth and neurological development in children and increasing basal metabolic rate.
FSH directly stimulates
Sertoli cells, facilitating spermatogenesis
stimulates the sertoli cells to promote the maturation of seminiferous tubules and spermatogenesis.
Blood is filtered in the glomerulus by
high hydrostatic pressure, which forces excess fluid and waste products into Bowman’s space.
Circulating blood enters the glomerulus through the
afferent arteriole and exits through the efferent arteriole.
juxtaglomerular cells in the kidney are located next to
the glomerulus (juxta = near/beside)
are derived from the smooth muscle cells of the afferent arteriole
When pressure is low in the afferent arteriole (due to a drop in blood pressure of the body), the juxtaglomerular cells respond by releasing
renin
Renin activates the renin-angiotensin-aldosterone system which restores
blood pressure through the mechanism as shown in the image below.
Without the activation of the renin-angiotensin-aldosterone system, it is more difficult for the body to
recover from a drop in blood pressure, and thus chronic hypotension may manifest.
kidney stones form as a result of
calcium and oxalate levels being high enough that they precipitate out of the filtrate, or urine, to form crystals known as kidney stones.
What molecule is regenerated during the Calvin Cycle?
RuBP
The Calvin cycle is the set of chemical reactions that take place during photosynthesis in
chloroplasts
Calvin cycle is a
This is a light-independent cycle as it takes place after the energy has been captured from sunlight during the light-dependent phase of photosynthesis.
The Calvin cycle consumes ATP and NADPH to produce
glyceraldehyde 3-phosphate (G3P) from CO2.
THREE turns of the Calvin cycle are required to produce a NET of
ONE molecule of G3P
only FIVE G3P are recycled to regenerate
THREE RuBP acceptor molecules.
SIX turns of the Calvin Cycle are required to produce
ONE molecule of glucose.
The Calvin cycle reactions can be divided into three main stages:
carbon fixation, reduction, and regeneration of RuBP (the CO2 receptor)
RuBP is also known as the
CO2 acceptor
plays a crucial role in the carbon fixation step of the Calvin cycle
The attachment of RuBP and CO2 catalyzed by the enzyme
rubisco ( RuBP carboxylase-oxygenase)
After three turns of the Calvin cycle,
6 molecules of G3P are produced;
5 of the 6 G3P molecules are used to regenerate 3 molecules of RuBP.
Commensalism
a relationship between living organisms of two species in which one species obtains benefits like locomotion, shelter, or support from the host species without either harming or benefiting it.
Mutualism –
a relationship in which both organisms benefit.
Parasitism
a relationship when one organism benefits but the other is harmed.
Which of the following events could lead to ecological succession in an already established ecosystem?
A. Newly formed sand dunes
B. Land formed from solidified lava
C. Deforestation
D. Seasonal change in sea levels
E. Permafrost
C
Option A. Newly formed sand dunes – This option is incorrect because newly formed sand dunes are pieces of land that did not exist before, making this an example of primary succession.
Option B. Land formed from solidified lava – This option is incorrect because land forming from lava would be classified as new land since the lava would not have existed there before. This is an example of primary succession.
Option D. Seasonal change in sea level – This option is incorrect because while seasonal changes in sea levels can alter the conditions of an ecosystem, they do not necessarily result in ecological succession unless they cause a significant disturbance or change to the existing community of species.
Option E. Permafrost – This option is incorrect because Permafrost is predominantly seen within tundra’s, and defines the frozen state of the ground that is seen majority of the year; therefore it can’t be considered a disturbance. It can support a small amount of vegetation.
Secondary succession
occurs when a natural habitat, that was previously occupied by vegetation and life, experiences a disturbance that eliminates all life forms, but then is able to become reoccupied by life/vegetation.
primary succession
occurs in essentially lifeless areas, such as regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier.
deforestation
deforestation can be followed by secondary succession as a pre-existing forest would experience a disturbance that would eliminate many sources of food and vegetation, and thus would eliminate many forms of life.
systemic circuit
distributes oxygenated blood containing nutrients to all body tissues via arteries, which carry blood away from the heart. These arteries leave from the left ventricle, as shown in the image below. When oxygenated blood reaches the capillaries within the systemic tissues, it delivers O2 and nutrients to the tissues and picks up CO2. Veins then return the deoxygenated blood back to the heart so that it can enter the pulmonary circuit
pulmonary circuit
pumps deoxygenated blood through the pulmonary arteries to capillaries in the lungs to facilitate gas exchange. The pulmonary arteries leave from the right ventricle, as shown in the image below. The capillaries are in close contact with lung alveoli, where the blood becomes reoxygenated. The pulmonary veins then return the oxygenated blood to the heart so that it can be pumped through the systemic circuit.
blood moving to lungs order:
When the blood picks up oxygen in the lungs, it then flows from the lungs in this direction:
Which of the following sphincters, if damaged, would disrupt the passage of digested material between small and large intestine?
ileocecal
ileocecal sphincter
is a sphincter muscle valve separating the small and large intestine.
The ileum
the longest part of the small intestine
joins the cecum, the first portion of the large intestine, at the ileocecal sphincter.
cardiac sphincter
also known as the esophageal sphincter
allows food to pass from the esophagus into the stomach.
Pyloric sphincter
pyloric sphincter allows chyme to pass from the stomach into the small intestine.
Esophageal sphincter
esophageal sphincter, also known as the cardiac sphincter, allows food to pass from the esophagus into the stomach.
Rectal sphincter
the rectal, or anal, sphincter, allows stool to pass through the rectum out of the anus.
Peroxisomes are membrane-bound organelles that are found in the cytoplasm of
eukaryotic cells
They play a key role in the oxidation of specific biomolecules.
peroxisomes
a major function of peroxisomes is
a major function is the breakdown of fatty acids through beta-oxidation.
H2O2is toxic, however, another peroxisomal enzyme, called _________ uses this H2O2 to oxidize other substrates.
catalase
Lysosomes
lysosomes function as the digestive system of the cell, serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself.
Nucleus
organelle that is responsible for housing the genetic information (DNA) of the cell.
Mitochondria
the powerhouse of the cell and are responsible for producing energy in the form of ATP.
Endoplasmic reticulum
endoplasmic reticulum serves many roles in the cell including calcium storage, protein synthesis, and lipid metabolism.
The majority of coelomate invertebrates develop as protostomes in which the oral (mouth) end of the animal develops from the
first developmental opening, the blastopore.
Examples of protostomes
include mollusks, arthropods and annelids.
In deuterostomes,
the blastopore becomes the anus; the oral end of the animal develops from the second opening. Examples of deuterostomes include echinoderms and chordates. Below is an illustration to help visualize this concep
A zymogen, also known as a proenzyme, is the
inactive form of an enzyme
Many enzymes are synthesized in their
inactive form and then activated when they reach their target tissue.
the zymogen pepsinogen is the inactive form
pepsin
Pepsinogen is secreted by
chief cells in the mucosal layer of the stomach
Once it is secreted into the stomach lumen, the hydrochloric acid causes it to cleave itself into its active form pepsin.
Pepsinogen is produced instead of pepsin because pepsin is a
very strong endopeptidase
if chief cells secreted pepsin, the mucosal layer would be damaged as the pepsin moved along the lumen.
Since pepsinogen is a zymogen, it is inactive and cannot catalyze any reactions; in other words, it must be activated before it can perform enzymatic functions.
Mechanical isolation:
the male and female genitalia of both species are physically incompatible.
Gametic isolation:
the male gametes cannot survive inside the female, or the female gametes do not allow the male gametes to fertilize them.
Habitual isolation:
the two species do not occupy the same location and do not come in contact.
Temporal isolation:
the two species mate at different times
Behavioural isolation:
the two species have different mating rituals and signals; hence they do not attract each other.
The deepest layer of the epidermis known as Stratum germinativum (also known as Stratum Basale), consists of a single row of stem cells that
continually divide to give rise to new stem cells.
one cell remains in the basal layer to continue dividing while the other begins differentiating into a mature skin cell known as a Keratinocyte.
As constant cell division pushes the skin cells outward through the epidermal layers, they fill with keratin, flatten, and lose their organelles.
The outermost layer of the epidermis, the
Stratum corneum
statrum corneum
is composed of 20–30 layers of these dead keratin-filled cells and functions as a physical barrier to protect the organism against pathogens, ultraviolet light, water loss, and injury.
stratum granulosum
lamellar granules
stratum spinosum
langerhan cells
keratinocyte
stratum basale
Divergent evolution
occurs due to an accumulation of differences between closely related species populations, leading to speciation.
Therefore, they become a different species to their ancestors and what was once one species has diverged into two.
convergent evolution
convergent evolution is when two species that are not related to each other by a recent common ancestor, independently evolve similar kinds of traits
Splitting of the centromeres occurs only in
mitosis
Facultative anaerobes are
make ATP by aerobic respiration if oxygen is present but are also capable of switching to anaerobic respiration or fermentation if oxygen is absent.
Obligate aerobes –
obligate aerobes are organisms that require oxygen to grow. Through cellular respiration, these organisms use oxygen to metabolize substances, like sugars or fats, to obtain energy. In this type of respiration, oxygen serves as the terminal electron acceptor for the electron transport chain.
Obligate anaerobes
obligate anaerobes are organisms that can only live in environments that lack oxygen. Unlike the majority of organisms in the world, these organisms are poisoned by oxygen.
Aerotolerant anaerobes
aerotolerant anaerobes are bacteria with an exclusively anaerobic (fermentative) type of metabolism, but they are insensitive to the presence of oxygen.
live by fermentation
microaerophiles
microaerophiles are microorganisms that require oxygen to survive, but requires environments containing lower levels of oxygen than that are present in the atmosphere.
If a bodybuilder injects himself with testosterone and other androgens regularly, we will see an increase in testosterone concentration in the body and
downregulation of natural testosterone production.
testosterone is produced from the
leydig or interstitial cells of the testes
Gonadotropin-releasing hormone (GnRH) is released from the hypothalamus and stimulates the
anterior pituitary to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
LH then stimulates the Leydig cells to produce
testosterone
As part of testosterone regulation, testosterone itself exerts
negative feedback on the hypothalamus and the anterior pituitary, reducing the release of GnRH and LH, respectively.
A special bacterium is designed to survive by eating disulfide bonds. Which form of macromolecule would it most likely consume?
proteins duh
Disulfide bonds are
sulfur-containing covalent linkages that contribute to the tertiary structure of proteins.
Moreover, disulfide bonds are the strongest type of bond that contributes to the tertiary structure of a protein and are visualized in the figure below.
Vascular plants which alternate between haploid and diploid forms and have flagellated sperm are best described as __________.
pterophyta
Pterophyta (ferns) are
vascular plants
alternate between haploid and diploid forms
reproduce via spores
have neither seeds or flowers
vascular
sporophyte is dominant phase
Bryophyta
avascular plants that alternate between haploid and diploid forms and have flagellated sperm.
moses
Coniferophyta
vascular plants that do not have flagellated sperm. An example of this is pines.
Angiosperms
vascular plants that alternate between haploid and diploid forms, but do not have flagellated sperm. An example of this is flowering plants.
In humans, the process of fertilization requires both sperm and an egg. At which stage of oogenesis does the egg have to be in order for fertilization to occur?
Secondary oocyte
primary oocytes are formed
before birth.
These cells will begin the first meiotic division, but be arrested in its progress in the first prophase stage.
Meiosis resumes at puberty, resulting in a secondary oocyte and the first polar body.
The release of a secondary oocyte from the ovaries is called
ovulation
The secondary oocyte commences meiosis II which arrests at metaphase and will not continue without fertilization
Fertilization of the secondary oocyte by the sperm occurs, after which the secondary oocyte completes
meiosis II resulting in a fertilized mature ovum.
Which of the following describes the process of a group of cells directing the development of another group of cells?
induction
process of cells influencing the development of other cells, specifically during differentiation. This is usually carried out using a cell-signaling cascade using signaling vectors such as growth factors. The image below illustrates this phenomenon.
Transfection –
transfection is the introduction of new genetic material into eukaryotic cells.
A mutation causes all of the mitochondria of a cell to be dysfunctional. Which of the following processes would likely not be affected by this mutation?
glycolysis
The only process of cellular respiration that does not occur within the mitochondria is
glycolysis
Pyruvate oxidation
once pyruvate (produced from glycolysis) enters the mitochondrion, it is converted to acetyl coenzyme A (acetyl CoA) via pyruvate oxidation.
This process occurs in the mitochondrial matrix.
Citric acid cycle
citric acid cycle breaks down acetyl-CoA to form CO2, ATP, NADH, and FADH2.
This process occurs in the mitochondrial matrix.
Electron transport chain
the electron transport chain begins with NADH and FADH2 donating electrons to cytochromes embedded in the inner mitochondrial membrane.
The energy harvested from these electrons moving to progressively lower free energy levels is coupled with ATP synthesis. Since the electron transport chain occurs in the inner mitochondrial membrane.
Oxidative phosphorylation
oxidative phosphorylation is the synthesis of ATP by using the energy gained from the redox reactions in the electron transport chain. This is unlike substrate-level phosphorylation, which directly generates ATP by having an enzyme transfer a substrate’s phosphate group to ADP.
Since oxidative phosphorylation depends on a functional electron transport chain in the inner mitochondrial membrane.
Phylum Echinodermata and Coelenterates display
radial symmetry
the body can be divided into five more or less similar portions around a central axis.
Which of the following phylum has radial symmetry?
echinodermata
Porifera demonstrate
asymmetrical body plan
Mollusca demonstrate
bilaterally symmetrical.
Arthropoda body plan
they are bilaterally symmetrical.
primary protein structure
sequence of a chain of amino acids
secondary protein structure
hydrogen bonding of the peptide backbone causes the amino acids to fold into a repeating pattern
tertiary protein structure
3D folding pattern of a protein due to side chain interactions
quaternary protein structure
protein consisting of more than one amino acid chain
When carbohydrates are low and alternative sources of energy are not available, the body may need to convert protein to glucose via the process of __________.
gluconeogenesis
Gluconeogenesis is the synthesis of glucose from
pyruvate and from other non-carbohydrate carbon substrates like proteins.
It is essentially glycolysis in reverse with a few differences, including the conversion of pyruvate to oxaloacetate and the use of phosphatases such as G6Pase instead of kinases to remove phosphate groups.
Gluconeogenesis takes place mainly in the
liver
his process occurs during periods of fasting, starvation, low-carbohydrate diets, or intense exercise and is highly endergonic
Ketogenesis
ketogenesis is the production of ketone bodies by the breakdown of fatty acids and ketogenic amino acids.
Glycogenesis –
glycogenesis is the formation of glycogen from glucos
Transamination
transamination is the transfer of an amino group to a ketoacid to form a new amino acid.
Lipogenesis –
lipogenesis is a process where acetyl-CoA is converted to triglycerides (fat).
In humans when a female is born, the development of her oocyte is arrested in which of the following stage?
prophase 1 of meiosis
A plant-like unicellular organism with a nucleus is best categorized under which kingdom?
protista
Monera
Nucleus: NO
Cell Organization: Unicellular
Cell wall: yes (pepti.)
Nutritional class: autotrophic / heterotrophic
Mode of nutrition: absorption
example: archaea, eubacteria
Surfactant is a substance produced by
Type II alveolar cells in the lung.
surfactant
It mainly reduces the surface tension in the alveoli.
surfactant reduces the elastic force that causes the alveoli to recoil and decrease in size.
Which of the following correctly describes an acrosomal reaction?
A. A reaction that prevents the entry of more sperm into the egg with a wave of Calcium ions that causes the egg’s protein envelope to harden and sperm receptors to degrade
B. A reaction that occurs after the blastula stage of development
C. A reaction that occurs when the two haploid nuclei of the sperm and egg fuse into a diploid nucleus
D. A reaction that degrades the protective coat and protein membrane surrounding the egg
E. A reaction that happens directly after the cortical reaction
D
The acrosome is an organelle over the anterior half of the sperm’s head. It contains digestive enzymes including hyaluronidase and acrosin. The acrosome reaction is a crucial step during gamete interaction in all species, including humans. It allows spermatozoa to penetrate the zone pellucida of the egg and fuse with the oocyte membrane. The zona pellucida is a thick, transparent, glycoprotein membrane that surrounds the cell’s plasma membrane. Spermatozoa unable to undergo the acrosome reaction will not fertilize intact oocytes.
The genetic variation of a population is MOST likely to be increased by which of the following processes?
mutationb
Non-inheritable trait
These traits are associated with learning, and are not genetically passed down from offspring to offspring.
Complete dominance
This is when the dominant allele completely masks the effect of the recessive allele.
Pleiotropy
Pleiotropy describes when a single gene affects multiple, seemingly unrelated features or aspects of an organism’s phenotype.
Co-Dominance
In co-dominance, both alleles in the genotype are seen in the phenotype simultaneously (in this example, the flower would have patches of red and white color if there was co-dominance).
Rods are a type of photoreceptors within the retina that are necessary for
night vision
vision in dimmer lighting
They contain pigments called rhodopsin, which undergo chemical change when exposed to light rays and cause these photoreceptor cells to signal bipolar cells near the retina
In which component of the eukaryotic cell does Kreb’s cycle take place?
mitochondrial matrix
A population of 100 lizards exists in Hardy-Weinberg equilibrium in which the lizard’s allele for short tail is dominant, and the allele for long tail is homozygous recessive. If 16 lizards were found to have long tails within a population, what is the allele frequency for lizards that have short tail?
To solve this question, we must use the Hardy-Weinberg principle and its equations:
p2 + 2pq + q2 = 1
p + q = 1
Where p is the frequency of the ‘L’ (dominant short tail) allele, and q is the frequency of the ‘l’ allele (recessive long tail) in the population. In the equation, p2 represents the frequency of the homozygous genotype LL, q2 represents the frequency of the homozygous genotype ll, and 2pq represents the frequency of the heterozygous genotype Ll. Given this, we already know that q2 = 0.16 from the question since that is how many long-tailed lizards are in the population.
Now since the question is asking for the allele frequency, we need to solve for p or q. If the question was asking for genotypes, we would be solving for either p2, q2, or 2pq. So if “p” is the frequency of the dominant short tail allele and “q” is the frequency of the recessive long tail allele in the population, we can use the Hardy-Weinberg equation to calculate the allele frequency of the short tail allele (p):
q2 = 0.16
Hence, q = 0.4
Use the equation p + q = 1 to find the predicted value of p.
p = 1 – 0.4 = 0.6
Hence, the allele frequency for short tail is 0.60.
How to solve these problems:
This question is another variation of a type of Hardy Weinberg question you may encounter on the DAT. We highly recommended that you know how to solve these types of questions for the DAT since they do show up occasionally.
