DAT Bootcamp 8 Biology
What part of the developing human embryonic blastocyst contributes to the placenta?
- Answer: Trophoblast - The inner cell mass will form the embryo. The inner cell mass differentiates into two cell types: epiblast and hypoblast. This is the bilaminar stage as there are two cell layers. - The hypoblast will contribute to the yolk sac, and the remainder undergoes apoptosis and disappears. - As the epiblast thickens, in birds, reptiles, and mammals a primitive streak starts to form. The primitive streak creates a left-right, and top-bottom axis for the developing embryo. - Epiblast cells invaginate inwards through the primitive streak to form three germ layers (endoderm, mesoderm, and ectoderm) in a process known as gastrulation. The primitive streak dictates where gastrulation occurs in these organisms.
24. All of the following interact with either DNA or RNA in bacteria, EXCEPT one. Which one is the EXCEPTION? A. Telomerase B. DNA polymerase C. tRNA D. RNA polymerase E. Helicase
Answer: A. Telomerase A: Telomerase Telomerase is not found in bacteria; prokaryotes have circular chromosomes, and telomerase's function is preserving the end of eukaryotic chromosomes. B: DNA polymerase DNA polymerase I fills in gaps left by RNA primers during prokaryotic DNA replication. DNA polymerase III replicates the leading and lagging strand during prokaryotic DNA replication C: tRNA tRNA interfaces with mRNA and brings amino acids to the ribosome during protein translation. D: RNA polymerase RNA polymerase synthesizes the various types of bacterial RNA. E: Helicase Helicase is a necessary enzyme in both prokaryotes and eukaryotes to unwind double stranded DNA, allowing for replication to occur.
8. Which part of the prokaryotic operon, if bound by a repressor protein, would prevent successful transcription by RNA polymerase? A. Spliceosome B. Operator C. Structural genes D. Promoter E. Regulatory genes
Answer: B A: Spliceosome Eukaryotic spliceosomes remove introns from RNA transcripts. They are not involved in the initiation of transcription by the RNA polymerase. B: Operator The operator is the region in the operon that, if bound by a repressor protein, will prevent RNA polymerase from transcribing DNA. C: Structural genes Structural genes are responsible for coding the product of a gene (i.e. its RNA or protein output, such as the enzymes produced when a gene is transcribed). D: Promoter The promoter is the sequence of DNA where RNA polymerase attaches to begin transcription - while binding of RNA polymerase to the promoter is critical for transcription, repressor proteins do not bind to the promoter. E: Regulatory genes Regulatory genes are responsible for producing repressor proteins and activator proteins that can assist or prevent the binding of RNA polymerase to the promoter region. Repressor proteins produced by regulatory genes bind at the operator. Regulatory genes may not be located within the operon, and can still exert control over the operon even when far away.
9. All of the following can affect the function of enzymes EXCEPT one. Which one is the EXCEPTION? A. Temperature B. Catalyzing an extreme number of reactions. C. pH D. cofactors. E. Substrate concentration
Answer: B A: Temperature Enzymes in the body function best at body temperature, and temperatures that are too high or too low can result in limited function or denaturing of the enzyme. B: Catalyzing an extreme number of reactions No matter how many reactions an enzyme has catalyzed, enzymes remain unchanged during reactions. An enzyme that has catalyzed many reactions would function no differently than an identical enzyme that has catalyzed only a handful of the same reaction. C: pH Enzymes in the stomach, for example, prefer a pH between 2 and 3. Similar to temperature, a pH that is too high or too low can adversely affect the function or cause denaturing of an enzyme. D: Cofactors Cofactors are non-protein components that can assist enzymes in their function. E: Substrate concentration Increasing the concentration of a substrate will increase the rate of action of the enzyme (until the enzyme's active site starts to saturate with substrate - eventually, the speed at which all the enzymes can work becomes the limiting factor, and the rate of enzyme catalysis plateaus).
30. All of the following characteristics are true of the phylum Arthropoda EXCEPT one. Which one is the EXCEPTION? A: Segmented body B: Closed circulatory system C: Spiral and determinate cleavage D: Excretion via Malpighian tubules E: Exoskeleton
Answer: B B: Closed circulatory system This is a false statement and therefore the answer choice is correct. Arthropoda have an open circulatory system.
3. Which of the following is a true statement about the cellular membrane? A: Phospholipids can freely dissolve into the extracellular fluid B: The tails of phospholipids are the source of all lipid content in the cell membrane C: Phospholipids can move around freely within the cellular membrane D: Integral membrane proteins attach primarily at the extracellular portion of the cellular membrane E: Small ions are allowed to pass directly through the cellular membrane via simple diffusion
Answer: C - A: Phospholipids are partially hydrophobic (lipid component). This means the phospholipid cannot (easily) diffuse out of the membrane - it is 'locked' in by the hydrophobic core. - B: Cholesterol is another lipid which is embedded in the cell membrane. - C: Phospholipids can move around within the membrane, as outlined by the fluid mosaic model of the cell membrane. - D: Integral proteins are embedded within the membrane and often are transmembrane (spanning the membrane). This means they pass through both the hydrophilic and hydrophobic parts of the membrane. - E: Ions cannot pass directly through the cellular membrane, and rely on protein transport channels to pass.
29. Which of the following is correct regarding the lac operon? A: The amount of lactose present affects the levels of cAMP B: Expression of lac repressor protein is increased or decreased depending on glucose levels C: Elevated allolactose levels inhibits the repressor protein D: E. coli uses lactose as its preferred energy source E: The lac operon is an example of a repressible operon
Answer: C A: Low glucose levels increase the production of cAMP. Lactose does not affect cAMP levels. B: The lac repressor protein gene is constitutively expressed. C: Allolactose is an isomer of lactose, and allolactose is the molecule that binds and inhibits the lac repressor protein. D: E. coli prefers to use glucose as its energy source, if glucose is available. E: The lac operon is an example of an inducible operon - it is repressed and needs to be induced to turn on.
Which pituitary gland hormone acts where to directly stimulate testosterone production?
Answer: C: Luteinizing hormone acting on the Leydig interstitial cells Correct. The Leydig cells of the testes produce testosterone. They are stimulated to do so by luteinizing hormone. - Growth hormone acting on the Sertoli cells Incorrect. Growth hormone functions to stimulate growth in many cells of the body. The Sertoli cells are not involved in testosterone production. They function to nourish sperm during their development.
16. What matching component between identical twins allows for donation of a kidney without the need for immunosuppression? A. Blood type B. Circulating antibodies C. Thymus and spleen D. Major histocompatibility complex molecules E.Lymph
Answer: D A: Blood type just represents what surface antigens are present on the blood cell. Blood type does not determine transplant compatibility. Just under 40% of people have O+ blood, but these people are not perfect donors for one another. Blood type is not the determining factor for whether a cell is recognized as self vs nonself, and the cells of the organ being transplanted (rather than blood) are the focus of concern in immune rejection. B: Circulating antibodies Identical twins likely will not have identical circulating antibodies. Circulating antibodies are a reflection of what pathogens the body has been exposed to. Identical twins living regular lives will have been exposed to different pathogens and will have different circulating antibodies. C: Thymus and spleen The thymus and spleen are where lymphocytes mature. However, identical twins would not have identical organs. The environment influences organ development, on top of genetic influence. Furthermore, having the same sites of lymphocyte maturation would not change whether or not lymphocytes produced would react to distinct markers on a transplanted organ that distinguish self from non-self. D: Major histocompatibility complex molecules Identical twins have identical major histocompatibility complex molecules (MHC), and therefore the cells from the organ donation will not be marked as foreign by the immune system. E: Lymph Lymph is the circulating fluid found in the lymphatic system, consisting of interstitial fluid and other components collected in the lymph vessels, including bacteria, fats, and proteins. Identical twins would not have identical lymph contents, as this would be variable based on environmental exposure.
38. All of the following statements about fixed action patterns are true EXCEPT one. Which one is the EXCEPTION? A: It is an instinctive behavior B: A sign stimuli is a simple, specific stimuli in the environment that elicits this response C: They are typically preserved amongst all members of a particular species D: Neuronal adaptation means the response can be significantly varied E: Once the stimulus elicits a response, the response cannot be stopped until the action is completed
Answer: D A: It is an instinctive behavior Fixed action pattern (FAPs) are instinctual processes that an animal does not need to be taught. B: A sign stimuli is a simple, specific stimuli in the environment that elicits this response A sign stimuli is the simple, recognizable feature in the environment that stimulates a fixed action pattern. An example of a sign stimuli is the red belly of a male insect which stimulates an attack by other male insects of the space species; this fixed action response can be elicited with an artificial red colored model. A sign stimuli is referred to as a releaser when between members of the same species (as in the insect example previously described). C: They are typically preserved amongst all members of a particular species Because of the instinctive nature of FAPs, almost all members of a species will have this action pattern. D: Neuronal adaptation means the response can be significantly varied One of the signature characteristics of FAPs is that they are a relatively unvarying pattern of behavior. The tradeoff of being an instinctual response that does not have to be learned is the lack of flexibility or adaptation in the response. E: Once the stimulus elicits a response, the response cannot be stopped until the action is completed Once an FAP is started, it must be completed. A common example is a goose's egg retrieval, studied by the famous ethologist Konrad Lorenz. If a goose sees an egg displaced from the nest (releaser), this elicits the goose to roll the egg back to the nest with its beak. If the egg is removed from in front of the goose during the course of this action, the goose will continue through with the pushing action until it has reached the nest - even though it is no longer pushing anything. Other observations Lorenz saw were that other objects that were similar in appearance to an egg could elicit the same response as an egg, acting as the releaser for the FAP. For example, a golf ball which looks like an egg, or even a fake egg that is too large (ie. a super-stimulus) to be an egg the goose laid could release the FAP.
11. For what purpose is the biological laboratory technique of fluorescence recovery after photobleaching (FRAP) used? A. Separating a heterogeneous sample into the individual, homogeneous compounds B. Counting the number of cells in a sample C. Detecting the quantity of a specific protein in a sample D. Detecting the movement of lipids and proteins within a cell E. Simultaneously measuring a cell's DNA expression of thousands of different genes
Answer: D A: The two main lab techniques for separation of heterogeneous samples are centrifugation and chromatography. B: Counting the number of cells in a sample is either done through cell plating and visual counting, spectrophotometry, or flow cytometry. C: The amount of specific protein in a sample is quantified using a Western blot. D: This is the best usage of FRAP. E: A microarray is a chip that allows a scientist to measure mRNA expression.
All of the following contribute to water's upward movement in tall trees EXCEPT one. Which one is the EXCEPTION?
Answer: [B]: Gravitropism This is a false statement and therefore the answer choice is correct. Gravitropism is the response to gravity by stems and roots, caused by the shift in concentration of auxins and gibberellins. This in turn affects growth in different sides of the plant. Gravitropism does not directly contribute to the upward movement of water in tall trees. - Adhesion, Root pressure, transpirational pull, cohesion all contribute to water's upward movement in tall trees.
Which phylum has the highest number of different species?
Arthropoda! The phylum Arthropoda has the highest number of different species. Arthropoda is thought to represent more than 80% of all known living species, representing huge diversity.
5. After meiosis I has completed, each daughter cell is
Haploid and the chromosomes are composed of two chromatids. - Before meiosis, the DNA is duplicated, and copied sister chromatids attach to each other by the centromere. Remember that sister chromatids that are still attached are only referred to as a single chromosome. In humans at this stage, the chromosome number is 46 and the chromatid number is 92. - After meiosis I, homologous chromosomes split. The diploid cell has become haploid. The daughter cells of meiosis I still contain chromosomes composed of two sister chromatids attached by the centromere. In humans at this stage, the chromosome number is 23 and the chromatid number is 46. - After meiosis II, sister chromatids split. The daughter cells contain individual chromosomes. In humans at this stage, the chromosome number is 23 and the chromatid number is 23.
Which of the following is a function of natural killer immune cells?
Inducing apoptosis in cancerous cells Natural killer cells defensive actions include creating holes in the cellular membrane of its target, which causes target cells lysis, and inducing apoptosis (programmed cell death) in rapidly dividing cells.
If a person were to be knocked unconscious due to a head injury, damage to which part of the brain would be of the most immediate and critical concern?
Medulla The medulla controls autonomic (involuntary) functions of the body like breathing, heart rate, and digestion. - When knocked unconscious, many of the brain's functions - including processing the high volume of sensory input and coordinating motor output - become temporarily irrelevant. - What remains critical is that the body's autonomic functions continue uninterrupted, as damage to the areas of the brain that regulate vital functions such as breathing and heart rate would be of immediate concern and can lead to death. -Identifying the correct answer only requires you to correctly identify the area of the brain responsible for the most vital functions.
Photolysis (the splitting of water to form electrons, hydrogen ions, and oxygen) takes place within the ---. The light dependent reactions of photosynthesis take place in the ... of the chloroplast. The light independent reactions of photosynthesis take place in the ... of the chloroplast. Cyclic photophosphorylation takes place on the ---- ---- (the connecting area between thylakoids). The --- of the chloroplast serves no known function.
Photolysis (the splitting of water to form electrons, hydrogen ions, and oxygen) takes place within the thylakoid lumen. The light dependent reactions of photosynthesis take place in the thylakoids of the chloroplast. The light independent reactions of photosynthesis take place in the stroma of the chloroplast. Cyclic photophosphorylation takes place on the stroma lamellae (the connecting area between thylakoids). The intermembrane space of the chloroplast serves no known function.