Punnet Square An organism with an unknown genotype is crossed with another organism that shows the recessive trait (aa). The Punnet square below shows the results. Which of the following is the unknown genotype? Unknown Unkonwn a Aa aa a Aa aa
A. a
B. Aa
C. aa
D. AA
The unknown genotype is Aa. This can be inferred from the Punnet square, which shows that half of the offspring are Aa and half are aa. This indicates that the unknown parent must have one dominant allele (A) and one recessive allele (a), making its genotype Aa.
The other options are not correct because they do not match the results shown in the Punnet square. If the unknown genotype was aa or AA, all of the offspring would have the same genotype as their parent. If the unknown genotype was a, it would not be a valid genotype as it only has one allele.
Therefore, the Correct Answer is B.
More Questions on TEAS 7 Science
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Q #1: Which of the following growth curves shows a population that is at its carrying capacity?
A. B
B. C
C. A
D. D
Answer Explanation
A population is said to be at its carrying capacity when it has reached the maximum number of individuals that can be sustained in a particular environment over a prolonged period of time, given the available resources and the prevailing environmental conditions.
In other words, carrying capacity refers to the maximum population size that a given ecosystem can support without being depleted of resources or experiencing environmental degradation. Once a population reaches its carrying capacity, its growth rate slows down and stabilizes, as individuals start to compete more intensely for resources such as food, water, and shelter, and mortality rates increase.
Carrying capacity is an important concept in ecology and population biology because it helps to explain the dynamics of natural populations and how they are influenced by changes in the environment, such as climate change, habitat loss, and human activities.
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Q #2: Which of the following structures is present in both prokaryotic and eukaryotic cells?
A. Endoplasmic reticulum
B. Cell membrane
C. Chloroplast
D. Golgi apparatus
Answer Explanation
The structure that is present in both prokaryotic and eukaryotic cells is the cell membrane ². The cell membrane is a thin layer that surrounds the cell and separates its internal environment from the external environment ². It is composed of a lipid bilayer and proteins and regulates the movement of substances into and out of the cell ².
The other options are not correct because they are not present in both prokaryotic and eukaryotic cells. The endoplasmic reticulum, chloroplast, and Golgi apparatus are organelles that are only found in eukaryotic cells ².
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Q #3: Hikers who found a human body at high altitude in the Italian Alps thought the man had died recently, but tests indicated he was shot with an arrow more than 5,300 years ago. Which of the following would be the best reason for prolonged preservation of the body?
A. The ultraviolet rays at such a high altitude caused all his molecules to be preserved.
B. The food that the person ate contained toxins that killed the bacteria that would have otherwise destroyed the body.
C. The body was frozen in the cold temperature of the Alps shortly after he died and remained frozen until it was found.
D. The arrow wound caused blood to flow out of the body which led the enzymes that would break down tissue to be cleared from the body.
Answer Explanation
The best reason for the prolonged preservation of the body is that it was frozen in the cold temperature of the Alps shortly after death and remained frozen until it was found. Freezing can preserve a body by slowing down or stopping the decomposition process.
The other options are not as likely to have caused prolonged preservation.
Ultraviolet rays can damage molecules rather than preserve them. Toxins in food would not necessarily kill all bacteria that could cause decomposition. Blood loss from an arrow wound would not necessarily clear all enzymes that could break down tissue.
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Q #4: Parasitic worm infestation is hypothesized to be damaging to the host. However, scientists have recently discovered that worm infestation can relieve the effects of certain autoimmune disorders. In which of the following ways should the hypothesis be modified, given the new findings?
A. Worm infestation prevents the body from immune malfunction.
B. Worm infestation reduces the severity of certain autoimmune disorders.
C. Lack of worm infestations is the cause of some autoimmune disorders.
D. Worm infestations exacerbate the body's immune reaction.
Answer Explanation
Given the new findings that worm infestation can relieve the effects of certain autoimmune disorders, the hypothesis should be modified to state that worm infestation reduces the severity of certain autoimmune disorders.
This option best reflects the new information and suggests a potential benefit of worm infestation in relation to autoimmune disorders. The other options do not accurately reflect the new findings and do not provide a clear modification to the hypothesis.
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Q #5: Which of the following is an efferent neuron that is responsible for releasing a neurotransmiter that stimulates a muscle cell to contract?
A. Motor neuron
B. Interneuron
C. Sensory neuron
D. Neuroglia
Answer Explanation
An efferent neuron that is responsible for releasing a neurotransmitter that stimulates a muscle cell to contract is a motor neuron ². Motor neurons carry signals from the brain to the peripheral nervous system in order to initiate an action. The neurotransmitter acetylcholine (ACh) is released by motor neurons at the neuromuscular junction in skeletal muscle, causing the muscle to contract ³.
The other options are incorrect because they do not accurately describe the type of neuron responsible for releasing a neurotransmitter that stimulates a muscle cell to contract. Interneurons are found within the central nervous system and facilitate communication between sensory and motor neurons. Sensory neurons carry information from sensory receptors to the central nervous system. Neuroglia are support cells for neurons and do not transmit nerve impulses.
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Q #6: Which of the following structures is an exocrine gland?
A. Pineal gland
B. Parathyroid gland
C. Parotid gland
D. Pituitary gland
Answer Explanation
The parotid gland is an exocrine gland that secretes saliva into the mouth. Exocrine glands secrete their products into ducts that carry the secretions to the body's surface or into body cavities. The other options are endocrine glands, which secrete hormones directly into the bloodstream. The pineal gland secretes melatonin, the parathyroid glands secrete parathyroid hormone, and the pituitary gland secretes several hormones that regulate various bodily functions.
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Q #7: Both digestion and absorption happen in which of the following parts of the digestive system?
A. Gallbladder
B. Esophagus
C. Stomach
D. Small intestine
Answer Explanation
Both digestion and absorption happen in the small intestine ¹. Digestion is the process by which food is broken down into small molecules that the body can absorb and use for energy, growth, and repair ¹. The final products of digestion are absorbed from the digestive tract, primarily in the small intestine ¹.
The other options are not correct because they do not accurately describe where both digestion and absorption happen in the digestive system. The gallbladder stores bile produced by the liver, but does not play a direct role in digestion or absorption. The esophagus transports food from the mouth to the stomach, but does not play a direct role in digestion or absorption. The stomach plays a role in digestion by churning food and mixing it with gastric juices, but most absorption occurs in the small intestine.
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Q #8: Which of the following terms describes the relaxation of the chambers of the heart during the cardiac cycle?
A. Tachycardia
B. Diastole
C. Systole
D. Bradycardia
Answer Explanation
The relaxation of the chambers of the heart during the cardiac cycle is called diastole ¹. The cardiac cycle is a sequence of events that occurs when the heart beats ². It consists of two phases: systole, when the heart contracts and pumps blood into circulation, and diastole, when the heart relaxes and fills with blood ².
The other options are not correct because they do not accurately describe the relaxation of the chambers of the heart during the cardiac cycle. Tachycardia is a rapid heart rate, bradycardia is a slow heart rate, and systole is the contraction of the heart chambers.
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Q #9: Which of the following classes of biological molecules includes enzymes?
A. Lipids
B. Vitamins
C. Carbohydrates
D. Proteins
Answer Explanation
Enzymes are a type of protein that catalyze chemical reactions in the body. Proteins are one of the four main classes of biological molecules, along with lipids, carbohydrates, and nucleic acids.
The other options are not classes of biological molecules that include enzymes. Lipids are a class of molecules that includes fats and oils, vitamins are organic compounds that are essential for normal growth and nutrition, and carbohydrates are a class of molecules that includes sugars and starches.
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Q #10: Which of the following ions binds to the troponin complex, initiating the contraction of a muscle?
A. Sodium
B. Potassium
C. Calcium
D. Phosphorus
Answer Explanation
When a muscle cell is stimulated by a nerve impulse, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm. The calcium ions bind to the troponin complex, which is a protein that regulates the interaction between actin and myosin filaments. The binding of calcium to troponin causes a conformational change that exposes the binding sites for myosin on the actin filaments. This allows the myosin heads to attach to the actin and pull the filaments past each other, resulting in muscle contraction.
