What is the name of the genetic disorder caused by the presence of an extra chromosome 21?
Turner syndrome
Klinefelter syndrome
Down syndrome
Huntington's disease
Correct Answer : C
Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21. It is also known as trisomy 21, because affected individuals have three copies of chromosome 21 instead of the normal two.
The extra chromosome 21 in Down syndrome occurs due to a random error in cell division, which leads to the production of an abnormal gamete (egg or sperm) with an extra copy of the chromosome. When this gamete fuses with a normal gamete during fertilization, the resulting zygote has 47 chromosomes instead of the usual 46, and develops into a fetus with Down syndrome.
Down syndrome is characterized by a range of physical and intellectual symptoms, including developmental delays, intellectual disability, distinctive facial features, heart defects, and increased risk of certain medical conditions such as leukemia and Alzheimer's disease. However, the severity and expression of these symptoms can vary widely among affected individuals.
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Related Questions
Correct Answer is A
Explanation
The data collected by the researcher on the number of cars passing through a busy intersection at different times of the day for a month would be most useful to analyze traffic patterns during rush hour.
Correct Answer is B
Explanation
- Lithium (Li) is a metal from Group 1 (alkali metals) on the periodic table.
- Bromine (Br) is a nonmetal from Group 17 (halogens).
- When a metal reacts with a nonmetal, an ionic bond forms, resulting in an ionic compound.
- Lithium donates one electron to bromine, forming Li⁺ (cation) and Br⁻ (anion), which attract each other to form LiBr (Lithium Bromide).
Analysis of Other Options:
- A. Coordinate compound → Involves a metal ion bonded to a ligand via coordinate (dative) bonds, not relevant here. ❌
- C. Organic compound → Organic compounds contain carbon, but LiBr does not. ❌
- D. Covalent compound → Covalent bonds occur between two nonmetals, but lithium is a metal. ❌
Correct Answer is B
Explanation
Transcription is the process by which DNA is copied into RNA. During transcription, the DNA molecule unwinds and RNA polymerase reads the DNA sequence and synthesizes a complementary RNA molecule using the DNA as a template.

Correct Answer is B
Explanation
The epididymis is a coiled tube located at the back of each testicle where the sperm mature and are stored until ejaculation. Sperm are produced in the testes and then transported to the epididymis where they undergo maturation and become motile. The epididymis provides a protective environment for the sperm, allowing them to mature and become more resilient to external stressors. During ejaculation, the sperm are transported from the epididymis to the vas deferens and then to the urethra for ejaculation.
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Correct Answer is D
Explanation
A double-blind study is a research design in which neither the participants nor the researchers know which group participants are assigned to. This is done to minimize bias and ensure that the results of the study are as objective as possible. In a double-blind study, the treatment and control groups are randomly assigned, and the participants and researchers are unaware of which group each participant is assigned to.
Option a) is an example of a randomized controlled trial, which is a common research design, but it is not necessarily double-blind.
Option b) is an example of an open-label study, in which both the participants and the researchers know which group each participant is assigned to.
Option c) is an example of a single-blind study, in which the participants do not know which group they are assigned to, but the researchers do.

Correct Answer is A
Explanation
Chlorophyll a is the primary pigment responsible for photosynthesis in plants. It is a green pigment that is essential for capturing light energy from the sun and converting it into chemical energy that can be used by the plant. Chlorophyll a absorbs light most efficiently in the blue and red parts of the spectrum, and reflects green light, giving plants their characteristic green color
Chlorophyll b is another type of chlorophyll that is also involved in photosynthesis, but it is not as abundant as chlorophyll a. Chlorophyll b absorbs light most efficiently in the blue and orange parts of the spectrum and reflects yellow-green light.
Carotenoids are pigments that are present in many plants and are involved in photosynthesis as well as protecting the plant from damage caused by excess light. Carotenoids are responsible for the orange, yellow, and red colors of many fruits and vegetables.
Anthocyanins are pigments that give plants their red, purple, and blue colors. While they are not directly involved in photosynthesis, they play a role in atracting pollinators and protecting the plant from damage caused by UV radiation.

Correct Answer is D
Explanation
The largest organ in the human body by surface area is the skin. It covers the enre external surface of the body and has an average surface area of about 20 square feet in adults.

Correct Answer is D
Explanation
- A. Adduction → Moving a limb toward the midline of the body. ❌
- B. Extension → Increasing the angle of a joint (e.g., straightening the arm or leg). ❌
- C. Flexion → Decreasing the angle of a joint (e.g., bending the elbow or knee). ❌
- D. Abduction → Moving a limb away from the midline (e.g., raising the arm or leg sideways). ✅
Correct Answer is B
Explanation
Isotonic and isometric contractions are two types of muscle contractions that differ in the amount of force produced and the movement of the muscle. In isotonic contractions, the muscle changes length and produces movement, such as lifting a weight. The force generated by the muscle remains constant throughout the movement. Isotonic contractions can be further classified as concentric contractions, in which the muscle shortens as it contracts, and eccentric contractions, in which the muscle lengthens as it contracts.
In contrast, isometric contractions occur when the muscle generates force without changing its length or producing movement. For example, holding a weight in a fixed position without moving it requires an isometric contraction. In an isometric contraction, the force generated by the muscle increases up to a maximum and then remains constant. Isometric contractions can be used to build strength and endurance in the muscle, but they do not produce movement.
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Correct Answer is A
Explanation
The nurse can logically conclude that:
✅ Treatment A results in the shortest recovery time.
- The data shows that Treatment A has a mean recovery time of 3 days, which is the shortest compared to Treatment B (5 days) and Treatment C (7 days).
The other statements are not supported by the given data:
❌ "Treatment C enhances patient satisfaction more than the others."
- There is no information about patient satisfaction, only recovery times.
❌ "Treatment B is as effective as Treatment A."
- Treatment B has a longer recovery time (5 days) compared to Treatment A (3 days), so it is not equally effective in terms of recovery speed.
❌ "Treatments A and B provide the same rate of recovery."
- Treatment A has a faster recovery time than Treatment B, so they do not have the same recovery rate.
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