Nokea
When an organism with an unknown genotype is crossed with another organism displaying the recessive trait (aa), the Punnett square shown above illustrates the outcomes. What is the unknown genotype?
- A. a
- B. Aa
- C. AA
- D. aa
Correct Answer: B
Rationale: In the provided Punnett square, the recessive trait (aa) is displayed. This means the known organism must be homozygous recessive (aa). When crossed with the unknown genotype, which is represented by a capital letter (A), it results in a 50% chance of producing heterozygous offspring (Aa). As the recessive trait is expressed in the outcomes, the unknown genotype must carry the dominant allele (A) alongside the recessive allele (a), making it heterozygous (Aa). Therefore, the correct answer is B, Aa.
You may also like to solve these questions
Which of the following occurs in an oxidation reaction?
- A. Removal of electrons
- B. Addition of carbon
- C. Addition of neutrons
- D. Removal of oxygen
Correct Answer: A
Rationale: In an oxidation reaction, the substance undergoes a process where it loses electrons, leading to an increase in its oxidation state. This loss of electrons is the key characteristic of oxidation. On the other hand, reduction involves the gaining of electrons. Therefore, the correct answer is the 'Removal of electrons' (Choice A). In oxidation reactions, the substance loses electrons, while in reduction reactions, the substance gains electrons. Understanding this transfer of electrons is fundamental in comprehending redox reactions, where both oxidation and reduction occur simultaneously.
Lithium has an atomic number of 3 and a mass number of 7. What is the number of protons in a lithium atom?
- A. 7
- B. 4
- C. 12
- D. 3
Correct Answer: D
Rationale: The number of protons in an atom is equal to its atomic number. In this case, lithium has an atomic number of 3, so it contains 3 protons. The mass number (7) includes both protons and neutrons, with the difference between the mass number and atomic number representing the number of neutrons. Therefore, the correct answer is 3 protons in a lithium atom.
Which one of the following structures drains oxygen-depleted blood from the kidneys?
- A. Ureter
- B. Renal artery
- C. Urethra
- D. Renal vein
Correct Answer: D
Rationale: The correct answer is D, Renal vein. The renal vein is responsible for draining oxygen-depleted blood from the kidneys back to the heart for reoxygenation. The ureter carries urine from the kidneys to the bladder, the renal artery supplies oxygenated blood to the kidneys, and the urethra is the tube that carries urine from the bladder out of the body. Therefore, in the context of blood drainage from the kidneys, the renal vein is the correct choice.
Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
- A. Sebum
- B. Water
- C. Urea
- D. Lysozymes
Correct Answer: C
Rationale: Urea is the correct answer. Sweat glands excrete urea in response to the breakdown of proteins and the formation of ammonia. Urea is a waste product resulting from the breakdown of proteins in the liver and is excreted in urine as well as through sweat. Sebum is an oily substance produced by the skin's sebaceous glands, water is excreted by various means but is not specifically a result of protein breakdown, and lysozymes are enzymes that help protect the body against bacterial infections.
If a portion of a strand of DNA bases reads 5' AGCTAGCGT 3', what would the sequence of bases on the complementary strand read?
- A. 3' AGCTAGCGT 5'
- B. 5' UCGAUCGCA 3'
- C. 3' TCGATCGCA 5'
- D. 5' TCGUTCGCU 3'
Correct Answer: C
Rationale: To determine the sequence of bases on the complementary DNA strand, you must apply the base pairing rules: adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). The given original sequence is 5' AGCTAGCGT 3'. Consequently, the complementary strand will read 3' TCGATCGCA 5'. Each base on one strand corresponds with its complementary base on the other strand, forming a sequence that complements the original one.