1. Which of the following best describes the inheritance of mitochondrial DNA (mtDNA)?
a) Paternal inheritance
b) Maternal inheritance
c) Both maternal and paternal inheritance
d) Independent assortment
Answer:
b) Maternal inheritance
Explanation: Mitochondrial DNA is inherited exclusively through the mother. This is due to the mitochondria in the egg cell contributing all of the mitochondria to the offspring, while the sperm contributes only nuclear DNA.
2. Why is mitochondrial DNA inherited only from the mother?
a) Sperm cells do not contain mitochondria
b) Mitochondria from the sperm are discarded after fertilization
c) Mitochondria in sperm are too weak to function
d) Mitochondria in the egg cell are more active than those in the sperm
Answer:
b) Mitochondria from the sperm are discarded after fertilization
Explanation: The mitochondria from the sperm are generally discarded during fertilization, so only the mitochondria from the egg, which contain mtDNA, are passed to the offspring.
3. What is the primary role of mitochondria in cells?
a) Protein synthesis
b) Energy production via ATP synthesis
c) Genetic inheritance
d) Waste removal
Answer:
b) Energy production via ATP synthesis
Explanation: Mitochondria are known as the powerhouse of the cell, as they are responsible for producing ATP, which is the main source of energy for cellular processes.
4. Mitochondrial DNA (mtDNA) is different from nuclear DNA because it: a) Contains double-stranded, circular DNA
b) Contains no genes
c) Is only found in muscle cells
d) Is inherited from both parents
Answer:
a) Contains double-stranded, circular DNA
Explanation: Unlike nuclear DNA, mitochondrial DNA is circular and exists in a double-stranded form. This structure is similar to the DNA of bacteria, suggesting an evolutionary relationship.
5. In mitochondrial inheritance, a mother with a mutation in mtDNA will pass it on to:
a) Only her sons
b) Only her daughters
c) Both her sons and daughters
d) Neither her sons nor daughters
Answer:
c) Both her sons and daughters
Explanation: Since mitochondrial DNA is inherited maternally, both male and female offspring will inherit mutations in the maternal mtDNA.
6. What is the total number of mitochondria typically found in a human cell?
a) 1 to 5
b) 10 to 50
c) 100 to 1000
d) 1000 to 5000
Answer:
c) 100 to 1000
Explanation: A typical human cell contains between 100 and 1000 mitochondria, depending on the cell’s energy needs.
7. What is the main reason mitochondrial diseases are passed maternally?
a) The mitochondria in the sperm are inactive
b) Sperm mitochondria are eliminated after fertilization
c) The egg contains the majority of mitochondria
d) Mitochondria are located in the nucleus
Answer:
b) Sperm mitochondria are eliminated after fertilization
Explanation: During fertilization, the mitochondria from the sperm are typically discarded, and the egg’s mitochondria are the ones that persist in the embryo.
8. Which of the following diseases is caused by mutations in mitochondrial DNA?
a) Cystic fibrosis
b) Leber’s hereditary optic neuropathy
c) Down syndrome
d) Hemophilia
Answer:
b) Leber’s hereditary optic neuropathy
Explanation: Leber’s hereditary optic neuropathy (LHON) is a disease caused by mutations in mitochondrial DNA, leading to vision loss.
9. Mitochondrial DNA contains genes for which of the following?
a) Protein synthesis
b) Energy production in the form of ATP
c) Cell division
d) Nuclear division
Answer:
b) Energy production in the form of ATP
Explanation: Mitochondrial DNA codes for proteins involved in the electron transport chain and ATP production, key processes for cellular energy.
10. Which of the following is NOT typically encoded by mitochondrial DNA?
a) rRNA
b) tRNA
c) mRNA
d) Histone proteins
Answer:
d) Histone proteins
Explanation: Mitochondrial DNA does not encode histone proteins; instead, it encodes tRNA, rRNA, and some of the proteins involved in the mitochondrial function, such as ATP production.
11. What is the role of the mitochondrial genome in the process of oxidative phosphorylation?
a) It encodes enzymes for the citric acid cycle
b) It encodes enzymes for DNA replication
c) It encodes proteins for the electron transport chain
d) It encodes proteins for protein synthesis
Answer:
c) It encodes proteins for the electron transport chain
Explanation: The mitochondrial genome contains genes that encode proteins essential for the electron transport chain, a key component of oxidative phosphorylation, which generates ATP.
12. How many base pairs are typically found in human mitochondrial DNA?
a) 1000
b) 16,500
c) 3 million
d) 6 billion
Answer:
b) 16,500
Explanation: The human mitochondrial genome consists of approximately 16,500 base pairs, which is much smaller than the nuclear genome.
13. Why do mutations in mtDNA often lead to mitochondrial diseases?
a) Because mtDNA codes for nuclear proteins
b) Because mitochondria are essential for energy production
c) Because mtDNA mutations do not affect cellular functions
d) Because mtDNA is passed from both parents
Answer:
b) Because mitochondria are essential for energy production
Explanation: Mitochondria are essential for ATP production, and mutations in mtDNA can disrupt this process, leading to energy deficiencies and resulting in mitochondrial diseases.
14. What is the inheritance pattern of mitochondrial diseases?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked
d) Maternally inherited
Answer:
d) Maternally inherited
Explanation: Mitochondrial diseases are inherited through the maternal line since only the mother contributes mitochondrial DNA to the offspring.
15. Which of the following mitochondrial disorders is characterized by a defect in the muscle’s energy production?
a) Kearns-Sayre syndrome
b) Parkinson’s disease
c) Huntington’s disease
d) Duchenne muscular dystrophy
Answer:
a) Kearns-Sayre syndrome
Explanation: Kearns-Sayre syndrome is a mitochondrial disorder that affects muscle cells, leading to muscle weakness and other symptoms due to energy production defects.
16. How does mitochondrial DNA differ from nuclear DNA in terms of replication?
a) It replicates independently of cell division
b) It replicates during cell division only
c) It uses RNA as a template
d) It is replicated by the same machinery as nuclear DNA
Answer:
a) It replicates independently of cell division
Explanation: Mitochondrial DNA replicates independently of cell division and uses its own set of replication machinery.
17. Which of the following statements about mitochondrial DNA is true?
a) Mitochondrial DNA is highly abundant in the nucleus
b) Mitochondrial DNA is inherited from both parents
c) Mitochondrial DNA is located inside the mitochondria
d) Mitochondrial DNA is found only in muscle cells
Answer:
c) Mitochondrial DNA is located inside the mitochondria
Explanation: Mitochondrial DNA is located within the mitochondria and is separate from the nuclear DNA, contributing to mitochondrial function.
18. Which cellular structure is responsible for the synthesis of proteins encoded by mitochondrial DNA?
a) Nucleus
b) Ribosomes in the cytoplasm
c) Ribosomes within the mitochondria
d) Endoplasmic reticulum
Answer:
c) Ribosomes within the mitochondria
Explanation: The proteins encoded by mitochondrial DNA are synthesized by ribosomes located within the mitochondria.
19. The presence of circular DNA in mitochondria supports which of the following theories?
a) Mitochondria are ancient bacteria
b) Mitochondria evolved from viruses
c) Mitochondria evolved from eukaryotic cells
d) Mitochondria are part of the nucleus
Answer:
a) Mitochondria are ancient bacteria
Explanation: The circular DNA found in mitochondria is similar to the DNA of bacteria, suggesting that mitochondria are the result of an ancient symbiotic relationship with a bacterium.
20. Which of the following statements about mitochondrial DNA is false?
a) It is inherited only from the mother
b) It is located in the mitochondrion
c) It encodes some of the proteins required for oxidative phosphorylation
d) It is usually inherited from both parents
Answer:
d) It is usually inherited from both parents
Explanation: Mitochondrial DNA is inherited exclusively from the mother, not both parents.
