86. Following statements were made about human mitochondrial genome:
A. The replication of both the H and L strands is unidirectional and begins at specific origins
B. Majority of the mitochondrial genes encode for protein products.
C. Though the mitochondrial genome is extremely compact, the genes never show any sequence overlap.
D. The CR/D-loop region of mitochondrial genome exhibits triple stranded structure.
E. Transcription of mtDNA starts bi-directionally from a common promoter region in the CR/D-loop region and continues round the circle.
Which one of the following options contains a combination of all correct statements?
(1) A, B, D
(2) A, D, E
(3) B, D, E
(4) B, C, D
Analysis of Each Statement
A. The replication of both the H and L strands is unidirectional and begins at specific origins.
-
Correct. Human mitochondrial DNA (mtDNA) has two distinct origins of replication: one for the heavy (H) strand (OriH) and one for the light (L) strand (OriL). Replication proceeds unidirectionally from these specific sites56.
B. Majority of the mitochondrial genes encode for protein products.
-
Incorrect. While mtDNA encodes 13 proteins essential for oxidative phosphorylation, it also encodes 22 tRNAs and 2 rRNAs. Thus, a significant portion of the mitochondrial genome codes for RNA, not proteins35.
C. Though the mitochondrial genome is extremely compact, the genes never show any sequence overlap.
-
Incorrect. The mitochondrial genome is compact and includes overlapping genes and some genes encoded on opposite strands, reflecting tight packing3.
D. The CR/D-loop region of mitochondrial genome exhibits triple stranded structure.
-
Correct. The displacement loop (D-loop) region contains a triple-stranded DNA structure formed by a short third strand of DNA, known as 7S DNA, which displaces one strand of the double helix56.
E. Transcription of mtDNA starts bi-directionally from a common promoter region in the CR/D-loop region and continues round the circle.
-
Correct. Transcription initiates from promoters located in the D-loop region, including one heavy strand promoter (HSP) and light strand promoters (LSP), and proceeds in both directions around the circular genome567.
Correct Combination of Statements
(2) A, D, E
Summary Table
| Statement | Correctness | Explanation |
|---|---|---|
| A | Correct | Unidirectional replication from specific origins for H and L strands |
| B | Incorrect | Mitochondrial genome encodes proteins and significant RNA genes |
| C | Incorrect | Some mitochondrial genes overlap or are tightly packed |
| D | Correct | D-loop region forms a triple-stranded structure with 7S DNA |
| E | Correct | Transcription initiates bidirectionally from promoters in the D-loop region |
Keywords
human mitochondrial genome, mtDNA replication, heavy strand, light strand, origin of replication, D-loop, triple-stranded DNA, mitochondrial transcription, mitochondrial promoters, mitochondrial gene organization
Conclusion
The human mitochondrial genome replicates unidirectionally from specific origins for both strands, features a triple-stranded D-loop region, and initiates transcription bidirectionally from promoters in the D-loop. However, the majority of mitochondrial genes do not encode proteins exclusively, and gene overlap does occur. Therefore, the correct set of true statements is A, D, and E.
Final answer:
(2) A, D, E
14 Comments
Mitali Saini
July 29, 2025The correct option is (2) A, D, E
Soniya Shekhawat
July 29, 2025Easy sir
Anisha jakhar
July 29, 2025Correct statements are A,D,E. Unidirectional replication from oriH and oriL, D loop has triple stranded DNA and transcription starts from promoter at d loop.
Mohini
July 30, 2025The correct answer is 2. A, D, E. After reading the options, I was a little bit confused about the correct answer, but then I read the explanation, and it became clear to me.
Santosh Saini
July 30, 2025The correct statement are A, D,E because human mitochondrial Genome replicate unidirectionally from oriH and oriL of both strands( heavy and light)
Kajal
July 30, 2025Option 2 is right
Unidirectional replication at specific region H and L
And D loop region form a triple stranded dna with 7S Dna and Transcription initiates bidirectionally from promotor in the D loop region
Deepshikha choudhary
July 31, 2025correct option is 2 ( A,D,E)
Alec Joseph
July 31, 2025Right ans. is 2- A,D and E.
Dharmpal Swami
August 1, 2025A D &E are write statement
SHOBHA SHARMA
August 1, 2025Answar A , D and E
unidirection replication form specific origins for H and L strand
D-loop regions forms a triple stranded structure with 7s dna
transcription initiates bidirectionally from promotors in the D-loop region
Manisha choudhary
August 3, 2025Human mitochondria m replication both light and heavy strand kaa replication unidiraactional hota h two specific ori hoti h
D loop m triple strand iska feature h
D loop m common promoter s bidirectional transcription hota h
Genome compact hota h gene overlapping krti h
13 protein oxidative phosphorylation and 22 trna and 2 r-rna k liye encoding krta h
Aafreen Khan
August 23, 2025Ans-A,D,E
Unidirectional replication from specific origins for H and L strands and D loop forms triple stand structure and transcription initiates bidirectional from promoter
Komal Sharma
September 29, 2025The human mitochondrial genome replicates unidirectionally from specific origins for both strands, features a triple-stranded D-loop region, and initiates transcription bidirectionally from promoters in the D-loop. However, the majority of mitochondrial genes do not encode proteins exclusively, and gene overlap does occur. Therefore, the correct set of true statements is A, D, and E.
Deepika Sheoran
November 7, 2025Option A,D,E is correct answer