Mitochondrial DNA (mtDNA) is crucial for cellular energy production, replicated by DNA polymerase gamma. Its replication is tightly controlled during embryogenesis to reduce mutation transmission. Human mtDNA contains 37 genes, with transcription varying by tissue, reflecting energy needs. The heart has the highest mitochondrial gene expression, influenced by factors like ACTH.
Show More
DNA polymerase gamma is a dedicated enzyme complex responsible for replicating mitochondrial DNA
TWINKLE helicase unwinds the DNA in a 5' to 3' direction, facilitating replication
Mitochondrial single-stranded DNA-binding proteins play a role in the replication of mitochondrial DNA
The mitochondrial bottleneck is a process that suppresses mtDNA replication during embryogenesis to minimize the transmission of deleterious mutations
The resumption of mtDNA replication is initiated in the trophectoderm cells of the blastocyst
Inner cell mass cells postpone mtDNA replication until they differentiate into specific cell lineages in response to developmental cues
Human mitochondrial DNA is a small, circular molecule comprising 37 genes, which are transcribed from both the heavy and light strands
The heavy strand encodes the majority of the proteins involved in the oxidative phosphorylation system, while the light strand encodes a single protein subunit and 8 tRNAs
The copy number of mtDNA varies widely among different cell types, from none in red blood cells to over a million in oocytes
Mitochondrial genes are transcribed as polycistronic transcripts, which are subsequently processed into individual mRNA, rRNA, and tRNA molecules
The processing of transcripts involves the precise cleavage at tRNA punctuation marks, recognized by their unique L-shaped structures
Transcription initiates at the displacement loop (D-loop) of the mitochondrial genome, driven by two distinct promoters, HSP1 and HSP2
The expression of mtDNA-encoded genes varies across tissues, correlating with their metabolic demands
External factors such as hormones can influence mitochondrial gene expression, as seen with adrenocorticotropic hormone (ACTH) stimulating the expression of mitochondrial protein-encoding genes in the adrenal cortex
00
The catalytic subunit of the enzyme complex is encoded by the ______ gene and has a molecular weight of ______.
POLG
140 kDa
01
The accessory subunits of the enzyme complex, each weighing ______, are encoded by the ______ gene.
55 kDa
POLG2
02
______ helicase assists in DNA unwinding during replication by moving in a ______ direction.
TWINKLE
5' to 3'
