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Molecular Genetics > Mitochondrial Replication > Flashcards

Mitochondrial Replication Flashcards

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Biology 101 flashcards
1
Q

triple-strand specific RNAse

A

needs a displaced strand in the RNA-DNA complex
- 3’ end of RNA primer is cut with triple-strand specific RNAse H

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2
Q

SAR11 clade

A
  • alphaproteobacteria, Rickesettsiales
  • able to handle oxygen
  • these were the ancient symbiont ancestor to eukaryotic mitochondria
  • this group of organisms represent 1 in 3 of cells in the ocean’s surface
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3
Q

how is mitochondrial DNA passed?

A
  • mitochondria are usually transmitted by the female
  • we all have maternal mitochondria only
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4
Q

D-loop

A
  • does not code for anything, free to mutate and used to study human evolution
  • molecular clock
  • old light strand is displaced and remains single-stranded
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5
Q

molecular clock region

A
  • D-loop
  • mutations in the D-loop
  • mutations do not affect gene product and is not selected against
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6
Q

what is the rate in which mitochondria have mutations?

A
  • mitochondria are 15 more likely to have mutations than the nuclear genome
  • this is because there are no histones and are more exposed to radiation and it exists as single strand DNA so it is subject to more oxidation, metabolic reaction that alters the bases
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7
Q

how many origins are there in human mitochondria and what direction does the replication fork go?

A
  • unidirectional
  • each strand of mitochondria has its own origin that fire at different times
  • 2 unidirectional replicons
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8
Q

what is the placement of mit-RNA genes?

A
  • position 57
  • the arrested 75 D-loop primer is used when the mtDNA is severely depleted - positions 151 and 191
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9
Q

light strand promoter

A
  • initiate transcription of mRNA
  • initiate RNA primers for DNA replication
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10
Q

which strand encodes (serves as template) the most genes?

A
  • heavy strand
  • outside of the circle
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11
Q

what are the three primers used in mitochondrial replication?

A
  • 2 for stress conditions and one for normal replication
  • stress conditions: origins 151 and 191
  • normal conditions: origins 57
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12
Q

what is the significance of the D-loop?

A
  • a primer
  • does not encode for anything
  • free to mutate with few constraints
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13
Q

how many origins of replications are present in the mitochondrial genome?

A

2 - one on the heavy strand and one on the light strand

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14
Q

what kind of replication priming occurs within the D-loop?

A

under stress conditions

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15
Q

what enzyme cuts the RNA primer in order to generate the end to be extended by DNA polymerase?

A

triple strand specific RNAseH

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16
Q

what are the composition of the D-loop of human mitochondria?

A
  • RNA portion of the primer is 600 bases
  • DNA portion of the primer 1,400 bases
  • the primer for replication of the H strand is comprised of an RNA-DNA composite molecule
  • single D-loop with an opening of 7S
17
Q

tetrahymena mitochondrial DNA

A
  • has 6 D-loops at a time (many origins), and plant chloroplasts have 2
18
Q

what is the origin of replication of mtDNA?

A
  • illustrates the principle that an origin may be used to initiate a single strand only in the case of D loops
  • another example is PhiX174 rolling circle replication
  • an origin can be a sequence of DNA that initiates DNA synthesis using one strand as a template
19
Q

what is mit RNA polymerase single subunit related to?

A
  • phage T7, T3, and SP6 polymerase
  • the protein-encoding RNA have a short polyA tail added at the 3’ end
20
Q

which enzyme processes the short RNA primer for synthesis of the H-strand of mitDNA?

A

triple strand-specific RNase H

21
Q

What is thought to be the ancestral organism group that gave rise to mitochondria?

A

Oxygen dwelling bacteria could deal with oxygen through oxidation and reduction
SAR11

22
Q

where did many mitochondrial genes migrate to?

A
  • nucleus
23
Q

where are the H and L strand origins located?

A
  • origin on the H strand to make L
  • origin on L strand to make H
24
Q

how does mitochondrial DNA replicate?

A
  • RNA primer within the D-loop is synthesized the new H strand
  • 3’ end of RNA primer is cut with triple-strand specific RNase H
  • old H strand is displaced and new H strand primed
  • RNA primer is extended with mtDNA polymerase to make a 1,400 base primer
  • L strand synthesis is initiated using origin on H strand
  • synthesis of L strand is initiated when its origin is exposed by the movement of the first replication fork
  • then the old H strand is displaced with the L strand is partially replicated and completes
  • the second strand is made with the old L strand and a new H strand is made
  • gaps in new strands sealed

Molecular Genetics (28 decks)

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