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Questions and Answers
What is the primary reason DNA must be tightly packed within a cell?
What is the primary reason DNA must be tightly packed within a cell?
- To fit within the limited space of the cell. (correct)
- To prevent degradation by cellular enzymes.
- To increase the rate of transcription.
- To facilitate DNA replication.
If a circular DNA molecule has more than the optimal number of turns, what type of supercoiling does it exhibit?
If a circular DNA molecule has more than the optimal number of turns, what type of supercoiling does it exhibit?
- Negative
- Linear
- Positive (correct)
- Relaxed
Which enzyme is responsible for adding or removing turns in a DNA coil?
Which enzyme is responsible for adding or removing turns in a DNA coil?
- Topoisomerase (correct)
- Ligase
- Helicase
- Polymerase
A 250 bp DNA molecule has 15 complete rotations. How would you describe this molecule?
A 250 bp DNA molecule has 15 complete rotations. How would you describe this molecule?
How does bacterial DNA organization primarily differ from eukaryotic DNA organization?
How does bacterial DNA organization primarily differ from eukaryotic DNA organization?
The nucleoid in bacteria refers to which structure?
The nucleoid in bacteria refers to which structure?
What is the predicted effect of neutralizing the positive charges on histone proteins?
What is the predicted effect of neutralizing the positive charges on histone proteins?
Which of the following is a characteristic of euchromatin?
Which of the following is a characteristic of euchromatin?
How many H2B histone proteins would you expect to find in a chromatin sample containing 100 nucleosomes?
How many H2B histone proteins would you expect to find in a chromatin sample containing 100 nucleosomes?
What is the significance of DNase I sensitivity in the study of chromatin structure?
What is the significance of DNase I sensitivity in the study of chromatin structure?
The study of variation in DNA methylation leading to different coat colors in mice exemplifies what type of change?
The study of variation in DNA methylation leading to different coat colors in mice exemplifies what type of change?
What typically happens to a chromosome that loses its centromere?
What typically happens to a chromosome that loses its centromere?
What is the primary function of telomeres?
What is the primary function of telomeres?
Which of the following is characteristic of telomeric DNA sequences?
Which of the following is characteristic of telomeric DNA sequences?
Most of the genes that encode proteins are found in which type of DNA?
Most of the genes that encode proteins are found in which type of DNA?
What is a key characteristic of moderately repetitive DNA in eukaryotes?
What is a key characteristic of moderately repetitive DNA in eukaryotes?
What is the primary difference between SINEs and LINEs?
What is the primary difference between SINEs and LINEs?
What genetic components does mitochondrial DNA (mtDNA) encode?
What genetic components does mitochondrial DNA (mtDNA) encode?
What is a key piece of evidence supporting the endosymbiotic theory for the origin of mitochondria and chloroplasts?
What is a key piece of evidence supporting the endosymbiotic theory for the origin of mitochondria and chloroplasts?
What does the concept of replicative segregation refer to in the context of organelle DNA?
What does the concept of replicative segregation refer to in the context of organelle DNA?
In organisms with traits encoded by mtDNA inherited from both parents, what is most likely occurring?
In organisms with traits encoded by mtDNA inherited from both parents, what is most likely occurring?
What accounts for the extensive size variation observed in flowering plant mtDNA?
What accounts for the extensive size variation observed in flowering plant mtDNA?
Compared to nuclear DNA, what is a distinctive characteristic of vertebrate mitochondrial DNA (mtDNA)?
Compared to nuclear DNA, what is a distinctive characteristic of vertebrate mitochondrial DNA (mtDNA)?
What is a primary similarity between chloroplast DNA and cyanobacteria DNA?
What is a primary similarity between chloroplast DNA and cyanobacteria DNA?
If a researcher detects sequences usually found in mitochondrial DNA (mtDNA) within the nuclear DNA of a cell, what could this suggest?
If a researcher detects sequences usually found in mitochondrial DNA (mtDNA) within the nuclear DNA of a cell, what could this suggest?
Which process describes a DNA molecule twisting upon itself due to being overwound?
Which process describes a DNA molecule twisting upon itself due to being overwound?
Which structure is created by the high folding of bacterial DNA?
Which structure is created by the high folding of bacterial DNA?
What is most likely the explanation for the variation in colors observed in mice with differential methylation?
What is most likely the explanation for the variation in colors observed in mice with differential methylation?
Which of the following factors would result in a chromosome being lost during mitosis?
Which of the following factors would result in a chromosome being lost during mitosis?
Which of the following best describes the telomere structure and function?
Which of the following best describes the telomere structure and function?
What is the classification of the majority of genes that encode for proteins?
What is the classification of the majority of genes that encode for proteins?
What is the length range of moderately repetitive DNA?
What is the length range of moderately repetitive DNA?
If a mutation occurred and a polypeptide could no longer be created by the organelle, which structure was most likely damaged?
If a mutation occurred and a polypeptide could no longer be created by the organelle, which structure was most likely damaged?
What observation led researchers to believe in symbiotic theory?
What observation led researchers to believe in symbiotic theory?
If an animal's mtDNA comes almost exclusively from the female parent, what type of inheritance is most likely?
If an animal's mtDNA comes almost exclusively from the female parent, what type of inheritance is most likely?
Flowering-plant mtDNA is extremely diverse and can be explained by the accumulation of which type of genetic component?
Flowering-plant mtDNA is extremely diverse and can be explained by the accumulation of which type of genetic component?
Why do human genetic diseases present at middle age often relate to mtDNA, but less so to nDNA?
Why do human genetic diseases present at middle age often relate to mtDNA, but less so to nDNA?
What accounts for the extensive size variation observed in yeast mtDNA?
What accounts for the extensive size variation observed in yeast mtDNA?
A DNA molecule 300 bp long has 30 complete rotations. How would you characterize this molecule?
A DNA molecule 300 bp long has 30 complete rotations. How would you characterize this molecule?
What main characteristic defines heterochromatin?
What main characteristic defines heterochromatin?
If a DNA molecule contains fewer than the optimal number of turns, what structural characteristic would you expect to observe?
If a DNA molecule contains fewer than the optimal number of turns, what structural characteristic would you expect to observe?
What structural outcome is caused by the activity of topoisomerase?
What structural outcome is caused by the activity of topoisomerase?
Imagine a scenario where a bacterial cell's DNA is prevented from forming nucleoids. What is the most likely consequence for the cell?
Imagine a scenario where a bacterial cell's DNA is prevented from forming nucleoids. What is the most likely consequence for the cell?
What would happen if a bacterial DNA lost its ability to form twisted loops?
What would happen if a bacterial DNA lost its ability to form twisted loops?
How might a mutation affecting histone proteins influence the characteristics of chromatin?
How might a mutation affecting histone proteins influence the characteristics of chromatin?
Which characteristic would most likely be found in heterochromatin?
Which characteristic would most likely be found in heterochromatin?
If a researcher is studying a region of chromatin that is highly sensitive to DNase I, what can they infer about this region?
If a researcher is studying a region of chromatin that is highly sensitive to DNase I, what can they infer about this region?
DNA methylation in gene regulation can lead to what outcome?
DNA methylation in gene regulation can lead to what outcome?
What is the likely outcome if a chromosome breaks and a fragment lacking a centromere is produced?
What is the likely outcome if a chromosome breaks and a fragment lacking a centromere is produced?
What is a crucial structural feature that enables telomeres to protect the ends of chromosomes?
What is a crucial structural feature that enables telomeres to protect the ends of chromosomes?
Which characteristic is commonly observed in telomeric DNA sequences?
Which characteristic is commonly observed in telomeric DNA sequences?
Which type of DNA sequence would you most likely find protein-coding genes?
Which type of DNA sequence would you most likely find protein-coding genes?
What characteristic is most commonly associated with moderately repetitive DNA?
What characteristic is most commonly associated with moderately repetitive DNA?
How do SINEs (Short Interspersed Nuclear Elements) differ from LINEs (Long Interspersed Nuclear Elements)?
How do SINEs (Short Interspersed Nuclear Elements) differ from LINEs (Long Interspersed Nuclear Elements)?
What essential function is carried out by genes encoded in mitochondrial DNA (mtDNA)?
What essential function is carried out by genes encoded in mitochondrial DNA (mtDNA)?
What observation provides the strongest support for the endosymbiotic theory regarding the origin of mitochondria?
What observation provides the strongest support for the endosymbiotic theory regarding the origin of mitochondria?
What is the concept of replicative segregation?
What is the concept of replicative segregation?
If an organism displays traits encoded by mitochondrial DNA (mtDNA) inherited from both parents instead of just one, what could be the cause?
If an organism displays traits encoded by mitochondrial DNA (mtDNA) inherited from both parents instead of just one, what could be the cause?
What characteristic of flowering plant mtDNA has led to extensive size variation compared to other eukaryotes?
What characteristic of flowering plant mtDNA has led to extensive size variation compared to other eukaryotes?
What is a distinguishing feature of vertebrate mitochondrial DNA (mtDNA) in comparison to nuclear DNA?
What is a distinguishing feature of vertebrate mitochondrial DNA (mtDNA) in comparison to nuclear DNA?
How does the DNA found in chloroplasts compare to that of cyanobacteria?
How does the DNA found in chloroplasts compare to that of cyanobacteria?
A researcher discovers mitochondrial DNA sequences integrated into the nuclear DNA of a cell. What process could explain this observation?
A researcher discovers mitochondrial DNA sequences integrated into the nuclear DNA of a cell. What process could explain this observation?
How does a chromosome fragment without a centromere typically behave during mitosis?
How does a chromosome fragment without a centromere typically behave during mitosis?
When compared to eukaryotic nuclear DNA, what statement accurately describes a characteristic of vertebrate mtDNA?
When compared to eukaryotic nuclear DNA, what statement accurately describes a characteristic of vertebrate mtDNA?
Flashcards
DNA Supercoiling
DNA Supercoiling
Tightly packing DNA to fit in small spaces; occurs in positive and negative forms.
Topoisomerase
Topoisomerase
Enzyme responsible for adding or removing turns in the DNA coil, aiding in supercoiling.
Nucleoid
Nucleoid
A clump of DNA that appears in bacteria.
Euchromatin
Euchromatin
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Heterochromatin
Heterochromatin
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Histone proteins
Histone proteins
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Nucleosome
Nucleosome
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Centromere
Centromere
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Telomere
Telomere
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Gene Family
Gene Family
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Uniparental Inheritance
Uniparental Inheritance
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Heteroplasmic Cells
Heteroplasmic Cells
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Organelle DNA
Organelle DNA
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Endosymbiotic Theory
Endosymbiotic Theory
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Study Notes
Large Amounts of DNA Packed into a Cell
- DNA must be tightly packed to fit within cells.
- E. coli DNA is about 1000 times longer than the cell itself.
Supercoiling
- Supercoiling is an additional coiling of the DNA helix, essential for compaction.
- Positive supercoiling involves overwinding the DNA.
- Negative supercoiling involves underwinding the DNA.
- Topoisomerases add or remove turns in the DNA coil.
Bacterial Chromosomes
- Most bacterial genomes consist of a single circular DNA molecule.
- The bacterial DNA appears as a clump called the nucleoid.
- Bacterial DNA folds into twisted loops.
- Bacterial DNA differ from eukaryotic DNA as it is not complexed with histone proteins and is circular.
Eukaryotic Chromosomes
- Chromatin structure is the organization of DNA with proteins.
- Euchromatin is a less condensed form of chromatin.
- Heterochromatin is a more condensed form of chromatin.
- Histone proteins are involved in DNA packaging.
- Chromatin is double-stranded helical DNA which is complexed with histones to form nucleosomes that folds up to produce a 30-nm fiber. Th 30-nm loops are compressed and folded to produce a 250-nm-wide fiber. Lastly, the tight coiling of the 250 nm fiber produces the chromatid of a chromosome.
- Changes in Chromatin structure also include: polytene chromosomes being created by repeated rounds of DNA replication with no cell division and chromosomal puffs displaying DNase I sensitivity that correlates with gene activity.
- Epigenetic changes, like methylation are reversible and due to environmental factors.
Centromeres
- Centromeres are constricted chromosome regions where spindle fibers attach.
- Chromosome fragments lacking centromeres are lost in mitosis.
Telomeres
- Telomeres are the ends of chromosomes that enable replication of linear chromosome ends.
- Characteristics of DNA sequence at the telomeres include a one stand that has guanine and adenine (or thymine) nucleotides, repeated sequence, and one strand protrudes beyond the other, creating single-stranded DNA at the end.
Eukaryotic DNA Sequence Variation
- Organisms vary in their amount of DNA per cell, known as C value.
- Denaturation involves melting temperature.
- Renaturation is the reassociation of DNA strands.
- Unique-sequence DNA includes gene families, which are similar but not identical copies of unique DNA sequences.
- Moderately repetitive DNA is 150-300 bp long that includes: tandem and interspersed repeat sequences where short interspersed elements, such as SINEs or Alu elements; and long interspersed elements LINEs.
- Highly repetitive DNA is less than 10 bp long and includes microsatellite DNA.
Organelle DNA (Mitochondria and Chloroplasts)
- Mitochondria and chloroplasts have their DNA.
- They encode some polypeptides, rRNA, and some tRNAs
- The endosymbiotic theory proposed that mitochondria and chloroplasts were once free-living bacteria.
- Organelles have uniparental inheritance of organelle-encoded traits where animal mtDNA is inherited almost exclusively from the female parent.
- Replicative segregation states: each cell has hundreds to thousands of organelles and heteroplasmic cells where organelles segregate randomly.
- Petite mutations in yeast, Neurospora mutations, Human diseases MERRF, LHON, NARP, KSS, CEOP traits and Cytoplasmic male sterility in plants are coded by mtDNA.
- Mitochondrial genomes are generally small where human mtDNA is circular and contains 16,569 base pairs and Flowering-plant mtDNA has extensive size variation.
- High mutation rate can be seen in vertebrate mtDNA.
- Damage to Mitochondrial DNA causes oxidative phosphorylation capacity to decline with age.
- Chloroplast sequences share similarity with DNA sequences in cyanobacteria.
- In the organization, chloroplast DNA is most similar to bacteria.
- Genetic information moves between Nuclear, Mitochondrial, and Chloroplast Genomes where: sequences normally found in mtDNA can be detected in nuclear DNA, from chloroplasts to mitochondria, and nuclear to mitochondrial as well as Horizontal gene transfer - mtDNA transfer from one plant to another.
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