Podcast
Questions and Answers
What is the primary distinction between a chromosome and chromatin?
What is the primary distinction between a chromosome and chromatin?
- Chromatin is the structure formed during cell division; chromosome exists only during interphase.
- Chromosomes are found only in prokaryotes, while chromatin is exclusive to eukaryotes.
- Chromosomes are linear DNA molecules, whereas chromatin consists of circular DNA.
- Chromatin refers specifically to DNA associated with proteins in eukaryotes; chromosome is a general term for DNA and associated proteins. (correct)
How does the presence of introns in eukaryotic genes affect the process of protein production?
How does the presence of introns in eukaryotic genes affect the process of protein production?
- Introns are removed from the pre-mRNA molecule through RNA splicing before translation. (correct)
- Introns directly code for additional amino acids, increasing the size of the protein.
- Introns alter the DNA sequence, leading to mutations during replication.
- Introns cause the ribosome to stall, slowing down translation.
Which of the following is NOT a crucial element for proper chromosome duplication and segregation?
Which of the following is NOT a crucial element for proper chromosome duplication and segregation?
- Telomeres
- Centromeres
- Ribosomes (correct)
- Origins of replication
During which phase of the cell cycle does chromosome replication occur?
During which phase of the cell cycle does chromosome replication occur?
What is the main function of histone proteins in eukaryotic cells?
What is the main function of histone proteins in eukaryotic cells?
Which histone protein is NOT considered a core histone found in the nucleosome core particle?
Which histone protein is NOT considered a core histone found in the nucleosome core particle?
What is the role of histone chaperones in nucleosome assembly?
What is the role of histone chaperones in nucleosome assembly?
CAF-1 is a histone chaperone involved in nucleosome assembly. What is its activity linked to?
CAF-1 is a histone chaperone involved in nucleosome assembly. What is its activity linked to?
Histone modification is a key mechanism for influencing chromatin function. Where do these modifications primarily occur?
Histone modification is a key mechanism for influencing chromatin function. Where do these modifications primarily occur?
The compaction of DNA is essential for fitting it within the nucleus. Imagine a mutation that inhibits the function of histone H1. What is the MOST likely consequence?
The compaction of DNA is essential for fitting it within the nucleus. Imagine a mutation that inhibits the function of histone H1. What is the MOST likely consequence?
Flashcards
Chromosome
Chromosome
A DNA molecule and its associated proteins.
Chromatin
Chromatin
DNA with its associated proteins in eukaryotic cells.
Histones
Histones
Small, basic proteins associated with DNA in chromatin.
Diploid cell
Diploid cell
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Introns
Introns
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Origins of replication
Origins of replication
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Centromere
Centromere
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Telomeres
Telomeres
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Sister chromatids
Sister chromatids
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Nucleosome
Nucleosome
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Study Notes
- Within cells, DNA associates with proteins; each DNA molecule and its associated protein is a chromosome.
- In eukaryotes, DNA with its associated proteins is called chromatin, and most associated proteins are small, basic proteins called histones.
Genome Organization and Diversity
- Chromosomes can be circular or linear, presenting different challenges for genome maintenance and replication.
- Most eukaryotic cells are diploid, with two copies of each chromosome (homologs), while some are haploid or polyploid.
- Genome size correlates with organism complexity, with more complex organisms having lower gene density.
- Eukaryotic genes often contain discontinuous protein-coding regions called introns, which are removed via RNA splicing.
Chromosome Duplication and Segregation
- Proper duplication and segregation require origins of replication, centromeres, and telomeres.
- Chromosome replication happens during the S phase, yielding duplicated chromosomes known as sister chromatids.
- Chromosome segregation takes place during mitosis (M phase).
Chromatin Structure and Regulation
- Chromatin's structure, the packaged form of DNA, can be modified to alter DNA accessibility.
- Chromosomes are less compact during interphase and condense during mitosis.
- Histones are the most common proteins associated with eukaryotic DNA.
- Core histones (H2A, H2B, H3, H4) constitute the protein core around which DNA is wrapped, histone H1 binds to linker DNA.
- The nucleosome exhibits an approximate twofold axis of symmetry.
- Histone amino-terminal tails are accessible for post-translational modifications.
Nucleosome Assembly
- Nucleosomes are assembled immediately after DNA replication.
- Histone chaperones guide the assembly of histones onto DNA.
- CAF-I assembles nucleosomes at recent DNA replication sites by associating with DNA replication machinery.
Higher-Order Chromatin Structure
- The 30-nm fiber has two models: the solenoid model and the "zigzag" model.
Histone Modification
- Modifications of histone amino-terminal tails change chromatin function.
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