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Questions and Answers
What is the complex of DNA and histone proteins called?
What is the complex of DNA and histone proteins called?
What is the function of histone H1 in chromatin structure?
What is the function of histone H1 in chromatin structure?
What is the term for the densely packed, gene-poor regions of chromatin?
What is the term for the densely packed, gene-poor regions of chromatin?
What are the repetitive DNA sequences that cap the ends of chromosomes?
What are the repetitive DNA sequences that cap the ends of chromosomes?
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What is the region where DNA replication is initiated?
What is the region where DNA replication is initiated?
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What is the term for the relatively open and accessible chromatin structure during interphase?
What is the term for the relatively open and accessible chromatin structure during interphase?
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Study Notes
Chromosomes: DNA Structure
Organization of DNA in Chromosomes
- Chromosomes are made up of a long DNA molecule wrapped around histone proteins (H2A, H2B, H3, and H4)
- This complex of DNA and histone proteins is called chromatin
- Chromatin is further condensed into nucleosomes, which are repeating units of chromatin
Structure of a Nucleosome
- A nucleosome consists of:
- 147 base pairs of DNA wrapped around a histone octamer (2 copies of each histone protein: H2A, H2B, H3, and H4)
- Linker DNA (20-80 base pairs) that connects nucleosomes
- Histone H1 that binds to the linker DNA and helps stabilize the chromatin structure
Levels of Chromatin Condensation
- Interphase chromatin: relatively open and accessible for gene expression
- Metaphase chromatin: highly condensed and visible as distinct chromosomes during cell division
- Heterochromatin: densely packed, gene-poor regions of chromatin
- Euchromatin: less compact, gene-rich regions of chromatin
Chromosome Structure
- A chromosome consists of:
- Centromere: a specialized region that plays a crucial role in chromosome segregation during cell division
- Telomeres: repetitive DNA sequences (TTAGGG in humans) that cap the ends of chromosomes
- Origins of replication: specific regions where DNA replication is initiated
- Genes: coding regions that are transcribed into RNA and translated into proteins
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Description
Learn about the organization of DNA in chromosomes, structure of nucleosomes, levels of chromatin condensation, and chromosome structure. Understand the roles of histone proteins, centromere, telomeres, and origins of replication.
