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Questions and Answers
What is the appearance of a specific character or trait called?
What is the genetic makeup of an individual termed?
Genotype
Euchromatin is densely packed and genetically inactive.
False
What protein provides structural support for a chromosome?
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A nucleosome is like a tiny spool that DNA can wind around, consisting of ______ base pairs of DNA.
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What do you call one half of a duplicated chromosome?
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What is the term for the complete set of genetic information in an organism?
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The ______ is formed by a complex of eight histone proteins.
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What structure organizes nucleosomes into a 30nm fiber?
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Study Notes
Chromosome Organization
- A chromosome is made of DNA and proteins, forming a thread-like structure located within the nucleus of cells.
- This structure is referred to as chromatin, a complex of DNA and proteins.
- Chromosomes are tightly packed structures of DNA, organized into units called nucleosomes.
- A nucleosome is a basic repeating subunit of chromatin, consisting of a segment of DNA wrapped around a core of eight histone proteins called an octamer.
- The octamer is made up of two copies of each of the four core histone proteins: H2A, H2B, H3, and H4.
- The DNA wraps around the histone octamer twice, forming a nucleosome.
- Multiple nucleosomes connected by linker DNA form a chain, which coils into a 30nm fiber called a solenoid.
- This solenoid structure helps compact and organize the DNA within the nucleus.
- The 3D structure of a protein is determined by the amino acid sequence and its folding process.
- The histone fold domain is the structural pattern of the core histones which is critical for their function.
- The histone fold domain is composed of three alpha helices connected by two loops.
- Histones are rich in the basic amino acids lysine and arginine, giving them a positive charge, which allows them to bind with the negatively charged DNA.
Cell Division and Reproduction
- A phenotype refers to the observable characteristics of an organism, which are determined by its genetic makeup.
- A genotype refers to the actual genetic makeup of an organism, represented by symbols.
- During cell division, chromosomes are duplicated, producing identical copies called chromatids.
- Before replication, a chromosome consists of one DNA molecule.
- After replication, the two DNA molecules are referred to as chromatids, connected at a region called the centromere.
- Each chromatid carries a complete copy of the genetic information from the original chromosome.
- The specific location of a gene on a chromosome is called its locus.
Euchromatin and Heterochromatin
- Euchromatin is a less densely packed form of chromatin found in a transcriptionally active nucleus.
- Euchromatin allows RNA polymerases and regulatory proteins to access DNA, facilitating gene expression.
- Heterochromatin is a more densely packed form of chromatin, found in regions of the chromosome that are genetically inactive.
- These regions are packaged tightly, preventing access to DNA by transcription factors, inhibiting gene expression.
Genome
- The genome refers to the complete set of genetic information in an organism.
- The genome consists of genes and other DNA sequences that make up the chromosomes inherited from parents.
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Description
Explore the structure and organization of chromosomes in this quiz. Learn about chromatin, nucleosomes, and the role of histone proteins in DNA packing. Test your understanding of how DNA is organized within the nucleus of cells.
