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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 for specific traits called?
Genotype
Heterochromatin is genetically active.
False
Euchromatin is less densely packed and is transcriptionally active.
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What is the role of histones in relation to DNA?
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A ______ is the basic repeating subunit of chromatin.
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How many histone proteins make up the histone octamer?
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What must be packaged into a nucleus with a diameter less than a human hair?
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What is the term for one half of a duplicated chromosome?
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A gene’s specific location along a chromosome is called its ______.
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Study Notes
Chromosome Organization
- Chromosomes are thread-like structures inside the nucleus of animal and plant cells
- Chromosomes are made up of DNA and proteins, namely histones, that package the DNA into a compact form.
- Histones are proteins rich in basic amino acids, lysine and arginine, giving them a positive charge
- DNA is negatively charged, enabling it to bind to histones
- DNA wraps around complexes of histone proteins, giving chromosomes a more compact shape
- Histones play a role in regulating gene expression
- A nucleosome is a tiny spool of DNA wrapped around a core of eight histone proteins
- Eight histone proteins come together to form a histone octamer, which is located at the center of the nucleosome
- A histone octamer is made up of two copies each of the histone proteins H2A, H2B, H3, and H4
- A chain of nucleosomes, consisting of six nucleosomes, is wrapped into a 30nm spiral called a solenoid
- The solenoid structure is a condensed chromatin fiber, playing a role in DNA packaging
- Chromatin refers to the mixture of DNA and proteins that form chromosomes.
- The structural pattern of core histones is known as the histone fold domain
- The 3D structure of a protein is determined by its amino acid sequence
- Correct protein folding is essential for protein function
- Histones are involved in organizing and packaging DNA within the cell nucleus
- Heterochromatin is densely packed or compacted chromatin, which is genetically inactive and transcription is inhibited in heterochromatin due to the tightly packaged DNA
- Euchromatin is less densely compacted chromatin, which is transcriptionally active, allowing for easier access to DNA by RNA polymerases and regulatory proteins
Terminology
- Phenotype: The appearance or expression of a specific trait, usually described with words; examples: "tall," "dwarf," "albino"
- Genotype: The genetic makeup of an individual for specific traits, usually expressed with symbols; examples: DD (tall), dd (short)
Genome and Chromosomes
- Genome: The complete set of genetic information in an organism
- Chromatid: One half of a duplicated chromosome
- Before replication, one chromosome consists of one DNA molecule
- During replication, the DNA molecule is copied, and the two molecules are known as chromatids
- A gene's specific location along the length of a chromosome is called its locus (plural loci)
- Our genome is made up of the genes and other DNA that make up the chromosomes we inherited from our parents
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Description
Test your understanding of chromosome organization and the role of histones in DNA packaging. This quiz covers key concepts such as nucleosomes, histone proteins, and the structure of chromatin. Challenge yourself and deepen your knowledge in genetics and molecular biology.
