10 Questions
What is the basic unit of chromatin structure?
Histone
Which type of chromatin is genetically active and consists of all functional genes?
Euchromatin
What is the major difference between prokaryotic and eukaryotic genomes in terms of DNA organization?
Eukaryotic DNA is much larger and organized into chromatin
Which part of a eukaryotic gene represents the coding sequence?
Exon
What is the function of histone proteins in chromatin structure?
They help condense DNA into a compact structure
Which type of chromatin stains very lightly and consists of all the functional genes?
Euchromatin
What is the term for the intervening sequence in a eukaryotic gene that does not code for protein?
Intron
Which feature presents a major information-processing challenge in multicellular eukaryotic genomes?
'One gene, many cell types' regulation
'Heterochromatin' is characterized as:
'Genetically inactive' chromatin
'Chromatin' in eukaryotes consists of:
'Double-stranded DNA wound around histone proteins'
Study Notes
Genome Organization
- A genome is an organism's complete set of DNA, comprising of nuclear and mitochondrial DNA, containing all the information needed to build and maintain the organism.
- Genome size is measured in base pairs and can increase by duplication, insertion, or polyploidization, or decrease due to deletions.
- Genomes of all organisms are arranged in a confined space, the nucleoid or nucleus, allowing for DNA transactions such as replication, transcription, and repair to occur at appropriate times.
Eukaryotic Genomes
- Eukaryotic genomes are arranged in the nucleus and are diploid, with DNA organized into multiple linear chromosomes.
- Eukaryotes and archaea use histone proteins, while bacteria use different proteins with similar functions.
- The primary structure of the eukaryotic genome consists of DNA wrapping around histone octamers, forming nucleosomes.
- Nucleoid proteins help maintain the supercoiled structure of the nucleic acid, distinct from histones in eukaryotic nuclei.
Eukaryotic vs. Prokaryotic Genomes
- Eukaryotes have larger genomes with fewer genes in a given length of DNA, with more noncoding DNA (10,000 times as much as prokaryotes).
- Prokaryotes have smaller genomes with more genes in a given length of DNA, with less noncoding DNA, and genes are not interrupted by introns.
Eukaryotic Genome Structure
- Eukaryotic genomes are linear and conform to the Watson-Crick Double Helix structural model.
- They have unique features of Exon-Intron organization of protein-coding genes, with intervening sequences representing RNA functionality.
Eukaryotic Genome Challenges
- The typical multicellular eukaryotic genome is much larger than that of a prokaryotic cell.
- Cell specialization limits the expression of many genes to specific cells, presenting an information-processing challenge.
Chromatin Organization
- Chromatin is the complex basis of DNA and protein that makes up chromosomes, consisting of linear, unbroken, double-stranded DNA.
- Chromatin is of two types: Euchromatin (genetically active, consisting of functional genes) and Heterochromatin (genetically inactive, with non-expressive genes).
Test your knowledge on genome organization, including the structure, size, and factors that can affect genome size such as duplication, insertion, and recombination. Learn about how genomes can shrink due to various processes.
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