How is DNA packaged in a eukaryotic cell?
In eukaryotes, however, genetic material is housed in the nucleus and tightly packaged into linear chromosomes. Chromosomes are made up of a DNA-protein complex called chromatin that is organized into subunits called nucleosomes.
Why is it called euchromatin?
Euchromatin is a lightly packed form of chromatin (DNA, RNA, and protein) that is enriched in genes, and is often (but not always) under active transcription. Euchromatin stands in contrast to heterochromatin, which is tightly packed and less accessible for transcription. 92% of the human genome is euchromatic.
Are initiated at sequences called Origins?
Nucleic Acid Synthesis DNA replication is initiated at discrete sequences called origin (ori) of replication to which DNA polymerase and accessory proteins bind and copy both strands, as predicted by the semi-conservative replication model (Fig.
What is chromosome packaging?
Chromosomal DNA is packaged inside microscopic nuclei with the help of histones. These are positively-charged proteins that strongly adhere to negatively-charged DNA and form complexes called nucleosomes. Nucleosomes fold up to form a 30-nanometer chromatin fiber, which forms loops averaging 300 nanometers in length.
How is DNA packaged in prokaryotic and eukaryotic cells?
The answer to this question lies in DNA packaging. Whereas eukaryotes wrap their DNA around proteins called histones to help package the DNA into smaller spaces, most prokaryotes do not have histones (with the exception of those species in the domain Archaea).
Why euchromatin is loosely packed?
At some places chromatin is densely packed to form darkly stainined heterochromatin. At other places chromatin is loosely packed. It is called euchromatin. It is transcriptionally active chromatin whereas heterochromatin is transcriptionally inactive and late replicating or heteropycnotic.
What are Euchromatic regions?
The euchromatin is a constant size region and includes sequences homologous to the X chromosome, Y-specific repetitive sequences, and all the genes identified in the Y chromosome, which include the now identified 27 distinct protein-coding genes or gene families.
What is Heteropycnosis?
[¦hed·ə·rō·pik′nō·səs] (cell and molecular biology) Differential condensation of certain chromosomes, such as sex chromosomes, or chromosome parts.
What is methylation and acetylation?
Adding an acetyl group to the tail (acetylation) neutralises the charge, making DNA less tightly coiled and increasing transcription. Adding a methyl group to the tail (methylation) maintains the positive charge, making DNA more coiled and reducing transcription.
What is the origin of replication in eukaryotes?
The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated. This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses.
What is the ori region for?
The Ori region from bacterial chromosomes plays a pivotal role in chromosome organization and segregation as it is replicated and segregated early in cell division cycle and its positioning impacts the cellular organization of the chromosome in the cell.
Which type of chromatin is densely packed?
At some places, chromatin is densely packed to form darkly stained heterochromatin. At other places, chromatin is loosely packed. it is called chromatin Chtornatin. It is transcriptionally active chromatin.
How many nucleotides are in a typical eukaryotic genome?
Typical eukaryotic genomes are composed of ________ chromosomes. DNA is composed of four nucleotides, A, C, G and T. Each codon is composed of three nucleotides. The number of possible codons is
What is a nucleosome made of?
Nucleosomes constitute the repeating unit of a structure in nucleus called chromatin. Chromatin is held over a scaffold of nan-histone chromosomal (or NI-K) proteins. At some places, chromatin is densely packed to form darkly stained heterochromatin.
What is the repeating unit of nucleus called?
Nucleosomes constitute the repeating unit of a structure in nucleus called chromatin. Chromatin is held over a scaffold of nan-histone chromosomal (or NI-K) proteins. At some places, chromatin is densely packed to form darkly stained heterochromatin. At other places, chromatin is loosely packed. it is called chromatin Chtornatin.