Nucleus and Chromosome Structures

• Nucleus and Chromosome structures

Nucleus

• The nucleus is a membrane-bound structure containing hereditary information and controls cell growth/reproduction.
• The nucleus is the most prominent organelle, surrounded by a nuclear envelope.

Nuclear Components

• Nucleolus
• Nuclear pore
• Nuclear envelope
• Nucleoplasm
• Chromatin

Nucleus Details

• The nucleus is the largest cellular organelle in animal cells
• The average nuclear diameter is 6 micrometers, occupying about 10% of the cell volume
• The viscous liquid within is called nucleoplasm, similar to cytosol.
• The nucleus appears as a dense, roughly spherical, or irregular organelle.
• The composition by dry weight: DNA 9%, RNA 1%, Histone Proteins 11%, Acidic Proteins 65%.
• The nuclear envelope consists of two nuclear membranes and an underlying nuclear lamina.
• The nucleus is surrounded by inner and outer nuclear membranes
• The outer nuclear membrane is continuous with the endoplasmic reticulum.
• Each nuclear membrane is a phospholipid bilayer permeable only to small molecules.
• Outer nuclear membranes join at nuclear pore complexes where molecules pass through.
• Underlying the inner nuclear membrane is the nuclear lamina, a fibrous network for structural support.
• Nuclear lamina consists of 60-80 kilodalton fibrous proteins called lamins.
• Nuclear lamina offer mechanical support and regulate cell events like DNA replication and cell division and participates in Chromatin organization.

Progeria

• Progeria was first described in 1886 by Jonathan Hutchinson and Hastings Gilford.
• The LMNA gene codes for lamin A.
• Progeria's cause is a point mutation in the LMNA gene, where cytosine is replaced with thymine.

Chromosome Position

• Chromosomes are located inside the nucleus.
• Chromosomes consist of coiled DNA molecules.

Chromosome History

• Chromosomes are rod-shaped, dark-stained bodies seen during metaphase of mitosis.
• Strausberger discovered chromosomes in 1875.
• The term chromosome was coined by Waldeyer in 1888.
• Term initiated as (Chroma= Colour and Soma = body)

Eukaryotic Chromosome Features

• Chromosomes are best visible during metaphase.
• Chromosomes bear genes in a linear fashion.
• The shape, size, and number of chromosomes vary in different species.
• Chromosomes can self-duplicate and mutate.
• Chromosomes are composed of DNA, RNA, and protein.

Chromosome Size

• Chromosome size is measured at mitotic metaphase in length and diameter.
• Plants usually have longer chromosomes than animals.
• Plant chromosomes are 0.8-7μm in length, while animal chromosomes are 0.5-4μm in length.
• Chromosome size varies from species to species.

Chromosome Diagram

• Chromatid
• Centromere
• Short arm
• Long arm

Ribosome Hub

• Nucleolus, made of proteins and RNA, is responsible for ribosome synthesis.

Understand the nucleus, a key cell structure containing hereditary information and controlling cell growth. Learn about its components like the nucleolus, nuclear pore, and envelope. Explore the nucleus's composition, size, and function within the cell.