Cell Biology: Chromatin, Genes, Karyotype, and Cell Types

Chromatin

Chromatin consists of strands of DNA at different degrees of condensation associated with proteins and scattered throughout the nucleoplasm. When the cell is going to divide, the chromatin filaments are organized and condensed to form thicker structures called chromosomes.

Genes

A gene is a unit of hereditary material. It is a fragment of nucleic acid that carries genetic information for a character, a protein, or a polypeptide chain. It corresponds to what Mendel called a hereditary factor.

Centriole

In animal cells, centrosomes present two small cylinders and consist of protein tubules.

Mitotic Spindle

The mitotic spindle forms when the nuclear membrane and nucleolus disappear.

Karyotype

A karyotype is a set of chromosomes from one species. There are two types:

• Heterochromosomes: They are very different from each other and are involved in sex determination, one X and one Y (XX for women and XY for men).
• Autosomes: These chromosomes are the same in both sexes.

Prokaryote

Prokaryotes have no nucleus, so the genetic material is in the cytoplasm. They present a cell wall, a plasma membrane forming mesosomes, a bacterial chromosome, ribosomes, flagella, and fimbriae.

Eukaryotes

The internal structure of eukaryotes is more complex. They have diverse membrane-delimited organelles, are larger, and present a plasma membrane, nucleus, cytoplasm, centrosomes, and organelles (endoplasmic reticulum, Golgi apparatus, ribosomes, mitochondria, lysosomes, and vacuoles).

Aerobic

An aerobic cell or organism is capable of living with oxygen.

Anaerobic

An anaerobic cell is unable to live with oxygen.

Autotrophs

Autotrophs can create their own food (e.g., plants).

Heterotrophs

Heterotrophs do not fabricate their own food (e.g., animals, some protists).

Cell Nucleus

The cell nucleus is the bulkiest structure of eukaryotic cells. It contains the vast majority of cellular DNA and genetic information. It consists of a nuclear envelope, nucleoplasm, nucleolus, and chromatin.

Kinetochore

A kinetochore is a protein structure that anchors spindle microtubules during cell division processes (meiosis and mitosis). It is located in a specific area of the chromosome, the centromere.