DNA: A spiraling chain-like molecule made up of 4 nucleotides labeled A, C, T, and G.
Gene: A long stretch of DNA with a specific sequence of nucleotides (A, C, T, G) that usually codes for proteins or a group of proteins.
Proteins: Interact with other proteins and molecules to form living cells; cells form tissues, tissues form organs, and organs form living creatures.
Genetic Variability: Individual traits, such as beak shape, are due to differences or mutations in genetic code, affecting protein shape, function, or reproduction.
What is a Chromosome?
Definition: An entire chain of DNA along with a group of stabilizing proteins.
Structure:
Visual misconception: DNA is not trapped inside a chromosome in a simple form; it is wrapped like a spool of yarn.
Composed of protein orbs called histones wrapped with DNA string.
DNA sequence is millions of nucleotides long and contains hundreds of genes.
Chromosome Condensation and Cell Reproduction
Condensed Form:
Chromosomes are tightly packaged during cell reproduction to ensure durability as the cell splits.
Normally exist loosely inside the cell nucleus.
Human Chromosomes:
Humans have 23 pairs of chromosomes, totaling 46.
Each cell contains a full set of chromosomes, but specific genes are active/inactive based on the cell type (e.g., eyeball vs. liver cells).
Inheritance and Genetic Variation
Parental Contribution:
One chromosome of each pair from mother, the other from father.
Both chromosomes in a pair generally contain the same genes, but with slight sequence variations due to mutations.
Source of Mutations:
Some mutations are ancestral, passed down through generations.
Others are unique, occurring in reproductive cells or early development.
Unique mutations represent new genetic information, potentially unique in the history of life.
Summary
A chromosome is a DNA chain with stabilizing proteins.
Humans typically have 23 pairs (46 chromosomes) in each cell.
Chromosomes are loose during most of a cell's life but condense for cell reproduction.
Genetic variation arises from mutations, some inherited and others unique.
Conclusion
Jon Perry explains the concept of chromosomes clearly in the animation.
Supported by viewers at patreon.com/statedclearly.