Zoom in on DNA | biology animations

Scientific concepts / discoveries / nature phenomena

Organ systems and organization in multicellular organisms

• Humans are described as being made of organ systems (e.g., circulatory system, digestive system).
• Each system contains organs, which contain tissues, which are made of cells.

Cellular structure

Cells contain organelles/compartments, including:

• Cell membrane
• Mitochondria
• Nucleus

Genetics: chromosomes and DNA

• The nucleus contains 23 pairs of chromosomes (total 46), including a sex-determining pair.
• Each chromosome is described as a long length of tightly coiled DNA.
• When unwound, DNA is wrapped around proteins called histones.
• DNA structure is a double helix, compared to a twisted ladder.

DNA nucleotides and base pairing

• DNA is composed of four nucleotides, distinguished by bases:
  • Adenine (A)
  • Cytosine (C)
  • Guanine (G)
  • Thymine (T)
• Base pairing rules:
  • A pairs with T
  • C pairs with G

Genes and genome

• The sequence/order of DNA bases in specific DNA sections called genes provides instructions for a cell’s structure and function.
• One complete set of DNA instructions for an organism is the genome.
• The genome, organized into chromosomes within the nucleus, directs how specialized cells function and coordinate with neighboring cells.

Biological hierarchy from molecules to organism

• DNA → genes/genome → specialized cells → tissues → organs → organ systems → growth and life of the organism

Researchers or sources featured

• No specific researchers or external sources are named in the provided subtitles.