DNA & RNA Carry Genetic Information (College Board AP® Biology)

The Genetic Material of Life

Continuity of Life

• Heritable molecules that are passed from one organism to the next through reproduction allow continuity of life

  • The heritable molecules include DNA and RNA which carry the genetic information required to produce new cells and organisms

DNA and RNA as the genetic material of living organisms

• Deoxyribose nucleic acid (DNA) carries the genetic code in all organisms

• This is the reason why the genetic code is said to be universal, it applies to all forms of life

• DNA is mainly found in the nucleus where it forms chromosomes

• It is also found in chloroplasts and mitochondria of eukaryotic cells

• Ribonucleic acid (RNA) is another type of nucleic acid which is the main component of ribosomes, which play an important role in protein synthesis 

  • Ribosomes are found in all forms of life

  • Some RNA is also found in the nucleus and cytoplasm

• Certain viruses (such as SARS-CoV-2) contain RNA as their genetic material (instead of DNA)

• These viruses cause a variety of different diseases, such as COVID-19, Ebola, mumps and influenza

• Viruses are not considered to be living organisms, since they are unable to replicate by themselves and they do not perform the main metabolic reactions such as respiration

• They are dependent on other living cells for replication and survival

• Viruses also lack a cellular structure, which is another reason they are not considered to be living

Ribosomes in all Life Forms

• Ribosomes are found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells

• Each ribosome is a complex of ribosomal RNA (rRNA) and proteins

• 80S ribosomes (composed of 60S and 40S subunits) are found in eukaryotic cells

• 70S ribosomes (composed of 50S and 30S subunits) in prokaryotes, mitochondria and chloroplasts

• Ribosomes are the site of translation in protein synthesis

  • A biochemical process important in all life forms

Common Ancestry

• Ancestry between organisms can be studied by tracing the lines of descent of heritable traits and identifying conserved mechanisms

  • Many key metabolic pathways are shown to be conserved across all living systems, including:

    • carbohydrate metabolism

    • energy metabolism

    • amino acids and nucleotide processing

• These conserved features indicate that all currently recognized domains originated from a common ancestor