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
- Many key metabolic pathways are shown to be conserved across all living systems, including:
- These conserved features indicate that all currently recognized domains originated from a common ancestor
