Category
Genetics
Explore the 13 entries currently assigned to this category. These counts describe this curated catalogue, not the size or rate of change of the field itself.
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Not a fact anymore
Every cell in one person's body contains exactly the same DNA sequence.
What we know now
A person's cells begin from one fertilized egg but accumulate mutations as they divide. The result is somatic mosaicism: genetically distinct cell lineages within the same body.
- Status
- Corrected
- Category
- Genetics
- Accepted for
- ≈62 years
- Changed approximately
- 2000s–present
Not a fact anymore
Identical twins remain genetically identical throughout life.
What we know now
Identical twins begin with nearly the same inherited DNA because they develop from the same fertilized egg. After the embryo splits, however, new DNA mutations can arise independently in either twin, so their genomes become slightly different over time.
- Status
- Corrected
- Category
- Genetics
- Accepted for
- ≈93 years
- Changed approximately
- 2000s–present
Not a fact anymore
The human genome contains about 100,000 protein-coding genes.
What we know now
Humans have roughly 20,000 protein-coding genes, not about 100,000. A protein-coding gene is a stretch of DNA whose information can be used to make a protein. The exact count continues to change slightly as genome annotation improves.
- Status
- Corrected
- Category
- Genetics
- Accepted for
- ≈16 years
- Changed approximately
- 2001–2004
Not a fact anymore
A gene in a complex organism is one continuous stretch of DNA that directly matches its messenger RNA.
What we know now
Many genes in animals, plants, fungi, and other organisms with cell nuclei are not one uninterrupted stretch of usable information. The first RNA copy contains sections that will be kept, called exons, and sections that will be removed, called introns.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈22 years
- Changed approximately
- 1977–1980s
Not a fact anymore
Each gene produces exactly one protein.
What we know now
One gene can produce several RNA or protein products through alternative splicing, different promoters, and other forms of RNA processing. Some genes produce functional RNA rather than protein.
- Status
- Superseded
- Category
- Genetics
- Accepted for
- ≈32 years
- Changed approximately
- 1970s–2000s
Not a fact anymore
Genetic information flows from DNA to RNA but never from RNA back into DNA.
What we know now
Cells can copy RNA back into DNA. An enzyme called reverse transcriptase performs this reaction. Retroviruses use it to make a DNA copy of their RNA genome, which can then be inserted into the DNA of an infected cell.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈15 years
- Changed approximately
- 1970–1975
Not a fact anymore
RNA cannot serve as hereditary material.
What we know now
Many viruses use RNA genomes, and RNA molecules can store, copy, and transmit hereditary information. Cellular organisms use DNA as their principal long-term genome, but heredity is not chemically restricted to DNA.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈12 years
- Changed approximately
- 1956–1957
Not a fact anymore
The normal human chromosome number is 48.
What we know now
Most human body cells contain 46 chromosomes, arranged in 23 pairs. Eggs and sperm normally contain 23.
- Status
- Corrected
- Category
- Genetics
- Accepted for
- ≈31 years
- Changed approximately
- 1955–1956
Not a fact anymore
Genes occupy permanently fixed positions in chromosomes and cannot move around the genome.
What we know now
Most genes remain at stable chromosome locations, but some DNA sequences can move. These transposable elements can cut or copy themselves into new positions, where they can disrupt genes, change gene activity, or contribute to genome evolution.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈35 years
- Changed approximately
- 1940s–1980s
Not a fact anymore
Genes pass only from parents to their offspring.
What we know now
Genes usually pass vertically from parents to offspring, but DNA can also move horizontally between unrelated organisms. This is especially common in microbes and can spread useful traits, including antibiotic resistance, without reproduction.
- Status
- Narrowed
- Category
- Genetics
- Accepted for
- ≈96 years
- Changed approximately
- 1920s–present
Not a fact anymore
Genes are made of protein because proteins are complex enough to carry hereditary information, while DNA is only a structural scaffold.
What we know now
DNA is the hereditary material in cellular organisms and many viruses. Its nucleotide sequence stores genetic information, while proteins perform many of the functions encoded by that information.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈29 years
- Changed approximately
- 1944–1950s
Not a fact anymore
Useful mutations arise because organisms need them when the environment changes.
What we know now
Mutations arise through biochemical processes without foreknowledge of which changes will be useful. Selection then increases variants that happen to improve survival or reproduction in a particular environment.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈43 years
- Changed approximately
- 1943–1950s
Not a fact anymore
Chromosomes are unrelated to Mendelian heredity and do not physically carry genes.
What we know now
Genes occupy loci on chromosomes. Chromosome segregation and recombination explain Mendelian inheritance, linkage, sex-linked traits, and genetic mapping.
- Status
- Overturned
- Category
- Genetics
- Accepted for
- ≈25 years
- Changed approximately
- 1902–1915
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