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Sexual reproduction gives rise to genetic diversity and variations by mixing and shuffling existing genes and traits. Mutations are the ultimate source of variation, because mutations give rise to NEW traits. Mutations add NEW genes to the gene pool. Random mutations can occur in both organisms that reproduce sexually and organisms that reproduce asexually.
If variations are necessary for natural selection to take place, then how can organisms that reproduce asexually ever evolve?!
Asexual reproduction involves ONE parent making an identical offspring. The parent clones their DNA and passes it on to the offspring. This is how single-celled organisms like bacteria reproduce.
But- the offspring doesn't always come out genetically identical.
But- the offspring doesn't always come out genetically identical.
A mistake can randomly happen at any time during DNA replication of cell division. If the DNA is not copied properly during asexual reproduction, the offspring will come out genetically different.
Mutations are defined as any change to the DNA base sequence. Mutations are mistakes that occur randomly during DNA replication.
Every cell that develops from the mutated cell will inherit the mutation through asexual reproduction
The only way for a single-celled organism to evolve is through random mutation.
Can mutations be passed on??
Can mutations be passed on??
- If a single-celled organism is copying itself and a mutation occurs, it will be passed on to its offspring cell. Every single cell created after this point will have the mutation. This is how bacteria and viruses evolve- there is a random mistake during DNA replication, and now, there is a new strain of the pathogen.
Don't forget, mutations happen randomly during cell division. If a mutation occurs when a gamete is being formed, then the mutation can be passed on to offspring through SEXUAL reproduction.
During fertilization, the zygote (first cell of the offspring) receives the mutation and it becomes a part of its genetic code.
ONLY mutations that are present in GAMETES can be passed on to offspring. Mutations in body cells cannot be passed on to offspring.
The zygote grows by MITOSIS. The zygote copies itself to make more cells. If the zygote received a mutated gene from the sperm or the egg, then ALL cells in the growing offspring will inherit the mutation.
Still confused? Watch this video!
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