Mixing DNA
Two parents give new combinations.
Speeding up variation
Copying DNA makes small changes only slowly. Two individuals in a population carry different changes collected over many generations.
What could happen if DNA from both were combined?
What this lesson covers
The idea
DNA copying alone generates variation slowly; sexual reproduction combines DNA from two individuals with different accumulated variations, creating novel combinations and so generating more variation.
Speeding up variation
Copying DNA makes small changes only slowly. Two individuals in a population carry different changes collected over many generations.
What could happen if DNA from both were combined?
- New combinations of variations
- No change at all
- The DNA would disappear
Combine the variations
Press Next step. Each block is a piece of DNA information. This is a picture, not a real DNA.
Faster variation
DNA copying alone makes variation slowly, because the copying is precise. Two individuals have different accumulated variations. When their DNA is combined, each combination is new, because it involves two different individuals.
DNA copying alone generates variation slowly. Sexual reproduction combines DNA from two individuals with different accumulated variations, creating novel combinations and so generating more variation.
Notes
DNA copying alone makes variation slowly. Sexual reproduction combines DNA from two individuals, creating novel combinations and more variation.
Check yourself
Why is the generation of variation by DNA copying alone slow?
How does sexual reproduction generate more variation?
Why is each combination of variations novel?
- DNA is never copied in a cell. DNA copying is a basic event in reproduction. It is just precise enough to make variation slow.
- DNA copying mechanisms are precise enough — correct. Yes!
- The copies are always completely different. The copies are similar to the original, so variation builds up only slowly.
- It copies the DNA of one individual twice. Sexual reproduction involves DNA from two different individuals, not one.
- It makes the DNA copying less accurate. The book says that if copying were less accurate, many DNA copies would not work with the cellular apparatus and would die.
- It combines DNA from two individuals with different accumulated variations — correct. Yes!
- It involves two different individuals — correct. Yes!
- It always uses the same two individuals. Each combination is novel because it involves two different individuals.
- It copies the variations of one individual. A combination comes from two individuals with different patterns of accumulated variations.