Two parents, one balanced set
Sexual reproduction and meiosis.
Mixing two sets
In sexual reproduction, a child gets genetic material from both parents. Each parent's cells have 46 chromosomes.
If the child simply received a full set from each parent, what do you think would be a problem?
What this lesson covers
The idea
In sexual reproduction two parents contribute genetic material to the offspring; to keep the chromosome number from doubling every generation, gametes are formed by a special cell division, meiosis.
Mixing two sets
In sexual reproduction, a child gets genetic material from both parents. Each parent's cells have 46 chromosomes.
If the child simply received a full set from each parent, what do you think would be a problem?
- The number of chromosomes would keep doubling
- The child would have no chromosomes
- The number would fall each time
Doubling or not?
Choose how the gametes are made, then move to generation 3. The numbers are an example for humans.
A special cell division
If every generation got a full set from both parents, the number of chromosomes would double each time. Meiosis solves this, so the number stays the same.
In sexual reproduction two parents contribute genetic material to the offspring. To keep the chromosome number from doubling every generation, gametes are formed by a special cell division, meiosis.
Notes
Sexual reproduction has two parents. Meiosis forms gametes so the chromosome number does not double every generation.
Check yourself
How many parents contribute genetic material in sexual reproduction?
Suppose each of two parents gave a child all 46 chromosomes (an example, not what happens). How many chromosomes would the child's cells have?
Answer: 92
46 + 46 = 92, which is double. Meiosis prevents this.
What special cell division forms gametes?
Why are gametes formed by meiosis?
- Two — correct. Yes!
- One. One parent is involved in asexual reproduction.
- Three. Sexual reproduction involves two parents.
- Mitosis. Mitosis gives identical daughter cells, as in asexual reproduction. Gametes are formed by meiosis.
- Meiosis — correct. Yes!
- Budding. Budding is a method of asexual reproduction in organisms such as hydra.
- So the offspring is identical to one parent. Offspring of sexual reproduction get genetic material from two parents.
- So the cell can float in air. Floating in air is a feature of spores, not a reason for meiosis.
- So the chromosome number does not double every generation — correct. Yes!