Meiosis and Mutations Flashcards
What is Meiosis?
Meiosis is the process of producing gametes.
What are gametes?
A gamete is a sex cell - either an egg or sperm. Gametes only have 1 set of chromosomes whereas a normal human cell has two.
What is fertilisation?
When sperm combines with the egg, forming a zygote (a fertilised egg which has a full set of chromosomes)
What are the three main ways that Meiosis creates variation?
• Independent assortment • Segregation • Crossing over
What are the stages of Meiosis?
What is independent assortment?
When the homologous (same) chromosomes line up randomly in metaphase I
Key thing to remember here is that the chromosomes are lining up randomly. This creates the most variation out of all three.
What is segregation?
When alleles separate into the gametes independently.
Each gamete only has one allele each, and 50% of the gametes have one allele and 50% of the gametes have the other.
What is crossing over?
When homologous chromosomes exchange genetic material with each other, creating recombinant chromosomes.
Essentially you are shuffling alleles between chromosomes.
What is a mutation?
A permanent change to the base sequence of the DNA molecule.
A-G-T-C-G-A A-G-T-C-A-A
T-C-A-G-C-T T-C-A-G-T-T
Why is a mutation important for genetic variation?
Because it creates completely new alleles e.g purple hair
In contrast to…
Meiosis just shuffles the current alleles; it does not create new alleles
What is the effect of mutations on Somatic and Gametic cells?
- A somatic cell is a non-sex cell whereas a gametic cell is a sex cell.
- Mutations occur in both however it can only be passed on to the next generation if it occurs in the gametic cells.
- If a mutation happens in a somatic cell… it wont be passed down to the next generation because it’s a non-sex cell.
