Meiosis Flashcards
What is meiosis used for?
To produce Gametes which are sex cells. No of chromosomes are halved from diploid to haploid Nd all daughter cells are genetically different
What does diploid mean?
When the chromosomes are present in homologous pairs (2n)
What does haploid mean?
Only one chromosome from each homologous pair is present
How does chromosome No. remain constant across generations?
When Haploid gametes fuse at fertilisation, diploid number is restored
Name the 2 stages that make up Meiosis and what is the end product?
Meiosis I - homologous pairs of chromosomes are seperated.
Meiosis II - The sister chromatids are seperated.
At the end, 4 haploid, genetically different gametes are produced from a single diploid parent cell
Explain the process of Crossing Over leading to genetically different gametes
It occurs in meiosis I and happens when chromosomes are in homologous pairs and will occur infrequently. There is an exchange of maternal and paternal alleles between the adjacent chromatids in the bivalent which leads to different combinations
What is a bivalent?
Another name for a homologous pair
Explain how Independent segregation of homologous pairs results in genetically different gametes
Each pair can line up independently of any other pair Due to this, the cells produced can contain different combinations of maternal and paternal chromosomes
How do you work out No. of different combinations?
2n where n equals the No. of homologous pairs
Explain what happens when there are mutations in meiosis in the chromosomes
Mutations can arise randomly. This is because of non disjunction of chromosomes during the first or second meiotic divisions.bchromsoomes don’t seperate properly leading to gametes having too many or not enough chromosomes
What is a homologous pair?
Two chromosomes, one from each parent, which have the same gene but different alleles
What happens during crossing over?
Chromatids of homologous pairs cross over and swap alleles
What is independent segregation?
Different combinations of chromosomes, the homologous pairs can line up in two different ways which will lead to genetic variation
