Chromosome Mutations Flashcards
(12 cards)
How do mutations in the number of chromosomes occur?
They arise spontaneously by chromosome nondisjunction during meiosis.
What is nondisjunction?
Nondisjunction is when the chromosomes in meiosis 1 do not separate equally or the chromatids in meiosis 2 do not separate equally in anaphase.
What are the two types of chromosomes disjunction?
Aneuploidy
Polyploidy
What is polyploidy?
Polyploidy is changes in whole sets of chromosomes.
What is made when polyploidy occurs?
Triploid gametes or tetraploid gametes.
What is aneuploidy?
Aneuploidy is changes in the number of individual chromosomes.
Describe how mutations in the number of chromosomes arise
- Spontaneously by chromosome non-disjunction during meiosis
- Homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis
- So some gametes have an extra copy of a particular chromosome and others have none.
What organism does polyploidy usually occur in?
Plants
Describe polyploidy.
1)Each homologous pair is doubled due to DNA replication in interphase.
2)In meiosis 1, all chromosomes fail to separate equally. One cell is empty and the other has the whole set of chromosomes.
3)In the empty cell, there is normal division in meiosis 2, chromatids separate equally. This leads to no chromosomes in a gamete.
4)In the cell with the whole set of chromosomes, the chromatids separate equally in anaphase. The resulting gametes are diploid cells.
What happens when the diploid cell fuses with a haploid cell?
It forms a triploid zygote.
What happens in aneuploidy?
It usually results in a gamete having one more or one fewer chromosome.
What is an example of aneuploidy?
Down syndrome
