Chapter 24 - Variation

Question 1

What is variation?

Answer 1

The differences between individuals of a species

Question 2

What causes variation?

Answer 2

• mutations
• environment
• variation from meiosis: random assortment, crossing over, non disjunction
• variation from fertilisation: random fertilisation

Question 3

What is random assortment?

Answer 3

• during anaphase 1, each pair of chromosomes segregates independently of every other pair
• segregation is a random process

Question 4

What is crossing over?

Answer 4

• during prophase 1 matching regions on homologous chromosomes break and then reconnect to the other chromosome
• crossing over creates new combinations of genes

Question 5

What is non-disjunction?

Answer 5

• failure of chromosomes to separate correctly
• monosomy: a chromosome is missing
• partial monosomy: part of a chromosome is missing
• trisomy: extra copy of a chromosome
• partial trisomy: part of an extra chromosome is attracted to another