[9.3] genetic diversity and adaptation

Question 1

how do you calculate the number of different chromosome combinations possible in each sex cell due to independent assortment?

Answer 1

use 2ⁿ, where n is the number of homologous pairs of chromosomes in the organism

• eg. in humans: 2²³ = 8,388,608
• kangaroo: 2¹⁶ = 65,536

Question 2

how do you calculate the number of different chromosome combinations possible in the offspring?

Answer 2

use (2ⁿ)ⁿ

• eg. in humans: (2²³)²³ = very big
• giraffe: (2⁶)⁶ = 6.87 × 10¹⁰

Question 3

what is the definition of genetic diversity?

Answer 3

the number of different alleles found within a species or population (population = all organisms of one species within a habitat)

Question 4

how can genetic diversity be reduced?

Answer 4

• inbreeding
• genetic bottle necks
• the founder effect

Question 5

what does a genetic bottle neck describe?

Answer 5

• an event that massively reduces the population before they can reproduce (eg. overhunting)
• this reduces the number of different alleles in the gene pool (number of different alleles)
• the survivors reproduce, making a large population with a high frequency of a small number of alleles
  > this is low genetic diversity

Question 6

what does the founder effect describe?

Answer 6

• when a small group of organisms from a colony start a new colony elsewhere
• members of the colony only breed within the group
• the new colony has a low genetic diversity but a higher frequency of certain alleles