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Genetic Change/Evolution

Genetic Change/Evolution. Evolution. The process in which new species develop from earlier forms. Evolution. The process in which new species develop from earlier forms. Normally occurs slowly, most often in response to a change in a species’ environment. . Evolution.

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Genetic Change/Evolution

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  1. Genetic Change/Evolution

  2. Evolution • The process in which new species develop from earlier forms.

  3. Evolution • The process in which new species develop from earlier forms. • Normally occurs slowly, most often in response to a change in a species’ environment.

  4. Evolution • The process in which new species develop from earlier forms. • Normally occurs slowly, most often in response to a change in a species’ environment. • Life is thought to have evolved from just a few unicellular organisms three billion years ago.

  5. Evolution • The process in which new species develop from earlier forms. • Normally occurs slowly, most often in response to a change in a species’ environment. • Life is thought to have evolved from just a few unicellular organisms three billion years ago. • Evolution happens through ‘changes in the frequency of alleles in a population’ – some alleles do better than others.

  6. Evolution • The process in which new species develop from earlier forms. • Normally occurs slowly, most often in response to a change in a species’ environment. • Life is thought to have evolved from just a few unicellular organisms three billion years ago. • Evolution happens through ‘changes in the frequency of alleles in a population’ – some alleles do better than others. • Freq. of an allele = occurrence of that allele total number of alleles

  7. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals.

  8. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals. • 30 – Aa, 10 – AA and 10 – aa

  9. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals. • 30 – Aa, 10 – AA and 10 – aa • For the A allele it occurs 30 times from Aa

  10. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals. • 30 – Aa, 10 – AA and 10 – aa • For the A allele it occurs 30 times from Aa • The A allele also occurs 20 times from AA (2x10)

  11. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals. • 30 – Aa, 10 – AA and 10 – aa • For the A allele it occurs 30 times from Aa • The A allele also occurs 20 times from AA (2x10) • The occurrence of the A allele is now 50 (30 + 20)

  12. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals. • 30 – Aa, 10 – AA and 10 – aa • For the A allele it occurs 30 times from Aa • The A allele also occurs 20 times from AA (2x10) • The occurrence of the A allele is now 50 (30 + 20) • There are 50 individuals with two alleles so that the total number of alleles is 100 (50x2)

  13. Example of how to work out allele frequencies • Suppose a gene pool were to contain 50 individuals. • 30 – Aa, 10 – AA and 10 – aa • For the A allele it occurs 30 times from Aa • The A allele also occurs 20 times from AA (2x10) • The occurrence of the A allele is now 50 (30 + 20) • There are 50 individuals with two alleles so that the total number of alleles is 100 (50x2) • Frequency of the A allele = 50/100 = 0.5

  14. Try these • Suppose a gene pool were to contain 60 individuals. 20 were BB, 30 were Bb and 10 were bb. Calculate the frequency of the B allele. • A gene pool has 120 individuals. 60 were Aa, 20 were AA and 40 were aa. Calculate the frequency of the A allele.

  15. Example of the evolutionary effect of the recessive allele (sometimes the ‘bad allele) • Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way.

  16. Example of the evolutionary effect of the recessive allele (sometimes the ‘bad allele) • Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. • Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa

  17. Example of the evolutionary effect of the recessive allele (sometimes the ‘bad allele) • Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. • Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa • If all the 10 individuals that showed this allele died or were forced to leave the population then:

  18. Example of the evolutionary effect of the recessive allele (sometimes the ‘bad allele) • Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. • Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa • If all the 10 individuals that showed this allele died or were forced to leave the population then: • Numerator is found from the Aaindiv. (30x1) = 30 a alleles

  19. Example of the evolutionary effect of the recessive allele (sometimes the ‘bad allele) • Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. • Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa • If all the 10 individuals that showed this allele died or were forced to leave the population then: • Numerator is found from the Aaindiv. (30x1) = 30 a alleles • Denominator is found from the 30 Aa individuals + the 10 AA individuals (30x2 + 10x2 = 80) – total alleles.

  20. Example of the evolutionary effect of the recessive allele (sometimes the ‘bad allele) • Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. • Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa • If all the 10 individuals that showed this allele died or were forced to leave the population then: • Numerator is found from the Aaindiv. (30x1) = 30 a alleles • Denominator is found from the 30 Aa individuals + the 10 AA individuals (30x2 + 10x2 = 80) – total alleles. • The frequency is now 30/80 = 0.375 – evolution is operating because there has been a change in allele frequencies.

  21. ‘Bad’ recessive alleles • Sickle-cell anaemia – red blood cells form a sickle shape. These abnormally shaped cells cause severe muscle pain and in extreme cases, death.

  22. ‘Bad’ recessive alleles • Sickle-cell anaemia – red blood cells form a sickle shape. These abnormally shaped cells cause severe muscle pain and in extreme cases, death. • Cystic fibrosis – carried by 1 in 20 pakeha. The affected individual secretes abnormally thick mucus. This affects both their digestive and respiratory systems. In the lungs it provides a thick breeding ground for bacteria.

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