Genetika Populasi_2

DASAR GENETIKA POPULASI

Po pu lat ion ge neti cs

• ge ne tic s truct ure of a p op ula tio n

Po pu lat ion ge neti cs

• ge ne tic s truct ure of a p op ulation group of individuals of the same species that can interbreed

Po pu lat ion ge neti cs

• ge ne tic s truct ure of a p op ulation • alleles • genotypes

group of individuals of the same species that can interbreed

Patterns of genetic variation in populations Changes in genetic structure through time

De scri bi ng ge neti c str uctu re

• gen otyp e f req uenci es (Frek ue nsi gen ot

• alle le f req uenci es (Freku ensi gen ) rr = white Rr = pink RR = red

De scri bi ng ge neti c str uctu re

• gen otyp e freque nci es • alle le f reque nci es 200 white

genotype frequencies:

500 pink

200/1000 = 0.2 rr 500/1000 = 0.5 Rr

300 red total = 1000 flowers

300/1000 = 0.3 RR

De scri bi ng ge neti c str uctu re

• gen otyp e freque nci es • alle le f reque nci es 200 rr = 400 r 500 Rr = 500 r = 500 R

allele frequencies: 900/2000 = 0.45 r

300 RR = 600 R 1100/2000 = 0.55 R total = 2000 alleles

fo r a populatio n with geno typ es:

calc ulate : Genotype frequencies

100 GG 160 Gg

140 gg

Phenotype frequencies

Allele frequencies

fo r a populatio n with geno typ es: 100 GG 160 Gg

calc ulate : Genotype frequencies 100/400 = 0.25 GG 260 0.65 160/400 = 0.40 Gg 140/400 = 0.35 gg

Phenotype frequencies 260/400 = 0.65 green 140/400 = 0.35 brown

140 gg

Allele frequencies 360/800 = 0.45 G 440/800 = 0.55 g

anoth er way to calc ulate Genotype frequencies alle le fr equenc ie s: 100 GG 160 Gg

0.25 GG 0.40 Gg 0.35 gg

G G g g

0.25 0.40/2 = 0.20 0.40/2 = 0.20 0.35

Allele frequencies 140 gg

360/800 = 0.45 G 440/800 = 0.55 g OR

[0.25 + (0.40)/2] = 0.45 [0.35 + (0.40)/2] = 0.55

Wh y i s ge neti c va riat ion impo rta nt?

variation

global warming

sur vi val

EXTI NCTION!! no variation

Wh y i s ge neti c va riat ion impo rta nt? north

south

variation north

south

no variation

Wh y i s ge neti c va riat ion impo rta nt? north

south

diverg en ce

variation north

south

no variation

NO DIVE RG ENCE!!

Ho w do es g en et ic s tru ctu re change ?

Ho w do es g en et ic s tru ctu re change ?

changes in allele frequencies and/or genotype frequencies through time

Ho w do es g en et ic s tru ctu re change ?

changes in allele frequencies and/or genotype frequencies through time

• mutation • migration • natural selection • genetic drift • non-random mating

Ho w do es g en et ic s tru ctu re change ? • muta tio n

spo ntaneous c hange i n DNA

• migration • natural selection

• creates new alleles • ultimate source of all genetic variation

• genetic drift • non-random mating

Ho w do es g en et ic s tru ctu re change ? • mutation

• mi grati on individua ls mov e into po pula tion • natural selection

• introduces new alleles “gene flow”

• genetic drift • non-random mating

Ho w do es g en et ic s tru ctu re change ? • mutation • migration

cert ain genot ype s pr oduce mo re off spri ng • differences in survival or reproduction

• nat ur al se lec tio n • genetic drift

di fferenc es in“ fitnes s”

• leads to adaptation

• non-random mating

Natu ral sel ection

Resistance to antibacterial soap Generation 1: 1.00 not resistant 0.00 resistant

Natu ral sel ection

Resistance to antibacterial soap Generation 1: 1.00 not resistant 0.00 resistant

Natu ral sel ection

Resistance to antibacterial soap Generation 1: 1.00 not resistant 0.00 resistant Generation 2: 0.96 not resistant 0.04 resistant

mut atio n!

Natu ral sel ection

Resistance to antibacterial soap Generation 1: 1.00 not resistant 0.00 resistant Generation 2: 0.96 not resistant 0.04 resistant Generation 3: 0.68 not resistant 0.32 resistant

Natu ral sel ection

Resistance to antibacterial soap Generation 1: 1.00 not resistant 0.00 resistant Generation 2: 0.96 not resistant 0.04 resistant Generation 3: 0.68 not resistant 0.32 resistant Generation 4: 0.12 not resistant 0.88 resistant

Natu ral s elect ion c an c au se popu lations to di verge north

south

diverg ence

Sel ecti on o n s ickle- cel l allele aa – abnormal ß hemoglobin ve ry l ow fitne ss sickle-cell anemia AA – normal ß hemoglobin vulnerable to malaria

int ermed. fitne ss

Aa – both (abnormal and normal) hi gh ß hemoglobins fitnes s resistant to malaria Selection favors heterozygotes (Aa). Both alleles maintained in population (a at low level).

Ho w do es g en et ic s tru ctu re change ? • mutation • migration

genetic ch ange by c hance alone

• natural selection • gen eti c dri ft • non-random mating

• sampling error • misrepresentation • small populations

Ge ne tic d rif t Before: 8 RR 8 rr

0.50 R 0.50 r

After: 2 RR 6 rr

0.25 R 0.75 r

Ho w do es g en et ic s tru ctu re change ? • mutation • migration • natural selection • genetic drift • non-random mating

cause changes in allele frequencies

Ho w do es g en et ic s tru ctu re change ? • mutation • migration • natural selection

ma ting c ombi nes all eles into g enotyp es

• genetic drift • non -random ma ting

• non-random mating non-random allele combinations

A A A A A a A A a A A 0.8 A 0.8

a 0.2

AA 0.8 x 0.8

aA 0.2 x 0.8

a 0.2 Aa 0.8 x 0.2

aa 0.2 x 0.2

aa x aa

Aa x Aa

aa

1AA:2Aa:1aa allele frequencies: A = 0.8 a = 0.2

genotype frequencies: AA = 0.8 x 0.8 = 0.64 Aa = 2(0.8 x0.2) = 0.32 aa = 0.2 x 0.2 = 0.04

MATERI PRAKTIKUM GENETIKA POPULASI • Buka Buku petunjuk praktikum • Melaksanakan percobaan Persilangan Acak sesuai dengan petunjuk di halaman 4 • Mengisi Lampiran 1 percobaan 1 dan percobaan 2 pada halaman 10

TUGAS PRAKTIKUM DI RUMAH • • • • •

Menjelaskan pelaksanaan percobaan hal 5-8 Tanpa seleksi, halaman 5 Seleksi lengkap halaman 6 Seleksi tidak lengkap halaman 7 Penghanyutan genetik (genetic drift), halaman 8