GENETIC DRIFT

GENETIC DRIFTAmalia Setyaningsih (3425120273 )Sri Yuliasih Wiyati (3425120272)

Mechanisms of EvolutionThere are several:Natural SelectionGene FlowGenetic DriftMutationsNon-random Mating

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Adalah perubahan dalam frekuensi suatu varian gen (alel) dalam suatu populasi akibat random sampling. (Ridley, 2004)Genetic Drift

Neutral TheoryTeori evolusi molekuler netral mengungkapkan perubahan evolusioner dan polimorfisme pada tingkat molekul karena terjadinya mutasi dan pergeseran gen secara acak. (Kimura, Raja, dan Jukes, 1968-1969)

Generation 1p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 CRCRCRCRCRCWCWCWCRCRCRCWCRCRCRCWCRCRCRCW

5Figure 23.9 Genetic drift.

5plantsleaveoff-springGeneration 1p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 CRCRCRCRCRCWCWCWCRCRCRCWCRCRCRCWCRCRCRCWCRCRCWCWCRCWCRCRCWCWCRCWCWCWCRCRCRCWCRCWGeneration 2p = 0.5 q = 0.5

6Figure 23.9 Genetic drift.

5plantsleaveoff-springGeneration 1p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 CRCRCRCRCRCWCWCWCRCRCRCWCRCRCRCWCRCRCRCWCRCRCWCWCRCWCRCRCWCWCRCWCWCWCRCRCRCWCRCWGeneration 2p = 0.5 q = 0.5 2plantsleaveoff-springCRCRCRCRCRCRCRCRCRCRCRCRCRCRCRCRCRCRCRCRGeneration 3p = 1.0 q = 0.0

7Figure 23.9 Genetic drift.

Penyebab Genetic Drift

Founder EffectFounder effect mengurangi variasi genetik dari populasi asli. Terjadi ketika sebuah koloni baru dimulai oleh beberapa anggota dari populasi asli.

Founder effect terjadi ketika sejumlah kecil orang dari satu populasi menemukan populasi baru yang reproduktif terisolasi dari yang asli.

Migration from EnglandPada tahun 1814, 15 orang Inggris menjajah Tristan da Cunha. Satu di antara penduduk koloni awal itu membawa suatu alel resesif retinitis pigmentosa.Frekuensi alel ini jauh lebih tinggi di Tristan da Cunha dibandingkan dengan frekuensi pada populasi di daerah asal.Studi Kasus Founder Effect1. Retinitis Pigmentosa

Microevolution10/16/2014G. Podgorski, Biol. 101010

Di antara 240 keturunan mereka yang tinggal di pulau ini, 4 orang buta oleh penyakit dan 9 lainnya adalah carrier.

Microevolution10/16/2014G. Podgorski, Biol. 101011

2. Amish child di kota Pennysylvania

Distribusi alel golongan darah O di penduduk asli dunia (pemukiman asli)

3. Distribusi Golongan Darah

14South & Central American Indians were nearly 100% type O for the ABO blood system. Since nothing in nature seems to strongly select for or against this trait, it is likely that most of these people are descendants of a small band of closely related "founders" who also shared this blood type

Distribution of blood types

Distribusi alel golongan darah B pada populasi asli dunia (migrasi asli)

15The global frequency patterns of the type B blood allele: Note that it is highest in central Asia and lowest in the Americas and Australia. However, there are relatively high frequency pockets in Africa as well. Overall in the world, B is the rarest ABO blood allele.

Out of Africa

Likely migration paths of humans out of AfricaMany patterns of human traits reflect this migration50,000ya10-20,000ya10-20,000ya

16Migration PathsAccording to the "Out of Africa" theory, modern humans appeared as a single African species nearly 100,000 years ago, then spread throughout the world (K.Wong, Is Out of Africa Going Out the Door?, Scientific American 281(2), August 1999).

Bottleneck Effect

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when populations are reduced to near extinction but then expand to large numbers. e.g. Northern elephant seals

Genetic driftNatural selectionGenetic Drift vs Natural Selection

Hasil dari genetic drift, jika terisolasi akan menyebabkan inbreeding dan perkawinan yang tidak acak. Di mana hasil dari inbreeding akan mengalami kepunahan dan hasil perkawinan yang tidak acak akan survive dan mengalami EVOLUSI.Genetic Drift dalam Evolusi