cho qua trinh thu tinh. ' V i du: Co 10 te bao sinh d u e diTc sd khai cua r u o i gia'm nguyen phan v d i so
ddt bkng nhau tao ra 640 te bao sinh tinh, qua g i a m phan cho cac linh trung binh
thudng, hieu sua't thu tinh cua tinh trilng la 5% cua trtfug la 40%. T i n h : 1) So lu'dng t i n h trung duTdc thu tinh v d i triJng?
2) So'ddt nguyen phan cua m o i te'bao sinh diic sd khai?
3) So lu'dng te' bao sinh tri^ng can co de hoan ta't qua trinh thu tinh?
Hitdngddn ,
1) So lifdng t i n h triing hinh thanh: 640 x 4 = 2560 tinh trung. „ , V d i hieu sua't thu tinh 5% ta tinh dUdc so'tinh triing thu tinh v d i triJng 1^: , V d i hieu sua't thu tinh 5% ta tinh dUdc so'tinh triing thu tinh v d i triJng 1^: ,
2 5 6 0 x 5% = 128 tinh triing.
2) So' ddt nguyen phan cua m o i te bao sinh d u e sd khai diTc gio'ng nhau nen
nioi te'bao sinh d u e sd khai diTc da sinh ra du'dc ^ ^ = 6 4 te'bao sinh tinh.
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Tijf d o suy ra so'ddt nguyen phan cua te'bao sinh d u e diTc 2" = 64 => n = 6 ddt. 3) Theo de bai, hieu sua't thu tinh cua triJng la 40%. D o d o tru-ng hinh thanh la
" " ~ ^ ^ ^ ^ = 320 te' bao triJug. CiJ moi te' bao sinh triJng qua giam phan tao ra 1
'riJfng, nen so' te bao sinh tnJng can c o la 320 te bao.
Ca'm nang ti; 6n va luygn thi Sinh hgc - Phung Duy B6'ng
Loai 6: Xac dinh so l i f d n g NST moi triTdng noi bao can cung cap cho cac te bao thiTc hien nguyen phan v a giam phan. ,»,.,,,, ^
Phu'dng phap giai loai loan nay la a p dung cong thiJc: i ( 1) So' Iifdng NST d d n mdi tu'dng du'cfng can cung cap: (2'' - 1) x 2n.
2) So lu'dng NST d d n mdi hoan toan can cung cap: {2^ - 2) x 2n. (k l a so ddt
nguyen phan, 2n la bo NST lu'dng boi cua loai).
Loai 7: Xac d j n h bp NST lu'dng boi cua loai:
Ap dung cong thiJc: 2n = (So' NST ddn moi tru'dng cung cap) / (2" - 1) Hoac 2n = (So NST d d n xoan ciTc dai)/2. Hoac 2n = So NST trong giao tiif x 2.
B A I T A P VAN D V N G
Bai 1: Mot hdp tiJ cua 1 loai sinh vat sau 7 ddt nguyen phan lien tiep, moi tru'dng noi bao d a cung cap nguyen lieu lu'dng du'dng vdi 1015 ddn. ^ ^
1) Tim bo NST lu'dng boi cua loai.
2) Khi loai do phat sinh giao tu" c6 may loai tinh trung, may loai triJng duTdc
tao ra khac nhau ve nguon go'c NST (khong trao d d i doan v a dot bien)
Bap so:
1) B p N S T 2 n = 8.
2) So' loai giao tuf khac nhau v e nguon goc NST l a 16.
Bai 2: Hai hdp tur cua mot loai nguyen phan lien tiep mot sd ddt, moi tru'dng noi bao da cung ca'p nguyen lieu lu'dng diTdng vdi 22792 NST d d n . Hdp tu' 1 c6 sd
ddt nguyen phan bang - sd^ddt nguyen phan cua hdp i\i 2. 6 k i giffa cua te bao, ngu'di ta dem du'dc 44 NST kep.
1) Tim bo NST lu'dng boi cua loai.
2) So ddt phan bao nguyen phan cija moi hdp
3) So' lu'dng NST ddn mdi hoan toan ma moi tru'dng can cung cap cho moi hdp tiJ thi/c hien cac ddi nguyen phan? tiJ thi/c hien cac ddi nguyen phan?
4) Ne'u trong qua trinh giam phan tao ra giao tuf va thu tinh xily ra binh ihu'dng
thi CO may loai giao tuf va may loai hdp i\i khac nhau ve nguon gd^c NST.
Dap so:
1) B p N S T 2 n = 44.
2) Goi sd^ddt nguyen phan cua hdp tuf 1 la k (k > 0, nguyen) Ihi so'ddt nguyen phan cua hdp tuf 2 la 3k. phan cua hdp tuf 2 la 3k.
22792
Ta CO phu'dng trinh: 2'' +2'^'' = + 2=>k=3=> So ddt nguyen phan cua
44 hdptuf 1 Ia3,hdptur21a9. hdptuf 1 Ia3,hdptur21a9.
3) So' NST ddn mdi hoan loan ma moi tru'dng cung cap ^ f 1'. «• >'S.