I. IVIUC TIEU 1. Kien thiirc
- HS giai thfch dugc tai sao Menden lai suy ra dugc quy luat cac cap alen phan li ddc lap nhau trong qua trinh hinh thanh giao tfl.
- Bie't van dung quy luat xac sudt de du doan kdt qua lai.
- HS bidt each suy luan ra kidu gen cua sinh vat dua tren ket qua phan li kieu hinh cua cac phep lai.
- HS neu dugc cdng thflc tdng qudt vd ti le phan li giao tfl, ti le kieu gen, kieu hinh trong cac phep lai nhieu cap tfnh trang.
- Giai thfch dugc co sd te' bao hgc cua quy luat phan li ddc lap.
2. KTnang
Ren mdt sd ki nang:
- Phan tfch, suy luan, khdi quat.
- Van dung If thuyet, todn hgc giai thfch kdt qua thf nghiem.
II. CHUAN B!
- Tranh hinh SGK phdng to.
- Bang 9 trang 40.
Thong tin bo sung:
Quy luat thfl ba cua Menden la quy luat di truyen dgc lap cdc tfnh trang dugc Menden neu ra dua tren su nghien cflu ve ddi sau cua cac kieu lai kep. O thi nghiem lai dau cd 2 tfnh trang (H.vang - tron, H.xanh - nhan, kf hieu A,a,B,b). F2 cho ti le 9:3:3:1. Nhu vay d F2 ngodi cac hat mang td hgp tfnh trang dac trung cho dang xudt phdt cdn xuat hien cdc hat mang td hgp tinh trang mdi, cd nghia la xay ra sir tai td hgp cdc tfnh trang cua dang xudt phat.
Dua vao su phan tfch chi tidt kieu lai nay va mdt loat kieu lai kep tuong tu Menden da kdt luain rdng cdc ydu td A,B cung nhu a, b d con lai AaBb khi tao cac td bdo sinh due thi phan bd ve cdc td bao nay mdt each hodn toan ddc lap ddi vdi nhau va cho cac td hgp khdc nhau vdi tan sd nhu nhau AB = Ab = aB = ab. Su td hgp cac giao tfl due va cdi trong cac phep lai xay ra mdt each hoan toan ngdu nhien vi the khi lai gifla 2 ca the Fl cd the bieu didn bdng cdng thflc sd hoc
(AB + Ab + aB + ab) x (AB +Ab + aB + ab) =
hoan toan phu hgp vdi tuong quan tim dugc trong thuc nghiem 9 A - B - 3 A - b b 3 a a B - laabb
9 vang tron : 3 xanh tran : 3 vang nhan : 1 xanh nhan.
Tdng quat
P: AABBCCDDeex aaBBccddEE Fl AaBbCcDdEe x AaBbCcDdEe
F2 (A + af (B + b)' (C + c)' (D + d)' (E + e)'
Tren CO sd phan tfch cac kieu phep lai Menden da phat bidu quy luat thfl ba cua di truyen nhu sau: " Cac ddi sau cua nhflng con lai cd mang trong minh mdt sd tfnh trang khac nhau, la thanh vien cua mdt day td hgp cd lien quan vdi cac day phat trien cua tflng ddi tfnh trang klhdc nhau. Didu dd chflng td hoat ddng cua mdi ddi tfnh trang trong di truydn ddc lap vdi cac ddi khdc d ca hai cay xudt phat"
III. HOAT DONG DAY - HOC 1. Kiem tra
- Trinh bay thf nghiem lai dau Ha Lan vdi mgt tfnh trang, tfl dd ddn den hinh thdnh hgc thuyet khoa hgc eua Menden.
- Giai thfch co sd td bdo hgc ciia quy luat phan li.
2. Trong tam
Lam sang td each thflc Menden van dung quy luat xdc suat de phat hien suf phan li ddc lap cua cac cap alen ra sao. Ngoai ra gido vien cdn giup HS hieu ro CO sd td bao hgc cua quy luat phan li ddc lap.
3. Bai mdi
GV ddn ddt: Tfl kdt qua phep lai mgt tfnh trang Menden tidp tue thf nghiem vdi hai, nhidu cap tfnh trang dng da giai thfch ket qua nhu the nao?
Hogt dpng 1
TIM HIEU THI NGHlfeM LAI HAI TINH TRANG Muc tieu:
- HS vidt duge so dd tdm tdt thf nghiem.
- Giai thfch duge ti le phan li kidu hinh, kidu gen bdng quy luat xac suat.
Hogt dpng cda GV - GV neu yeu cdu:
+ Tdm tdt thf nghiem lai hai tfnh trang cua Menden.
+ Nhan xet kdt qua.
- GV nhan xet, danh gia va giup HS hodn thien kie'n thflc.
Hogt dpng cda HS - HS nghien cflu SGK trang 38.
- Vidt so dd lai.
- Suy luan vd su phan li kidu hinh, phan li cap alen trong qua trinh hinh thanh giao tfl.
- Dai dien HS vidt tren bang.
- Ldp nhan xet bd sung.
Npi dung
* Thi nghiem
Pt/c H. vang, tron x H. xanh, nhan Fl: 100% hat vang, tron Fl tu thu pha'n
F2: 315 hat vang, tron 108 hat vang, nhan 101 hat xanh, tron 32 hat xanh, nhan ti le: 9 : 3 : 3 : 1
* Nhan xet:
- F2: xuat hien 2 td hgp kieu hinh khac bd me (bidn di td hgp).
- Xet rieng tflng cap tfnh trang (Mau sdc, dang vd, hat) ddu cd ti le 3:1.
- Cdc cap nhan to di truydn quy dinh cac tfnh trang khac nhau phan li ddc lap trong qua trinh hinh thanh giao tu.
Hogt dpng cda GV Hogt dpng cua HS Noi dung - GV hdi: Vi sao chi
dua tren su phan li kidu hinh d F2 Menden lai suy ra dugc cdc cap alen quy dinh cac tfnh trang phan li ddc lap trong qua trinh hinh thanh giao tfl?
- GV neu vdn de:
Dua vao dau ma Menden cd the di ddn ke't luan cac cap nhan to di truydn trong thf nghiem tren lai phan li ddc lap trong qua trinh hinh thanh giao tfl?
- GV ggi y:
+ Sfl dung toan xac sudt thd'ng ke ldp 11.
+ Tfnh sd kieu hinh trdi vd cac tfnh trang d ddi con.
+ Tinh so kieu hinh ddng trgi va ddng lan d ddi con.
- GV nhan xet, ddnh gia.
- GV giup HS hieu each van dung toan xac suat de tfnh todn sd lieu.
- HS thao luan nhdm va tra ldi dugc.
+ Ddi vdi mdi tfnh trang thi ti le phan phan li kieu hinh la 3:1.
+ Ti le 9: 3:3: 1 la tfch cua t i l e (3:1) X (3:1).
+ Chflng td cdc cap alen phan li ddc lap nhau.
- HS trao ddi nhdm van dung todn xac sudt de tfnh dugc.
+ Sd ca the con cd kidu hinh ddng trdi ve cac
Hogt dpng cda GV Hogt dpng cua HS Npi dung
- GV hdi: Quy luat phan li ddc lap cua Menden diing trong nhiing dieu kien nao?
- GV nhan xet, danh gia va giup HS hoan thien kidn thflc.
tfnh trang bang sd con cd kieu hinh ddng lan vd cac tinh trang (1/16).
+ Sd ca the con cd kidu hinh trdi ve cdc tfnh trang la 9/16.
+ HS nhan xet: Ket qua tfnh xac sudt phu hgp vdi kdt qua d bang F2 trang 39.
- HS van dung kidn thflc sinh hgc 9 va cac kdt qua d quy luat 1 va 2 cua Menden de tra ldi - Ldp thao luan ->
thdng nha't y kidn.
Kdt qua:
Ti le phan li kidu hinh d F2.
9/16 vang tron (A -B).
3/16 vang nhan (A - bb) 3/16 xanh tron (aaB-).
1/16 xanh nhan (aabb)
Didu kien nghiem dung quy luat phan li ddc lap - Bd me di jjigp tfl ve ca 2 cap gen.
- Tfnh trang trdi hoan toan.
- Sd lugng cd the con lai ldn.
- HS bidt khai quat kien thflc de hinh thanh cdng thflc di xac dinh kieu gen, kieu hinh d the' he sau.
Hogt dpng cda GV Hogt dpng cda HS Npi dung - GV dua cau hdi ddn
ddt:
+ Tai sao trong phep lai cua minh Meden lai sfl dung ddng thudn chung?
+ Viec Menden tidn hanh rdt nhieu thf nghiem lai (thuan, nghich) cd lgi nhu thd nao?
+ Cac cap alen phan li ddc lap da tao ra rat nhidu bidn di td hgp, dieu dd cd y nghia gi?
- HS thao luan nhdm, van dung kidn thflc de tra ldi.
- Yeu cdu neu dugc:
+ Co the thudn chung cd kidu gen ddng nhat, thd he Fl khdng bi phan tinh.
+ Menden tidn hanh lai nhidu thf nghiem de kiem tra, kiem nghiem gia thuyet. Con lai nhidu de phan tich so sanh ket qua va tim ra quy luat.
+ Du doan su phan li d cac the he.
Hogt dpng cua GV Hogt dpng cda HS Npi dung
- GV nhan xet, ddnh gid va giup HS hoan thien kidn thflc (phan biet dugc y nghia thuc tidn va y nghia If luan cua quy luat).
+ Tao ngudn gen phong phu cho tidn hod.
- Dai dien nhdm tra ldi -^ HS nhan xet.
* Y nghia If luan:
- Cdc cap alen phan li dgc lap thi qua trinh sinh san hflu tfnh se tao ra sd lugng ldn bidn di td hgp lam nguyen lieu eho qud trinh tidn hod, dd cung la nguyen nhan lam cho sinh vat ngay cdng da dang phong phu.
- Sinh vat cd nhidu kha nang thfch nghi vdi didu kien mdi trudng sdng thudng xuyen thay ddi.
* Y nghia thuc tidn:
- Neu bidt cac gen quy dinh tfnh trang phan li ddc lap thi du dodn dugc ket qua phan li kieu hinh d ddi sau.
- Tfl su da dang cua sinh vat giup con ngudi dd tim ra nhung tfnh trang cd lgi cho minh.
- Nhd lai gidng cd thd td hgp lai cac gen dd tao ra nhidu gidng mdi cd nang sudt cao.
Hogt dpng cda GV - GV yeu cdu HS thuc hien lenh T d muc III trang 40.
- GV nhan xet, danh gid.
- GV cd the cho bai tap de yeu cdu HS dp dung cdng thflc tdng quat.
Hogt dpng cda HS - HS nghien cflu bang 9 trang 40.
- Nhan biet quy luat vd sd cap di hgp vdi sd loai kidu gen, kidu hinh.
- HS cd the minh boa bdng kdt qua d phep lai
1,2 tinh trang cua Menden.
- HS vidt cdng thflc len bang -^ ldp nhan xet.
Npi dung
Tdng qudt:
- n la sd cap gen di hgp.
- Sd lugng cac loai giao tfl 2"
- Sd lugng cac loai kidu hinh 2"
- Sd loai kieu hinh 2".
- T i l e kieu hinh (3+1)"
- Sd loai td hgp F2 (3+1)".
4. Kiem tra danh gia
- GV yeu cdu HS tdm tdt kien thflc cua bai hgc.
- GV cho HS lam bdi tap trdc nghiem.
Cau 1. Trudng hgp nao sau day ddi con cd ti le kidu gen bang ti le kieu hinh a) Trgi hoan toan c) Phan li ddc lap
b) Trgi khdng hoan toan d) Phan li
Cau 2. Didu kien quan trgng nhdt de quy luat phan li ddc lap nghiem dung la
a) P. thudn chung
b) Mdt gen quy dinh mdt tinh trang tuong fltig c) Trdi - lan hoan toan
d) Mdi gen quy dinh mdt tfnh trang tuong phan ndm tren nhiing cap NST tuong ddng khdc nhau
Cau 3. Co thd mang kidu gen AaBbDdEeFf khi giam phan cho sd loai giao tfl la
a: 4; b - 8; c: 16; d: 32
C^u 4. Cho cd the mang gen AabbDDEeFf tu thu phan thi so td hgp giao tfl tdi da la:
a: 32; b: 64; c: 128; d: 256 5. Dan do
- Hgc bai, tra ldi cau hdi SGK.
- On tap kidn thflc vd gen, alen.
Bai 10
TlTdNG TAG GEN