Dihybrid Cross - Class 10 Science

Mendel Ka Agla Sawaal 🤔

Ek trait (lakshan) ka hisaab toh Mendel ne sulajha liya. Par asli zindagi mein toh jeev mein hazaron trait hote hain. Toh agla sawaal saaf tha:

❓ Kya do alag trait ek doosre se bandhe hue hain, ya wo alag-alag safar karte hain?

Yani — agar koi beej gol aur peela hai, toh kya uske bachchon mein gol hamesha peele ke saath hi aayega? Ya gol beej hara bhi ho sakta hai?

Ye sawaal itna zaroori kyun hai? Kyunki agar trait aapas mein chipke hue hote, toh nayi kism banana lagbhag namumkin ho jaata — aap kabhi ek achha trait lekar doosra kharab trait chhod nahi paate.

🫛 Prayog — Do Trait Ek Saath

Mendel ne beej ke do trait chune:

Trait	Dominant	Recessive
Beej ka aakaar	R — Gol (Round)	r — Jhurriwala (wrinkled)
Beej ka rang	Y — Peela (Yellow)	y — Hara (green)

📋 Cross ka poora safar

P generation: Shuddh gol-peela (RRYY) × shuddh jhurriwala-hara (rryy)

F₁ generation: Saare beej gol aur peele nikle — genotype RrYy. Yahan tak koi hairaani nahi, dono dominant trait dikhe.

F₂ generation: Ab Mendel ne F₁ ko aapas mein cross karaya — RrYy × RrYy. Aur yahin asli kamaal hua.

🎉 F₂ mein chaar tarah ke beej mile — aur do tarah ke beej aise the jo kisi bhi parent mein the hi nahi: gol-hara aur jhurriwala-peela. Inhe recombinants (naye mel) kehte hain.

Yani trait ek doosre se bandhe hue nahi the — wo alag-alag safar kar rahe the!

🔲 16 Khaano Wala Punnett Square

RrYy paudha chaar tarah ke gametes banata hai: RY, Ry, rY, ry. Isiliye square 4×4 = 16 khaano ka hota hai.

Dihybrid cross ka 16-khaana square — 9:3:3:1 ratio, aur beech ke do rang naye mel hain.

💡 16 khaane yaad karne ki zaroorat nahi!

9:3:3:1 ko yaad karne ka aasaan tareeka: har trait alag se 3:1 deta hai. Toh dono ko guna kar do:

Gol : jhurriwala = 3 : 1 aur Peela : hara = 3 : 1
Gol-peela = 3/4 × 3/4 = 9/16
Gol-hara = 3/4 × 1/4 = 3/16
Jhurriwala-peela = 1/4 × 3/4 = 3/16
Jhurriwala-hara = 1/4 × 1/4 = 1/16

Bas! Poora square banaye bina jawab mil gaya. Exam mein ye tareeka bahut samay bachata hai.

📜 Niyam 3 — Law of Independent Assortment

📌 Law of Independent Assortment (independent assortment ka niyam)

Gamete (yugmak) banate waqt ek trait ke allele doosre trait ke allele se bilkul swatantra roop se baante jaate hain. Yani "R kis taraf gaya" isse koi farak nahi padta ki "Y kis taraf gaya".

🎲 Do Sikke Wali Soch

Socho aapke haath mein do sikke hain — ek ₹1 ka, ek ₹5 ka. Aap dono ek saath uchaalte hain.

Kya ₹1 ka head aane se ₹5 ke sikke par koi asar padta hai? Bilkul nahi. Dono apni marzi se girte hain. Isliye chaar mumkin natije barabar aate hain: HH, HT, TH, TT.

Beej ke trait bhi bilkul aise hi hain. "Gol ya jhurriwala" ek sikka hai, "peela ya hara" doosra sikka. Dono ek doosre ki parwah kiye bina gamete mein jaate hain. Isiliye chaar mel milte hain — do puraane aur do bilkul naye.

⚠️ Ek zaroori shart: ye niyam tabhi lagta hai jab dono gene alag-alag chromosome par hon. Mendel bahut khushkismat the — unke saaton trait aise hi nikle. Agar do gene ek hi chromosome par paas-paas hon, toh wo saath chalte hain aur 9:3:3:1 nahi milta. Ise linkage kehte hain, jo Mendel ke baad pata chala.

🌍 Ye Itna Bada Kyun Hai

Independent assortment sirf ek prayog ka nateeja nahi — ye samjhata hai ki duniya mein itni variation (vividhata) aayi kahan se.

🔢 Ginti Kar Ke Dekho

Insaan mein 23 jodi chromosome hote hain. Gamete banate waqt har jodi se koi ek chromosome swatantra roop se chunna jaata hai.

Toh kitne alag tarah ke gametes ban sakte hain?
2²³ = 83,88,608 (lagbhag 84 lakh!)

Ab ek sperm aur ek ovum milte hain, toh mumkin bachche:
84 lakh × 84 lakh ≈ 70 kharab (7 × 10¹³)

Aur isme crossing over (chromosome ke tukdon ka aadaan-pradaan) abhi joda hi nahi hai! Isiliye ek hi maa-baap ke do bachche kabhi bilkul ek jaise nahi hote — sivaay identical twins ke, jo ek hi zygote se bante hain.

🇮🇳 India Connection

Independent assortment hi wo wajah hai jisse plant breeding mumkin hai. Bharat ki mashhoor Pusa Basmati chawal ki kisme isi par bani hain — vaigyanikon ne basmati ki khushbu ko ek kism se aur zyada paidavar + kam din mein pakna doosri kism se liya, aur dono ko ek hi paudhe mein le aaye.

Agar trait aapas mein bandhe hote, toh aisa jodna namumkin hota — aapko khushbu ke saath purani kism ki kam paidavar bhi majboori mein leni padti. Ek bageeche mein matar ginne wale paadri ka siddhaant aaj bharat ke chawal niryaat ka aadhaar hai.

🧠 Apne Aap Ko Test Karo

Q1. RrYy × RrYy cross ka phenotype ratio kya hai?

Q2. RrYy paudha kitne tarah ke gametes banata hai?

Q3. Dihybrid cross mein "recombinant" kya hote hain?

Q4. Law of Independent Assortment kab laagu NAHI hota?

Q5. F₂ mein "jhurriwala aur hara" beej kitne hisse mein milega?

🔲 Builder ko dihybrid mode par daal kar 16 khaane khud bharte dekho!

Open Punnett Builder →

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