Pehle Shabd Seekh Lo 📖
Aage badhne se pehle 6 shabd samajh lena zaroori hai. Ek baar ye clear ho gaye toh poora chapter aasaan lagega — warna sab gadbad ho jaayega.
| Shabd | Matlab | Udaharan |
|---|---|---|
| Gene | DNA ka wo tukda jo ek trait (lakshan) ka nirdesh rakhta hai | Lambai ka gene |
| Allele | Ek hi gene ke alag-alag roop | T (lamba) aur t (chhota) |
| Dominant | Jo trait dikh jaata hai — bade akshar se | T |
| Recessive | Jo chhup jaata hai — chhote akshar se | t |
| Genotype | Andar ke allele ka jodha (jo likha hai) | TT, Tt ya tt |
| Phenotype | Bahar se jo dikhta hai | Lamba ya chhota |
📌 Sabse zaroori baat: har jeev mein har gene ki DO copies hoti hain — ek maa se, ek pita se. Isiliye genotype hamesha do akshar ka hota hai: TT, Tt ya tt. Kabhi ek akshar akela nahi likhte.
Jab dono allele same hon (TT ya tt) — use homozygous (shuddh) kehte hain. Jab dono alag hon (Tt) — use heterozygous (sankar) kehte hain. "Homo" = same, "hetero" = alag. Mendel ki "pure line" ka matlab hi tha homozygous.
🔲 Punnett Square — Sabse Kaam Ka Auzaar
Punnett square ek chhota sa table hai jisme hum saare mumkin bachche dikhate hain. Banane ka tareeka bilkul seedha hai:
Step 1. Dono parents ka genotype likho. Maan lo dono
Tt × Tt hain.
Step 2. Har parent se gametes nikaalo — gamete (yugmak) mein hamesha
sirf ek allele jaata hai. Tt se do tarah ke gametes banenge: T aur
t.
Step 3. Ek parent ke gametes upar likho, doosre ke baayen taraf.
Step 4. Har khaane mein upar wala + baayen wala allele mila do. Bas — ho gaya!
📌 Ab samajh aaya na ki F2 mein chhota trait wapas kaise aaya? Kyunki Tt paudhe ke andar t allele chhupa baitha tha. Jab do Tt mile aur dono ne t gamete diya — tt ban gaya aur chhota trait phir dikh gaya.
📜 Mendel Ke Do Niyam
📌 Niyam 1 — Law of Dominance (dominance ka niyam)
Jab do alag allele saath hon (Tt), toh sirf dominant wala dikhta hai. Recessive
chhupa rehta hai, par khatam nahi hota — wo agli peedhi mein ja sakta hai.
📌 Niyam 2 — Law of Segregation (segregation ka niyam)
Gamete banate waqt do allele alag ho jaate hain, aur har gamete mein
sirf ek allele jaata hai. Yahi wajah hai ki Tt se aadhe gametes T aur aadhe t hote
hain.
Ye niyam hamesha sach hai — koi apwaad nahi. Isliye ise Mendel ka sabse mazboot
niyam maana jaata hai.
Ye ek probability (sambhavna) hai, guarantee nahi — bilkul sikke ki tarah. Sikka 4
baar uchaalne par hamesha 2 head aur 2 tail nahi aate. Par 1000 baar uchaalo toh lagbhag aadhe-aadhe
aa hi jaate hain.
Isiliye Mendel ne hazaron paudhe ginne zaroori samjhe. Unke asli aankde the 787 :
277 = 2.84 : 1 — theek 3 nahi, par kaafi kareeb. Agar wo sirf 8 paudhe ginte toh shayad kuch samajh
hi nahi aata.
🕵️ Test Cross — Chhupa Hua Genotype Pakdo
Ek asli samasya socho: aapke saamne ek lamba paudha hai. Wo TT hai ya Tt? Bahar se dono bilkul ek jaise dikhte hain! Toh pata kaise karein?
Jawab: use recessive (tt) paudhe se cross karo. Isi ko test cross kehte hain.
Bharat ke beej banane wale kendra (jaise ICAR aur rajya ke krishi vishwavidyalaya)
aaj bhi test cross ka istemaal karte hain. Kisan ko shuddh (homozygous) beej dena
zaroori hai — kyunki sankar beej se agli fasal mein trait bikhar jaate hain aur
khet mein kuch paudhe achhe, kuch kharab nikalte hain.
Isi wajah se kisanon ko har saal naya hybrid beej khareedna padta hai — kyunki
hybrid (F1) beej se ugi fasal ke beej F2 hote hain, aur unme 3:1 wala bikhraav
aa jaata hai. Ye sirf company ki chaal nahi, seedha Mendel ka niyam hai.
👥 Insaanon Mein Bhi Wahi Niyam
Mendel ne matar par kaam kiya, par yahi niyam humpar bhi lagte hain. Kuch aasaan udaharan:
| Trait | Dominant | Recessive |
|---|---|---|
| Kaan ki lau (earlobe) | Latakti hui | Chipki hui |
| Gaal ka gadda (dimple) | Hai | Nahi hai |
| Jeebh mod'na (tongue rolling) | Mod sakte hain | Nahi mod sakte |
| Baalon ki hairline | Widow's peak (V shape) | Seedhi |
Sawaal: Ravi aur uski patni Meena dono ke gaal par gadda (dimple) hai, par dono
heterozygous (Dd) hain. Unke bachche ke gaal par gadda hone ki probability kitni hai?
Hal: Cross hai Dd × Dd.
Gametes: Ravi se D ya d, Meena se D ya d.
Mumkin bachche: DD, Dd, Dd, dd
Jinke gadda hoga: DD, Dd, Dd = 3 mein se 4
Jawab: Gadda hone ki probability = 3/4 = 75%, aur bina gadda =
1/4 = 25%.
Dhyaan do: ye har bachche ke liye alag-alag 75% hai. Agar pehla
bachcha bina gadde ka paida hua, toh doosre ke liye phir bhi 75% hi rahega — probability
"yaad" nahi rakhti.
🩺 Recessive rog aur India: kuch bimariyan recessive hoti hain — jaise
sickle cell anaemia aur thalassaemia. Inme bimari tabhi hoti hai
jab bachche ko dono parents se kharab allele mile. Jinke paas sirf ek kharab allele
ho unhe carrier kehte hain — wo bilkul theek rehte hain par allele aage bhej sakte
hain.
Isiliye bahut kareebi rishtedaaron mein shaadi se khatra badh jaata hai — kyunki
ek hi parivaar mein wahi carrier allele hone ki probability zyada hoti hai. Bharat ke kai ilaakon mein
shaadi se pehle muft thalassaemia jaanch ki suvidha hai — ye jaanch karwana samajhdari
hai, sharm ki baat nahi.
🧠 Apne Aap Ko Test Karo
🔲 Punnett Square Builder mein apna cross chalao aur ratio turant dekho!
Open Punnett Builder →