Practice Flashcards
Flip to reveal answersWhat is a monohybrid cross?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 7 Flashcards — Monohybrid crosses & Punnett grids
Sign up free to track progress and get spaced-repetition review schedules.
Question
What is a monohybrid cross?
Answer
A cross that follows the inheritance of **one gene** (with two alleles) from parents to offspring.
Question
Why does each gamete carry only one allele of a gene?
Answer
Because the two alleles **segregate** during meiosis — one goes into each gamete.
Question
What is the difference between genotype and phenotype?
Answer
**Genotype** = the alleles you carry (e.g. Bb); **phenotype** = the observable characteristic those alleles produce.
Question
What genotype and phenotype ratios come from Bb × Bb?
Answer
Genotype **1 BB : 2 Bb : 1 bb**; phenotype **3 dominant : 1 recessive**.
Question
Two carrier parents — what is the chance of an affected child?
Answer
**1/4 (25%)** each pregnancy, because only the homozygous-recessive (e.g. dd) cell is affected.
Question
Why can two unaffected parents have an affected child?
Answer
The disease allele is **recessive**: both parents are unaffected **carriers** (Dd), and if both pass on d the child is **dd** and affected.
Question
How do you turn a Punnett-grid ratio into a probability?
Answer
Each of the four cells is equally likely, so count the matching cells out of 4 (e.g. **1 in 4 = 1/4 = 25%**).
Read the notes
Full study notes for Monohybrid crosses & Punnett grids
Topic 4.8 hub
Inheritance
More from Topic 4.8
All flashcards in this topic
Biology exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free