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All 10 Flashcards — Genetics vocabulary & alleles
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Question
Define a gene.
Answer
A **length of DNA that codes for one characteristic** (e.g. the gene for stem length).
Question
Define an allele.
Answer
One particular **version of a gene** (e.g. a 'tall' allele and a 'short' allele).
Question
Define genotype.
Answer
The **alleles an organism carries** for a gene — written as a pair of letters, e.g. **Tt**.
Question
Define phenotype.
Answer
The **observable characteristic** an organism shows, produced by its genotype (e.g. 'tall').
Question
What is a dominant allele, and how is it written?
Answer
An allele whose effect **shows with only one copy**; written as a **capital letter** (e.g. T).
Question
What is a recessive allele, and how is it written?
Answer
An allele whose effect **shows only with two copies**; written as a **small letter** (e.g. t).
Question
What does homozygous mean? Give examples.
Answer
Having **two of the same allele** for a gene — e.g. **TT** (homozygous dominant) or **tt** (homozygous recessive).
Question
What does heterozygous mean? Give an example.
Answer
Having **two different alleles** for a gene — e.g. **Tt**.
Question
Why is a recessive allele hidden in a heterozygote?
Answer
The **dominant allele is expressed and masks** the recessive one, so the recessive characteristic is not shown.
Question
When does a recessive phenotype appear?
Answer
Only in a **homozygous-recessive** organism (e.g. tt) — one with **no dominant allele** to mask the recessive one.
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Inheritance
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