What is $\text{Mendelian}$ $\text{Genetics}$? 🧑🔬
**$\text{Mendelian}$ $\text{Genetics}$** is the foundation of modern genetics, based on the work of **$\text{Gregor}$ $\text{Mendel}$** and his experiments with $\text{pea}$ $\text{plants}$. He discovered that traits are passed down in discrete units (which we now call **$\text{genes}$**), and these units separate and combine in predictable ways.
Key $\text{Vocabulary}$ and $\text{Concepts}$ 🔑
$\text{Allele}$
A variation of a gene (e.g., the $\text{allele}$ for tall vs. short pea plants).
$\text{Genotype}$
The genetic makeup; the actual $\text{alleles}$ inherited ($\text{e.g.,} \text{ TT}, \text{ Tt}, \text{ or } \text{tt}$).
$\text{Phenotype}$
The physical appearance resulting from the $\text{genotype}$ ($\text{e.g.,}$ $\text{tall}$ $\text{plant}$ or $\text{short}$ $\text{plant}$).
$\text{Homozygous}$ / $\text{Heterozygous}$
$\text{Homo}$ ($\text{TT}$ or $\text{tt}$) means the $\text{alleles}$ are the $\text{same}$. $\text{Hetero}$ ($\text{Tt}$) means they are $\text{different}$.
Mendel's $\text{Three}$ $\text{Laws}$ 📜
1. $\text{Law}$ of $\text{Dominance}$
When an organism is **$\text{heterozygous}$** ($\text{Tt}$), the **$\text{dominant}$ $\text{allele}$** ($\text{T}$) will mask, or cover up, the expression of the **$\text{recessive}$ $\text{allele}$** ($\text{t}$).
2. $\text{Law}$ of $\text{Segregation}$
During $\text{gamete}$ ($\text{sex}$ $\text{cell}$) formation, the two $\text{alleles}$ for a trait separate from each other so that each $\text{gamete}$ receives only one $\text{allele}$.
3. $\text{Law}$ of $\text{Independent}$ $\text{Assortment}$
Genes for different traits can segregate ($\text{separate}$) independently during the formation of $\text{gametes}$. ($\text{e.g.,}$ $\text{the}$ $\text{allele}$ $\text{for}$ $\text{height}$ $\text{separates}$ $\text{independently}$ $\text{from}$ $\text{the}$ $\text{allele}$ $\text{for}$ $\text{seed}$ $\text{color}$).
Interactive $\text{Punnett}$ $\text{Square}$ ($\text{Monohybrid}$ $\text{Cross}$) 📊
Use the $\text{Punnett}$ $\text{Square}$ below to calculate the genetic probability of offspring. **$\text{Tall}$** ($\text{T}$) is $\text{dominant}$ to **$\text{short}$** ($\text{t}$).
Probabilities (Click a square to check its $\text{genotype}$!)
Genotype $\text{Ratio}$: 1 $\text{TT}$ : 2 $\text{Tt}$ : 1 $\text{tt}$
Phenotype $\text{Ratio}$: 3 $\text{Tall}$ : 1 $\text{Short}$ (75% $\text{Tall}$, 25% $\text{Short}$)
Practice Problems ($\text{Genotype}$ $\text{Check}$)
For the $\text{genotype}$ shown, what is the correct term to describe it?
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