Genotype — Definition & Overview

What's Genotype?

Genotype is the genetic makeup of an organism. It's basically which alleles an organism has for a specific gene or trait. This is what causes genetic variations.

You can think of it as the letters or alleles we use to describe a gene. So, for a specific trait, it would be something like homozygous recessive or codominant.

Let's take a look at the picture below. It shows a cross between two pea plants. One plant has the genotype YY (homozygous dominant) with a yellow pod color. The other is yy with a green pod color. When crossed, the offspring are all heterozygous Yy with yellow pods (F$_1$). The offspring of F$_1$ are crossed with each other, and the results (F$_2$) are shown in a Punnett square. Here, we can see that YY and Yy plants are yellow, while only yy plants are green. This example shows us how an organism's genotype leads to its phenotype.

P.S. Here's a trick for remembering these terms:

Pheno kinda sounds like physical. So, pheno-type = physical-type

Geno kinda sounds like gene. So, geno-type = gene-type

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Genotype}}$ : The genetic makeup of an organism

$\color{#8925AE}{\text{Phenotype}}$ : The physical characteristics of an organism

$\color{#8925AE}{\text{Dominant}}$ : The stronger of two expressed genes

$\color{#8925AE}{\text{Recessive}}$ : The weaker of two expressed genes. Only shown if a gene is homozygous recessive

$\color{#8925AE}{\text{Heterozygous}}$ : Two different kinds of allele, one dominant and one recessive

$\color{#8925AE}{\text{Homozygous}}$ : Two of the same type of allele, both dominant or both recessive

$\color{#8925AE}{\text{Punnet Square}}$ : A method of determining the odds of which traits the offspring of two organisms will inherit

(Video) Genotype vs. Phenotype | Understanding Alleles

by 2 Minute Classroom

A genotype refers to all the genes that a single organism possesses. When studying genetics, the word is often used to talk about the set of genes for a specific trait. This video by 2 Minute Classroom talks about the differences between the terms genotype and phenotype.

For example, let's look at the inheritance pattern of eye color. We might refer to the genotype as the alleles someone has for the gene that determines eye color.

The alleles determine the phenotype an organism will have. For example, a dominant allele could code for brown eyes, while a recessive allele could code for blue eyes. Genetic engineering takes advantage of this relationship by editing the genotype to reach a goal phenotype.

Definition of Genotype

An organism's genotype is its unique set of genes. You can't see it from the outside, at least not without some nifty scientific equipment. The exact code of your genes can be determined by DNA sequencing or genome sequencing. The genotype (along with environmental factors) determines the phenotype, which is an organism's observable traits. Examples of phenotypes include things like hair color and body shape.