The O blood type is a recessive allele and for the punnett square it will be written as “oo”. Both A and B are considered co-dominant meaning that both the A and the B are present on the females blood cells. Let’s say a female has a blood type of AB and a male has the blood type of O. In the case of incomplete dominance, the flower would blend the two colors to form a pink petals.Īnother example where we can use a punnett square is with blood types. For example, if a flower had the dominant allele of Red and the dominant allele of White the flower petals will show spots of red and white.
In some cases, there are two dominant alleles that are present and causes no blending. Genotype of Parent 1 (blue eyes) and Parent 2 (brown eyes).Īs you can see there is a 50% chance that the homozygous recessive trait of blue eyes will be shown on their next kid, a 50% chance that the heterozygous dominant trait of brown eyes is given on the next offspring, and a 0% chance of a homozygous dominant trait given to the offspring. To begin, write the two letters of the blue-eyed female on top and the two letters of the brown brown-eyed male on the side. Next, we’re just going to match the letters down each square and look at the possible outcomes if they had offspring. In heterozygous alleles, the capital letter will always come first. A Punnet square is a monohybrid cross and is going to be used to compare the traits of the example given earlier.įor traits that have either two capital letters or two lowercase letters are known as a homozygous trait and for traits that have alternating letters are known as heterozygous traits. For the example, assume that the male has the “Bb”.Ī monohybrid cross is a cross between two organisms with different variations of one trait. The reason why brown eyes can be represented as “Bb” is that the capital “B” is dominant over the lowercase “b”. Therefore, if a female has blue eyes they can be represented by “bb” and if a male has brown eyes this can be represented as “BB” or “Bb”.
For example, blue eyes are a recessive trait and brown eyes are a dominant trait. Dominant alleles are represented by capital letters and recessive alleles are represented by lowercase letters. A dominant allele is one that will be more overpowering than another allele and a recessive allele is an allele that can be overpowered by a dominant allele. With alleles, there are two main types of alleles that are essential. An allele is a pair of genes on a chromosome that determine a hereditary trait. Genes are used to pass traits from parent to offspring. If it is was “X” and “X” this set would belong to a female.Įach human cell has 23 pairs of chromosomes and each chromosome consists of hundreds of thousands of different genes. The “Y” and the “X” chromosome determine that this set of chromosomes belongs to a male. There are 23 pairs of chromosomes in the body.
#RECESSIVE AND DOMINANT TRAITS HOW TO#
Before talking about how to use a Punnett square, the next important topic is alleles and the different types of alleles. Scientists use this as a way to predict a trait or genotype that comes from two different people or organisms. Know how to use a Punnett Square to predict inheritance for a monohybrid cross.Ī Punnett square is a grid formed by 4 squares to form a larger square.