What are the phenotypes and genotypes for the ABO blood groups? If both parents are type AB bloo

What are the phenotypes and genotypes for the ABO blood...

Key Concepts

Probability and Expected Ratios

Using principles of probability in combination with Mendelian inheritance, one can predict the proportionate outcomes (expected ratios) of different genotypes and phenotypes based on the parental alleles. This probabilistic approach is essential for understanding how traits, such as blood type, are passed from parents to their children.

Mendelian Inheritance and Punnett Squares

Mendelian inheritance describes the basic principles of genetic transmission, where alleles segregate and combine during reproduction according to predictable patterns. A Punnett square is a visual tool used to predict the possible genetic outcomes of a cross, allowing one to calculate the likelihood of specific genotypes and phenotypes in the offspring.

Dominance and Codominance

The ABO blood system demonstrates both dominance and codominance. The A and B alleles are codominant, meaning that if an individual inherits an A allele from one parent and a B allele from the other, both antigens are expressed, resulting in the AB blood type. In contrast, the O allele is recessive to both A and B, so its effects are only seen when an individual inherits two O alleles.

Alleles

Alleles are different versions of a gene found at the same locus on a chromosome. In the context of the ABO blood group system, there are three key alleles that determine blood type: one for the A antigen, one for the B antigen, and one for the absence of either antigen (often labeled as O). These alleles combine in various ways to form the genetic makeup for an individual's blood type.

Genotype versus Phenotype

The genotype refers to the genetic constitution of an individual, specifically the combination of alleles they carry, while the phenotype is the observable trait that results from this genotype. In the ABO system, different combinations of the alleles (genotypes) correspond to the different blood types (phenotypes) observed.

Transcript

00:01 So when we think about blood type, it's a little bit different because our blood type shows something called co -dominance, meaning that you can have two different alleles, but instead of one allele being dominant over the other allele, both alleles are dominant, and you'll show both traits.

00:18 So what i mean by this is that we really have three combinations, or not three combinations, but three different alleles that you could possibly get.

00:29 You can get a, b, or o.

00:32 O is our classic recessive, meaning that a person will only have o blood type if both alleles they receive from a parent are of o blood type.

00:43 And b show the co -dominence that i was talking about, meaning that if you have an individual who got the a allele from mom and the b allel from dad, their blood type is going to be a -b, not a - or b.

00:58 So that's usually denoted with a little eye like this, and an a for a blood type.

01:08 If both alleles are a blood type, so an individual with only a blood type would look like this.

01:15 An individual with only b blood type would look like this.

01:22 It's a little bit hard to draw, those small bs.

01:24 And an individual with a b blood type would look something like this, where they're showing both alleles as one is not dominant over the other.

01:40 But an individual with o blood type would look like that.

01:45 So they would have the recessive alleles, so recessive trait.

01:50 So for a person, i'm just going to put a and b because it's much easier, who has a .b.

01:58 Blood type and mates with another person who has a .b.

02:03 Blood type.

02:04 What are their kids going to have? what possible combinations, what their children then have? so we're going to draw our prentonit square because it's pretty classic.

02:16 So there is a chance that an individual would purely have a blood type...

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