A mix-up in a hospital ward caused a mother with O and MN blood types to think that a baby given

A mix-up in a hospital ward caused a mother with O and MN...

A mix-up in a hospital ward caused a mother with $\mathrm{O}$ and $\mathrm{MN}$ blood types to think that a baby given to her really belonged to someone else. Tests in the hospital showed that the doubting mother was able to taste PTC (see problem 9). The baby given to her had O and MN blood types and had no reaction when the bitter PTC chemical was placed on its tongue. The mother had four other children with the following blood types and tasting abilities for PTC: 1. type $A$ and $M N$ blood, taster 2. type $B$ and $N$ blood, nontaster 3. type A and M blood, taster 4. type $A$ and $N$ blood, taster Without knowing the father's blood types and tasting ability, can you determine whether the child is really hers? (Assume that all her children have the same father.)

A mix-up in a hospital ward caused a mother with $\mathrm{O}$ and $\mathrm{MN}$ blood types to think that a baby given to her really belonged to someone else. Tests in the hospital showed that the doubting mother was able to taste PTC (see problem 9). The baby given to her had O and MN blood types and had no reaction when the bitter PTC chemical was placed on its tongue. The mother had four other children with the following blood types and tasting abilities for PTC:
1. type $A$ and $M N$ blood, taster
2. type $B$ and $N$ blood, nontaster
3. type A and M blood, taster
4. type $A$ and $N$ blood, taster
Without knowing the father's blood types and tasting ability, can you determine whether the child is really hers? (Assume that all her children have the same father.)

Key Concepts

PTC Tasting Genetics

PTC tasting is a genetic trait determined by a single gene with two alleles, where the tasting allele is dominant over the non-tasting allele. An individual who can taste PTC will have at least one copy of the dominant allele, while only those with two copies of the recessive allele are non-tasters. This trait is a useful genetic marker in studies of inheritance and can be used in combination with other genetic markers to assess or dispute biological relationships.

Genetic Inheritance Patterns (Dominance, Recessiveness, and Codominance)

Understanding genetic inheritance patterns is essential to interpret traits passed from parents to offspring. Traits such as ABO blood type follow dominance and recessiveness rules, while systems like MN exhibit codominance. These basic principles allow predictions about the genotypes and phenotypes that can be produced in specific crosses, which is key when analyzing whether a given child could inherit particular characteristics from their parents.

ABO Blood Group Inheritance

The ABO blood group system is determined by multiple alleles (commonly A, B, and O) with a clear dominance hierarchy: both A and B are dominant over O. This inheritance pattern explains how a parent with a certain type can pass on alleles to produce a range of blood types in their offspring. Knowledge of the ABO system can be used in parentage testing by comparing the expected genotype or phenotype possibilities from the parents to those observed in the child.

MN Blood Group Inheritance

Unlike the ABO system, the MN blood group system is codominant, meaning that both M and N alleles are equally expressed when present. Each individual inherits one allele from each parent, resulting in three possible phenotypes: M, N, or an MN heterozygote. This codominant nature provides additional information when making genetic comparisons among family members, especially useful in cases of dispute in parentage testing or in studies of genetic relatedness.

Transcript

00:01 So we're looking at a mother who thinks that she got the wrong baby, the hospital.

00:09 And the hospital uses a number of indicators to determine if the baby is actually burned.

00:20 The abo shows co -dominence and incomplete dominance.

00:30 We have multiple alleles in human abio blood type.

00:39 Ia and ib show codominence.

00:44 And ia and i -b show complete dominance over little i, which is o.

01:00 So complete dominance and co -dominance.

01:04 This gives us a number of different ways to get to blood type a, b, a -b, and o.

01:13 So we're talking blood type a, you can have capital ia, capital ia, or capital ia little i so there's our complete dominance so those are both these two are both blood type a blood type b we see the same kind of setup here where we have two choices to homozygous ib or heterozygous ib little i type o blood can only be two little eyes because it's recessive blood type ab can only be ia, iab.

02:03 And there's our codominance.

02:06 The other piece that they're using is the m and n blood type.

02:12 These are codominent.

02:14 So i mean they're going to have the m indicator, i'm going to have the n indicator, or i'm going to have mn, which is both.

02:26 And then the last indicator that they're using is tasting of ptc.

02:33 Ptc tasting is dominant.

02:39 So here's a straight dominance and recessiveness.

02:43 And then you're a non -tasteau.

02:46 So with those three things in mind, i, a, i, b, a little i, co -dominance and complete dominance, m and n, which are pro -div, dominant and then ptc, capital t, lowercase t, complete dominance.

03:04 Okay, so let's go look at the mom, has a blood type o, mn, and she has the ability to taste.

03:30 So we know she's a capital t blank as far as we know right now.

03:35 So she's o m -n -t.

03:41 The baby that's given to her is o -m -n, no -taster.

03:52 So right away we can say, well, is that possible? well, with mom, so this is mom, and there's the baby one, we'll call it.

04:04 With these two, it certainly is possible if mom has here, if she has a lowercase t, now, mom could be two uppercase t's, two capital t's, which would be that was impossible.

04:20 But at least for now, we'll just kind of discount that and say, mom is heterozygous, this baby with her as to have impossible.

04:28 Now, we have to look at dad, but we don't have his blood.

04:35 So instead, we have the testing from the other children.

04:40 So this is the baby in question.

04:45 But let's look at her other children.

04:47 So we have child one is blood type a, m, n, and is a taster.

05:02 So we don't, again, we don't know necessarily what the other t is, so let's put a blank there.

05:09 Child 2 is blood type b, n, and n and a non -taster.

05:23 Three is blood type a with m and is a taster...