Link to Genetics Student Learning Guide

1. Blood type: An Introductory Slideshow

Start by viewing this slideshow.

Note that if you can’t view the slideshow below, don’t worry: it’s all covered below. It’s something in your District’s network settings that’s blocking your view (and as much as I’d like to share this with you, I can’t). Sorry!

2. Reading: Blood Type and blood transfusions

The ABO blood type system is based on glycoproteins (proteins attached to polysaccharides) found on the surface of red blood cells.

ABO_blood_type,-modified
“ABO blood type” by InvictaHOG – via Wikimedia Commons
  • If your red blood cells have the A glycoprotein, your blood type is type A.
  • If you have the B glycoprotein, you’re type B.
  • If you have both glycoproteins, you’re type AB.
  • If you don’t produce either glycoprotein, you’re type O.

The presence or absence of these membrane glycoproteins is of no selective advantage or disadvantage –unless you’re getting a blood transfusion. Here’s how it works.

Our immune system can recognize molecules, and decide if those molecules belong to us, or if they indicate the presence of an infection. Molecules perceived as foreign are known as antigens. In response to an antigen, your immune system will counterattack with proteins called antibodies. One of the effect of antibodies is to create big clumps of invading cells. These clumps are later swallowed up and disposed of by another part of the immune system – white blood cells.

Modified from an upload by Apers0n at en.wikipedia
Clumping of red blood cells (on left). Blood on the right is not clumped. Modified from an upload by Apers0n at en.wikipedia

In the case of the ABO blood type system, this makes certain blood transfusions helpful, and others deadly. If you’re type O, and you receive blood that has the A or B glycoprotein, your immune system will perceive these cells as invaders. The subsequent clumping (called agglutination) causes shock and death.

People with blood type AB have both glycoproteins on their blood cells. As a result, any type of transfused blood (A, B, AB or O) can be received without a reaction.

Having read that, see if you can complete the chart and reading below.

[qwiz qrecord_id=”sciencemusicvideosMeister1961-Blood type, Interactive Reading (genetics)”]

[h]Blood Type, Interactive Reading

[q labels = “right”]If the donor blood will cause clumping in the recipient, put a “yes.” If not, put “no.”

  CLUMPING IN BLOOD RECIPIENT (receiver)?
A B AB O
 BLOOD
DONOR
O  _____  _____  _____  _____
A  _____  _____  _____  _____
B  _____  _____  _____  _____
AB  _____  _____  _____  _____

[l]yes

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]no

[fx] No. Please try again.

[f*] Excellent!

 

[q]Type O is the universal _______. If you’re Type ___, you can give blood to people with type A, B, ____, or O blood. Type AB, by contrast, is the universal __________.

If you’re type A, you can give blood to people with type ___ blood, and people with type AB blood. However, if a person with type A, B, or O blood receives blood from a person with type ____ blood, the result will be _________, and death.

[l]A

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]AB

[fx] No. Please try again.

[f*] Correct!

[l]O

[fx] No, that’s not correct. Please try again.

[f*] Correct!

[l]clumping

[fx] No, that’s not correct. Please try again.

[f*] Good!

[l]donor

[fx] No. Please try again.

[f*] Correct!

[l]recipient

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[/qwiz]

3. The Genetics of ABO Blood Type

The ABO system is under control of a gene found on chromosome 9. Three alleles can be found on the locus for the blood type gene.

  • The A allele codes for the A glycoprotein.
  • The B allele codes for the B glycoprotein.
  • The o allele codes for nothing. (Note that I wrote “o” in lower case on purpose, as we’ll see below).

Three alleles? You might be thinking that we only have two parents. How can you inherit three alleles?”

The answer is that you can’t. As with any system of alleles, in the ABO system any individual can only have two alleles. But in the human population, three alleles exist. Any individual is only going to possess two of those alleles. But there are other people who may have the third allele.

This type of genetic situation is called multiple alleles. And while, based on the genetics that you’ve learned so far, multiple alleles might seem weird or exceptional, it’s actually common (and might, in fact, be the norm). However, in most introductory biology courses, the ABO system is the only multiple allele scenario that you’ll learn about.

In addition to multiple alleles, the ABO system has one more feature that might be new to you. In a typical Mendelian trait, alleles are either dominant or recessive. In a heterozygote, one allele shows up in the phenotype and one is completely masked. But in the ABO system, the A allele and the B allele are co-dominant. That means that both alleles get expressed in the phenotype. That’s what happens if you inherit an A allele and a B allele. You express both genes, and, as a result, your red blood cells will have both the A glycoprotein and the B glycoprotein.

At the same time, both the A allele and the B allele are dominant to the o allele, which is recessive. For example, in a heterozygote who inherits both an A and an o allele, the blood type will be Type A–just as much type A as in an individual who is homozygous A (AA).

Having read what’s above, let’s see if you can complete the chart below:

[qwiz qrecord_id=”sciencemusicvideosMeister1961-Blood Type Genotypes and Phenotypes Table (genetics)”]

[h]Blood Type Genotypes and Phenotypes Table

[q]Use the symbols to complete the chart

Description of Genotype Genotype in symbols Blood Type
Homozygous A __  __ A
Heterozygous A __  __ ___
Homozygous B __  __ ___
Heterozygous B __  __ ___
(same as genotype)  __  __ ___
Homozygous o __  __ ___ 

[l]A

[fx] No. Please try again.

[f*] Correct!

[l]B

[fx] No. Please try again.

[f*] Great!

[l]AB

[fx] No. Please try again.

[f*] Good!

[l]O

[fx] No. Please try again.

[f*] Excellent!

[l]o

[fx] No. Please try again. Remember that lower case o is the allele. O is the blood type.

[f*] Good!

[/qwiz]

4. Extending Your Learning

There’s a lot more to learn about blood type. For example, none of what you read about above deals with the Rh system, which is connected to blood types like A+, B-, O+, etc. To learn more about Blood type and its inheritance, follow these links (or other ones that you find on your own: let me know if you find something good)

Record what you’ve learned in your student learning guide.

5. Solving Blood Type Problems

You solve genetics problems involving blood type in pretty much the same way as you solve any other type of problem. The same six steps I advocated in the last tutorial apply here (click on the link if you need to review).

[qwiz style=”border: 3px solid black;” qrecord_id=”sciencemusicvideosMeister1961-Guided Punnett Square, Blood Type (Genetics)”]

[h]Guided Punnett Squares: ABO Blood Types

[q]A woman who is heterozygous type A has a child with a man who is type O. What are the probably genotypes and phenotypes of the offspring?

Genotypes of the parents

Mother:  ___ ___
Father:   ___ ___

Father
__   __
Mother __ ___  ___ ___  ___
__ ___  ___ ___  ___

Genotype ratio in offspring:
____ AA: ____Ao: ___BB:___ Bo: ___AB: ____oo

Phenotype ratio in offspring:
______ Type A: ____Type B: ____ Type AB: _____Type O

[l]A

[fx] No. Please try again.

[f*] Excellent!

[l]B

[fx] No. Please try again.

[f*] Correct!

[l]o

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]AB

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]O

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]0%

[fx] No. Please try again.

[f*] Great!

[l]25%

[fx] No. Please try again.

[f*] Excellent!

[l]50%

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]75%

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]100%

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[!!!!] Problem 2[/!!!!]

[q]A woman who is heterozygous type A has a child with a man who is heterozygous type B. What are the probably genotypes and phenotypes of the offspring?

Genotypes of the parents

Mother: ___ ___
Father:  ___ ___

Father
 __     __
Mother __ ___  ___ ___  ___
__ ___  ___ ___  ___

Genotype ratio in offspring:

_____ AA: ____Ao: _____ BB: ____Bo:_____ AB: _____oo

Phenotype ratio in offspring:

_____ Type A:_____ Type B:_____ Type AB:_____ Type O

[l]A

[fx] No. Please try again.

[f*] Excellent!

[l]B

[fx] No. Please try again.

[f*] Great!

[l]o

[fx] No. Please try again.

[f*] Excellent!

[l]0%

[fx] No. Please try again.

[f*] Good!

[l]25%

[fx] No, that’s not correct. Please try again.

[f*] Correct!

[l]50%

[fx] No. Please try again.

[f*] Correct!

[l]75%

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]100%

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[x]

[restart]

[/qwiz]

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