1. Allele Frequency
In the previous tutorial, we introduced some basic population genetics concepts, including gene pool, allele, and fixed alleles.
Allele frequency is another key concept in population genetics. An allele is an alternative version of a gene. Allele frequency is how common an allele is in a gene pool. It’s usually stated as a decimal or a percentage.
1.a. Counting Alleles
Here’s an example. The table below represents the alleles for one gene in a population of 20 mice. In this population, we’re going to look at two phenotypes: albino (white, with no pigmentation), and normal (pigmented). Two alleles control this phenotype: “A” codes for normal color, and “a” codes for albino coloration.
|
|
|
| aa | Aa | AA | AA | aa |
| AA | aa | Aa | Aa | AA |
| AA | aa | AA | AA | aa |
| Aa | Aa | aa | Aa | aa |
To find the frequency of the “a” allele, start by counting each “a” allele within this gene pool. If an individual’s genotype is “aa” then count two “a” alleles. If the individual is “Aa,” then count one “a” allele. In other words, in the first row, you’d count a total of five “a” alleles.
Go ahead and count up all the “a” alleles in each row of the gene pool. Drag the correct number into the column on the right. Then drag the total into the lower right.
[qwiz style = “border: 2px solid black;” qrecord_id=”sciencemusicvideosMeister1961-Pop-gen: Counting Alleles Exercise 1″]
[h]Counting alleles
[q labels = “top”]
| aa | Aa | AA | AA | aa | ___ |
| AA | aa | Aa | Aa | AA | ___ |
| AA | aa | AA | AA | aa | ___ |
| Aa | Aa | aa | Aa | aa | ___ |
| Total of “a” alleles in this population | ___ | ||||
[l]1
[fx] No, that’s not correct. Please try again.
[f*] Correct!
[l]2
[fx] No. Please try again.
[f*] Excellent!
[l]3
[fx] No, that’s not correct. Please try again.
[f*] Great!
[l]4
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]5
[fx] No, that’s not correct. Please try again.
[f*] Excellent!
[l]6
[fx] No, that’s not correct. Please try again.
[f*] Great!
[l]7
[fx] No. Please try again.
[f*] Excellent!
[l]8
[fx] No. Please try again.
[f*] Great!
[l]9
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]10
[fx] No. Please try again.
[f*] Good!
[l]11
[fx] No. Please try again.
[f*] Good!
[l]12
[fx] No. Please try again.
[f*] Correct!
[l]15
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]20
[fx] No, that’s not correct. Please try again.
[f*] Great!
[/qwiz]
1.b. Figuring out allele frequencies
To figure out the frequency of “a”, take the number of “a” alleles, and divide by the total number of alleles for this gene. Since there are 20 individuals, there are a total of 40 alleles. 20/40 = ½ or 0.5 or 50%.
Here are a few questions to check to see if you’re getting this.
[qwiz random = “true”;style = “border: 3px solid black;” qrecord_id=”sciencemusicvideosMeister1961-Pop-gen: Allele Frequency”]
[h]Allele frequency
[i]
|
|
[q]In this gene pool, the frequency of “a”, expressed as a fraction, is
| aa | aa | AA | Aa | aa |
| AA | aa | aa | Aa | aa |
[c]MTAvMjA=[Qq]
[c]MTQv MjA=[Qq]
[c]Ni8yMA==[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuIEZyb20geW91ciBhbnN3ZXIsIEkmIzgyMTc7bSBndWVzc2luZyB0aGF0IHlvdSBqdXN0IGNvdW50ZWQgaW5kaXZpZHVhbHMgd2hvIGFyZSAmIzgyMjA7YWEuJiM4MjIxOyBZb3UgaGF2ZSB0byBjb3VudCB0aGUgYWxsZWxlcyBpbiB0aGUgaGV0ZXJvenlnb3RlcywgdG9vLg==[Qq]
[f]TmljZSBqb2IuIFRoZXJlIGFyZSAxNCAmIzgyMjA7YSYjODIyMTsgYWxsZWxlcywgc28gdGhlIGZyZXF1ZW5jeSBvZiAmIzgyMjA7YSYjODIyMTsgaXMgMTQvMjAuIE9mIGNvdXJzZSwgdGhhdCYjODIxNztzIGJlc3QgcmVkdWNlZCB0byA3LzEwLCBidXQgdGhhdCB3YXNuJiM4MjE3O3QgYW4gb3B0aW9uJiM4MjMwOw==[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuIEZyb20geW91ciBhbnN3ZXIsIEkmIzgyMTc7bSBndWVzc2luZyB0aGF0IHlvdSBjb3VudGVkIHRoZSAmIzgyMjA7QSYjODIyMTsgYWxsZWxlIGluc3RlYWQu
Cg==[Qq]
[q]In this gene pool, the frequency of “a”, expressed as a percentage is
| aa | aa | AA | Aa | aa |
| AA | aa | aa | Aa | aa |
[c]MzAl[Qq]
[c]NTAl[Qq]
[c]Nz Al[Qq]
[c]ODAl[Qq]
[c]OTAl[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]RXhjZWxsZW50LiBUaGVyZSBhcmUgMTQgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIG91dCBvZiBhIHRvdGFsIG9mIDIwIGFsbGVsZXMuIDE0LzIwID0gNzAl[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu
Cg==[Qq]
[q]In this gene pool, the frequency of “A”, expressed as a percentage is
| aa | aa | AA | Aa | aa |
| AA | aa | aa | Aa | aa |
[c]Mz Al[Qq]
[c]NTAl[Qq]
[c]NzAl[Qq]
[c]ODAl[Qq]
[c]OTAl[Qq]
[f]RXhjZWxsZW50LiBUaGVyZSBhcmUgNsKgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIG91dCBvZiBhIHRvdGFsIG9mIDIwIGFsbGVsZXMuIDYvMjAgPSAzMCU=[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgJS4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu
Cg==[Qq]
[q]In this gene pool, the frequency of “A”, expressed as a decimal is
| aa | aa | AA | Aa | aa |
| AA | aa | aa | Aa | aa |
[c]MC4y[Qq]
[c]MC 4z[Qq]
[c]MC41[Qq]
[c]MC43[Qq]
[c]MC45[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgZGVjaW1hbC4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]WWVzLiBUaGVyZSBhcmUgNiAmIzgyMjA7QSYjODIyMTsgYWxsZWxlcywgb3V0IG9mIGEgdG90YWwgb2YgMjAgYWxsZWxlcy4gNi8yMCA9IDAuMw==[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgZGVjaW1hbC4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgZGVjaW1hbC4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[f]Tm8uIFlvdSBoYXZlIHRvIGNvdW50IGFsbCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMsIGFuZCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMuwqBDb252ZXJ0IHRvIGEgZGVjaW1hbC4gTWFrZSBzdXJlIHlvdSBjb3VudCB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMu[Qq]
[/qwiz]
2. Allele frequency case study: The Peppered Moth
Let’s apply the idea of allele frequency to a famous case study of evolutionary biology: the peppered moth. This moth has two forms: mostly light-colored, with specks of black (which is where the “peppered” part of the name comes from) and a much darker form. The allele for dark coloration is dominant.
The allele frequency for this coloration gene varies in different populations and has also changed over time. In the mid-1800s, in moth populations that lived in forests where tree trunks were covered with white-colored lichens, dark moths were rare (2% of the population), with 98% of the moths having the typical peppered form.
Once you know the frequency of each phenotype, you can use a formula to calculate the allele frequencies (we’ll learn about this formula in the next tutorial in this series). Using that formula, you can determine that the frequency of the recessive allele (for light coloration) was about 99%, while the frequency of the dominant allele was about 1%.
The frequency of the dominant allele was so rare because it produced a phenotype that, in certain forests, was deadly. It’s not that the allele made the moths unhealthy. Rather, it was all about camouflage. The peppered moth, when it’s not flying, rests on the trunks of trees. Here’s what light and dark-colored moths look like on a light-colored tree. If you were a bird, which color moth would be easier for you to find?
Over time, mostly as a result of industrial pollution that killed the lichens and covered the tree trunks with dark soot, the population (and its gene pool) changed. By 1895, 95% of the moths were dark-colored. That means that the frequency of the alleles had shifted: the recessive allele had fallen to just over 2% frequency, while the dominant allele was now at 98% frequency.
3. Misconception Alert! “Dominant Allele” does not mean “Most Common Allele”
The case of the Peppered moth allows us to demolish a misconception about genes and populations: the false idea that dominant alleles, because they’re dominant, must be common. Intuitively, it makes sense: if these alleles are dominant, why don’t they come to dominate? However, this intuition is wrong. What we’ll see is that the frequency of an allele has nothing to do with whether it is dominant or recessive.
Read below, dragging in the correct term as needed
[qwiz style=”width: 600px; border: 1px solid black;” qrecord_id=”sciencemusicvideosMeister1961-Pop-gen: Dominant Alleles Misconception Alert”]
[h]Misconception Alert: Dominant Alleles
[i]
[q labels = “top”]
Let’s start by looking at some data about diseases caused by dominant alleles. One such disease is Achondroplasia: it’s a form of dwarfism. If you inherit the gene for this condition, you’ll be born with extremely _______ limbs. The condition is rare: According to the US national library of medicine, (http://ghr.nlm.nih.gov/condition/achondroplasia) the condition occurs in between 1/15,000 and 1/40,000 newborns. So, it’s caused by a dominant allele, and it’s _____.
The same is true of Huntington’s disease, a disease of the nervous system, also caused by a dominant allele. Huntington’s is extremely ______: it shows up in 3 to 7 of every 100,000 births in people of European ancestry. It’s even less common in some other populations, including people of Japanese, Chinese, and African descent.
[l]short
[fx] No. Please try again.
[f*] Great!
[l]rare
[fx] No. Please try again.
[f*] Great!
[q labels= “top”]
Similarly, think of other phenotypes which in a genetic sense, are recessive. If you went up to Norway or Sweden, you’d see a lot of people with blond ______ and blue eyes. While both of these phenotypes are caused by multiple genes, the dominant alleles for darker hair and brown eyes are both somewhat rare in these populations, while the __________ alleles (for blond hair and blue eyes) are much more common.
The confusion might come from the word “dominant.” When we think of something that’s dominant, we think that it should be able to overcome something less dominant. But while that works in the genotype and phenotype of a single person, with dominant alleles __________ recessive alleles, it doesn’t work in a population’s gene pool.
We can extend this idea a little further. Dominant alleles, as we’ve seen, won’t increase in __________. And unless certain processes are at work in a gene pool, any allele’s frequency will stay about the same. If allele frequencies are changing, then some evolutionary process is at work in that population. In an upcoming tutorial in this series, we’ll start looking at what those processes are.
[l]frequency
[fx] No. Please try again.
[f*] Correct!
[l]hair
[fx] No. Please try again.
[f*] Good!
[l]masking
[fx] No, that’s not correct. Please try again.
[f*] Correct!
[l]recessive
[fx] No, that’s not correct. Please try again.
[f*] Great!
[/qwiz]
4. Allele frequencies and fixed alleles in dogs
For a final example, let’s think about allele frequencies in dogs. If you buy a dog with a pedigree (a dog of a known breed), then you’re buying a certain look and disposition. You can count on this because dog breeds are controlled populations where the gene pool is closely guarded by dog owners who care about the breed. In other words, if you buy a Rhodesian Ridgeback, you can be assured that your new puppy had two parents who were both Rhodesian Ridgebacks. For all the traits that define the breed, these dogs are completely homozygous. Most of the defining alleles, in other words, are fixed and would have an allele frequency of 1.0 (or 100%) in these very artificial gene pools.
If your preference is for mutts, then your dog is probably heterozygous for many genes. As a result, when you breed two mutts, the offspring’s appearance is much less predictable.
5. Checking Understanding
Got it? In this module, we’ve examined the concept of allele frequency.
If you feel that you understand this concept well, take this brief quiz. If not, carefully re-read the material above, and then take the quiz.
[qwiz style=”width: 600px; min-height: 0px; border: 3px solid black;” qrecord_id=”sciencemusicvideosMeister1961-Pop-gen: Allele Frequencies, Checking Understanding”]
[h]Quiz: Allele frequencies in populations
[q topic= “determining_allele_frequency”]Allele frequency is
[c]IHRoZSB0b3RhbCBudW1iZXIgb2YgaG9tb3p5Z291cyBpbmRpdmlkdWFscyBmb3VuZCBpbiBhIHBvcHVsYXRpb27igJlzIGdlbmUgcG9vbC4=[Qq]
[c]IFRoZSBudW1iZXIgb2YgZG9taW5hbnQgYWxsZWxlcyBmb3VuZCBpbiBhIGdlbmUgcG9vbC4=[Qq]
[c]IHRoZSBwZXJjZW50YWdlIG9yIGZyYWN0aW9uIG9mIGFsbCBhbGxlbGVzIGZvciBhIH NwZWNpZmljIGdlbmUgcmVwcmVzZW50ZWQgYnkgb25lIHNwZWNpZmljIGFsbGVsZS4=[Qq]
[f]IE5vLiBNZWFzdXJpbmcgdGhlIG51bWJlciBvZiBob21venlnb3RlcyB3aWxsIG1vdmUgeW91IHRvd2FyZCBmaWd1cmluZyBvdXQgdGhlIGFsbGVsZSBmcmVxdWVuY3ksIGJ1dCB0aGF04oCZcyBub3QgdGhlIGJlc3QgYW5zd2VyLiBBbGxlbGUgZnJlcXVlbmN5IGlzIHNpbXBseSBob3cgY29tbW9uIGFuIGFsbGVsZSBpcyBpbiBhIGdlbmUgcG9vbC4=[Qq]
[f]IE5vLiBNZWFzdXJpbmcgdGhlIG51bWJlciBvZiBkb21pbmFudCB3aWxsIG1vdmUgeW91IHZlcnkgY2xvc2UgdG93YXJkIGZpZ3VyaW5nIG91dCB0aGUgYWxsZWxlIGZyZXF1ZW5jeSwgYnV0IHRoYXTigJlzIG5vdCB0aGUgYmVzdCBhbnN3ZXIuIEFsbGVsZSBmcmVxdWVuY3kgaXMgc2ltcGx5IGhvdyBjb21tb24gYW4gYWxsZWxlIGlzIGluIGEgZ2VuZSBwb29sLg==[Qq]
[f]IFllcy4gQWxsZWxlIGZyZXF1ZW5jeSBpcyBzaW1wbHkgaG93IGNvbW1vbiBhbiBhbGxlbGUgaXMgaW4gYSBnZW5lIHBvb2wsIHJlcHJlc2VudGVkIGJ5IGEgcGVyY2VudGFnZSBvciBhIGZyYWN0aW9uLg==
Cg==[Qq]
[q topic= “determining_allele_frequency”]The letters below represent the alleles for a single gene that controls fur color in a population of mice. In this population, the frequency of the ‘a’ allele is
| aa | Aa | aa | Aa |
| Aa | aa | aa | aa |
| aa | Aa | aa | Aa |
[c]IDUwJQ==[Qq]
[c]IDE5LzI0LCBv ciA3OS4xNiU=[Qq]
[c]IDcvMTIgb3IgNTguMzMl[Qq]
[f]IE5vLiBJdCBsb29rcyBsaWtlIHlvdSBjb3VudGVkIG9ubHkgdGhlICYjODIyMDthJiM4MjIxOyBhbGxlbGUgaW4gaG9tb3p5Z291cyByZWNlc3NpdmVzICgmIzgyMjA7YWEmIzgyMjE7KS4gVG8gZ2V0IHRoZSBwcm9wZXIgZnJlcXVlbmN5LCB5b3UgaGF2ZSB0byBjb3VudCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZSBpbiB0aGUgaGV0ZXJvenlnb3RlcywgdG9vLiBSZWNvdW50IGFsbCB0aGUgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZXMsIGFuZCBkaXZpZGUgYnkgdGhlIHRvdGFsIG51bWJlciBvZiBhbGxlbGVzIGluIHRoaXMgcG9wdWxhdGlvbiAoMjQpLg==[Qq]
[f]IEV4YWN0bHkuIFRoZXJlIGFyZSAxOSAmIzgyMjA7YSYjODIyMTsgYWxsZWxlcyBvdXQgb2YgYSB0b3RhbCBvZiAyNCBhbGxlbGVzIGluIHRoaXMgcG9wdWxhdGlvbi4gVGhhdCBtZWFucyB0aGUgZnJlcXVlbmN5IGlzIDE5LzI0LCBvciA3OS4xNiU=[Qq]
[f]IE5vLiA3LzEyIGlzIHRoZSBmcmVxdWVuY3kgb2YgaG9tb3p5Z291cyByZWNlc3NpdmVzwqAgKCYjODIyMDthYSYjODIyMTspIGluIHRoaXMgcG9wdWxhdGlvbiBvZiAxMi4gVGhlIGZyZXF1ZW5jeSBvZiAmIzgyMjA7YSYjODIyMTsgaXMgZm91bmQgYnkgY291bnRpbmcgZXZlcnkgJiM4MjIwO2EmIzgyMjE7IGFsbGVsZSBhbmQgZGl2aWRpbmcgYnkgdGhlIHRvdGFsIG51bWJlciBvZiBhbGxlbGVzIGluIHRoZSBwb3B1bGF0aW9uICgyNCku
Cg==[Qq]
[q topic= “determining_allele_frequency”]The letters below represent the alleles for a single gene that controls fur color in a population of mice. In this population, the frequency of the dominant allele is
| aa | Aa | aa | Aa |
| Aa | aa | aa | aa |
| aa | Aa | aa | Aa |
[c]IDUvMTIsIG9yIDQxJQ==[Qq]
[c]IDIwLzI0LCBvciA4My4zMyU=[Qq]
[c]IDUvMjQsIG9yIG Fib3V0IDIxJQ==[Qq]
[f]IE5vLiA1LzEyIGlzIHRoZSBmcmVxdWVuY3kgb2YgaW5kaXZpZHVhbHMgd2hvIGhhdmUgdGhlIGRvbWluYW50IHBoZW5vdHlwZS4gVG8gZmluZCB0aGUgZnJlcXVlbmN5IG9mIHRoZSBkb21pbmFudCBhbGxlbGUgKCYjODIyMDtBJiM4MjIxOyksIHlvdSBoYXZlIHRvIGNvdW50IGV2ZXJ5ICYjODIyMDtBJiM4MjIxOyBhbGxlbGUsIGFuZCB0aGVuIGRpdmlkZSBpdCBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMgaW4gdGhlIHBvcHVsYXRpb24gKDI0KS4=[Qq]
[f]IE5vLiBJIHRoaW5rIHRoYXQgeW91IGNvbmZ1c2VkIHdoaWNoIGFsbGVsZSBpcyB0aGUgZG9taW5hbnQgYWxsZWxlIGFuZCB3aGljaCBvbmUgaXMgcmVjZXNzaXZlLiAmIzgyMjA7QSYjODIyMTsgaXMgdGhlIGRvbWluYW50IGFsbGVsZS4gQ291bnQgYWxsIHRoZSAmIzgyMjA7QSYjODIyMTtzLCBhbmQgZGl2aWRlIGJ5IHRoZSB0b3RhbCBudW1iZXIgb2YgYWxsZWxlcyB0byBnZXQgdGhlIGFuc3dlci4=[Qq]
[f]IFBlcmZlY3QuIFRoZXJlIGFyZSA1ICYjODIyMDtBJiM4MjIxOyBhbGxlbGVzLCBvdXQgb2YgYSB0b3RhbCBvZiAyNCBhbGxlbGVzIGluIHRoaXMgcG9wdWxhdGlvbi4gVGhhdCBtYWtlcyB0aGUgZnJlcXVlbmN5IG9mwqAgJiM4MjIwO0EmIzgyMjE7wqA1LzI0LCBvciBhYm91dCAyMSU=
Cg==[Qq]
[q topic= “determining_allele_frequency”]The letters below represent the alleles for a single gene that controls fur color in a population of mice. In this population, the frequency of the recessive allele is
| Aa | aa | aa | Aa | aa | aa | Aa | aa |
| Aa | aa | AA | Aa | Aa | aa | Aa | aa |
[c]IDIz[Qq]
[c]IDIzLzMyLCBv ciA3MS45JS4=[Qq]
[c]IDE2LzMyIG9yIDUwJQ==[Qq]
[f]IE5vLiBJdCBsb29rcyBsaWtlIHlvdSBjb3VudGVkIHRoZSBudW1iZXIgb2Yg4oCYYeKAmSBhbGxlbGVzIGNvcnJlY3RseSwgd2hpY2ggaXMgYSBnb29kIHN0YXJ0LiBCdXQg4oCYZnJlcXVlbmN54oCZIGlzIGFib3V0IHRoZSBwcm9wb3J0aW9uIG9mIGEgc3BlY2lmaWMgYWxsZWxlIGluIGEgZ2VuZSBwb29sLg==wqAgTm93LCBkaXZpZGUgdGhlIG51bWJlciBvZiByZWNlc3NpdmUgYWxsZWxlcyBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMgdG8gZ2V0IHRoZSBmcmVxdWVuY3kgb2YgJiM4MjIwO2EuJiM4MjIxOw==[Qq]
[f]IENvcnJlY3QuIFRoZXJlIGFyZSAyMyAmIzgyMjA7YSYjODIyMTsgYWxsZWxlcywgYW5kIDMyIGFsbGVsZXMgaW4gdG90YWwuIFRoZSBmcmVxdWVuY3kgb2YgJiM4MjIwO2EmIzgyMjE7IGluIHRoaXMgZ2VuZSBwb29sIGlzIDIzLzMyLCBvciA3MS45JQ==[Qq]
[f]IE5vLiBJdCBsb29rcyBsaWtlIHlvdSBmb3Jnb3QgdG8gY291bnQgdGhlICYjODIyMDthJiM4MjIxO2FsbGVsZXMgaW4gdGhlIGhldGVyb3p5Z290ZXMuIENvdW50IEFMTCBvZiB0aGUg4oCYYeKAmSBhbGxlbGVzLCB0aGVuIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMgKDI0KQ==
Cg==[Qq]
[q topic= “determining_allele_frequency”]The letters below represent the alleles for a single gene that controls fur color in a population of mice. In this population, the frequency of the dominant allele is
| Aa | aa | aa | Aa | aa | aa | Aa | aa |
| Aa | aa | AA | Aa | Aa | aa | Aa | aa |
[c]IDUwJQ==[Qq]
[c]IDIzLzMyLCBvciA3MS45JS4=[Qq]
[c]IDkvMzIgb3 IgMjguMSU=[Qq]
[f]IE5vLiBJdCBsb29rcyBsaWtlIHlvdSBjb3VudGVkIHRoZSBmcmVxdWVuY3kgb2YgaW5kaXZpZHVhbHMgd2l0aCBhIGRvbWluYW50IHBoZW5vdHlwZS4gV2hhdCB5b3UgbmVlZCB0byBkbyBpcyBjb3VudCBldmVyeSBpbnN0YW5jZSBvZiB0aGUgJiM4MjIwO0EmIzgyMjE7IGFsbGVsZSwgYW5kIGRpdmlkZSBieSB0aGUgdG90YWwgbnVtYmVyIG9mIGFsbGVsZXMgaW4gdGhlIHBvcHVsYXRpb24u[Qq]
[f]IE5vLiBZb3UgZmlndXJlZCBvdXQgdGhlIGZyZXF1ZW5jeSBvZiB0aGUgcmVjZXNzaXZlIGFsbGVsZSwgJiM4MjIwO2EuJiM4MjIxOyBOb3cgdXNlIHRoZSBzYW1lIG1ldGhvZCB0byBmaWd1cmUgb3V0IHRoZSBmcmVxdWVuY3kgb2YgdGhlIGRvbWluYW50IGFsbGVsZS4=[Qq]
[f]IFllcy4gVGhlcmUgYXJlIDkg4oCYQeKAmSBhbGxlbGVzLCBhbmQgMzIgYWxsZWxlcyBpbiB0b3RhbCwgZm9yIGEgZnJlcXVlbmN5IG9mIDI4LjEl
Cg==[Qq]
[q topic= “determining_allele_frequency”]If an allele is fixed in a population, then its frequency would be
[c]IDAsIG9yIDAl[Qq]
[c]IDAuNSwgb3IgNTAl[Qq]
[c]IDEuMCwgb3 IgMTAwJQ==[Qq]
[f]IE5vLiBJZiBhbiBhbGxlbGUgaXMgZml4ZWQsIHRoZW4gaXTigJlzIHRoZSBvbmx5IGFsbGVsZSBmb3IgdGhhdCBnZW5lIGluIHRoZSBwb3B1bGF0aW9uLiBBbiBhbGxlbGUgd2hvc2UgZnJlcXVlbmN5IGlzIDAgZG9lc27igJl0IGV4aXN0IGluIHRoZSBwb3B1bGF0aW9uLiBOZXh0IHRpbWUsIGNob29zZSBhbm90aGVyIGFuc3dlci4=[Qq]
[f]IE5vLiBJZiBhbiBhbGxlbGUgaXMgZml4ZWQsIHRoZW4gaXTigJlzIHRoZSBvbmx5IGFsbGVsZSBmb3IgdGhhdCBnZW5lIGluIHRoZSBwb3B1bGF0aW9uLiBBbiBhbGxlbGUgd2hvc2UgZnJlcXVlbmN5IGlzIDAuNSB3b3VsZCBtYWtlIHVwIGhhbGYgb2YgdGhlIGFsbGVsZXMgaW4gYSBwb3B1bGF0aW9uIGZvciBhIHNwZWNpZmljIGdlbmUuIE5leHQgdGltZSwgY2hvb3NlIGFub3RoZXIgYW5zd2VyLg==[Qq]
[f]IEV4YWN0bHkuIElmIGFuIGFsbGVsZSBpcyBmaXhlZCwgdGhlbiBpdOKAmXMgdGhlIG9ubHkgYWxsZWxlIGZvciB0aGF0IGdlbmUgaW4gdGhlIGdlbmUgcG9vbC4=wqAgaXRzIGZyZXF1ZW5jeSB3b3VsZCBiZSAxLjAsIG9yIDEwMCUu
Cg==[Qq]
[q topic= “determining_allele_frequency”]Which of the following is true about purebred dogs?
[c]IEZvciBtb3N0IG9mIHRoZSBnZW5lcyBpbiB0aGUgZG9nIGdlbm9tZSwgcHVyZWJyZWQgZG9ncyBhcmUgbW9yZSBoZXRlcm96eWdvdXMgdGhhbiBtdXR0cy4=[Qq]
[c]IFRoZXkgaGF2ZSBtYW55IG1vcmUgZml4 ZWQgYWxsZWxlcyB0aGFuIG11dHRzLg==[Qq]
[f]IE5vLiBQdXJlYnJlZCBkb2dzIGhhdmUgYmVlbiBicmVkIGZvciB0aGUgcHJlZGljdGFibGUgdHJhaXRzIG9mIHRoZWlyIGJyZWVkLiBGb3IgdGhlc2UgdHJhaXRzLCBtZW1iZXJzIG9mIGEgcHVyZWJyZWQgYnJlZWQgYXJlIG1vc3RseSBob21venlnb3VzLg==[Qq]
[f]IFllcy4gUHVyZWJyZWQgZG9ncyBoYXZlLCB0aHJvdWdoIHRoZSBwcm9jZXNzIG9mIHNlbGVjdGl2ZSBicmVlZGluZywgYmVjb21lIGV4dHJlbWVseSBob21venlnb3VzIGF0IG1hbnkgYWxsZWxlcywgbGVhZGluZyB0byBtYW55IGZpeGVkIGFsbGVsZXMgd2l0aGluIHRoZWlyIHBvcHVsYXRpb25zLg==
Cg==[Qq]
[q topic= “determining_allele_frequency”]A group of breeders is trying to create a new breed of dog. As they do, which of the following would you expect to be true?
[c]IEZvciBlYWNoIHRyYWl0IHRoYXQgdGhlIGJyZWVkZXJzIGFyZSB0cnlpbmcgdG8gZGVmaW5lLCB0aGUgZnJl cXVlbmN5IG9mIHRoZSBhbGxlbGVzIGZvciB0aGF0IHRyYWl0IHNob3VsZCBiZSBzdGVhZGlseSByaXNpbmcu[Qq]
[c]IEZvciBlYWNoIHRyYWl0IHRoYXQgdGhlIGJyZWVkZXJzIGFyZSB0cnlpbmcgdG8gZGVmaW5lLCB0aGUgZnJlcXVlbmN5IG9mIHRoZSBhbGxlbGVzIGZvciB0aGF0IHRyYWl0IHNob3VsZCBiZSBzdGVhZGlseSBmYWxsaW5nLg==[Qq]
[f]IFllcy4gQnJlZWRlcnMgd2lsbCBzZWxlY3QgZm9yIHRoZSBuZXcgcGhlbm90eXBlIHRoZXnigJlyZSB0cnlpbmcgdG8gY3JlYXRlLiBBcyB0aGV5IGRvLCB0aGUgZnJlcXVlbmN5IG9mIHRoZSBhbGxlbGVzIGZvciB0aG9zZSBwaGVub3R5cGVzIHdpbGwgc3RlYWRpbHkgcmlzZS4=[Qq]
[f]IE5vLiBJdOKAmXMgdGhlIG9wcG9zaXRlLiBCcmVlZGVycyB3aWxsIHNlbGVjdCBmb3IgdGhlIG5ldyBwaGVub3R5cGUgdGhleeKAmXJlIHRyeWluZyB0byBjcmVhdGUuIEFzIHRoZXkgZG8sIHdoYXQgd2lsbCBoYXBwZW4gdG8gdGhlIGZyZXF1ZW5jeSBvZiB0aGUgYWxsZWxlcyBmb3IgdGhvc2UgdHJhaXRzPw==
Cg==[Qq]
[q topic= “natural_selection_in_gene_pools”]True or false? In any population, the most common allele is the dominant allele.
[c]VHJ1ZQ==[Qq]
[c]RmFs c2U=[Qq]
[f]IE5vLiBUaGUgZnJlcXVlbmN5IG9mIGFuIGFsbGVsZSBoYXMgbm90aGluZyB0byBkbyB3aXRoIHdoZXRoZXIgaXTigJlzIGRvbWluYW50IG9yIHJlY2Vzc2l2ZS4=wqAgSnVzdCB0aGluayBhYm91dCB0aGUgZmFjdCB0aGF0IHNvbWUgZGlzZWFzZS1yZWxhdGVkIGFsbGVsZXMgYXJlIGRvbWluYW50LCB5ZXQgcmFyZSAobGlrZSB0aGUgYWxsZWxlIGZvciBhY2hvbmRyb3BsYXN0aWMgZHdhcmZpc20pLiBPciB0aGUgZmFjdCB0aGF0IGluIHRoZSBTY2FuZGluYXZpYW4gY291bnRyaWVzLCBzb21lIHBoZW5vdHlwZXMgY29udHJvbGxlZCBieSByZWNlc3NpdmUgYWxsZWxlcyAoYmx1ZSBleWVzLCBmb3IgZXhhbXBsZSkgYXJlIHRoZSBtb3N0IGNvbW1vbi4=[Qq]
[f]IENvcnJlY3QuIFRoZSBmcmVxdWVuY3kgb2YgYW4gYWxsZWxlIGhhcyBub3RoaW5nIHRvIGRvIHdpdGggd2hldGhlciBpdOKAmXMgZG9taW5hbnQgb3IgcmVjZXNzaXZlLiBSZWNlc3NpdmUgYWxsZWxlcyBjYW4gYmUgbW9yZSBjb21tb24gdGhhbiBkb21pbmFudCBhbGxlbGVzLiBJdCBhbGwgZGVwZW5kcyBvbiB0aGUgYWxsZWxlLCB0aGUgZXZvbHV0aW9uYXJ5IGhpc3Rvcnkgb2YgdGhlIHBvcHVsYXRpb24sIGFuZCBzZWxlY3RpdmUgcHJlc3N1cmVzIGZyb20gdGhlIGVudmlyb25tZW50Lg==[Qq]
[x]
[restart]
[/qwiz]
Links
At this point, there are two pathways. Choose the one for your course.
- COLLEGE OR AP BIO: If you’re following our AP Bio or College Bio sequence, proceed to The Hardy Weinberg Equation (the next tutorial in this series)
- HIGH SCHOOL: If you’re following our high school sequence, proceed to our tutorial about Natural Selection in Gene Pools.