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ETD 42 A. Why are colorblind boys more commmon than girls? B. How does this connect to Morgan's Flies?
January 16, 2014 at 7:58am


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Kelli Vetter
January 18, 2014 at 8:24pm

Parent: Kelli explained the why males are more apt to be color blind than females. She explained that the colorblindness is a recessive trait and is carried on the X chromosome and that it is the female gamete that will ultimately decide whether the colorblind trait is passed on.  Since the Y chromosome has no effect on the trait, the XX and XY pairing of a recessive trait is more likely to be passed on to the XY pair. This is like Morgan's flies because the fly had to receive the recessive X-linked trait, which was more likely to occur because the male only needs one of the recessive traits because they only receive one X chromosome.

Student: First, I took a blank piece of paper and I drew the maternal genotype, which was heterozygous for colorblindness, and a paternal genotype which was recessive for colorblindness. I drew this out with a punnett square to show my dad the possible genotypes that the offspring could have. I told my dad that boys were more susceptible of getting the x-linked trait because they only need one of the recessive traits, unlike girls who need two of the recessive traits because they possess the (XX) sex-chromosome. This was like Morgan's flies because the recessive trait was the white eye. More males expressed this trait because the white eye allele lied on the X chromosome, so the males only had to receive one of the recessive X rather than the females who had to receive both recessive X.

Sophie Wulfing
January 21, 2014 at 7:40pm

Parent:  The allele for color-blindness is found on the x-chromosome.  This means girls need to have both parents pass a color-blind allele in order to be color-blind.  Implies Dad is color-blind, and Mom is a carrier.  Boys only inherit color-blindness from their mother, their mother has the only x-Chromosome.

Morgan's flies.  Red is the normal eye; while breeding flies Morgan found a single male with white eyes.  Bred this fly with others, more males inherited white eyes than the ladies.  He realized that some traits (their loci) sit on the sex chromosome.  Ratio of males vs. females can tell if a trait is on the sex chromosome.

Sophie- This is about the only thing I remember form 9th grade science because I found it so interesting. I had to review how to make a punnent square with the X and Y, with wild types. This is also a good reminder to the fact that we inherit many traits, all on different chromosomes, which explains linked, unlinked genes, as well as crossing over

Brett Babbel
January 23, 2014 at 8:08pm

Parent Response: Learned that because guys have a Y chromosome its easier for a guy to inherit colorblindness because they don't have the other X chromosome like females that gives them another chance of getting the dominant gene to prevent the colorblindness. 

student Response: this helped me better understand how some traits and disorders like colorblindness are passed on through the generations. It made me wonder if maybe breast cancer was linked to a gene and was maybe even connected to a sex linked gene because you see a lot more girls with this mutation then in males. And i did some research and found out that although you cant inherit the cancer people with relatives with breast cancer have a much higher chance of getting it in their life. So maybe a gene is passed down that makes it so you are more prone to the the cancer? 

Kevin turek
January 25, 2014 at 9:51am

Parent: I learned that because men have only one x chromosome that they are a lot more likely to get colorblindness because, colorblindness is a sex linked chromosome on the X chromosome. And if a guy gets it on one then he is doomed to be colorblind while females have 2 X's and because of this girls have another chance not to be colorblind. Then Kevin told me that this is just like flies that have white eyes as it seemed mostly males had this weird trait as females would have to get it on both chromosomes and this is highly unlikely.

Student: My mom already knew guys get this trait more but she didn't really understand why. However I seemed to grasp this concept in the midst of explaining it. It made sense once I actually explained it in my own words.

Selena Clem
January 27, 2014 at 9:52pm

Parent: Colorblindness is a sex linked trait, so boys are more likely to have it than girls. If the mother is colorblind and the father isn't then none of the girls will be colorblind, but they will be carriers, while all of the boys will be colorblind because their Y chromosome doesn't counteract the recessive gene of colorblindness. Morgan did a similar experiment involving fruit flies. He test crossed white eyed and red eyed flies and found the white eyes to be sex linked.

Student: The trait for colorblindness is found on the X chromosome. if the mom is colorblind then boys have 100% chance of getting the trait, if mom is a carrier then boys will have a 50% chance of inheriting the trait, it's all dependent on the mom's genotype. Morgan's flies were test crossed for the traits of red eye vs white eye and Morgan found the white eyed trait to be a sex linked gene.

Madison Boggan
January 12, 2015 at 4:51pm

Parent: It is more common for boys to be colorblind because colorblindness is a sex-linked trait. Since the gene is on the X chromosome and it is recessive, it is more common in boys as they only have on x chromosome but girls have two. For a girl to be colorblind both of her x's must carry the colorblind trait as to where only has to inherit one x with the colorblind trait.  Morgan was a scientist who studied genes through studying eye color in flies. 

Student: I told my mom that boys inheriting colorblindness versus a girl is like this: a hungry boy is satisfied with getting only one scoop of ice cream (one X with the colorblind trait) and he will immediately eat the ice cream because he's happy with what he can get. As for a girl, she's more picky and waits until she get's two scoops of her favorite type of ice cream (two X's with the colorblind trait). 

Talesh Patel
January 25, 2015 at 2:57pm

Parent: This was an interesting topic for me because my nephew and cousin are color blind.  Talesh explained that colorblindness is linked to x chromosomes which boys get only one of and so if the chromosome is affected then they will be affected by color blindness.  Girls receive 2 x chromosomes and both must carry of the colorblindness gene to affect girls, and onthe other hand the gene could be recessive and the girl might be a carrier.  Morgan's flies refers a study on linked genes.  Morgan was a scientist who studies fruit flies to find out about parental and recombinant types.  He found Males in the "grandkids" generation had red or white eyes whereas females had only red eyes. 

Student: I told my mom that boys are more likely to be colorblind because they only have one X chromosome. Because the Y doesn’t carry the trait and girls have 2 X chromosomes, girls have to have 2 affected chromosomes in order to be colorblind while boys only need 1. I explained this using a punnett to show the traits. This relates to Morgan’s flies because the X-linked traits were more often expressed in males (white eyes) then females because the females didn’t receive two affected X-chromosomes.

Chloe Hobson
January 25, 2015 at 6:56pm

Student: I explained that colorblindness is a sex-linked trait. It is difficult to have a colorblind female because you need a colorblind dad AND a female carrier as the mom. For a boy, you only need one of these to be true. This relates to Morgan's flies because only males had white eyes. The gene for white eyes was an x-linked gene. 

Parent: I was aware that males were much more likely to be colorblind, but it was interesting to discover the reason behind this. If the mother is a carrier, then 50% of boys  will have color blindness. Males are hemizygous. I learned  how this connects to Morgan and white eyed flies. I now know that a trait as simple as eye color could be sex-linked. 

Veda Ting
January 25, 2015 at 8:26pm

Parent: I learned that males have one X chromosome one Y and females have two X chromosomes. I also learned that colorblindness is sex-linked and recessive and it's linked to the X chromosome. For the girl, the only way that she will be colorblind is if both of her X chromosomes are recessive. Females can also be carriers of the colorblind gene without having it. Males are more likely to have colorblindness because they only have one X chromosome. I learned Morgan was a scientist who studied fruit flies and the sex-linked traits too. 

Student: I told my mom that for colorblindness, the trait is linked with the X chromosome. I then showed her the Punnett squares and compared the chances of getting colorblindness with having the only carriers of the trait, actually having the sex-linked trait, and not having the trait at all. 

Anne Sweeney
January 20, 2016 at 9:22pm

Parent: First of all colorblindness is an x-linked recessive trait which that means that it is sex-linked. Sex-linked is a gene carried with one sex. The mom is a carrier for the trait so when crossed the male is most likely to receive that recessive trait. They only way for the female to be colorblind is if both the mom and dad are colorblind. Anne also explained the connection to Morgan’s flies and how the x-linked recessive trait showed up there too.

Student: It was very beneficial to explain how the x-linked recessive trait worked in this example and was made more clear the more I had to keep re-explaining examples to my mom trying to come up with different analogies for her to understand. I also used the punnett squares to show her where the gene ended up and made someone colorblind or not. The fly connection was easier to explain since it had the same concepts but used differently.

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