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Dihybrid Cross Punnett Squares + MCAT Shortcut (Mendelian Genetics Part 2)
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- Опубликовано: 1 май 2020
- Leah4sci.com/genetics presents: Dihybrid Cross Punnett Squares + MCAT Ratios Shortcut
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In this video you’ll learn how to do a more complex Punnett Square, specifically for a dihybrid cross when following the rules of independent assortment. You’ll learn a MCAT shortcut for calculating the phenotypic ratios of a dihybrid cross that can also be applied to a cross of parents with homozygous dominant or homozygous recessive genotypes.
In this video:
[2:06] Introduction to Dihybrid Cross
[3:05] Wrong Way to do Punnett Square
[6:44] Ratio of Monohybrid & Dihybrid Cross
[9:52] Solving Dihybrid Mathematically
[12:52] Sample Dihybrid Cross Problem
[14:53] Sample Homozygous Recessive Problem #2
Links and Resources Mentioned
MCAT Math: Leah4sci.com/MCATMath
This is Video #2 in the Genetics Series. Catch the entire MCAT Genetics Video Series Along with the Genetics Series Cheat Sheet on my website at leah4sci.com/genetics
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God bless you for uploading a genetics series (one of my worst subjects); please keep them coming!
Thank you Jason! :)
This is what they teach in any of the mcat prep courses (TPR and Kaplan) you’re basically getting it free here thank you Leah!
Idk if you already planned to but could you go over pedigree analysis and determining if it’s autosomal, x linked etc.
Thanks Josh. I plan to do a beginner pedigree video next
Thank you so much Leah for posting this. This helps students like me who can't afford big prep MCAT courses but can still have an excellent instructor like you who clearly knows the MCAT tricks... Thank you for your generosity... Mendelian genetics are not my favorite subject, but you do an excellent job with your explanations and shortcuts!
You're so welcome! And thank you for your kind words!
Thank you so much! I'm not sitting MCAT, but GAMSAT and feel like Mendelian genetics and punnets always come up. This will make it so much easier and waste less time if this topic comes up!
You're very welcome!
WOWWW!! I am literally mind blown. I could not figure out how to do these without wasting a bunch of time. Thank you so so much, Leah! You are a life saver
You're very welcome, I'm glad this cleared it up for you!
Thank you for this! Not studying for the MCAT, but instead the CLEP Natural Sciences exam and this greatly simplified things for me.
Glad to hear it was helpful! You're so welcome.
The funny thing is I’m not here for the MCAT, I’m just here to study for my genetics class exam and found this great shortcut video for ratio & probabilities
Glad it was helpful!
Literally just had a practice question with a dihybrid cross, thank you for this 🙏🏼
Happy to help!
This was beyond helpful. Thanks so much leah!!
You're so welcome!
You are the only reason I got A's in both my Organic Chemistry courses in college! Also, I have always struggled with dihybrid crosses but this was such an amazing explanation and easy way to apply this topic to MCAT questions. Thank you immensely!
You're so very welcome, I'm happy to have helped you in orgo and now in your MCAT prep!
Thank you for doing what no text book can explain. Literally this is what I've been trying to figure out for the last 3 days. Thank you!!!!
You're very welcome! So happy to hear this helped you understand!
thank you!!!, One question on the example 14:56, if we are looking for the percentage of TtBb, since the second gene doesnt contain T or B, it has a 0% chance. So when calculating, we dont include the 0% since 1/2 x 1/2 x 0 x 0 = 0. We just include the 1/2 x 1/2 for the 1st gene.
The example at 14:56 asks for the percentage of offspring that will be homozygous recessive in both genes, ttbb. Not for the percentage of TtBb offspring.
Since I don't offer tutoring over social media, to get help with questions like yours and more, I recommend joining my MCAT Study Hall. For more details, visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/
love how I have to learn all this in high school lmao -_- but at least I have Leah to help me so that's a win!
Oh wow! Happy I can help you out!
THANK U QUEEN
You're welcome!
Really helpful, thank you Leah!
You're so welcome, I'm glad it was helpful!
Hi! For the example you give at 15:30, it seems like you are just taking the ratio of big and little from each parent to get Tt=1/2, Bb= 1/2 and tt= 2/2, and bb= 2/2. I don't understand where you are getting the #s.
Thanks for asking! Yes, that is exactly what I’m doing! I am finding the probability of each parent donating a recessive allele to the offspring in either trait. Then, I multiply all individual probabilities to get a final answer for the chance that the offspring is homozygous recessive in both traits.
Hi Leah,
Thank you very much for that. Very clear and very informative. I was wondering when your videos on pedigrees will be available?
Kind regards,
Thanks Alex. Hoping for this or next week
@@Leah4sciMCAT Thanks Leah. Look forward to it. Lets build on this video - how would you work through this question if you were only told that, say, the parent expressed the dominant phenotype and the other parents expressed the recessive phenotype and you were asked to solve the ratio. I.e. Parent 1: T_C_ , Parent 2: ttcc? This is definitely a question that would stump a few. An explanation would be greatly appreciated.
Great video !!!
Thank you
thankyou!!!!! my brain was litteraly dying, this is a big help
I'm so glad to hear it! Always happy to help!
Thank you greatly. What great explanations that you give.
You're very welcome!
you're awesome thanks Leah
You're so welcome!
This is really helpful
I'm so glad you think so! Thanks for watching.
How would you apply the fraction technique if you want to know what fraction of the offspring in a dihybrid cross are heterozygous for both characteristics?
This particular genetic cross is not what I address in the video. And unfortunately, I don't offer tutoring over social media . For help with questions like this and more, I recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/
Thank you!
You're welcome!
When you pick something and carry it through, why do you do it one letter at a time? Would it result the same if I took TB and carried it through versus taking it one at a time? I tried carrying the entire thing and it was the same and faster. please let me know!
THANK YOU LEAH
Yes, it would result in the same solution. I choose to do it one letter at a time because I find that to be the fastest method for most, but if your method seems faster for you, do it that way. And you're very welcome!
Thank you for replying me. I do watch your videos they help me. How do you find the probability of TTBb?
I'm sorry, but I don't offer tutoring over social media. For help with questions like this and more, I recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/
Does this work with pretty much with any Dihybrid Cross? Because while I absolutely have headaches over this subject because Biology has never been my favorite but it's required so I at least have to understand it
Yes! This shortcut applies to any dihybrid cross.
Also for the first question where we find the answer for T_bb (time stamp 13:19) , what were we looking for? I understand how we got 20% but does that mean 20% of dominant T? was that the answer?
In this question, we were calculating the percentage of offspring in a dihybrid cross that were tall with yellow flowers WITHOUT having to draw the entire Punnett square. The answer was 3/16, or approximately 20%, of offspring were tall with yellow flowers (genotype T_bb).
thank you!!!
You're very welcome!
Thank you 🙏
You’re welcome 😊
U saved my life 😂♥️
Happy to help!
I should have seen this before taking my quiz 1 :(
Hope the quiz went well, otherwise! Thanks for watching.
@@Leah4sciMCAT because of this I managed to pass the exam!!! i though I would get a failing grade.
Thank you!!!
There is error B comes before small t.
At which specific point in the video do you think there is an error? I don't believe there is a correct or incorrect order in these Punnett square problems.
This is great method, but I am reluctant with memorizing number schemas because I don't think the MCAT Gods are gonna bless us with two perfectly heterzygotic dihybrids. Unless you know something we don't XD! Love your vids tho
Thanks :)
Does this work for something besides TtBb x TtBb
Yes, both Punnett squares and the shortcut taught in this video should work for any given genetic cross.
@@Leah4sciMCAT thank you
What if there was a zero?
In reference to?
For example
You have to find a phenotypic ratio of gghhNN
To the given genotype of
GghhNN x GGHhnn
25% playback speed @ 6:00 thank me later (or never)
Good idea
I love you
Thanks
Shortcut at 6 minutes...
:)
This subject is not mine , please please.. Tell me which country you belonged , don't fear mam I can't reached your home ..
I don't even know what to make of your comment Jiya