AUTOSOMAL LINKAGE and DIHYBRID INHERITANCE- A-level Biology inheritance genetic crosses and ratios

[@mynamsjoon921]

i’ve been struggling so much with the entire genetics topic but this cleared things up really well !! thank you so much!!

[@MissEstruchBiology]

yay I'm so plenty helped

[@shihababrar6282]

No doubt, this one is the best explanation I have come through

[@MissEstruchBiology]

Thank you so much! Really pleased you found it helpful 😀

[@millykunda4537]

This video made everything easier

[@MissEstruchBiology]

Glad it helped you Milly :)

[@Indeax]

Thank you for this, I clearly understand autosomal linkage now :)

[@MissEstruchBiology]

ah that's great, really pleased it helped to you 😀

[@leoah1948]

Thank you for this video! It was so clear and beneficial !!

[@MissEstruchBiology]

You're so welcome and I'm so pleased it was clear 😊

[@redainaafridi4133]

Thank you so much for this video, I have my mocks coming up so it was very useful. Subscribed! ❤️

[@MissEstruchBiology]

So glad it helped 😊 Good luck with your mocks

[@aizakashifshakoor6284]

Finally some1 who's explanation makes sense

[@MissEstruchBiology]

awww thank you and so pleased it helped

[@samuelmwaka1953]

thanks a lot ma'am i love your work it really helps a lot

[@MissEstruchBiology]

My pleasure 😊

[@KBMFilms2020]

Miss isnt there a mistake at 15:48 , on the final four different chromosomes shouldnt the stick show "Y" on the top and not "y"

[@khaledbelalouache4237]

thank you for the clear explanation :)

[@MissEstruchBiology]

You're welcome 😊 Glad it was helpful!

[@leahlester2620]

Yay! Thanks again for the great videos😊

[@MissEstruchBiology]

You're welcome! Glad you are enjoying them. Have you checked out the daily quizzes on my @missestruch instagram?

[@omarabdallah2588]

so in autosomal linkage is it the fact that No crossing over takes place or is it No independent assortment takes place ?

[@emilylongstaff9384]

I don't understand when you are doing the parental genotypes, how do you know for example round is Rr or RR if it doesn't say in your question whether it is homozygous or heterozygous?

[@MissEstruchBiology]

They would have to tell you this or give you information to work it out. Sometimes they should the alleles present on the chromosome and sometimes you work it out from the genotypes or their parents/,offspring if that's given. Hope that helps ☺

[@omarabdallah2588]

so is autosomal linkage the norm and it always is the case but the 4 phenotypes are only formed due to crossing over and this is what allows dihybrid inheritance also is crossing over only rare in autosomal linkage or is it rare in general ? i hope my Q makes sense thanks so much for ur time i appreciate it !

[@whomerdoodles]

Hi, sorry at 7:47 are you saying hetero includes RY?

[@MissEstruchBiology]

Hello, I can't hear the bit you are referring to at the minute, but heterozygous is when you have two different alleles for one gene. In this example RrYy is heterozygous for both genes RrYY is heterozygous for just the R gene rrYy is heterozygous for just the Y gene Hope that helps

[@whomerdoodles]

@@MissEstruchBiology Yeah that helps, thanks

[@indybASMR]

This is so helpful thankyou

[@MissEstruchBiology]

You're so welcome 😁

[@itsarmie3162]

great video once again, quick question- why at 6:03 is it 100% HETEROZYGOUS and not homozygous? bit confused :)

[@MissEstruchBiology]

Hello It's because in that example, one parent only has dominants alleles (RY) and the other only had recessive (ry) and as the offspring will inherit one allele from each parent, that will mean it is always heterozygous (RrYy) Hope that helps

[@itsarmie3162]

@@MissEstruchBiology got it, thanks a lot :)

[@sss-sl3nu]

what do you at 11.48 when talking about crossing over

[@safiyak8459]

Hi miss, I have a question at 17:58 how do you know the yellow and round peas are (RRYY), when they could be (RrYy)

[@izzyfowles6907]

i think she said that they are homozygous dominant! RrYy would happen if they were heterozygous !

[@lisa-mariematthews3889]

Do we have to know mendels peas or is it just used as an example?

[@y.3.y.3edits41]

Hi ma’am i have a question as its really not making sense to me. Is crossing over impossible in autosomal linkage? Because if it wasn’t then surely more than two possible combinations would be made. Also if crossing over is possible in autosomal, then surely there would be no difference between that and dihybrid?? Thanks

[@lolaxmed9046]

why are the gametes for the dihybrid in pairs instead of just one for each characteristic just like the monohybrid?

[@MissEstruchBiology]

hello, because dihybrid is looking at the inheritance of two genes together whereas monohybrid is just lookin at the inheritance of one gene. Hope that helps. 😊

[@lawalquadri7504]

Thanks 😊 🤩

[@MissEstruchBiology]

you're welcome :D

[@scottmorris3116]

wouldn't epistasis also alter the 9:3:3:1 Mendelian ratio?

[@MissEstruchBiology]

yes it would!

[@jamalsafeer7405]

Beautiful

[@MissEstruchBiology]

I hope it helps

[@lvndrwoo2235]

this has saved me and my exam is in two hours😭

[@Bellastar-ccs]

Hi Miss,good afternoon.I was wondering about this topic do I need to know about Blood types?By that do I need to know about them having antigens(this is how you can tell if its A,B,or O)and the antibodies ect .Do I need to know that in depth for this topic or no? Thank you for your time.

[@MissEstruchBiology]

hello, no you don't it just comes up often as an application question

[@Bellastar-ccs]

@@MissEstruchBiology So just knowing what blood types phenotype &genotype e.g Type A has the genotype of I^A I^A or I^AI^O & what blood a recipient can receive e.g Donor A can only be given to recipient A or AB,it that enough?(It just because I did a lesson on Blood types and I was wondering what else I needed to know.Also,thank for your reply:) )

[@MissEstruchBiology]

@bellastarmartin4601 you don't have to recall that information, just work it out from information they might give

[@moa7651]

When doing punnet squares do we put gametes into the boxes on top and left? so if we have RRYY gametes are RR and YY? and for previous examples IAIO would it be IA and IO?

[@MissEstruchBiology]

you always need one copy of each letter (eg RY and RY), and yes top and left

[@olpp1757]

at 16:00 to get yellow and round offspring why is it RRYY and not RrYy as well? Thanks :)

[@MissEstruchBiology]

Hello, You are correct, that there could be some which are RrYy, as shown at 15.00 minutes, at 16.00 I just simplified to the homozygous examples.

[@olpp1757]

@@MissEstruchBiology Hi, thank you for replying! Very helpful. So when you cross two heterozygous parents (RrYy): The phenotype of offspring that show that RY are linked and ry are linked are RRYY, RrYy for yellow and round peas and rryy for green and wrinkled peas. So what about when you cross a double heterozygote with a homozygous recessive for both genes? Would there be any difference? I hope this makes some sense. Thanks :)

[@sanyasuleman6171]

U LEGEND!!

[@MissEstruchBiology]

haha ahh thank you!! 😊

[@pariparii]

[@anubhavphukan5720]

Hi there what specification is this for?

[@MissEstruchBiology]

this is aqa

[@allenk117]

Hello, thanks for the explanation, one question. How do you know when to use dyhybrid or autosomal? Would the question telll you that the genes are linked so that means it’s autosomal? If not specified it’s dihybrid? Thanks

[@MissEstruchBiology]

In an autosoma linkage question it I'd always dihybrid as it's two genes. But in a question, yes, they would give you information so you would know it was autosomal linkage and not just dihybrid of two genes on different chromosomes.

[@wolfgangamadeusmozart1816]

Hi Miss, I had a question: Are the 4 different gamete possibilities in dihybrid inheritance as a result of independent segregation and crossing over? Because if you model it such that the gametes YY and yy sit directly under RR and rr during meiosis, then the only possible combinations at the end of meiosis 2 are RY and ry. Is it purely as a result of independent assortment and chromosomal synapsis (chiasmata) that these 2 other possibilities are present? And if yes, does that mean that per round of meiosis only 2 different combos are possible and that the 4 combinations are as a result of abstractly modelling EVERY physically possible type?

[@MissEstruchBiology]

The 4 possible gametes are only possible if crossing over occurred in this example. If there was no crossing over then there would only be 2 possibilities. Hope that helps.

[@Eagleeye-si8je]

why couldnt the chromosome posses alleles Yr for example instead of YR, why are both of the dominant alleles of the gene carried on the same homologous chromosome. is it not possible to posses the recessive allele for one trait and the dominant allele for another trait on the same chromosome which would result in Yr gametes for example.

[@MissEstruchBiology]

Hey, that is possible,but for this party example the two dominant alleles for both genes were linked. They will always tell you which alleles for each gene are linked.