GCSE Biology Revision "Family Trees"

[@Study_comeback123]

2024 anyone..????

[@BeautyPlays2011]

me lol

[@AhmedHussain-yg9lb]

Me

[@fabiolakisa6416]

Who is here 12 hours remaining for there paper just for a brief session 😂😂. Im soo going to PASSSSS. I APPRECIATE ALL YOUR EFFORT. THANK YOU I DON'T THINK THAT IS EVEN ENOUGH

[@mariaanwar5304]

me

[@AsianRayyan]

yup

[@livwake]

who's here the night before :)

[@WhinedUp2004]

22 minutes before 😭😭😭

[@aliyecetindag5578]

Morning of 😂

[@areebahaque5916]

Meh

[@jeongbun2386]

Meeee

[@jxlly1404]

Literally the morning before

[@polymerwario]

One more night until the second Bio Exam and these videos being formed into GCSE paper-specific playlists for each one has allowed me to transcend, thank you 🙏

[@ryou6453]

I'm you a year ago hi

[@outlander271]

Clearly and concisely explained. Excellent!

[@aidanstrong1061]

Would you recommend watching your videos at a faster playback speed? Thanks, as ever, for making them!

[@Freesciencelessons]

No I think if you rush revision, it won't work as well. Just give yourself plenty of time. If time is really short, then you could increase the playback speed.

[@phone5579]

i have a day to learn all of paper 2

[@OhThatsAbbyyy]

Macron Summers same!

[@ellieroberts3654]

literally me

[@erinthomas5463]

Dude same you have plenty of time

[@tiktok-ul8pv]

Once again thank you for the great videos we as students appreciate your hard work

[@fok3624]

“Give one piece of evidence that cystic fibrosis is caused by a recessive allele” The answer to this question was incredibly vague in my opinion, could anyone help me answer it PLEASE?

[@Freesciencelessons]

Neither parent had the cystic fibrosis phenotype but one of their offspring did so the allele must be recessive.

[@charlie-ei6rd]

this video made everything click

[@k3nz1e73]

scared for monday 😫

[@theangry0077]

godsend🙏🏻🙏🏻

[@hamishlongley5253]

Really helpful

[@gxvz64]

Thanks again 🔝

[@kj6164]

That's my family tree sorry i had to :)

[@gxvz64]

🤦‍♂️

[@sasharuva3190]

No bad vibes just good energy 🤪

[@nameusero-pq3sz]

Hahahahhaha

[@zaraahsan4114]

@@sasharuva3190 if you know abt them then you know abt me

[@sizxi]

Thank you so much!

[@billyh8684]

I love the way he says trees

[@eshahanwartirmizi1267]

How do you know it’s recessive or dominant ?!

[@alexstone9099]

The dominant allele is a capital letter and the recessive is lower case. But for the actual disease you have to learn it if that's what you mean and in this case you just need to learn polydactyl and cystic fibrosis.

[@jakemiller2147]

@@alexstone9099 great that helped a lot, thanks!

[@hannah-rk2lr]

Hi, would they give us a code of what each of the filled in squares or circles mean? Or would we just be expected to know that a filled in square for cystic fibrosis means that they have it?

[@edgarolmedo7166]

they will tell you

[@solanada8450]

Why does person 3 have a heterozygous genotype, could it not also be homozygous? (3:17)

[@Freesciencelessons]

Because they'd have to have inherited a polydactyly allele from both parents. If you have the polydactyly allele then you have polydactyly. However, we can see that the person's mother does not have polydactyly so they cannot have the polydactyly allele.

[@manahilirshad2258]

I like the other music better :(

its the same isn't it?

[@ramenlifts]

How will I know which allele is dominant or recessive. Will it be given in the question?

[@Freesciencelessons]

Not with a family tree. You have to work it out from the offspring. I show you how to do it with both recessive and dominant alleles in the examples in the video.

[@Yash-df5jo]

For the last one, is it not possible the father could be DD, so then there will be 100% chance that the child has Polydactyly? I figured this out using a punnet square. Is it because if you inherit polydactyly from ONE of your parents, then you only have ONE of the dominant alleles?

[@Freesciencelessons]

If you mean person 1, they cannot have any polydactyly alleles as they do not have polydactyly.

[@hilluvz]

2025 anyone?

[@chantelle5170]

@ 3:20 how would you know that the genotype is 'Pp' not 'PP' ??? Since it's dominant alleles are both answers correct?

[@milliemilkshake123]

well it has a dominant allele so it doesn't matter if it is PP or Pp as the person has still got polydactyly, it only needs one dominant.

[@gemmanorfolk5210]

Isn't it because person 1 doesn't have polydactyly at all, so it could on be PP if they had it too as well as person 2, if that makes sense

[@chantelle5170]

oh i understand thanks!

[@Rektxtgx]

yes gemma is correct, if you do a level this topic gets a lot more confusing aha

[@mahanawaz5422]

Hi sir, quick question; why do both parents have to be heterozygous, can only one of them be heterozygous to have an off-spring which has cystic-fibrosis. If so wouldn’t this affect the percentage in question 3?

[@Freesciencelessons]

No that cannot work. To have cystic fibrosis, a person has to have TWO copies of the CF allele (as it is recessive). That means they have to inherit one copy from BOTH parents. In other words both parents have to be heterozygous (or possible homozygous).

[@mahanawaz5422]

Freesciencelessons ah that makes sense now, thank you so much, your video is amazing

[@serenity7637]

3:16 couldn't they also have homozygous dominant alleles? Im confused.

[@nelsonmaclure4734]

Hello! I'm not sure if this is still helpful but I'll add my response anyways. No. They couldn't as we know that the genotype of the father is 'pp' as polydactyly is a dominant allele and therefore if it was present (whether heterozygous or not) the father would have polydactyly. In this case he does not, so his genotype must be 'pp'. Therefore, we know that person 3 must be heterozygous as one of the alleles from the father and the mother must be inherited to the offspring. As the father is homozygous recessive, one of the alleles inherited by person 3 will be a recessive one. Although we don't know the genotype of the mother, we know it must have at least one dominant allele as polydactyly is caused by dominant alleles. This is where person 3's other allele 'P' comes from. 'P' from mother (who defo has polydactyly) and 'p' from father (who does not). Sorry if this explanation is unclear, this was my best attempt. Good luck with GCSES!

[@shadyyyy7380]

na thats impossible because person 1's genotype is pp, meaning its impossible to inherit the second dominant allele from them.

[@mochamilksubs]

no because to have the alleles "PP", both parents would have to have the dominant allele "P", which person 1 doesn't have (their alleles are pp) and so person 3 could only have one dominant allele which would be from person 2 since person 2 has polydactyly

[@ben8939]

no because the father would have to have polydactyly for it to be homozygous and since it is a dominant disease it only has to show up once to be passed on therefore it can be heterozygous as it will only be coming from the mothers side - good luck for bio tomorrow if you’re doing it!

[@alicekeeling]

1 doesn’t have any Polydactyly alleles (they will be pp) because it is dominant, so if they had any of the Polydactyly alleles, they would have Polydactyly. However, 2 has Polydactyly, so they either have Pp or PP alleles. Either way, because 1 has no Polydactyly alleles, it’s impossible for 3 to inherit two doninant alleles because 1 has none

[@jackanderson1620]

wheres the revision workbook that you reference ?

[@nfn15]

if you click on the i in the top right

[@destined0645]

Is it dominant can't it be PP and Pp

[@begumsara9907]

Is the key at the top the same for all Family Trees. I understand that each question will refer to different disorders, but does the key remain the same and do we need to memorise the key for the exam

[@Freesciencelessons]

With a family tree, you would normally be given a key. You need to be able to apply the key so you don't need to memorise one. Also, the typical questions that tend to come up in exams are the ones that I discuss in the video so definitely learn those.

[@begumsara9907]

@@Freesciencelessons Thank you so much!

[@YJbeats]

Nice nice nice

[@MOBunbox]

At 3:48 can the person also have pp as their alleles as they are affected with polydactyly

[@sarujanrupan4831]

No because polydactyly is dominant

[@tahmidchoudhury1013]

In your alcohol video why doesn't the structural diagram for methanol have a bond between the oxygen and hydrogen while the other alcohols do?

[@Freesciencelessons]

It's OK to draw the bond or not draw the bond in this case. We know that it's there.

[@tahmidchoudhury1013]

Freesciencelessons got it! thanks!

[@fahimaakhtar3152]

what are the phenotypes of the parents?

[@UltimateChamp]

Who's here right before the exam in 2023 😢 💀

[@MF-wg5xy]

Sir,Im in year 10 and as i heard the curriculum is changed and it will be harder for us..What type of questions do i need to revise mostly(for example practical theory or mathematical questions)? Thank You..

[@AceOfSpades4413]

Metin_Rss i think the curriculum has changed a bit, but it’s mainly the questions in the papers which are harder as apparently too many people get vet=ry high marks and want to ‘widen the grade range’. So answering you question, yes you could get more mathematical questions which require more thought and quality when answering.

[@idontusethisanymore1933]

Hi sir, have you created videos on micropropagation too?

[@patron7520]

he only does aqa gcse spec

[@hocuspocusdiddlydocus5290]

When will the revision workbooks be out?

[@Freesciencelessons]

Chemistry 1 and Physics 1 are out now. Biology 1 is coming soon. www.freesciencelessons.co.uk/workbooks/shop/

[@honorscarborough7129]

Will you be told in the exam that polydactyly is dominant and cystic fibrosis is recessive? Or do we have to learn them

[@Freesciencelessons]

They are stated in the spec so I think you should learn them. They may be given in the exam but they may not.

[@arakurd6351]

it depends on your exam board so just look at your specification. for edexcel they dont even mention the names of any inherited disorders e.g. cystic fibrosis, polydactyly, etc, so they will tell you in the exam whether it is recessive or dominant, and what the diseases actually do to u.

[@MsDestiny2002]

you changed your intro!

[@shaheer_04]

boss.

[@tomcornes4496]

Hello Mr Icziewicz

[@JoshuaAyala]

PP

[@dann7598]

This is confusing

[@livwake]

who's here the night before :)