Genes: Hitchhiker's thumb, Hair Colour and Eye Colour?

Question

I can bend both thumbs so that they are completely back and so can my dad, but my mum and my siblings can't. If it is recessive why can I do it? Also, my mum has brown eyes and so do my siblings but I have got my dad's blue eyes. They (my mum and siblings) have brown hair but I've got blonde like my dad. Surely all of us would have got my mum's more dominant genes?

Answer 1

not necessarily, the thing that makes up DNA ar called alleles they come in pairs, they are either dominant (usually abbreviated to a capital letter) or a recessive (abbreviated as a lowercase letter)

if there is at least 1 dominant gene, they get what it has but both have to be recessive to gain a recessive attribute

eg

blonde hair (B) is dominant while red hair (b) is recessive

if you had B and B you will get blonde hair

if you had B and b you will get blonde hair

if you had b ad b you will get red hair

hitchhikers thumb (h) is recessive and normal is dominant(H)



your dad had a h h allele so he can bed his thumb

your mum had a H h allele so she cant but she still carries the gene



so when your parents egg and sperm met you took alleles from both sides, you took one h of your dad and the h off your mum so you get a hh meaning you have hitchhikers thumb

Answer 2

You inherit one set of genes from your mum and another set from your dad.



Imagine the gene for brown eyes is B and the gene for blue eyes is b. The blue eye gene is recessive and the brown eye gene is dominant. Someone with just one B gene has brown eyes, you only have blue eyes if both sets of genes are b.



Your mum must have Bb genes - one B and one b. She therefore has brown eyes, because the B gene is dominant over the b gene. Your dad has blue eyes, so he must have two copies of the b gene.



When eggs and sperm are made only one set of genes is included, so when fertilisation takes place the baby gets only two sets of genes, one from the father and the other from the mother.



Your dad can only give you a b gene, because that's all he has. Your mum has a choice, she can give you a B or a b. If her egg contains a B gene, the child has brown eyes like your siblings. If her egg contains a b gene, the child has blue eyes like you. It's a 50/50 chance, so to have lots of brown eyed siblings is a little unusual, but not impossibly so.



My explanation is all a bit simplistic, most traits have more than one gene so it's a bit of a complex picture. Hope it helps :)

Answer 3

1

Answer 4

you were the lucky one that took after your dad, not all of you can take after your mother.