Pedigrees

[eloeloelo]

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when you look at pedigrees curly hair is dominant and straight hair is recessive.
where does 'wavy' hair fit in? is it under curly because its not co-dominant?

[Niksta123]

Is your question one related to an actual HSC past question/or trial paper?

Or are you just talking about when you're looking at a pedigree?

Normally you 1 trait that dominant & 1 thats recessive...

You don't normally have a trait that is in between - at least I have never seen a question like that. if you have specific question to do with this please send it through - and I might be able to help you more specifically.

[~kiki]

Originally Posted by Niksta123

Is your question one related to an actual HSC past question/or trial paper?

Or are you just talking about when you're looking at a pedigree?

Normally you 1 trait that dominant & 1 thats recessive...

You don't normally have a trait that is in between - at least I have never seen a question like that. if you have specific question to do with this please send it through - and I might be able to help you more specifically.

niksta-- there is a thing called co-dominance. The example we use in our bio class for co-dominance is roan cattle. They come in three different colour variations, red, white and "pink" (red hair with long white hairs despersed throughout)... If a red and a white parent were to breed together then some of their offspring may be "pink" (roan) some will be white and some will be red (depending on whether the parents are hetero or homozygous).

Eloe-- I wouldn't be sure of the answer to your question, although I believe that with hair colour and type its all relative. Probably not the best way to put it :P... But for example, brown hair may be dominant over both blonde hair and red hair, but blonde hair may be dominant over red hair. If we're talking hair type, I think wavy hair is dominant over both curly and straight hair. I know wavy and curly hair definately aren't put together because the hair folicle for each is a different shape.

[Niksta123]

thanks for reminding me about co-dominance....i've done example to do with roan cattle, i guess i have never seen a co-dominant qu on hair! hahaa...

it might help to see a specific question about the hair...so we can understand exactly what they want...??

[nadz001]

ok i think u guys mixed this up coz co-dominance is when bothe genes of an allel are exposed for example a black cow mates with a white cow they will produce a cow that has white n black in,
There is also somthing called incomplete domince the is when do the offspring has a blended colour from parents, eg a white flower is pollunated with a red flower the offspring of that will be pink colour, so um thinkin of ur questiojn i thinkin not 100% sure but it may be incomplete dominance due to both alles of straigh hair n curly hair is blended to form wavy hair, i think u should call hsc phone line jus to be sure though

[hellopian]

Wavy hair would be the result of a heterozygous cross, because the alleles for straight/curly hair are co-dominant. If you think about it, wavy hair isn't quite curly, yet isn't quite straight, so it wouldn't really fit under curly, but in between.

"The alleles for curly hair and straight hair are examples of alleles for a trait that are codominant. Individuals with curly hair are homozygous for curly hair alleles. Individuals with straight hair are homozygous for straight hair alleles. Individuals who are heterozygous, with one of each allele have wavy hair, which is a blend of the expressions of the curly and straight hair alleles."

There is also the Snapdragons where one is red the other white and when a heterozygous cross is produced it is pink. I remember learning about the Roan cattle too.

[nadz001]

Originally Posted by hellopian

Wavy hair would be the result of a heterozygous cross, because the alleles for straight/curly hair are co-dominant. If you think about it, wavy hair isn't quite curly, yet isn't quite straight, so it wouldn't really fit under curly, but in between.

"The alleles for curly hair and straight hair are examples of alleles for a trait that are codominant. Individuals with curly hair are homozygous for curly hair alleles. Individuals with straight hair are homozygous for straight hair alleles. Individuals who are heterozygous, with one of each allele have wavy hair, which is a blend of the expressions of the curly and straight hair alleles."

There is also the Snapdragons where one is red the other white and when a heterozygous cross is produced it is pink. I remember learning about the Roan cattle too.

yea ur rite as u wrote the alles r blended therefore it will be incomplete dominane , co dominance is when the two alles r expressed not blended

[hellopian]

Oh ok yeah I understand now, like the roan cattle is co-dominant because the phenotype of the heterozygous is expressed but not blended (shows both white and red hair folicles, while with the hair the phenotype is blended, which is a change from the original homozygous phenotype, which is incomplete dominance.) Sorry for the rant, just helped me understand it, hope that's right.

[nadz001]

YEa soo i jus remember if in a pedigree they will show u three types of phenotypes, it co domince, i dnt think they will eva show a pedigree of incomplete dominace jus watch wat for key word "blended" for that links to incomplete dominance

[eloeloelo]

thanks for your answers guys
it wasn't from a past question, i was just curious thanks for humoring me

[Buiboi]

codominance = Red + white alleles= red and white hairs

incomplete dominance=red + white=Pink

but we arent required to know incomplete dominance...its not in the syllabus so yeah ...but u do need to know codomiance

why doesnt codominance satisfy mendels ratios?

is it because there is no dominant or recessive trait?

and is the heterozygous...red and white hair phenotype considered a THIRD phenotype or what? cuz if so i can say that mendels ratios doesnt account for a 3rd phenotype? or does this 3rd phenotype only apply to the incodominance (pink=3rd phenotype)???

[Buiboi]

codominance = Red + white alleles= red and white hairs

incomplete dominance=red + white=Pink

but we arent required to know incomplete dominance...its not in the syllabus so yeah ...but u do need to know codomiance

why doesnt codominance satisfy mendels ratios?

is it because there is no dominant or recessive trait?

and is the heterozygous...red and white hair phenotype considered a THIRD phenotype or what? if so i can say that mendels ratios doesnt account for a 3rd phenotype? or does this 3rd phenotype only apply to the incodominance (pink=3rd phenotype)???

[shivosky]

Its like eye colour.... whilst there is only 1 dominant gene (i think its brown but dnt quote me on it) and i strictly recessive (blue..again dnt quote me) each person has a differnt coloured eye and iris if only by a fraction of a shade. i assume this is similar for hair but in all characteristics...some genes though whilst dominant can express co-dominance when a different gene is recessive. Dna is so complex and genetics so random speculation is all we can do...thats why its called the "Genetic Theory"....so basically wat im sayin is there are so many differnt genes for slight characteristis that with all the factors and variables, anythig is possible (within logical reasoning :P)

hope this helped..WOO go bio

[Brontecat]

with hair colour brown is the dominant trait and blonde the recessive trait - however, is it possible for co-dominance to occur like in the shorthorn cattle where people have individual brown hairs and indicidual blonde hairs?

[Timothy.Siu]

Originally Posted by Brontecat

with hair colour brown is the dominant trait and blonde the recessive trait - however, is it possible for co-dominance to occur like in the shorthorn cattle where people have individual brown hairs and indicidual blonde hairs?

i'm pretty sure people do.
heaps of people have 2 different colour hairs naturally.