Dominant recessive genes? phenotype, allele, genotype?

Question

i really can;t understand them, i've been reading the but i still can't differentiate them, im really confused on what the role of allele to phenotype, genotype to dominant? etc etc.

please help

Answer 1

OKay, hum, well you know they way we have 26 pairs of chromosones? Heres a pair:

homologis pair of chromosones

|                       |

|                       |

|                       |

*                      *

|                       |

|                       |

^                      ^

|                       |

|                       |

This is a pair of chromosones. They always travel together. The only time the would be split up is mitosis or miosis. (cell growth or gamete production) The *'s and ^'s are alleles. The same alleles are lined up beside each other as shown.

Lets say that the * indicates the alleles for eye colour. You inherited one * from your mum and the other * from your dad. Still with me?

So you have TWO genes for eye colour.

Lets say that one of the stars is the gene for blue eye colour and the other star is the gene for brown eye colour. Though you on the other hand have brown eyes. Wait a minute, you also have a blue gene! Why dont you not have blue eyes?

This is because the brown gene is DOMINANT and the blue gene is RECESSIVE.

Basically, the brown gene cancells out the blue gene, so you're PHENOTYPE is brown. (phenotype is your OUTWARD appearance)

Though, your GENOTYPE is Brown and Blue. (genotype is what alleles you have)

You can tell a persons phenotype by looking at someone. Got it?

So. You're Genotype is written Bb.

Capital B for the dominant Brown allele.

Small b for the recessive Blue allele.

(only one letter is used and that is the letter of the dominant allele)

Lets say you have two dominant brown alleles. your Phenotype would be brown, your Genotype would be written as BB.

How about you have two recessive blue alleles? Your phenotype would be Blue, your genotype would be bb.

So you only need one dominant brown allele to be brown eyed but TWO recessive blue alleles to be blue eyed.

A person looking at you wouldnt be able to tell if you had a blue allele or not.

Though if you had blue eyes they would be sure that you had two blue alleles

Because the only way to have blue eyes is if you had two recessive blue alleles.

But for brown eyes you could either have one brown allele or two.

Ok?

Hope you understand it now. :)

Answer 2

Usually you get two genes for each thing in your body for example elts use hair.

You get one gene form your mom and another from your father.

These are call alleles in other words- Different versions of a same gene.

Curly haire gene, straight hair gene in so one you see.

Phenotype is the way you physically look. So if you have blue brown eyes there you go the phenotype for your eyes is blue.

Do not get it confuse with genotype. Genotype is the way your genes are.

You might have inhereted a gene for brown eyes from your mom and another from you dad. But guess what you might have a blue eye gene from you mom and a brown gene from your dad.

The thing is Brown eyes are DOMINANT which means that it doesn't matter if you had a blue eye gene your eyes are going to be brown.

finally recessive is the opposite of dominant. Blue eyes are recessive therefore for you to have them you have to inherit a blue eye gene from your dad and from your mom

Lets Recap

Allele - Different versions of a allele. (Gene for blue eyes, brown eyes, Green eyes)

Dominant - If you have a gene that is dominant it will be the one express in you body no matter what other allele you have inhereted.

Recessive - The gene that can easily be overpowered by the dominant gene. For it to be expressed you need two versions of the same allele one from you mom and another from your dad.

Phenotype - The way you look Physically.

( Look at the prefix - Ph ) - Physical

Genotype - The way your genes look you can say. The alleles that you have.

remember your Punnet Squares they will help you

Answer 3

allele is the different forms of a certain homologous gene, for example, the alleles for eye colour can be green eyes, brown eyes or blue eyes.

phenotype is a trait that is obvious and can be "seen" by others. for example, you would say that a brown cat's phenotype is brown fur(which is dominant in this example) but it's genotype is BB, if it is dominant homozygous.

so if there is a genetic cross between a homozygous dominant brown cat (BB) and recessive black cat (bb), the genotype ratio is all four F1 offspring are Bb, but the phenotype ratio is all are brown, because brown is dominant over black, so when it is heterozygous (having a combination of both alleles Bb), the fur is brown.

check out this website for more http://www.biology.arizona.edu/mendelian...