zarahh09
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brown eyes are dominant (B) and blue eyes are recessive (b).

if theses are the genotypes:
BB
Bb
bb

what would the phenotypes be? is it this:
BB - brown eyes
Bb - brown eyes
bb - blue eyes
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CMP2222
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(Original post by zarahh09)
brown eyes are dominant (B) and blue eyes are recessive (b).

if theses are the genotypes:
BB
Bb
bb

what would the phenotypes be? is it this:
BB - brown eyes
Bb - brown eyes
bb - blue eyes
whenever there is a capital letter/dominant that is always the one expressed even if there is a recessive. so the recessive does not get shown/not visible.

If it is just say bb then it would be blue eyes as there is no dominant available
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zarahh09
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(Original post by CMP2222)
whenever there is a capital letter/dominant that is always the one expressed even if there is a recessive. so the recessive does not get shown/not visible.

If it is just say bb then it would be blue eyes as there is no dominant available
was i right or no ?
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macpatgh-Sheldon
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(Original post by zarahh09)
"brown eyes are dominant (B) and blue eyes are recessive (b)."
Hi although this statement does convey the meaning, it is strictly speaking the allele that determines the phenotype of brown eyes that is dominant NOT the brown eyes per se, and the corollary for blue eyes.

Alternatively, you can say that brown eyes are inherited as a dominant trait.

Your inferences as to the phenotypes expressed in individuals carrying the respective genotypes are all correct; however, it would help you to understand and remember the principles if you use the correct terminology.

Let me cite a different example to clarify the point for you:-
In sex-linked recessive inheritance e.g. in haemophilia or in red-green colour "blindness" [protanomalous trichromatism i.e. all three types of cones are present [hence "tri"] but the red cones in the retina malfunction - dw at all about this example if you find it confusing - just ignore], the Y chromosome in the male is known as a "sleeping partner" i.e. it does not contribute anything to the phenotypic expression OR has no effect on the synthesis of clotting factor IX [deficiency of this factor results in deficient blood clotting hence risk of haemorrhage - this disease runs in the royal family you might know], or on colour vision, so an abnormal X chromosome in a male [oc male has XY] will result in the man/boy having haemophilia or the colour vision defect, whereas a woman/girl would need both X chromosomes [oc a girl has XX] to suffer the anomalies.

Dominance simply means that, as another member says, the dominant allele that we represent with an upper case letter dominates over/overrides the recessive allele represented with a lower case letter, yeah?

It is not so much that the dominant allele "is not available" - it is more that the dominant allele is not present in that individual cos he/she has not inherited it from either of his/her parents, happy?

If still struggling, please feel free to PM me - I shall explain from a different angle.

M [specialist biology tutor]
Last edited by macpatgh-Sheldon; 2 months ago
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