A dominant allele is a version of a gene that will be expressed when present. A recessive allele is only expressed when no dominant alleles are present. For example, brown eyes are a dominant allele and blue eyes are recessive. A person with brown eyes might have a recessive blue allele present, but it is not expressed. A person with blue eyes definitely does not have a dominant brown allele present. Two people with brown eyes can have a child with blue eyes, if they each had a recessive blue allele (not expressed because the dominant brown allele was present) and passed them down to the child, who would have only recessive blue alleles, and no dominant brown allele to hide it.
2006-11-30 05:54:09
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answer #1
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answered by DavidK93 7
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Most traits (ie red hair or green eyes) are composed to two alleles, one allele from each parent. Usually these are represented as a pair of letters, usually the dominant allele is represented with a capital letter, and the recessive with a lower case letter.
For this explanation lets use brown hair dominant (B) and blonde hair recessive (b).
For a dominant trait to display itself only one of the alleles needs to be the dominant allele. So a person would have brown hair if their alleles were Bb or BB.
Recessive traits require that both alleles be of the same make up. So you would only get a blond person if their alleles were bb.
Hope that helps!
K
2006-11-30 05:58:46
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answer #2
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answered by Kaedence 2
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The rough coated allele is dominant. We just did this in class a few weeks ago. R=rough coat r = smooth coat. When two animals have recessive alleles (rr and rr) they will only produce that offspring. However, if the animal has a dominant allele, it is either Rr or RR. This is why if you cross it with another guinea pig you may get both types. And, if one of the parents is RR (dominant for rough coat) it will always produce rough coated children. This is kind of hard to explain over the internet..oh well. Hope it helps. :)
2016-05-23 05:24:51
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answer #3
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answered by Anonymous
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dominant allele is the dominant part of the chromosome, that has a higher chance of being phenotypically displayed.
recessive allele is the recessive part of chromosome, if it is paired with a dominant it will not be phenotypically displayed. if it is paired with another recessive allele it will display its recessive trait phenotypically
2006-11-30 05:58:06
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answer #4
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answered by sadeqq 1
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Remember that for most genes, you have two copies of each gene that you inherited from your mother and your father. Each copy of the gene could be different. For example one copy may give you blue eyes while another may give you brown.
So, what color are your eyes if you have both the brown and blue eye version of the eye color gene? Brown. This is where the idea of dominant and recessive comes in. Dominant means that one of the versions trumps the other. In our example here, brown is dominant over blue so you end up with brown eyes.
The way people write out dominant and recessive traits is the dominant one gets a capital letter and the recessive one a lower case letter. So for eye color, brown is B and blue is b. As I said above, people have two versions of each gene so you can be BB, Bb, or bb—BB and Bb have brown eyes, bb, blue eyes.
Versions of genes are often dominant because the recessive version actually does nothing. In the eye color example above, the brown version of the gene makes a pigment that turns your eye brown but the blue version does not make a blue pigment. Instead, it makes no pigment and an eye without pigment is blue.
As you can probably guess, if the blue version of the eye color gene made a pigment, then you’d get some mix of brown and blue. There are some cases like this for people. One of the easiest to understand is hair. There are two “hair type” genes, curly and straight. If you have two copies of the curly version, you have curly hair and if you have two copies of straight hair version, you have straight hair.
What kind of hair do you have if you have a copy of each? Wavy. Each of these versions contributes something so that you get a mixture of the two. You would write this out as CC is curly, SS is straight and CS is wavy.
For pure dominant and recessive traits, I’ve listed a bunch below that you could discuss with your class.
Bent pinky:
The dominant version of the gene causes distal segment of pinky finger to bend distinctly inward toward the ring (fourth) finger.
Mid-digital hair:
People lacking hair in the middle segments of the fingers have two recessive versions of the gene.
Tongue rolling:
People with a dominant allele can roll their tongues into a tube shape. People with two recessive versions are non-rollers and can not learn to roll their tongues.
Ear lobes:
Recessives have attached ear lobes. People with a dominant version of the gene have detached ear lobes.
Thumb crossing:
In a relaxed interlocking of fingers, left thumb over right results from having 1 or 2 copies of the dominant version of the gene. People with 2 recessives place right thumb over left.
2006-11-30 09:34:08
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answer #5
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answered by BS 2
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dominant is one that shows up in your kid.
recessive doesn't show up for seveal generations until both parties have the allele.
2006-11-30 06:00:33
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answer #6
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answered by shanna 1
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