Biology questions

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1

<p>I know this is an ugly looking pedigree chart, but you get the point.. :D</p>

<p>so the question states that squares indicate males and circles indicate females</p>

<ol>
<li>Based on this information, the allele causing the shaded traits is likely
A. codominant
B. x-linked recessive
C.autosomal dominant
D. Y-linked
E. x-linked dominant</li>
</ol>

<p>I know the answer is B and I got it correctly but I wanna make sure I did for the right reason, so is it x-linked because it only affected men (it could have also affected women but the possibility that it affects men is higher) and recessive because only two were affected and because the F1 was all either unaffected or carriers so the two parents had to be homozygous dominant and homozygous recessive?</p>

<ol>
<li>what is the probability that individual 3 is a carrier?</li>
</ol>

<p>A. 0%
B. 25%
C. 50%
D. 75%
E. 100%</p>

<p>the answer is C is that because individual 1 is Aa and because individual two has to be Aa too because if he were to be an AA it would be impossible for individual 4 to be homozygous recessive so on the punnet square it would give a 25% : 50% (the answer) : 25%</p>

<ol>
<li>what is the probability that individual 2 is a carrier?
A. 0%
well I dont get why the answer is 0 :S</li>
</ol>

<p>guys I need to understand the right way to approach those type of questions I'm struggling with them.. =S
<a href="http://postimage.org/image/ey421p9g/%5B/url%5D"&gt;http://postimage.org/image/ey421p9g/&lt;/a>
[url=<a href="http://postimage.org/image/ey421p9g/%5D%5Bimg%5Dhttp://s2.postimage.org/ey421p9g/pedigreechart.jpg%5B/img%5D%5B/url"&gt;http://postimage.org/image/ey421p9g/]

http://s2.postimage.org/ey421p9g/pedigreechart.jpg

[/url</a>]</p>

2

<ol>
<li>Yes Correct, but if you want to go to even more details.</li>
</ol>

<p>It can’t even E, X-linked dominant because because the two daughters of F1 aren’t affected. The dad will automatically gives all of his daughters an affected X Chromosome, and since it’s dominant they should show the trait, but they don’t.</p>

<p>It can’t be C, Autosomal dominant. If it was autosomal dominant than individual 1 is homozygous recessive because she isn’t affected by it, and the only way to not be affected by it is if you don’t have that gene at all since it’s dominant. But the husband of 1 is also not affected, But they have a child that is affected, which is impossible, because they’re both homozygous recessive. </p>

<p>It can’t be A, Codominant because that … doesn’t make sense, and kinda impossible to show using a pedigree. </p>

<p>It can’t be D, Y-link, because the SAt never tests Y-link traits. And if it is then the male of F1 should be affected since he must get a defected y chromosome from his dad. </p>

<ol>
<li><p>C is the answer. Individual 1 is X<em>X(using X</em> as affected X chromosome). The person individual 1 marry must be regular XY, because if his X is affected, he must show the trait, which he doesn’t. Individual 3 is a girl. She must get a regular X from his dad and either a affected X* or a normal X from her mom. That’s 50% chance.</p></li>
<li><p>I agree with you that A is not 100% correct because it’s ambiguous and debatable. . The wife of P1’s son can be a carrier, which can makes their daughter 2, a carrier.</p></li>
</ol>