AP Biology : Understanding Autosomal and Sex-Linked Inheritance
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Example Question #21 : Understanding Autosomal And Sex Linked Inheritance
A certain mutation is a sex-linked recessive. If a father is not affected and the mother is affected, what is the probability that the couple will have an affected son?
If a disease is sex linked recessive, the disease resides on the x-chromosome (unless otherwise stated). The question asks about males, who genetically have one x-chromosome and one y-chromosome. The easiest way to solve this problem is to create a punnet square (shown below).
As you can see, there is a 100% chance that the males will be affected. Similarly, there is a 100% chance that the daughters will be carriers of the disease. As a side note, the daughters will not be affected because they have one "good" x-chromosome to compensate for the "bad" x-chromosome that carries the mutation.
Example Question #1671 : Ap Biology
Which of the following is not an example of trisomy?
Patau
Kleinfelters
Edwards
Turners
Downs
Turners
Trisomy is a condition of an extra chromosome copy, such as in Patau (trisomy 13), Edwards (trisomy 18), Kleinfelters (XXY), and Downs (trisomy 21). Turners syndrome is a condition of monosomy (X).
Example Question #23 : Understanding Autosomal And Sex Linked Inheritance
Using the genotype below, and assuming there is no gene linkage present, answer the following question.
AABbCcDdEeFf
How many different possible gametes could be formed?
Each homozygous pair of alleles will result in 100% identical dominant or recessive alleles, therefore cross multiple "1" for each homozygous pair and multiple "2" for each heterozygous pair.
Therefore, the appropriate multiplication for determining the number of possible gene combinations is
Example Question #171 : Evolution And Genetics
Which of the following does not result from nondisjunction of homologous chromosomes during meiosis?
Monosomy X (Turner's Syndrome)
Trisomy 18 (Edward's Syndrome)
Trisomy XXY (Klinefelter's)
All of these result from nondisjunction
Trisomy 21 (Down's Syndrome)
All of these result from nondisjunction
All of the following are results of a nondisjunction event. Trisomy and monosomy disorders may occur as a result of improper separation in diploid human meiosis events.
Example Question #172 : Evolution And Genetics
Disease A is inherited through an autosomal recessive process. What is the probability that two unaffected carriers of this disease will produce an offspring that inherits disease A?
25%
75%
50%
100%
0%
25%
The correct answer is 25% because each parent has a 50% chance of giving up their recessive allele to the offspring. There are two parents so the probability will be:
Example Question #26 : Understanding Autosomal And Sex Linked Inheritance
A man with a sex-linked disorder for color-blindness and a woman with a normal genotype have two children. What is the probability that both of them will be carriers?
75%
50%
25%
100%
0%
25%
The man's genotype can be written as 
Their possible children are represented by the Punnett square shown here:
Any sons will inherit the 
For two children, the probability is 
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