A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
A man's paternal grandfather had galactosemia. This is a rare disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia but whose parents did not. The woman is now pregnant with their first child.
Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.
General Hints
When analyzing a pedigree, there are a few rules of thumb:
When calculating probabilities, two rules are useful for predicting the ratios of offspring produced in genetic crosses:
Punnett squares are also useful tools for determining probability. If you see a certain ratio of affected to unaffected individuals in a generation, it may be helpful to draw the Punnett square to determine the genotype of the parent. For instance, if both the parents are carriers of a recessive trait, you would expect to see a 3:1 ratio, whereas if only one parent is a carrier, you would not have any affected offspring. If an heterozygote is crossed to a homozygous individual (a testcross), you would expect a 1:1 ratio in the progeny. Similarly, a cross between two heterozygotes would yield a 3:1 ratio if it is an example of dominance, or a 1:2:1 ratio if it is "incomplete dominance." This can be easily visualized by drawing Punnett squares with each of the possible genotypes represented.
To Summarize
So, there are a couple of rules to remember when analyzing a pedigree and calculating probability.
In general, if a trait is expressed in every generation, it is probably dominant. If it skips generations, it is probably recessive. Finally, if it seems to affect males more often than females, it is likely to be x-linked.
The probability of having a particular genotype can be calculated using either the product or addition rules. If you want to examine the probability of two children inheriting a particular trait, you would use the multiplication rule. The probabilities are multiplied together to determine the probability of two or more independent events occurring together. If you want to examine the probability of at least one of the two children inheriting a particular trait, you would use the addition rule. The probability of any one of two or more mutually exclusive events is calculated by adding the probabilities of these events.