biology quesion

[DrHJ]

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can anybody please explain this question:
If a person is a carrier for a genetic defect that is autosomal dominant, and they subsequently have four children with someone who is not a carrier. How many of their children will hypothetically inherit the genetic defect?

• ¼
• 2/4
• ¾
• 4/4

 

[ThunderSplash]

Autosomal just means the defect isn't sex-linked. It weird that it says a dominant carrier, but I assume the first person's genotype would be Aa. The non-carrier would be aa. A quick monohybrid cross would yield the following offspring: Aa,Aa,aa,aa. So I would say the answer would be half or 2/4.

 

[DAT Destroyer]

can anybody please explain this question:
If a person is a carrier for a genetic defect that is autosomal dominant, and they subsequently have four children with someone who is not a carrier. How many of their children will hypothetically inherit the genetic defect?

• ¼
• 2/4
• ¾
• 4/4

This question is a little flawed. If an individual has an Autosomal Dominant genotype, that individual is not a carrier, he/she has the disease.

If that individual is Heterozygous Dominant for that disease, and marries a Homozygous recessive person, then using punnett square, there is a 50% chance that offspring inherits this disease, so 1/2 (2/4).

Hope this helps.

 

[DrHJ]

This question is a little flawed. If an individual has an Autosomal Dominant genotype, that individual is not a carrier, he/she has the disease.

If that individual is Heterozygous Dominant for that disease, and marries a Homozygous recessive person, then using punnett square, there is a 50% chance that offspring inherits this disease, so 1/2 (2/4).

Hope this helps.

thank you

 

[DAT Destroyer]

thank you

Keep up the good work!

Nancy

 

[Rambunctious]

This question is a little flawed. If an individual has an Autosomal Dominant genotype, that individual is not a carrier, he/she has the disease.

If that individual is Heterozygous Dominant for that disease, and marries a Homozygous recessive person, then using punnett square, there is a 50% chance that offspring inherits this disease, so 1/2 (2/4).

Hope this helps.

Great catch! But couldn't you have the disease and also be termed as an asymptomatic carrier?

 

[DAT Destroyer]

Great catch! But couldn't you have the disease and also be termed as an asymptomatic carrier?

You can if the disease is Autosomal Recessive, not Autosomal Dominant.

 

[DrHJ]

Evolution Question:
This question is Q14 of Evolution chapter in Cliff AP Biology.
The answer is Sympatric Speciation. My confustion is why isn't it Direction Selection. It doesn't say that this situation ended up to the birds with intermediate beak size. (new species)

A recently introduced species of seed-eating birds occupies an island where small and large seeds are available. Beak size in the bird population varies from small to large, allowing some birds to be more successful at eating small seeds, while others are more successful at eating large seeds. Birds with intermediate beak size must exert additional effort to eat seeds.

 

[DAT Destroyer]

Evolution Question:
This question is Q14 of Evolution chapter in Cliff AP Biology.
The answer is Sympatric Speciation. My confustion is why isn't it Direction Selection. It doesn't say that this situation ended up to the birds with intermediate beak size. (new species)

A recently introduced species of seed-eating birds occupies an island where small and large seeds are available. Beak size in the bird population varies from small to large, allowing some birds to be more successful at eating small seeds, while others are more successful at eating large seeds. Birds with intermediate beak size must exert additional effort to eat seeds.

In this question, they are presenting 2 species of birds that have an ability of eating different size seeds.

In directional selection there is a shift in the overall population towards the species that are more favored by the current environment.

This question presents no evidence that one species produces more offspring than the other, nor that there are more birds with one type of beak than the other. Therefore, it is not directional selection.

However, in Sympatric speciation, 2 different species can live and thrive in the same geographical area. Since there are both small and large size seeds present, birds with both large and small beaks can live on the island, because both species have the necessary resources.

If the question said that the island had more large seeds than small, (or vice versa) and over a period of time more birds with large beaks were observed, this would imply "directional selection"


Hope this helps.

 

[DrHJ]

In this question, they are presenting 2 species of birds that have an ability of eating different size seeds.

In directional selection there is a shift in the overall population towards the species that are more favored by the current environment.

This question presents no evidence that one species produces more offspring than the other, nor that there are more birds with one type of beak than the other. Therefore, it is not directional selection.

However, in Sympatric speciation, 2 different species can live and thrive in the same geographical area. Since there are both small and large size seeds present, birds with both large and small beaks can live on the island, because both species have the necessary resources.

If the question said that the island had more large seeds than small, (or vice versa) and over a period of time more birds with large beaks were observed, this would imply "directional selection"


Hope this helps.

Thank you very much for your clear explanation.