What are the chances that someone is carrier of a recesive disease, given the info in details?

find chances

wrote...

2 years ago

What are the chances that someone is carrier of a recesive disease, given the info in details?

hi,
what are/how to calculate the chances that someone is carrier (but healthy) of a recesive disease, given the fact that her sister is carier and healthy?

thanks Slight Smile

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bio_man

wrote...

Educator

2 years ago

How do you know the sister is a carrier? What's the genetic trait that we're dealing with here?

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find c.

wrote...

2 years ago

I know the sister is healthy, but has a child that is sick (bb), so it means she has b and B, right? (B-healthy, b-not healthy)
The genetic trait is Cystic fibrosis

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bio_man

wrote...

Educator

2 years ago

She has a child who has the trait.

The mother of this child doesn't have the trait, so she's likely a carrier.

The only way she'd have a child with this trait is if her father has the genotype bb (meaning he has cystic fibrosis) or if the father is also a carrier (Bb, heterozygous).

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find c.

wrote...

2 years ago

Quote from: bio_man (2 years ago)

She has a child who has the trait. The mother of this child doesn't have the trait, so she's likely a carrier. The only way she'd have a child with this trait is if her father has the genotype bb (meaning he has cystic fibrosis) or if the father is also a carrier (Bb, heterozygous).

thank you!
but how can I calculate the chances that she is a carrier?
It is possible that her father has bb or Bb or BB, and same for her mother (but not both bb or BB together), right?
so can I calculate the chances for a carrier daughter, for each of these 3*3=9 options, then divide by 9? (I got 0.5 but not sure)

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bio_man

wrote...

Educator

2 years ago Edited: 2 years ago, bio_man

If she's a carrier, here's the possible scenario:

Scenario 1:

Father is a carrier
Mother is carrier

*	B	b
B	BB	Bb
b	Bb	bb

If this is the case, the chances she is a carrier is 2/4 or 1/2 (50%)

Scenario 2:

Father has the condition
Mother carries no gene for the condition (or vice versa)

*	b	b
B	Bb	Bb
b	Bb	Bb

In this case, there's a 100 percent chance she is a carrier.

Scenario 3:

Father is a carrier
Mother carries no gene for the condition (or vice versa)

*	B	b
B	BB	Bb
B	BB	Bb

In this case, 1/2 chance she's a carrier.

Does that make more sense?

1 Vote

find chances

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find c.

wrote...

2 years ago

thank you

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