Question

# If two normal (disease free) parents each carry the recessive allele for cystic fibrosis, what is...

If two normal (disease free) parents each carry the recessive allele for cystic fibrosis, what is the chance one of their children could inherit the disease?

Select one:

25% (1 out of 4)

100% (all children)

75% (3 out of 4)

50% (2 out of 4)

No children

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If Woody Guthrie had children with a women with Huntingtons Disorder, which is true?

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no children would have it

two out of four children having the disorder is the probability

all children would have it

three out of four children having the disorder is the probability

one out of four children having the disorder is the probability

This is a good example of codominace

Select one:

four o'clock flower

hemophila

color blindness

human AB blood type

cystic vibrosis

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Question:

If two normal (disease free) parents each carry the recessive allele for cystic fibrosis, what is the chance one of their children could inherit the disease?

Select one:

25% (1 out of 4)

Explanation:

Cystic fibrosis is an autosomal recessive inheritance. We assume that C allele is responsible for normal condition and c allele is responsible for cystic fibrosis disease. So, C is dominant over c. If two normal (disease free) parents each carry the recessive allele for cystic fibrosis the genotype of the parent is Cc (heterozygous).

Gametes for Cc are C and c.

 C c C CC (normal) Cc (normal) c Cc (normal) cc (cystic fibrosis)

Genotypic ratio— CC:Cc:cc = 1:2:1

Phenotype ratio— normal : cystic fibrosis = 3:1

Thus, the chance one of their children could inherit the disease is 25% (1 out of 4)

Question:

If Woody Guthrie had children with a women with Huntingtons Disorder, which is true?

Select one:

two out of four children having the disorder is the probability

Explanation:

Huntingtons Disorder is an autosomal dominant inheritance. So, only one copy of defective gene is enough to develop the disease. We assume that H allele is responsible for Huntingtons Disorder and h allele is responsible for normal condition. So, H is dominant over h. The genotype of Woody Guthrie is hh (homozygous recessive), because he is normal and the genotype of his wife is Hh (heterozygous) because she has the Huntingtons Disorder and most of the case in this disorder one has only one copy of defective gene.

Gamete of hh is h and h; gamete of Hh is H and h.

 h h H Hh (Huntingtons Disorder) Hh (Huntingtons Disorder) h hh (normal) hh (normal)

Genotypic ratio in— Hh:hh = 2:2 = 1:1

Phenotype ratio— Huntingtons Disorder : normal = 2:2 = 1:1

Thus, two out of four children having the disorder is the probability.

Question:

This is a good example of codominace

Select one:

human AB blood type

Explanation:

AB blood group in human is an example of co-dominance. In heterozygous condition (IAIB) the characters of both alleles IA and IB are produced.

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