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Answer:
The phenotypic ratio for the neurofibromatosis gene would be 1:1.
This is because woman has one dominant allele for neurofibromatosis, so there would be 50% of female gametes with dominant allele for neurofibromatosis. On the other hand, man is normal, so there would be all normal male gametes. Therefore, half of their progeny would have neurofibromatosis from mother.
Further explanation:
A). Dominant autosomal genetic disease.
A dominant autosomal genetic disorder can be defined as disorder, in which one mutated copy of gene (allele) is sufficient to affect the person. It is known as autosomal disorder as genes for this disease are present on autosomes.
B). Red-Green Color blindness.
Red-green color blindness is a sex-linked recessive genetic disorder, which mutated gene is present on X chromosome (sex chromosome). It is know as recessive as it is expressed only if both the recessive copies of X chromosomes are present.
C). Phenotype.
Phenotype of an individual can be defined as a set of features or characteristics, which are observable or expressed physically. For example, height, color of eye or hair, or observable traits for a disease
D).Phenotypic ratio of for diseased gene in children.
People with autosomal dominant disorder are affected with disorder either in heterozygous or homozygous dominant conditions. In this case, female is heterozygous and affected.
Assume genotype of woman is Aa (where 'A' represents dominant allele and 'a' represents recessive allele for neurofibromatosis).
On the other hand, man is normal for neurofibromatosis as he has both recessive alleles for neurofibromatosis. Assume genotype of man is aa (both recessive alleles).
Even if the man is affected with color blindness, there is no role of color blindness (a sex-linked disorder) in inheritance of neurofibromatosis, which is an autosomal disorder.
So, the phenotypic ratio for neurofibromatosis can be determined as:
Parents: Woman X Man
(Aa) (aa)
Gametes: ↓ ↓
A a a
(50%) (50%) (100%)
Children: Aa (with diseased phenotype) = 50%
aa (normal normal phenotype) = 50%
(For more information please find the Punnet square attached with answer).
Thus, phenotypic ratio for the neurofibromatosis would be 1:1 as 50% of their children are affected with disease.
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Grade: 5-9.
Subject: Biology
Subchapter: Genetics
Keywords: Autosomal dominant genetic disorder, color-blindness, X-linked recessive trait, phenotypic ratio.
The phenotypic ratio of neurofibromatosis gene will be 1:1 that is the 50% of the offspring will be affected.
Further Explanation:
Homozygous is the condition in which a particular gene has similar alleles present on a homologous chromosome. While on the contrary heterozygous condition is when a particular gene has dissimilar alleles present on the homologous chromosome.
If we take an example of Height where (T) represent tall and (t) represents dwarf, the homologous and heterologous condition can be represented as,
TT – tall homozygous condition
Tt- tall heterozygous condition
Autosomal dominant genetic disease- In this condition only one ‘dominant’ gene is enough to cause a disease or a condition. This occurs in only autosomes that is 22 pairs of chromosome other than one sex chromosome. In short the diseases which are caused by transfer of dominant autosomes which are affected are autosomal dominant genetic disease.
Neurofibromatosis- This is a genetic disorder which causes development of tumors in nerve tissue. These tumors can develop in any part from nerves, spinal cord or brain.
Let us consider the condition given in the problem,
Woman is heterozygous for neurofibromatosis- Nn
Man is homozygous recessive for neurofibromatosis- nn
The gametes which can be formed from Nn is N and n, while from nn two gametes n and n can be formed as shown in the image attached below.
The punnett square showing the number of offspring there genotype and phenotypes can be visualized in the image attached below.
We have the genotypic and phenotypic ratio as,
Genotypic ratio- 1 : 1
1 heterozygous dominant: 1 homozygous recessive
Phenotypic ratio- 1 : 1
1 neurofibromatosis: 1 non- neurofibromatosis
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Answer Details:
Grade: High school
Subject: Biology
Chapter: Genetics
Keywords:
Heterozygous, homozygous, neurofibromatosis, dominant, recessive, genetic disease, color blindness, children, offspring, phenotypic ratio, genotypic ratio, Heterozygous dominant, homozygous recessive.
