Huntington's disease ia an autosomal dominant disorder. A heterozygous female mates with a nondiseased male. What is the chance a child will have the disease? 1) 0% 2) 25% 3) 50% 4) 75% 5) 100%
Anatomy and Physiology of Special Sensory Organs
Sensory organs can be labeled as special sensory structures that permit sight, hearing, odor, and flavor. Sensory structures permitting proprioception, touch, thermal, and pain perception can be classified as more advanced sensory organs. The sensory neurons are trained to find out modifications in the external and internal conditions so that a person's body can react to that change. A stimulus is the first signal that is recognized by any sensory receptor of the body. Stimulus is an impulse generated when there is a change in the surroundings of a person. For example, a heated environment will alert the brain through the thermal sensory organs and generate a reflex accordingly.
Sensory Receptors
The human sensory system is one of the most complex and highly evolved structures, which processes a myriad of incoming messages. This well-coordinated system helps an organism or individual to respond to external stimuli, appropriately. The sensory receptors are an important part of the sensory system. These receptors are specialized epidermal cells that respond to external environmental stimuli. These receptors consist of structural and support cells that form the peripheral unit of the receptor and the neural dendrites which receive and detect the external stimuli.
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**Genetics and Heredity: Understanding Autosomal Dominant Disorders**
**Question:**
Huntington's disease is an autosomal dominant disorder. A heterozygous female mates with a nondiseased male. What is the chance a child will have the disease?
1) 0%
2) 25%
3) 50%
4) 75%
5) 100%
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**Explanation:**
Huntington's disease is an example of an autosomal dominant disorder. This means that only one copy of the mutated gene is required for an individual to exhibit symptoms of the disease. In genetic terms, dominant alleles mask the expression of recessive alleles in heterozygous individuals.
**Genotype Symbols:**
- Let \( H \) represent the dominant allele for Huntington's disease.
- Let \( h \) represent the normal recessive allele.
**Parent Genotypes:**
- Heterozygous female: \( Hh \)
- Nondiseased male: \( hh \)
**Punnett Square Analysis:**
To determine the probability of their offspring inheriting Huntington's disease, we use a Punnett square to evaluate the combinations of alleles.
| | \( h \) (Male) | \( h \) (Male) |
|---------|:---------------:|:---------------:|
| \( H \) (Female) | **Hh** | **Hh** |
| \( h \) (Female) | **hh** | **hh** |
**Results:**
From the Punnett square, we see that there are four possible combinations for the offspring:
- 2 out of 4 (50%) are **Hh** (showing the disease)
- 2 out of 4 (50%) are **hh** (normal)
**Conclusion:**
The chance that a child will inherit Huntington's disease from these parents is **50%**.
**Answer:** 3) 50%
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Understanding genetic principles through examples like Huntington's disease can provide crucial insights into heredity and medical genetics. For more details and explorations, check our topics on Genetic Disorders and Hereditary Patterns.
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