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Q10:
What is pedigree analysis? Suggest how such an analysis, can be useful.
Solution :
1. Definition of Pedigree Analysis
Pedigree analysis is the systematic study of an inherited trait or disorder across multiple generations of a family, represented as a visual chart or diagram known as a pedigree or family tree. [Per Principles of Mendelian Inheritance]. It serves as a tool to determine the mode of inheritance—whether autosomal dominant, autosomal recessive, X-linked dominant, or X-linked recessive—by observing the distribution of phenotypes within related individuals.
2. Symbolic Notation in Pedigree Analysis
To ensure universal clinical and academic communication, pedigree charts utilize standardized symbols. The following SVG illustrates the basic constituents of a pedigree.
3. Utility and Application of Pedigree Analysis
Pedigree analysis provides essential data for genetic counseling and medical diagnostics. Its utility is categorized as follows:
| Application | Methodological Justification |
|---|---|
| Determining Inheritance Patterns | By identifying whether a trait skips generations (recessive) or appears in every generation (dominant), researchers calculate the probability of phenotypic expression. |
| Genetic Counseling | Allows families to understand the risk of transmitting hereditary disorders such as Hemophilia, Cystic Fibrosis, or Phenylketonuria to offspring. |
| Diagnostic Validation | Supports the tracking of lethal alleles that may be masked in the heterozygous state [By Hardy-Weinberg Principle applications]. |
| Predictive Probability | Enables the use of Punnett square logic at the population or family level to estimate the likelihood of a child inheriting a specific allele combination. |
4. Analytical Procedure
To analyze a pedigree effectively, the following steps are performed:
- Step 1: Identify Presence/Absence: Determine if the trait appears in every generation. If it does not, the trait is likely recessive.
- Step 2: Evaluate Sex Distribution: If the trait appears predominantly in males, it suggests an X-linked recessive mode of inheritance [Per Sex-Linked Inheritance theory].
- Step 3: Test Cross Verification: Assign genotypes to individuals in the pedigree (e.g., $AA, Aa, aa$) and check for logical consistency across parental and $F_1$ generations.
Final Solution: Pedigree analysis is the study of a family history regarding a particular trait to determine its inheritance pattern. It is invaluable for diagnosing hereditary genetic disorders, providing risk assessment for prospective parents, and mapping the transmission of alleles through generations, thereby acting as a critical tool in clinical genetics and medical diagnosis.
More Questions from Class 12 Biology Principles of Inheritance and Variation EXERCISES
- Q1: Mention the advantages of selecting pea plant for experiment by Mendel.
- Q1: Mention the advantages of selecting pea plant for experiment by Mendel.
- Q2(a): Differentiate between the following – (a) Dominance and Recessive
- Q2(a): Differentiate between the following – (a) Dominance and Recessive
- Q2(b): Differentiate between the following – (b) Homozygous and Heterozygous
- Q2(b): Differentiate between the following – (b) Homozygous and Heterozygous
- Q2(c): Differentiate between the following – (c) Monohybrid and Dihybrid.
- Q2(c): Differentiate between the following – (c) Monohybrid and Dihybrid.
- Q3: A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced?
- Q3: A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced?
- Q4: Explain the Law of Dominance using a monohybrid cross.
- Q4: Explain the Law of Dominance using a monohybrid cross.
- Q5: Define and design a test-cross.
- Q5: Define and design a test-cross.
- Q6: Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.
- Q6: Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.
- Q7(a): When a cross in made between tall plant with yellow seeds (\(TtYy\)) and tall plant with green seed (\(Ttyy\)), what proportions of phenotype in the offspring could be expected to be (a) tall and green.
- Q7(a): When a cross in made between tall plant with yellow seeds ((TtYy)) and tall plant with green seed ((Ttyy)), what proportions of phenotype in the offspring could be expected to be (a) tall and green.
- Q7(b): When a cross in made between tall plant with yellow seeds (\(TtYy\)) and tall plant with green seed (\(Ttyy\)), what proportions of phenotype in the offspring could be expected to be (b) dwarf and green.
- Q7(b): When a cross in made between tall plant with yellow seeds ((TtYy)) and tall plant with green seed ((Ttyy)), what proportions of phenotype in the offspring could be expected to be (b) dwarf and green.
- Q8: Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in \(F_{1}\) generation for a dibybrid cross?
- Q8: Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in (F_{1}) generation for a dibybrid cross?
- Q9: Briefly mention the contribution of T.H. Morgan in genetics.
- Q9: Briefly mention the contribution of T.H. Morgan in genetics.
- Q10: What is pedigree analysis? Suggest how such an analysis, can be useful.
- Q11: How is sex determined in human beings?
- Q11: How is sex determined in human beings?
- Q12: A child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.
- Q12: A child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.
- Q13(a): Explain the following terms with example (a) Co-dominance
- Q13(a): Explain the following terms with example (a) Co-dominance
- Q13(b): Explain the following terms with example (b) Incomplete dominance
- Q13(b): Explain the following terms with example (b) Incomplete dominance
- Q14: What is point mutation? Give one example.
- Q14: What is point mutation? Give one example.
- Q15: Who had proposed the chromosomal theory of the inheritance?
- Q15: Who had proposed the chromosomal theory of the inheritance?
- Q16: Mention any two autosomal genetic disorders with their symptoms.
- Q16: Mention any two autosomal genetic disorders with their symptoms.
CBSE Solutions for Class 12 Biology Principles of Inheritance and Variation
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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