4. For a gene present on human chromosome 4, the maximum number of alleles that may be detected by sequencing the genome of 5 males and 10 females is _____.
Maximum Number of Alleles Detected for a Gene on Human Chromosome 4
Introduction
Genes exist in different alternative forms known as alleles. In diploid organisms such as humans, each autosomal gene is present in two copies because homologous chromosome pairs are inherited from both parents. One allele is inherited from the mother and the other from the father. Consequently, every individual carries two alleles for each gene located on an autosome, although the two alleles may be identical (homozygous) or different (heterozygous).
When analyzing DNA sequences from multiple individuals, geneticists often ask how many alleles can theoretically be detected. The answer depends on whether the gene is located on an autosome or on a sex chromosome. Since chromosome 4 is an autosome, every male and every female possesses two copies of chromosome 4, contributing two alleles each for any gene located on this chromosome.
Correct Answer
Correct Answer: 30 Alleles
Detailed Explanation
Human chromosome 4 is an autosome, not a sex chromosome. Every normal human, irrespective of sex, possesses two copies of chromosome 4 because humans are diploid organisms.
Therefore:
- Each male contributes 2 alleles.
- Each female also contributes 2 alleles.
The total number of individuals is:
5 males + 10 females = 15 individuals
Since every individual contributes two alleles:
Total Alleles = Number of Individuals × 2
Total Alleles = 15 × 2 = 30
The question asks for the maximum number of alleles that could be detected. This assumes that every chromosome carries a unique allele, making all 30 chromosome copies genetically different.
Step-by-Step Calculation
Step 1: Count the Number of Individuals
Number of Males = 5
Number of Females = 10
Total Individuals = 15
Step 2: Determine the Number of Alleles per Individual
Chromosome 4 is an autosome.
Each person possesses:
2 copies of chromosome 4
Therefore, each person contributes:
2 alleles
Step 3: Calculate the Total Number of Alleles
Total Alleles = 15 × 2
Total Alleles = 30
Calculation Summary
| Parameter | Value |
|---|---|
| Number of Males | 5 |
| Number of Females | 10 |
| Total Individuals | 15 |
| Alleles per Individual | 2 |
| Total Maximum Alleles | 30 |
Why Both Males and Females Contribute Equally
Because chromosome 4 is an autosome, males and females possess exactly the same number of copies. Unlike genes located on the X or Y chromosome, autosomal genes are present in two copies in both sexes. Therefore, every individual contributes two alleles regardless of gender.
Autosomal vs Sex Chromosome Genes
| Feature | Autosomal Gene | X-Linked Gene | Y-Linked Gene |
|---|---|---|---|
| Male Copies | 2 | 1 | 1 |
| Female Copies | 2 | 2 | 0 |
| Chromosome 4 | Yes | No | No |
Examples of Allele Counting
| Individuals | Autosomal Alleles |
|---|---|
| 1 person | 2 |
| 5 people | 10 |
| 10 people | 20 |
| 15 people | 30 |
Biological Significance
Allele counting is fundamental in population genetics, evolutionary biology, genome sequencing, and medical genetics. Determining the number of alleles present within a population enables scientists to estimate genetic diversity, calculate allele frequencies, detect mutations, identify disease-associated variants, and study evolutionary relationships. Modern genome sequencing projects routinely analyze millions of alleles across large human populations to understand genetic variation and disease susceptibility.
Final Answer
Total Individuals = 5 + 10 = 15
Chromosome 4 is an autosome.
Each individual possesses two copies of chromosome 4.
Total Alleles = 15 × 2 = 30
Correct Answer: 30 Alleles
