Draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written.


AB/ab

Verified step by step guidance

1. Step 1: Understand the notation AB/ab. This represents a diploid organism with two homologous chromosomes. The uppercase letters (A and B) represent dominant alleles, while the lowercase letters (a and b) represent recessive alleles. The slash (/) separates the alleles on the two homologous chromosomes.
2. Step 2: Draw the homologous chromosomes. Represent each chromosome as a horizontal line. Place the alleles A and B on one chromosome (representing the dominant alleles) and the alleles a and b on the other chromosome (representing the recessive alleles). Ensure the genes are in the same order on both chromosomes.
3. Step 3: Label the chromosomes. Indicate that one chromosome contains the alleles AB (dominant alleles) and the other contains ab (recessive alleles). This helps clarify the genotype visually.
4. Step 4: Indicate the gene order. Since the problem specifies that the genes reside on the chromosome in the order written, ensure that gene A is placed before gene B on both chromosomes. This maintains the correct sequence.
5. Step 5: Verify the diagram. Double-check that the alleles are correctly placed on the homologous chromosomes and that the gene order matches the given genotype (AB/ab). This ensures the diagram accurately represents the genetic information.

Key Concepts

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same structure and gene sequence but may carry different alleles. Each parent contributes one chromosome to the pair, resulting in genetic variation. Understanding their structure is crucial for visualizing how alleles are arranged and inherited during meiosis.

Alleles

Alleles are different versions of a gene that can exist at a specific locus on a chromosome. For example, in the genotype AB/ab, 'A' and 'a' are alleles for one gene, while 'B' and 'b' are alleles for another. The combination of alleles determines the organism's traits and is essential for understanding genetic variation and inheritance patterns.

Genotype Representation

Genotype representation involves denoting the genetic constitution of an organism, typically using letters to signify different alleles. In the notation AB/ab, the slash indicates that the organism is heterozygous for two genes, with one chromosome carrying the alleles 'AB' and the other 'ab'. This representation is vital for analyzing genetic crosses and predicting offspring genotypes.