The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.
    Cross 1:  P₁: Male leopard x male mottled
             F₁: All mottled
             F₂: 70 mottled, 22 leopard
    Cross 2:  P₁: Male mottled x female leopard
             F₁: All mottled
             F₂: 50 mottled, 18 leopard
Propose two different genetic crosses that would allow you to determine the genotype of one mottled frog from the F₂ generation.

Verified step by step guidance

1. Step 1: Understand the inheritance pattern. The problem states that the dorsal pigment pattern is controlled by an autosomal gene. The F₁ generation is all mottled, suggesting that mottled is dominant over leopard. The F₂ generation shows a ratio of mottled to leopard, which indicates Mendelian inheritance.
2. Step 2: Define the genotypes. Assign symbols to the alleles: 'M' for the dominant mottled allele and 'm' for the recessive leopard allele. A mottled frog could have the genotype MM (homozygous dominant) or Mm (heterozygous). A leopard frog would have the genotype mm (homozygous recessive).
3. Step 3: Design the first genetic cross. To determine the genotype of a mottled frog from the F₂ generation, cross the mottled frog with a homozygous recessive leopard frog (mm). If the mottled frog is heterozygous (Mm), the offspring will show a 1:1 ratio of mottled to leopard. If the mottled frog is homozygous dominant (MM), all offspring will be mottled.
4. Step 4: Design the second genetic cross. Alternatively, cross the mottled frog with another mottled frog from the F₂ generation. If both frogs are heterozygous (Mm), the offspring will show a 3:1 ratio of mottled to leopard. If one frog is homozygous dominant (MM) and the other is heterozygous (Mm), the offspring will show a 1:0 ratio of mottled to leopard.
5. Step 5: Analyze the offspring ratios. Based on the phenotypic ratios observed in the offspring from either cross, you can determine whether the mottled frog from the F₂ generation is homozygous dominant (MM) or heterozygous (Mm).

Key Concepts

Autosomal Inheritance

Autosomal inheritance refers to the transmission of genes located on the autosomes, which are the non-sex chromosomes. In this case, the dorsal pigment pattern of frogs is controlled by an autosomal gene, meaning that both males and females have two copies of the gene that can influence the trait. Understanding this concept is crucial for predicting the inheritance patterns and phenotypic ratios observed in the offspring.

Reciprocal Crosses

Reciprocal crosses involve mating individuals of different phenotypes in both possible combinations to determine the influence of parental genotypes on offspring traits. In the given scenario, the reciprocal crosses between leopard and mottled frogs help to establish whether the mottled phenotype is dominant over the leopard phenotype. Analyzing the results from these crosses aids in understanding the genetic basis of the observed traits.

Phenotypic Ratios

Phenotypic ratios represent the relative frequencies of different phenotypes in the offspring resulting from a genetic cross. In the F₂ generation of the crosses described, the observed ratios of mottled to leopard frogs provide insights into the underlying genotypes of the parents. By analyzing these ratios, one can infer the possible genotypes of the mottled frogs and design further crosses to confirm their genetic makeup.