a scientist is studying the inheritance of two characteristics in plants: red flowers (rr and rr), which are…

a scientist is studying the inheritance of two characteristics in plants: red flowers (rr and rr), which are dominant to yellow flowers (rr), and green leaves (gg and gg), which are dominant to yellow leaves (gg). she crosses a double heterozygous (rrgg) with a double recessive (rrgg), and expect to see a 1 : 1 : 1 : 1 ratio in the offspring. instead, she sees these results: | genotype | rrgg | rrgg | rrgg | rrgg | | --- | --- | --- | --- | --- | | predicted outcome | 500 | 500 | 500 | 500 | | actual outcome | 900 | 900 | 100 | 100 |

a scientist is studying the inheritance of two characteristics in plants: red flowers (rr and rr), which are dominant to yellow flowers (rr), and green leaves (gg and gg), which are dominant to yellow leaves (gg). she crosses a double heterozygous (rrgg) with a double recessive (rrgg), and expect to see a 1 : 1 : 1 : 1 ratio in the offspring. instead, she sees these results: | genotype | rrgg | rrgg | rrgg | rrgg | | --- | --- | --- | --- | --- | | predicted outcome | 500 | 500 | 500 | 500 | | actual outcome | 900 | 900 | 100 | 100 |

Answer

Explanation:

Step1: Identify the cross type

The cross is between a double heterozygous ((RrGg)) and a double recessive ((rrgg)). In a typical independent assortment (if genes are unlinked), the expected ratio is (1:1:1:1) for the four genotypes.

Step2: Analyze the actual vs predicted

The predicted outcome for each genotype is 500. But actual outcomes are 900 (for (RrGg) and (rrgg)) and 100 (for (Rrgg) and (rrGg)). This deviation from the expected (1:1:1:1) ratio suggests that the genes for flower color (R/r) and leaf color (G/g) are linked. The parental combinations ((RrGg) and (rrgg)) are more frequent, and the recombinant combinations ((Rrgg) and (rrGg)) are less frequent, indicating that the alleles are linked on the same chromosome and crossing - over occurred less frequently to produce the recombinant genotypes.

Step3: Calculate the recombination frequency (optional for understanding)

Total offspring (= 900 + 900+100 + 100=2000) Recombinant offspring (= 100 + 100 = 200) Recombination frequency (=\frac{200}{2000}=0.1) or 10%, which is a measure of the distance between the two linked genes.

Answer:

The genes for flower color (R/r) and leaf color (G/g) are linked (not assorting independently), with the parental genotypes ((RrGg) and (rrgg)) being more frequent in the offspring due to linkage, and the recombinant genotypes ((Rrgg) and (rrGg)) being less frequent as they result from crossing - over.