In watermelons the allele for green color and for short shape are dominant over the alleles for striped color and for long shape. A plant with long striped fruit is crossed with one heterozygous for both characteristics. The results are:
green, short: 14
green, long: 96
striped, short: 80
striped, long: 10
Assuming the parents of the heterozygous plant were homozygous for both traits, you can predict that: (which statements are true/false and why?)
a. the genes for colour and shape are on separate chromosomes
b. the genes for color and shape are so close together on the same chromosome that no crossovers have occured
c. the alleles for green color and long shape are on the same chromosome
d. the alleles for striped color and short shape are on the same chromosome
THIS IS WHAT I HAVE:
a. false, because the results are not 50% recombiant offspring.
b. false, crossover has occured as the offspring are not identical to parents
c. ?
d. ?
Thanks for the help in advance!
a. False, because the results are not 50% recombinant offspring.
b. False, crossover has occurred as the offspring are not identical to parents.
c. False, the alleles for green color and long shape are on different chromosomes.
d. False, the alleles for striped color and short shape are on different chromosomes.
To determine the correct answers for statements c and d, let's analyze the results of the cross.
The cross involves a plant with long striped fruit (which we'll represent as SSLL) and a heterozygous plant for both characteristics (which we'll represent as SsLl).
From the given results:
- Green, short (ssll): 14
- Green, long (Ssll): 96
- Striped, short (ssLl): 80
- Striped, long (SsLl): 10
From these results, we can infer the following:
c. The alleles for green color and long shape are on the same chromosome.
From the cross results, we see that there are both green, long (Ssll) and green, short (ssll) offspring. This indicates that the allele for green color (S) is separate from the allele for long shape (L) because recombination occurred. Therefore, statement c is false.
d. The alleles for striped color and short shape are on the same chromosome.
The cross results show that there are both striped, short (ssLL) and striped, long (SsLL) offspring. This suggests that the alleles for striped color (s) and short shape (L) are independent of each other because recombination occurred. Therefore, statement d is false.
The correct answers are:
a. False
b. False
c. False
d. False
Based on the given results, we can make the following predictions:
a. False: The fact that the results are not in a 1:1:1:1 ratio suggests that the genes for color and shape are not on separate chromosomes. If they were on separate chromosomes, we would expect a more equal distribution of the different combinations of color and shape.
b. False: The fact that there are non-parental combinations (green, long and striped, short) indicates that crossovers have occurred. Crossovers are the result of the exchange of genetic material between homologous chromosomes during meiosis.
c. True: The observation that the green color and long shape are found together in the offspring (green, long: 96) suggests that the alleles for green color and long shape are on the same chromosome.
d. True: The fact that the striped color and short shape are also found together in the offspring (striped, short: 80) suggests that the alleles for striped color and short shape are on the same chromosome.
To summarize:
a. False: The genes for color and shape are not on separate chromosomes.
b. False: Crossovers have occurred.
c. True: The alleles for green color and long shape are on the same chromosome.
d. True: The alleles for striped color and short shape are on the same chromosome.