True or False? Having pelvic spines is always advantageous to a stickleback. In one sentence, explain your answer. True or False? Dramatic changes in traits, such as the loss of limbs, can occur through mutations affecting a single gene. Provide evidence for your answer. Below is a simplified schematic representation of some of the genetic elements involved in the regulation of Pitx1 gene expression (from HHMI BioInteractive). The large grey rectangle represents the protein-coding region of the Pitx1 The smaller rectangles to the left (b and c) are regulatory switches (networks of regulatory genes); each one allows a specific binding protein to interact with it and turn on the Pitx1 gene in a particular tissue. When expressed, the Pitx1 gene is transcribed and then translated to generate the Pitx1 protein. A deletion at location (a) causes a frameshift mutation, which means that a different mRNA is produced. Recall that mRNA is like the recipe for making a protein. How likely is it that a functional Pitx1 protein would be produced in the jaw? _ In the pelvis? _ Justify your answers in one or two sentences. If the entire region (b) was deleted, would you see a functional Pitx1 protein in the jaw? _ In the pelvis? Justify your answers in one or two sentences. ÂÂ
The Evolution of the Stickleback Fish. Watch the ~15 minute video, Making of the Fittest: Evolution of the Stickleback Fish (https://youtu.be/Pv4Ca-f4W9Q) and the 1 minute video “Stickleback Fish Environment� (https://youtu.be/IRqLy3Oz-oM), both from the Howard Hughes Medical Institute. Answer the questions that follow:
True or False? Having pelvic spines is always advantageous to a stickleback. In one sentence, explain your answer.
True or False? Dramatic changes in traits, such as the loss of limbs, can occur through mutations affecting a single gene. Provide evidence for your answer.
Below is a simplified schematic representation of some of the genetic elements involved in the regulation of Pitx1 gene expression (from HHMI BioInteractive). The large grey rectangle represents the protein-coding region of the Pitx1 The smaller rectangles to the left (b and c) are regulatory switches (networks of regulatory genes); each one allows a specific binding protein to interact with it and turn on the Pitx1 gene in a particular tissue. When expressed, the Pitx1 gene is transcribed and then translated to generate the Pitx1 protein.
A deletion at location (a) causes a frameshift mutation, which means that a different mRNA is produced. Recall that mRNA is like the recipe for making a protein. How likely is it that a functional Pitx1 protein would be produced in the jaw? ___ In the pelvis? _ Justify your answers in one or two sentences.
If the entire region (b) was deleted, would you see a functional Pitx1 protein in the jaw? _ In the pelvis? __ Justify your answers in one or two sentences.
The Correct Answer and Explanation is :
True or False? Having pelvic spines is always advantageous to a stickleback.
False. The presence of pelvic spines is not always advantageous to a stickleback; it can be disadvantageous in environments where predators can easily target the spines. For example, in freshwater environments with fewer predators, some stickleback populations evolve to lose their pelvic spines because the energy expenditure of growing and maintaining them is not worth the limited benefit in defense.
True or False? Dramatic changes in traits, such as the loss of limbs, can occur through mutations affecting a single gene.
True. The loss of limbs in stickleback fish has been shown to occur due to mutations in a single gene, Pitx1. In sticklebacks, the loss of pelvic spines is a well-documented example where a mutation in the Pitx1 gene can result in a significant morphological change (the reduction or loss of pelvic spines), showing that dramatic changes in traits can be caused by a single gene mutation.
How likely is it that a functional Pitx1 protein would be produced in the jaw?
Unlikely.
A frameshift mutation at location (a) would result in a different mRNA being produced, which would likely lead to a nonfunctional or misfolded protein. The mutation would disrupt the normal translation process, making it unlikely that a functional Pitx1 protein is produced in the jaw.
How likely is it that a functional Pitx1 protein would be produced in the pelvis?
Unlikely.
Since the mutation at location (a) results in a frameshift, the altered protein would likely fail to activate the Pitx1 gene correctly in the pelvis, leading to the absence of pelvic spines.
If the entire region (b) was deleted, would you see a functional Pitx1 protein in the jaw?
Yes.
Region (b) is a regulatory switch for the Pitx1 gene. If it is deleted, the Pitx1 protein could still be produced in other tissues, like the jaw, if the necessary regulatory elements in other regions of the gene are intact.
If the entire region (b) was deleted, would you see a functional Pitx1 protein in the pelvis?
No.
Region (b) is required for the Pitx1 gene to be expressed in the pelvis. If it were deleted, the protein would not be produced in the pelvis, which could result in the loss of pelvic spines, as seen in some populations of sticklebacks.
Summary: The evolution of traits in sticklebacks, such as the presence or absence of pelvic spines, demonstrates the role of genetic regulation in adaptation to environmental pressures. The Pitx1 gene plays a crucial role in the development of pelvic spines. Mutations in this gene, such as those affecting regulatory regions or causing frameshift mutations, can lead to dramatic changes in morphology like the loss of limbs or spines. These changes can occur due to alterations in a single gene, with the likelihood of producing a functional protein being influenced by the specific mutations and the regulatory elements involved.