Predicting Changes in Genotype and Phenotype Frequencies in Rock Pocket Mouse Populations
In this assignment, you will use the provided case study about rock pocket mice to analyze how environmental changes can affect the genotype and phenotype frequencies in a population. You will make predictions, interpret data, and explain your reasoning using evidence from the case study. This assignment will help you understand the relationship between genetic variation, natural selection, and population changes.
Group 1
Use the information and images provided to answer the following questions about the relationship between fur color and environment in rock pocket mice.
Source 1.1
Rock pocket mice live in the Sonoran Desert in the southwestern United States and Mexico. Over time, volcanic eruptions affected the environments where the mice live. These eruptions covered parts of the ground in dark volcanic rock.
In this activity, you will explore how this change impacted rock pocket mouse populations. You will make observations, analyze and interpret data, and support claims with evidence. These skills are essential in science and many other fields.
Source 1.2
Figure 1. Four different rock pocket mice living in their natural environments.
A: Light colored mouse on a light colored background
B: Dark colored mouse on a dark colored background
C: Dark colored mouse on a light colored background
D: Light colored mouse on a dark colored background
Source 1.3
How quickly natural selection work? "The Making of the Fittest: Natural Selection and Adaptation" tells the story of a living example of Darwin's process of natural selection and shows how quickly a trait can spread through a population when natural selective pressure is strong.
The rock pocket mouse shows how different genetic changes can lead to the same adaptation — a coat color that hides the rock pocket mice from predators, such as owls. Explore a classic case study in natural selection and evolution with your science students.
Question 1a
Describe how the fur color of the rock pocket mice in the images relates to their environment.
Question 1b
Which mice are most likely to survive in its environment?
Group 2
Read the information about the MC1R gene and how it affects fur color in rock pocket mice.
Source 2.1
A rock pocket mouse’s fur color is affected by a protein called MC1R, which stands for melanocortin 1 receptor. The MC1R protein is encoded by a gene called Mc1r.
Mc1r gene nucleotide sequence in mice comes from two different populations: • a population of mostly light-colored mice living on light-colored desert rock • a population of mostly dark-colored mice living on the Pinacate lava flow (an area covered by dark volcanic rock)
Question 2a
Explain how a change (mutation) in the Mc1r gene can lead to a change in the fur color of a rock pocket mouse.
Source 2a.1
Figure 2. A summary of the processes by which genes (such as Mc1r) are used to make proteins (such as MC1R). First, during transcription, cells use the genetic information in DNA to create an RNA message (mRNA). Then, during translation, the mRNA is used to build a protein. The cell “reads” the mRNA sequence in groups of three nucleotides at a time, called codons. Each codon determines which amino acid is added to a growing protein.
Question 2b
If a volcanic eruption creates more areas of dark volcanic rock, what do you predict will happen to the frequency of the dark-fur allele (gene version) in the local mouse population over several generations?
Group 3
Use your understanding of natural selection and genetic variation to answer the following question.
Question 3a
Describe how natural selection can change the frequency of a genotype or phenotype in a population over time. Use the rock pocket mouse as an example in your explanation.
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