Albinism: From Genotype to Phenotype

Albinism: From Genotype to Phenotype Directions Part 1: Read the introduction section on the Canvas page, “Albinism: from Genotype to Phenotype,” and answer the questions below. 1.​ About how many people do they estimate suffer from albinism? 1 in 17,000 to 20,000 2.​ Why is melanin important for humans? By not making this, what is a major consequence for people with albinism? It is an extreme susceptibility to, and high risk of, fatal skin cancer due to a lack of this protection. 3.​ Referencing your answer to #2, why does it make sense that people who live close to the equator have a darker skin tone? Because there in the sun and in hot weather. 4.​ How many types of albinism are found in humans? There are 20 types of albinism found in humans 5.​ Albinism is caused by a mutation in a gene. Research and describe what a mutation is. Lastly, describe how a mutation can cause a frameshift in an amino acid sequence. Mutation Definition: any permanent change in the DNA sequence of an organism Frameshift in Amino Acid Sequence: a genetic "disaster" that occurs when the number of nucleotides (DNA bases) added or deleted is not a multiple of three. Mutation Type Addition/Insertion Deletion Substitution Description Does it Cause A Frameshift? In genetics, an Addition (also known as an Insertion) occurs when one or more extra DNA base pairs are inserted into a gene sequence. occurs when one or more DNA base pairs are lost or removed from a gene sequence. occurs when one DNA base is swapped out for a different one YES YES NO a type of substitution where a DNA base is swapped, but the amino acid sequence remains exactly the same Silent NO 6.​ What mutation types (addition, deletion, substitution) do you think can be a silent mutation? Explain your reasoning. Substitution is the primary mutation type that results in a silent mutation, while additions (insertions) and deletions are rarely silent unless they occur in specific multiples. 7.​ Organize your thoughts: by reviewing the phenotypic traits that appear in humans with this genetic disorder in the reading above, complete the table below. white creamy white white yellow light colored blue/hazel none specifically African reddish brown reddish blue/brown black africans creamy white yellow blue/hazel east asian TYR OCA2 TYRP1 SLC45A2 8.​ Reviewing your table, what do all types of albinism have in common? Use the traits discussed in the reading as evidence. 9.​ Construct an explanation below that explains why there are different variations of this disorder and why it results in the same basic phenotype. Cite specific evidence without copying any part of the passage directly below. Directions Part 2: Procedures: Please read this section after your complete part 1. PLEASE REFERENCE THE AMINO ACID CHART ON CANVAS FOR TRANSLATION 1.​ Each student will analyze one of four genes: TYR, OCA2, TYRP-1, or SLC45A2. Pick one of the genes and continue on to the next step. 2.​ Each form has an original DNA strand and 3 different mutated strands. For each, you will transcribe the mRNA sequence and then translate the mRNA into the amino acid sequence (AAs). 3.​ With a colored pencil, or using an app in which you can draw on, you will then do the following: • First, circle the mutation(s) on each of the three mutated strands that differ from the original DNA strand at the top of your form. (Note: not all sequences start at beginning of gene.)​ • Second, lightly shade over each codon that differs in the mRNA strand from the original mRNA strand at the top of your form.​ • Lastly, lightly shade over each amino acid that differs in the amino acid sequence from the original amino acid sequence at the top of your form 4.​ Using the amino acid sequences, match one of them to the “Individual” cards on the Canvas page to view the phenotype. Once your analysis is complete, fill out the table below. Analysis: Making sense of your data Your gene is: ____________________ Individual # _______ & ______ Mutation Mutation Type Cite Your Evidence Here for Mutation Type Gene Affected? Mutation 1 Mutation 2 Mutation 3 Mutation Table Questions: 1.​ Which of the mutations caused a change in phenotype? WHY? 2.​ Which mutation type did NOT cause a change in phenotype? WHY? Directions Part 3: Flow Chart for Protein Synthesis: By creating a flow chart below, trace the steps from DNA through to the resulting phenotype. It has been started for you below. BEFORE completing your flow chart, please watch the video in Canvas under the albinism lab page referenced earlier. The following words must appear in this flow chart: ​ Translation​ Amino acid(s) Protein​ Gene ​ mRNA tRNA Phenotype