![]() MRNA mutated codon: 5’–AAC UCC ACC UGC ACA–3’ Altered Amino Acid: N-Asn-Ser-Thr-Cys-Thr-C Extracellular Domain IIIĪmino Acids 105 → 109 3’–CGGGACCGGTGGACC–5’ You only need to transcribe/translate the 3base codons with the mutations and the corresponding amino acids! Extracellular Domain IĪmino Acids 015 → 019 3’–TTGAGGTGGzCGTGT–5’ Compare the DNA sequences of the wild-type and mutant Mc1r alleles to identify the locations of these mutations. There are 5 mutations in this allele (one per sequence). Mutant Mc1r allele (dark phenotype) The sequences below are for the mutant (dark coloured) Mc1r allele. MRNA Strand (identify 5’,3’): 5’–CUU GUC CAC CAA GGU–3’ Amino Acid Strand (identify N,C): N-Leu-Val-His-Gln-Gly- C MRNA Strand (identify 5’,3’): 5’–AUG CUU GCA CCC CUC–3’ Amino Acid Strand (identify N,C): N-Met-Leu-Ala-Pro-Leu-C Intracellular Domain IIIĪmino Acids 230 → 234 3’–GAACAGGTGGTTCCA–5’ MRNA Strand (identify 5’,3’): 5’–CGG GCU CGG UGG CGG–3’ Amino Acid Strand (identify N,C): N-Arg-Ala-Arg-Trp-Arg-C Transmembrane VĪmino Acids 210 → 214 3’–TACGAACGTGGGGAG–5’ MRNA Strand (identify 5’,3’): 5’–GCC CUG GCC ACC CGG–3’ Amino Acid Strand (identify N,C): N-Ala-Leu-Ala-Thr-Arg-C Intracellular Domain IĪmino Acids 160 → 164 3’–GCCCGAGCCACCGCC–5’ MRNA Strand (identify 5’,3’): 5’–AAC UCC ACC CGC ACA–3’ Amino Acid Strand (identify N,C): N-Asn-Ser-Thr-Arg-Thr-C Extracellular Domain IIIĪmino Acids 105 → 109 3’–CGGGACCGGTGGGCC–5’ Extracellular Domain IĪmino Acids 015 → 019 3’–TTGAGGTGGGCGTGT–5’ The amino acid position in the protein sequence is provided for each segment. Note: the actual gene contains 951 base pairs (317 amino acids). Use the sequences provided to determine the complementary mRNA sequence and the translated amino acid strand. Wild-type Mc1r allele (light phenotype) Below are five 15 base DNA nucleotide sequences from the wild-type (light coat colour) Mc1r allele template DNA strand. The mutated allele of the Mc1r gene, however, triggers melanocytes to increase the production of eumelanin, resulting in the dark coat-colour phenotype. The melanocytes of wild-type (non-mutant) mice produce much more pheomelanin than eumelanin (or almost no eumlanin) the result is a sandycoloured mouse. This receptor is found embedded in the membrane of specialized cells called melanocytes, which you have also examined. The mouse Mc1r gene is located on mouse chromosome 16 (rock pocket mice have n=23 just like humans), and encodes a protein called the Melanocortin-1-Receptor (MC1R), which you have seen in each of the last two review activities. The synthesis of these pigments is controlled by the products of several genes, including the Mc1r gene. The Mc1r Gene: The coat colour of rock pocket mice is determined by two pigments: eumelanin, which is darkcoloured and pheomelanin, which is light-coloured. Their analysis led to the discovery of a mutation in the Mc1r gene which is involved in coat-colour determination. Researchers analyzed the data from these two populations in search of the genetic mutation responsible for the dark color. Scientists have collected data from a population of primarily darkcoloured mice living in an area of basalt called the Pinacate lava flow in Arizona, as well as from a nearby light-coloured population. However, populations of primarily dark-coloured rock pocket mice have been found living in areas where the ground is covered in a dark rock called basalt caused by geologic lava flows thousands of years ago. Most rock pocket mice have a sandy, light-coloured coat that enables them to blend in with the light color of the desert rocks and sand on which they live. The Rock Pocket Mouse: The rock pocket mouse, Chaetodipus intermedius, is a small, nocturnal animal found in the deserts of the south-western United States. In this activity we will further examine the genetic and molecular basis for the production of fur colour. In the review activities for modules 1 and 2, we learned about a protein called MC1R that is found in the cell membranes of specific mouse cells called melanocytes, whose job it is to produce the pigment melanin, which gives mice the colouration of their fur. To prepare for this module, in the review activities for the first 3 modules we will be examining the molecular, cellular, and genetic basis for mouse coat colour. ![]() ![]() Laroche: Mouse Colouration During module 4 on evolution, we will spend several classes examining the evolutionary significance of fur colour in a certain group of mice from the Sonoran desert in the South-Western United States.
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