Question #1: In 1966, a mouse was found in the Jackson Laboratory colony that seemed to be excessive in weight as compared to its wildtype siblings from the same litter. The allele that was assigned to this mouse was called "db". Given the data from the original 1966 paper below, a) is there evidence of a genetic basis for an increased overall weight of the mutant mouse? b) Is this mutant phenotype encoded by a dominant or recessive gene? Please provide an explanation of your answers. Table 1. Body weight of diabetic (dbdb) and normal (++ and + db) mice. Sexes are combined. Age (weeks) 2- 3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-22 23-54 No. of mice 6 12 25 20 16 12 10 11 11 11 7 5 11 5 dbdb Av. 6.7 14.8 19.8 25.4 28.3 32.4 34.5 34.3 37.9 39,4 38.1 44.4 45.3 45.9 Weight (g) Range 7- 10 9- 20 10-27 AGIGTAAAC 14- 34 18-39 21-42 31-41 31-44 32- 45 32-46 34- 51 32-62 37-61 last two nucleotides of the 106 bp No. of mice 7 21 16 19 17 17 5 26 ++and+ db Av. 7.6 11.3 16.9 18.5 19.8 21.9 27.3 28.9 Weight (g) Range 7-9 9-13 In 1996, the genetic basis of this mutation was mapped to the leptin gene and no large chromosomal variations were found in the db variant or around the leptin gene as compared to wildtype siblings. c) What was the likely mechanism by which this mutation arose in the mutant mouse? .exon...AG|GTAAGT...intron... 43 882843 76686 15- 21 15- 23 16- 28 19- 28 Also in 1996, the genetic basis of the change was found to be a mutation in the splice site of the exon, with a single mutation of G to T. d) What was the likely lab technique used to identify this nucleotide change? AG GGAAAC 20-36 20-38 wt/wt db/db consensus