Download In the organism Draco vulgaris (common house dragon, a diploid

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In the organism Draco vulgaris (common house dragon, a diploid organism), the enzyme acetaldehyde
reductase (fire1 ) is abundantly expressed in the salivary glands (in wild-type D. vulgaris) and catalyzes
the conversion of acetaldehyde to ethanol (with complementary oxidation of NADH to NAD+). Ethanol is
required for fire-breathing. The gene model for fire1 is:
The active site that catalyzes the acetaldehyde to ethanol reaction is in exon 3. Just upstream of exon 3
is a binding site for the protein Ext2 (indicated by the *), which is not expressed in the salivary glands in
wild-type D. vulgaris. When Ext2 binds upstream of exon3, that exon is spliced out of the mature mRNA.
Another protein, Ext3, is expressed only in the salivary glands, and binds to the promoter of ext2, which is
why ext2 is not expressed in the salivary glands.
Draw a diagram indicating the regulatory relationships between the genes fire1, ext2, and ext3, and firebreathing activity.
The following mutant alleles have been identified by genome sequencing:
i. fire1-1 : A mutation in exon 3 of fire1 that disrupts the active site
ii. fire1-2 : A mutation in the Ext2 binding site upstream of exon 3 of fire1
iii. ext2-1 : A mutation in the DNA binding domain of ext2
iv. ext2-2 : A mutation in the Ext3 binding site in the promoter of ext2
v. ext3-1 : A mutation in the DNA binding domain of ext3
Based on this information, fill in the expected phenotype for the following genotypes. Asssume that:
i. unspecified genes are homozygous for wild-type,
ii. proteins are equally effective at wild-type and half-wild-type abundance,
iii. the possible phenotypes are:
a) fire-breathing (ethanol produced in salivary glands)
b) no fire-breathing (no ethanol produced in salivary glands)
c) lethal (ethanol produced in other tissues, causes flammable embryos)
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genotype
phenotype
fire1/fire1-1
fire1-1/fire1-1
fire1/fire1-2
fire1-2/fire1-2
ext2/ext2-1
ext2-1/ext2-1
ext2/ext2-2
ext2-2/ext2-2
ext3/ext3-1
ext3-1/ext3-1
fire1/fire1-1 ext2-1/ext2-1
fire1-1/fire1-1 ext2-1/ext2-1
ext2-1/ext2-1 ext3-1/ext3-1
fire1-1/fire1-1 ext3-1/ext3-1
fire1-2/fire1-2 ext3-1/ext3-1
fire1-1/fire1-2
fire1/fire1-1&2
fire1/fire1-1&2 ext2/ext2-1
ext2-1/ext2-2
ext2/ext2-1&2
ext2-1/ext2-2 fire1-1/fire1-2
ext2-1/ext2-2 fire1-2/fire1-1
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