Question

5. A gene in the nuclear genome of an organism appears to be an ortholog of a gene in the mitochondrial genome of another species. A friend argues that this is evidence against the endosymbiotic theory. Is this a valid argument?

		No, because during evolution of different taxa, transfer of genes between the nuclear and mitochondrial genomes is common, and different species have undergone transfer of different genes.
		No, because there is no way mitochondrial genes could end up in the nuclear genome of a species.
		The argument’s validity will depend on whether the mitochondrial genomes in question are linear or circular.
		Yes, because ribosomal RNAs are never encoded by the mitochondrial genome.
		Yes, because it is likely that the gene in question is a rRNA gene.

**9. If you were interested in understanding all the genes necessary for the development of the human heart, which of these approaches would be an effective one to take?

		Perform a mutagenesis screen in Drosophila for all the mutations that lead to defective heart development, then identify and study all the mutated genes.
		Perform a mutagenesis screen in zebrafish to identify mutations in all genes necessary for normal heart development, then identify and study each mutated gene.
		Dissect developing hearts from salamander embryos, then extract mRNA from the heart tissue to determine which genes are expressed.
		Dissect developing hearts from mouse embryos, then extract mRNA from the heart tissue to determine which genes are expressed.
		all of the above are correct.

**10. Let’s say that you discovered a mutation in a gene in a human family that has an inherited disease showing an autosomal recessive pattern of inheritance. You suspect that the mutated gene might be responsible for the inherited disease and want to know more about it. You also know that this gene has orthologs in a diverse array of vertebrate species including mouse, zebrafish and frogs. Which approach would be the best to understand more about the function of the gene?`

		Use crispr technology to mutate the gene in zebrafish and study the phenotype of homozygous mutants.
		Determine the mRNA and protein expression patterns of the gene in mouse to see whether the expression is in tissues that are affected in human patients.
		Make a transgenic Drosophila line that expresses the protein to see whether it causes an abnormal phenotype.
		Sequence the mitochondrial genomes of the female family members showing the disease.
		Two of the above answers are correct.

Answer 1

Answer 5 ) No, because during evolution of different taxa, transfer of genes between the nuclear and mitochondrial genomes is common, and different species have undergone transfer of different genes.

During the course of evolution , mitochondrial DNA or plastid DNAs are transferred to nuclear genomes.These are called as numt (nuclear-mitochondrial ) and npt (nuclear-plastid ) sites.

There are several pseudogenes that are not expressed in mitochondria and plastids but they get transferred to nucleus where they acquire cis-regulatory sequences of nucleus and start expressing.

These phenomenon are quite frequently observed in plants.