True or False. Explain your reason for each statement. 1. Reactive oxygen specie

Question

True or False. Explain your reason for each statement.

1. Reactive oxygen species are produced in the cell as a consequence of metabolism, especially due to transfer of electrons from quinone to molecular oxygen in the electron transport chain. These ROS molecules are the primary cause of mutations in the mitochondrial genome.

2. Transposons comprise the majority of DNA in some eukaryotes’ genomes. The cells’ only defense against the activity of these transposons is to methylate their genes to prevent insertion of the transposons and introduction of frameshift mutations.

3. A eukaryotic promoter region in front of a gene is flipped in position due to a chromosomal transversion. However, the regulatory elements are still arranged normally relative to the transcriptional start site of the gene. The gene immediately next to the promoter would no longer be expressed.

Explanation / Answer

1. It is true; Reactive oxygen species are produced in the cell as a consequence of metabolism, especially due to transfer of electrons from quinone to molecular oxygen in the electron transport chain. These ROS molecules are the primary cause of mutations in the mitochondrial genome.

ROS produce intracellularly by multiple mechanisms not only in mitochondria, but also in cell membrane, peroxysomes and endoplasmic reticulum. The most potent ROS is NADPH oxidase. Too much damage due to mutation in mitochondria can lead to apoptosis.

2. It is true; Transposons comprise the majority of DNA in some eukaryotes’ genomes. The cells’ only defense against the activity of these transposons is to methylate their genes to prevent insertion of the transposons and introduction of frameshift mutations.

Transposons constitute more than one third in some mammalian organisms. DNA methylation mostly restricted to transposons only. This methylation prevent the transposition of transposons in the genome and there by protecting from lacerate the genome.

3. It is False; If promoter region is flipped due to transversion, the regulatory elements present in the promoter region also get flipped and will not function, hence no gene expression of gene next to this promoter.

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