(a)
To determine: The fraction of the total haploid genome that the 500 copies of the ribosomal RNA genes represent.
Introduction: The genes encoding ribosomal RNA during oogenesis in Xenopus laevis is the best studied example of gene amplification. The unamplified number of ribosomal RNA genes is about 500 per haploid genome. After amplification, the oocyte contains about 500,000 ribosomal RNA genes per haploid genome. This level of amplification is necessary to allow the egg cells to synthesize 1012 ribosomes that accumulate during the two months of oogenesis in this species. Each ribosomal RNA gene consists of about 13,000 base pairs, and the genome size of Xenopus is about
(b)
To determine: The total size of the genome after amplification of the ribosomal RNA genes and the proportion of this that the amplified ribosomal RNA genes represent.
Introduction: The genes encoding ribosomal RNA during oogenesis in Xenopus laevis is the best studied example of gene amplification. The unamplified number of ribosomal RNA genes is about 500 per haploid genome. After amplification, the oocyte contains about 500,000 ribosomal RNA genes per haploid genome. This level of amplification is necessary to allow the egg cells to synthesize 1012 ribosomes that accumulate during the two months of oogenesis in this species. Each ribosomal RNA gene consists of about 13,000 base pairs, and the genome size of Xenopus is about
(c)
To determine: How long oogenesis would have to extend if the genes had not been amplified.
Introduction: The genes encoding ribosomal RNA during oogenesis in Xenopus laevis is the best studied example of gene amplification. The unamplified number of ribosomal RNA genes is about 500 per haploid genome. After amplification, the oocyte contains about 500,000 ribosomal RNA genes per haploid genome. This level of amplification is necessary to allow the egg cells to synthesize 1012 ribosomes that accumulate during the two months of oogenesis in this species. Each ribosomal RNA gene consists of about 13,000 base pairs, and the genome size of Xenopus is about
(d)
To determine: The reason why genes have to be amplified when the gene product needed by the cell is RNA but not usually when the desired gene product is a protein.
Introduction: The genes encoding ribosomal RNA during oogenesis in Xenopus laevis is the best studied example of gene amplification. The unamplified number of ribosomal RNA genes is about 500 per haploid genome. After amplification, the oocyte contains about 500,000 ribosomal RNA genes per haploid genome. This level of amplification is necessary to allow the egg cells to synthesize 1012 ribosomes that accumulate during the two months of oogenesis in this species. Each ribosomal RNA gene consists of about 13,000 base pairs, and the genome size of Xenopus is about
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Becker's World of the Cell (9th Edition)
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