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03:03You are participating in a study group preparing for an upcoming genetics exam, and one member of the group proposes that each of you draw the structure of two DNA nucleotides joined in a single strand. The figures are drawn and exchanged for correction. You receive the accompanying diagram to correct: What is wrong with the way the nucleotides are joined?
You are participating in a study group preparing for an upcoming genetics exam, and one member of the group proposes that each of you draw the structure of two DNA nucleotides joined in a single strand. The figures are drawn and exchanged for correction. You receive the accompanying diagram to correct: Draw this single-stranded segment correctly.
Suppose that future exploration of polar ice on Mars identifies a living microbe and that analysis indicates the organism carries double-stranded DNA as its genetic material. Suppose further that DNA replication analysis is performed by first growing the microbe in a growth medium containing the heavy isotope of nitrogen (¹⁴N) that the organism is then transferred to a growth medium containing the light isotope of nitrogen (¹⁴N) and that the nitrogen composition of the DNA is examined by CsCl ultracentrifugation and densitometry after the first, second, and third replication cycles in the ¹⁴N-containing medium. The results of the experiment are illustrated here for each cycle. The control shows the positioning of the three possible DNA densities. Based on the results shown, what can you conclude about the mechanism of DNA replication in this organism?
Go to the OMIM website (https://www.ncbi.nlm.nih.gov/omim) and type 'dyskeratosis congenita autosomal dominant 1' (DKCA1) into the search bar. The result will include a clickable link to the disorder that has an OMIM number of 127550. Review the OMIM information you retrieve and notice that this disorder is caused by a mutation of a telomerase gene that results in abnormally rapid shortening of telomeres and the appearance of disease symptoms at progressively younger ages in successive generations of the affected families. Use this and other information on OMIM to assist with this problem. Go to reference number 15 at the bottom of the OMIM page for a link to a 2004 paper by Tom Vulliamy and colleagues that appeared in the journal Nature Genetics. Click on the 'Full text' option and download a copy of the paper. Look at Table 1 of the paper on page 448. This table lists the lengths of telomeres measured in members of the families in this study. Telomeres shorten with age, and the telomere lengths in Table 1 are age-adjusted. The negative numbers for telomere lengths in the table indicate that telomeres are shorter than average for age, and the more negative the number, the shorter the telomere. Based on Table 1, the discussion in the Vulliamy et al. (2004) paper, and information available on OMIM, answer the following:
How do telomere lengths in children compare with telomere lengths of their parents?
Go to the OMIM website (https://www.ncbi.nlm.nih.gov/omim) and type 'dyskeratosis congenita autosomal dominant 1' (DKCA1) into the search bar. The result will include a clickable link to the disorder that has an OMIM number of 127550. Review the OMIM information you retrieve and notice that this disorder is caused by a mutation of a telomerase gene that results in abnormally rapid shortening of telomeres and the appearance of disease symptoms at progressively younger ages in successive generations of the affected families. Use this and other information on OMIM to assist with this problem. Go to reference number 15 at the bottom of the OMIM page for a link to a 2004 paper by Tom Vulliamy and colleagues that appeared in the journal Nature Genetics. Click on the 'Full text' option and download a copy of the paper. Look at Table 1 of the paper on page 448. This table lists the lengths of telomeres measured in members of the families in this study. Telomeres shorten with age, and the telomere lengths in Table 1 are age-adjusted. The negative numbers for telomere lengths in the table indicate that telomeres are shorter than average for age, and the more negative the number, the shorter the telomere. Based on Table 1, the the discussion in the Vulliamy et al. (2004) paper, and information available on OMIM, answer the following:
Why are telomeres of people with DKCA1 shorter than average?
