Concept explainers
CASE STUDY | Crippled ribosomes
Diamond Blackfan anemia (DBA) is a rare, dominantly inherited syndrome characterized by bone marrow failure, birth defects, and a significant predisposition to cancer. Those affected with DBA usually develop anemia in the first year of life, have abnormal numbers of cell types in their bone marrow, and have an increased risk of developing leukemia and bone cancer. At the molecular level, DBA is caused by a mutation in any of 11 genes that encode ribosomal proteins. The common feature of all these mutations is the disruption of ribosome formation, ultimately affecting the stability or function of ribosomes.
Many questions about this disorder remain to be answered.
Why might some cells in the body, such as those in bone marrow, be more susceptible to ribosomal protein mutations than other cell types?
Want to see the full answer?
Check out a sample textbook solutionChapter 13 Solutions
Essentials of Genetics
- Discuss Concepts A mutation occurs that alters an anticodon in a tRNA from 3-AAU-5 to 3-AUU-5. What effect will this mutation have on protein synthesis?arrow_forwardIPSCs are nearly identical to human embryonic stem cells in terms of gene expression, but there may be other ways in which they are not equivalent. For example, the telomeres of IPSCs often vary in length, with many IPSCs cells having telomeres shorter than those of embryonic. How might shortened telomeres affect the life-span of IPSCs or of differentiated cells derived from them?arrow_forwardIf mRNA is complementary to the DNA template strand and the DNA template strand is complementary to the DNA nontemplate strand, then why are base sequences of mRNA and the DNA nontemplate strand not identical? Could they ever be?arrow_forward
- 1. Certain proteins that stimulate expression of a gene bind to DNA in a sequence specific manner and also induce conformational changes in the DNA. Describe the purpose of thses two modes of interaction with the DNA. 2. Draw the structures of the amino acid side chains that correspond to the following histone modification: a) acetylation of lysine; b) phosphorylation of serine; c) phosphorylation of histidine. How do thses modifications change the character of their respective side chain?arrow_forward2) Myoclonal epilepsy and ragged red fiber disease (MERRF) is a human condition named for the ragged red fibers of skeletal muscle cells and myoclinic epilepsy in affected individuals. People with this disorder have a mutation in a mitochondrial gene for a tRNA, specfically that for lysine. Why are affected individuals always heteroplasmic?arrow_forward2a) Suppose you have a gene in which a single base substitution has created the nonsense mutation 5'TAA3' (which will be transcribed into 5'UAA3' in the mRNA - but recall that mutations are changes in the DNA sequence). Name all the amino acids that could have been coded for by the original, unmutated codon at that position in the gene.arrow_forward
- 1. Given that a faulty ribosomal protein is the culprit and causes DBA, discuss the possible role of normal ribosomal proteins. Why might bone marrow cells be more susceptible to such a mutation than other cells? 2. A couple with a child affected with DBA undergoes in vitro fertilization (IVF) and genetic testing of the resulting embryos to ensure that the embryos will not have DBA. However, they also want the embryos screened to ensure that the one implanted can serve as a suitable donor for their existing child. Their plan is to have stem cells from the umbilical cord of the new baby transplanted to their existing child with DBA, thereby curing the condition. What are the ethical pros and cons of this situation? 3. While a stem cell transplant from an unaffected donor is currently the only cure for DBA, genome-editing technologies may one day enable the correction of a mutation in a patient’s own bone marrow stem cells. However, what specific information would be needed, beyond a…arrow_forward2a) In prokaryotes, a small ribosomal subunit can potentially get on an mRNA anywhere it can find enough space to do so. Once a small ribosomal subunit has bound to an mRNA, it will scan along that mRNA in the 5' to 3' direction looking for a start codon at which to initiate translation. How does the small ribosomal subunit distinguish a start codon from any other AUG codon that simply codes for methionine in the middle of a coding sequence?arrow_forward1. In the human gene for the beta chain of haemoglobin (the oxygen-carrying protein in the red blood cells), the first 30 nucleotides in the amino-acid-coding region is represented by the sequence:3'-TACCACGTGGACTGAGGACTCCTCTTCAGA-5'. What is the sequence of the partner strand?arrow_forward
- 1. Given the following three mRNA sequences, which 2 sequences code for the same protein?#1 AGU UUA GCA ACG AGA UCA#2 UCG CUA GCG ACC AGU UCA#3 AGC CUC GCC ACU CGU AGU 2. Look at the following sequence: THE FAT CAT ATE THE RAT. Delete the first H and regroup the letters in groups of three- write out the new groups of three. Does the sentence still make sense? What type of mutation is this an example of?arrow_forward1Need help:. draw valine-aminoacyl tRNA synthetase. Show the tRNAs and the valine amino acid. You can use the one-letter code for valine (V) and do not have to draw the amino acid structure. Label the tRNA and amino acid binding sites on the enzyme. Explain the function of valine-aminoacyl tRNA synthetase and explain why there are 20 related enzymes in every cell.arrow_forward3a) In a hypothetical cell where "wobble" pairing was not allowed (i.e. every codon must be matched by a tRNA anticodon that is its perfect complement), how many tRNAs would be required to service all of the threonine codons?arrow_forward
- Biology: The Unity and Diversity of Life (MindTap...BiologyISBN:9781305073951Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa StarrPublisher:Cengage LearningBiochemistryBiochemistryISBN:9781305577206Author:Reginald H. Garrett, Charles M. GrishamPublisher:Cengage LearningBiology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning
- Biology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStax