USMLE Biochemistry Videos & Books

2022-05-30 08:17:01 ओपन / कमेंट

2022-05-30 08:16:02 A 4-year-old boy is brought to the physician for fatigue and persistent bone pain. Physical examination shows diffuse lymphadenopathy and multiple purpura over his arms and legs. Laboratory analysis reveals anemia and thrombocytopenia, and a peripheral blood smear shows lymphoblasts. After further workup,
he is diagnosed with acute lymphoblastic leukemia and started on a chemotherapy regimen that includes doxorubicin. This agent intercalates between DNA base pairs and inhibits DNA replication, a process that normally occurs at sites known as replication forks. As the replication forks move across the DNA molecule, 2 distinct daughter strands are formed. ओपन / कमेंट

2022-05-29 20:15:31 Educational objective: Multiple origins of replication make eukaryotic DNA replication quick and effective despite the large size and complexity of the genome compared to that of prokaryotic organisms. ओपन / कमेंट

2022-05-29 08:15:15 ओपन / कमेंट

2022-05-29 08:14:01 A genetic researcher is comparing the DNA replication process of prokaryotic and eukaryotic cells. In an experiment, Escherichia coli and human cells are cultured in separate media containing tagged nucleotides and their rates of DNA replication are determined. Although the eukaryotic genome is significantly larger
and more complex than that of the prokaryote, eukaryotic DNA replication still occurs in a timely manner. ओपन / कमेंट

2022-05-28 20:14:01 Educational objective: Transfer RNA (tRNA) is a small, noncoding form of RNA that contains chemically modified bases (eg, dihydrouridine, ribothymidine, pseudouridine). tRNA has a CCA sequence at its 3'-end that is used as a recognition sequence by proteins. The 3' terminal hydroxyl group of the CCA tail serves as the amino acid binding site. ओपन / कमेंट

2022-05-28 08:14:01 ओपन / कमेंट

2022-05-28 08:13:01 A series of experiments is being conducted to determine the structure and function of different types of bacterial RNA. Cultures of Staphylococcus aureus are exposed to chemicals that lyse the bacterial cells, and the RNA molecules are then extracted. A specific RNA consisting of 90 nucleotides is purified for
further analysis. It is found to contain high amounts of chemically modified bases such as dihydrouridine, pseudouridine, and ribothymidine, and its secondary structure arises from base pairing within the chain. ओपन / कमेंट

2022-05-27 20:13:02 Educational objective: Intellectual disability, gait or posture abnormality, eczema, and a musty body odor in a toddler are signs of phenylketonuria (PKU). Most infants with PKU are born to 2 heterozygous carrier parents. The probability that heterozygous carrier parents will transmit an autosomal recessive disease such as PKU to a child is 114. ओपन / कमेंट

2022-05-27 08:13:02 ओपन / कमेंट