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Questions and Answers
What is the primary focus of molecular diagnostics?
What is the primary focus of molecular diagnostics?
Which type of nucleic acid is considered the centerpiece for research and clinical analysis in molecular biology?
Which type of nucleic acid is considered the centerpiece for research and clinical analysis in molecular biology?
Which of the following areas is NOT a clinically important subdivision of molecular diagnostics?
Which of the following areas is NOT a clinically important subdivision of molecular diagnostics?
What role does molecular pathology play in the field of molecular biology?
What role does molecular pathology play in the field of molecular biology?
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How has the field of molecular biology influenced the development of therapeutics?
How has the field of molecular biology influenced the development of therapeutics?
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Which type of diseases does molecular diagnostics help to treat?
Which type of diseases does molecular diagnostics help to treat?
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What is one major outcome of the research successes in molecular biology?
What is one major outcome of the research successes in molecular biology?
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What significance do circulating tumor cells and nucleic acids have in molecular diagnostics?
What significance do circulating tumor cells and nucleic acids have in molecular diagnostics?
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What role do restriction enzymes and DNA ligase play in genetic engineering?
What role do restriction enzymes and DNA ligase play in genetic engineering?
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The Southern blot method is primarily used to test for which of the following?
The Southern blot method is primarily used to test for which of the following?
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What results from homologous recombination during meiosis?
What results from homologous recombination during meiosis?
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What is a de novo variant?
What is a de novo variant?
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Which technique was developed in 1986 and is fundamental to molecular diagnostics?
Which technique was developed in 1986 and is fundamental to molecular diagnostics?
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What is the main purpose of DNA sequencing technologies in genetic studies?
What is the main purpose of DNA sequencing technologies in genetic studies?
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How do human cells typically die?
How do human cells typically die?
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What is the function of microarray technology in molecular diagnostics?
What is the function of microarray technology in molecular diagnostics?
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What is the primary goal of sequencing diverse interacting RNAs like piRNA?
What is the primary goal of sequencing diverse interacting RNAs like piRNA?
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How do the projects like the Exome Aggregation Consortium (ExAC) contribute to molecular diagnostics?
How do the projects like the Exome Aggregation Consortium (ExAC) contribute to molecular diagnostics?
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What key discovery was made by the encyclopedia of DNA elements (ENCODE) project?
What key discovery was made by the encyclopedia of DNA elements (ENCODE) project?
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Which of the following databases has sequenced over 60,000 exomes to study genetic variation?
Which of the following databases has sequenced over 60,000 exomes to study genetic variation?
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What is a significant future impact of advancements in molecular diagnostics?
What is a significant future impact of advancements in molecular diagnostics?
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What type of variation do projects like the 1000 Genomes Project focus on?
What type of variation do projects like the 1000 Genomes Project focus on?
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What is a characteristic of the binding of DNA strands that is significant for molecular diagnostics?
What is a characteristic of the binding of DNA strands that is significant for molecular diagnostics?
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Which of the following statements about piRNA is true?
Which of the following statements about piRNA is true?
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Study Notes
Background
- Molecular diagnostics studies the origin of disease at the molecular level, primarily focusing on nucleic acids like DNA.
- Molecular pathology is a related field that researches and analyzes the blueprints of living organisms (DNA).
- Past successes in molecular biology, demonstrated by numerous Nobel Prizes, are now applied for clinical diagnostics and developing treatments.
- This study of molecular biology covers fundamental principles, including genomics, nucleic acid analysis, and specific subfields like microbiology, genetics, and cancer diagnostics.
Historical Developments in Genetics and Molecular Biology
- Gregor Mendel's work (1866) on inheritance laid the groundwork for genetics.
- Thomas Morgan's research (1910) linked genes to chromosomes.
- Griffith's experiments (1928) and Avery, MacLeod, and McCarty's (1944) findings determined DNA as the genetic material.
- Hershey and Chase (1952) definitively proved DNA, not protein, as the genetic material.
- Erwin Chargaff's observations on the equal ratios of nitrogenous bases (A=T, G=C) were crucial.
- Rosalind Franklin and Maurice Wilkins' X-ray crystallography data helped Watson and Crick (1953) determine the DNA double helix structure. This discovery significantly impacted biological understanding.
- Meselson and Stahl (1958) demonstrated semiconservative DNA replication.
- Arthur Kornberg's discovery of DNA polymerase.
- Marshall Nirenberg's work (1965) cracked the genetic code.
Molecular Biology Essentials
- DNA, the primary genetic material, comprises two strands of a sugar-phosphate backbone, held together by hydrogen bonds between complementary bases (adenine-thymine and guanine-cytosine).
- DNA exists as a double helix, with these strands oriented antiparallel (5' to 3' and 3' to 5').
- In cells, DNA is organized into nucleosomes, which are coiled further into chromosomes.
- Humans have 23 pairs of chromosomes (22 autosomes, 1 sex chromosome pair (XX or XY)).
- A haploid set of chromosomes comes from each parent.
- A typical diploid cell contains pairs of chromosomes (both alleles) containing different genetic sequences than the other allele.
- Cell division includes DNA replication, ensuring one copy of the genome is provided to each cell.
Nucleic Acid Structure and Function
- DNA primarily consists of a deoxyribose sugar, phosphate group, and four nitrogenous bases (adenine, guanine, cytosine, and thymine).
- Nucleotides are the basic building blocks, consisting of a deoxyribose sugar, a nitrogenous base, and a phosphate group. Triphosphate nucleotides form new DNA strands by connecting through phosphodiester bonds.
- The double helix structure of DNA, with complementary bases paired (A-T and G-C), makes DNA replication possible and efficient.
- The DNA sequence dictates the precise order of amino acids in proteins.
Ribonucleic Acid (RNA) Structure and Function
- RNA, similar to DNA, contains a ribose sugar, but with an additional hydroxyl group on the 2' carbon.
- RNA's nitrogenous bases include adenine, guanine, cytosine, and uracil.
- The different types of RNA perform distinct functions, including mRNA, tRNA, and rRNA.
- mRNA (messenger RNA) carries the genetic code from DNA to ribosomes. mRNA is synthesized during transcription.
- tRNA (transfer RNA) reads the code in mRNA and carries amino acids to the ribosomes during translation.
- rRNA (ribosomal RNA) is the primary component of the ribosomes, which synthesize proteins.
Gene Structure
- Eukaryotic genes contain exons (protein-coding regions) and introns (non-protein-coding regions).
- Introns are removed from the pre-mRNA transcript during a process called splicing, leaving only exons in the mature mRNA to be translated to protein.
Ribonucleic Acid Transcription and Splicing
- Transcription produces RNA using DNA as a template.
- RNA polymerase catalyzes this process.
- In eukaryotic cells, RNA polymerase II transcribes into messenger RNA, using DNA as a template.
- Three phases of transcription include initiation (start of transcription), elongation, and termination. The resulting pre-mRNA is modified through addition of a 5' cap, a 3' polyadenylation tail, and splicing of introns.
- Proteins called transcription factors bind to promoter regions to regulate transcription.
Translation
- Translation converts mRNA's genetic code into a polypeptide sequence, a process that occurs in the cytoplasm on ribosomes.
- Transfer RNAs (tRNAs) carry amino acids to the ribosome according to the mRNA sequence.
- Amino acids are linked together to form a polypeptide chain.
- This process occurs through steps initiation, elongation, and termination.
DNA Replication
- DNA replication is a fundamental process for cell division.
- It follows a semiconservative mechanism, ensuring each new DNA molecule contains one original strand and one newly synthesized strand.
- Helicase unwinds the DNA double helix.
- DNA polymerase synthesizes complementary strands using the original strands as templates.
- Okazaki fragments are synthesized discontinuously in the lagging strand.
- DNA ligase joins the fragments, completing replication.
DNA Repair Mechanisms
- DNA repair mechanisms replace damaged or incorrect bases in the DNA molecule.
- Different mechanisms depending on the type of damage to fix the damage.
- Base excision repair, nucleotide excision repair, mismatch repair, and homologous recombination repair are examples of various different mechanisms.
- Errors in repair mechanisms and factors can lead to cancer or other genetic diseases.
Epigenetics
- Epigenetics describes heritable changes in gene expression without alterations to DNA sequence
- Epigenetic modifications often modify DNA accessibility or influence protein binding to DNA.
- DNA methylation, chromatin modification (histone modifications include acetylation and methylation, and noncoding RNAs are examples of epigenetic modification types.
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