Tobias Chapter 2 - Molecular and Cell Biology Flashcards
What is the genetic basis for the Golden retriever centronuclear myopathy?
Also known as Type-II Muscle Fiber Deficiency
Mode of inheritance: Autosomal recessive
Mutation in the protein tyrosine-phosphatase-like member A (PTPLA).
What are the nucleotides that compose DNA Vs RNA?
DNA:
“Purines are All Good! (A,G)” → Adenosine, Guanine
“Pyrimidines need CT” (C,T) → Cytosine and Thymine
RNA:
“Purines are All Good! (A,G)” → Adenosine, Guanine
“Pyrimidines - See You!” (C,U) → Cytosine and Uracil
What is the role of telomerase in mammalian cells?
Reverse transcriptase adds specific DNA sequence repeats to the telomere region DNA, thereby preventing the shortening of 50-100pb, which follows each cell division. Without telomerase, the cell would eventually reach a critically short telomere length, entering senescence.
What is a codon, and what amino acid does the “start codon” usually decode?
Codons are sequences of three nucleotides in the mRNA, translated into an amino acid. The start codon usually transcribes methionine, so most polypeptides begin with this amino acid.
Why does gene expression
have a transcription step? Why isn’t a DNA sequence translated directly into the amino acid sequence of a polypeptide?
1) DNA is very tightly packed. Translating proteins from DNA would require unwinding of the DNA spiral - an energy-inefficient process. It would also increase the chance of loss of genetic material.
2) DNA is also locked in the nucleus, and ribosomes (protein-making machinery) is in the cytoplasm. A “messenger” (mRNA) is necessary to communicate the two.
3) Transcription is the most important step where cells regulate how much of certain proteins will be produced. Without this step, cells would lose control over protein production.
What are the three phases of transcription?
Initiatiation
Elongation
Termination
What is the role of the “promoter” in gene expression?
Small coding sequence upstream of a sequence of DNA that specifies the position of the transcription unit (segment of DNA to be transcribed into mRNA). They can promote or block the recruitment of RNA polymerase.
What is the role and importance of “transcription factors”
Transcription factors are proteins that bind multiple promoter sequences, effectively controlling transcription. Transcription factors are essential for development, cell signaling, and cell cycle. They are also excellent targets for therapeutic measures to modulate healthy and diseased cells.
What are “housekeeping genes”
Constitutive ribosomal proteins and histones are expressed across all cell types and are involved in routine cell metabolism.
What are epigenetics? Give two examples
Epigenetics is the study of how cells regulate genetic activity without altering DNA. Examples include X-chromosome inactivation (balances expression between ♀︎/♂︎ ) and teratogenesis (alteration of embryonic genetic expression by external factors)
What is a nonsynonymous mutation?
A type of point mutation (single nucleotide pleomorphism - SNP) within a coding sequence that alters protein sequence or length.
What is a missense mutation?
A mutation that alters an AA codon, resulting in altered protein structure and function.
What is linkage disequilibrium, and what is its usefulness from a diagnostic point of view?
Linkage disequilibrium is the association between alleles in different loci with greater frequency than would be expected by chance. This can identify markers associated with genetic traits without identifying specific mutations.
What is a Study of Association?
Without pedigree information, Association studies determine whether a particular form of a genetic marker occurs more frequently in subjects with a particular trait or disease than in those without the trait or disease of interest.
What is a transcriptome? How is it clinically relevant?
A set of mRNA molecules present in a cell or population of cells, which can be quanti ed through techniques such as reverse transcription quantitative PCR (qPCR). This can be used to measure the genetic expression of genes decoding proteins associated with naturally and experimentally occurring diseases (i.e., OA).
