Molecular Biology exam questions (2)

Morphological Features of Metaphase Chromosomes

• Banding pattern, position of the centromere, and chromosome length are morphological features.
• Number of chromosomes is not a morphological feature; it's a numerical characteristic.

tRNA Transport

• tRNA transports amino acids, not peptides, codons, or proteins.

RNA Tertiary Structure Interactions

• Not all interactions are involved: Formation of an A-type helix, interactions of arm stems, and binding of basic proteins/ions are involved.
• Formation of non-canonical pairs/triplets is also a critical interaction.
• Creation of an A-type helix, Interactions of arm stems with other arm stems, Binding of basic proteins or ions that neutralize the negative charge of RNA are involved in the formation of a tertiary structure of RNA. The exclusionary statement is the formation of non-canonical pairs/triplets.

Pseudouridine Loop (T-loop) of tRNA

• The T-loop contains an unpaired CCA sequence at the 3' end. It does not contain a D-loop, mobilize the tRNA directly, or contain the ribosome binding site.

Receptors for Neurotransmitters

• Ionotropic (ion-channel-coupled) receptors are designed for rapid responses to neurotransmitters.

DNA Replication Irreversibility

• Hydrolysis of pyrophosphate (PPi) to inorganic phosphate (Pi) during DNA replication makes the process irreversible.

Combinatorial Control of Gene Expression

• Combinatorial control involves the coordinated action of multiple transcriptional regulators for proper gene expression.

Mitogen-Activated Protein Kinase (MAPK)

• MAPK is a serine-threonine kinase that plays a crucial role in cellular signaling pathways, receiving the final phosphorylation signal from Ras activation.
• MAPK is the final serine-threonine kinase following the activation of Ras protein.

Glycoprotein Components

• Oligosaccharides are a component of glycoproteins, in addition to the protein itself. Lipids and metal ions aren't components of glycoproteins.

Carbohydrate Subunit Classification

• Carbohydrates with more than 10 subunits are called polysaccharides.

HSC Collection via Apheresis

• HSCs are collected using fluorescent antibodies that specifically target the CD34 surface protein.

Codon-Anticodon Bonds

• Hydrogen bonds form between codon-anticodon bases.

Lipid Bilayer Hydrophobic Components

• Hydrophobic components are located inside the lipid bilayer.

DNA Repair via MGMT

• Direct repair (DR) involving the MGMT protein removes the oxygen-bound methyl group from O6 of guanine.

Histone Not in Nucleosome Core

• Histone H1 is not part of the nucleosome core.

Mitotic Cyclin Concentration

• The concentration of mitotic cyclin (cyclin B) is highest in the M phase of the cell cycle.

Programmed Cell Death (Apoptosis)

• Apoptosis occurs when a cell-death intracellular program is initiated, and it's not limited to embryonic development or requiring energy.

Amino Acids in Human Proteins

• There are 20 basic amino acids found in human proteins.

Protein Secondary Structure

• The hydrogen bond between the NH and CO of amino acid residues i and i+3 stabilizes the α-helix.

Interphase Phases

• Interphase includes the G1, S, and G2 phases.

Nucleotide Excision Repair

• Nucleotide excision repair involves XPG and XPF endonucleases cutting DNA strands around the damage, helicases unwinding the DNA, the damaged DNA being removed, and DNA polymerase and ligase synthesizing and sealing the new DNA strand.
• Step that does NOT occur in nucleotide excision repair is the "Removal of the damaged nitrogenous base by specific DNA glycosylase".

Chromosome Arm Length

• A metacentric chromosome has arms of equal length.

Smallest Living Unit

• A cell is the smallest living unit.

Chromosome Position Between Divisions

• Chromosomes occupy distinct territories in the interphase nucleus, not the nucleolus.

RNA Structure with Apical Loops

• Apical loops (hairpens) exist in the secondary RNA structure.

Sodium-Potassium Pump

• The sodium-potassium pump is categorized as primary active transport.

Secondary Lysosome Formation

• A secondary lysosome is the result of the fusion of a primary lysosome with a phagosome.

mRNA and Ribosomes

• When mRNA attaches to a ribosome, the large and small subunits join and begin translation, not separating or changing sedimentation rate.

Lysosome Function

• Lysosomes break down carbohydrates, proteins, fats, and nucleic acids.

Heterochromatin in Interphase

• Heterochromatin is genetically inactive, stains dark under the microscope, and is in a condensed state during interphase.

Orphan Receptors and Ligands

• "Orphan" receptors are intended for unknown ligands.

Electron Transport Chain Location

• The electron transport chain occurs in the inner membrane of the mitochondria.

Membrane Transport and Phagosome Formation

• Phagosome formation utilizes phagocytosis, which is a type of endocytosis.

Interphase DNA Shortening

• Interphase DNA condenses approximately 10,000 times to form metaphase chromosomes.

Aerobic Respiration and Compound

• Oxygen is necessary for aerobic respiration.

DNA Condensation with Histone H1

• Histone H1 is involved in the formation of the 30nm fiber during DNA condensation.

Circulatory Transport Ligands

• Hormones and neurotransmitters are transported through the circulatory system.

Phospholipid Movement

• Lateral diffusion and rotational motion of phospholipids in cell membranes are catalyzed by enzymes; not transverse “flip-flop” movement.

Codon Definition

• A codon is three nucleotides of RNA.

START Codon Recognition in Eukaryotes

• The START codon is recognized through the binding of the small ribosomal subunit, mRNA, and initiator tRNA. This involves scanning from the 5' end.

Glycolipid Component

• Sphingosine is a component of glycolipids.

DNA Sequence for Duplex Formation

• 5’-AAGCCGTT-3’ can form a DNA duplex with itself.

EDTA Role in Blood Analysis

• EDTA is an anticoagulant that prevents blood clotting by binding calcium ions.

Midori Green Safety

• Midori Green is toxic and requires safety precautions like gloves and eye protection.

Midori Green Use

• Midori Green stains DNA for visualization during gel electrophoresis.

DNA Helix Structure

• DNA forms a double-stranded, right-handed helix.

PCR Denaturation Step

• The denaturation step in PCR separates the DNA strands by breaking hydrogen bonds.

Mitochondria Function

• Mitochondria generate ATP through cellular respiration.

PCR Annealing Temperature

• The annealing temperature typically ranges from 50-65°C in PCR.

Biological Membrane Structure

• Biological membranes consist of a fluid bilayer of phospholipids with embedded proteins.

DNA Components

• DNA is composed of nucleotides with a phosphate group, sugar, and nitrogenous base.

Agarose Composition

• Agarose is a polysaccharide derived from seaweed.

Lipid Rafts

• Lipid rafts are lipid-rich regions in cell membranes involved in signaling and trafficking.

Chromosome Types

• Chromosomes can be prokaryotic or eukaryotic; types include metacentric, submetacentric, acrocentric, and telocentric.

Autosomes vs. Allosomes

• Autosomes are non-sex chromosomes, and allosomes are sex chromosomes.

Mitochondria Cristae Function

• Cristae increase the surface area of the mitochondria, which is important for ATP production.

Centrosome Function

• Centrosomes organize microtubules and form the mitotic spindle.

Kinetochore Function

• Kinetochores attach chromosomes to the spindle during cell division.

Cell Water Content

• Cells are typically 50-70% water.

PCR Positive Control Role

• A positive control in PCR ensures the process is working by using a known sample.

Stem Cells

• Stem cells are cells that can divide and differentiate into various cell types.

Interphase Cell Cycle Phase

• Interphase is the phase of the cell cycle where the cell is preparing for division, growing, or completing other essential activities. Not actively dividing or completing mitosis.

Cell Signaling

• Cell signaling, in the context of junxacrina, is the process by which cells respond to external signals to regulate growth and other processes; not directly about junxacrina protein synthesis.

Cell Cycle Regulation

• The progression through the cell cycle is primarily controlled by cyclin-dependent protein kinases (CDKs), with cyclins needed for proper enzymatic activity.

Mitogens

• Mitogens are extracellular signal molecules that stimulate cell proliferation.

PCR Cycle DNA Copies

• After 6 PCR cycles, there are 64 copies of DNA.

Primary Active Transport

• Primary active transport moves molecules from low to high concentration using energy from ATP.

Totipotent Stem Cells

• Totipotent stem cells can form all cell types in the body, including extra-embryonic tissues.

Protein Kinase C (PKC)

• PKC adds phosphate groups to proteins, regulating cellular processes.

DNA Structure

• DNA is a double-stranded molecule composed of nucleotides, with each nucleotide containing a nitrogenous base, a five-carbon sugar, and a phosphate group.

Amino Acid Core Structure

• The core structure of an amino acid has a central carbon atom bonded to an amino group, carboxyl group, and a hydrogen atom (and a side chain that varies).

Amino Acid Backbone

• The backbone of an amino acid, neglecting hydrogen atoms, is C-C-N.

Number of Amino Acids

• There are 20 standard amino acids found in natural proteins.

RNA Concentration in a Cell

• RNA concentration in a typical cell is estimated at 1-5% or 30-40%.

Dominant RNA Type

• Ribosomal RNA (rRNA) is the most dominant type of RNA in a cell.

Potassium and Sodium Ion Concentration

• Potassium (K⁺) ions are most concentrated intracellularly, and sodium (Na⁺) ions are most concentrated extracellularly.

Cholesterol in Cell Membranes

• Cholesterol modulates membrane fluidity, helping to maintain flexibility and stability.

PCR Positive Control Function

• A positive control in PCR verifies the analysis process is functioning by using a known sample.

Cellular Respiration Purpose

• Cellular respiration breaks down glucose to produce ATP.

Cellular Respiration Sequence

• Cellular respiration follows the sequence: Glycolysis → Krebs cycle → Electron transport chain.

Carbohydrate Chain Length and Solubility

• Longer carbon chains in carbohydrates make them less soluble in water.

Carbohydrate Classification by Subunits

• Carbohydrates with more than 10 subunits are called polysaccharides; those with up to 10 are oligosaccharides.

Cytoplasm Ribosome Function

• Ribosomes floating freely in the cytoplasm produce proteins that function within the cell's cytosol.

Amyloplast Contents

• Amyloplasts primarily contain starch grains.

First Amino Acid in Proteins

• The first amino acid in proteins produced by mitochondria, chloroplasts, and bacteria is N-formylmethionine.

PCR Annealing Temperature Impacts

• Setting the annealing temperature too high in PCR prevents primers from binding to the template DNA.

Cytoplasm Components

• The cytoplasm is primarily composed of water, salts, and organic molecules.

Disulfide Bridges in Protein Structure

• Proteins with disulfide bridges primarily exhibit tertiary structure.

Nitrogenous Base Types

• Adenine and guanine are double-ring (purine) bases; cytosine, thymine, and uracil (in RNA) are single-ring (pyrimidine) bases.

Genetic Code Degeneracy

• Degeneracy of the genetic code means that multiple codons can specify the same amino acid, mostly differing at the third nucleotide position.

Thiol-Containing Amino Acid

• Cysteine contains a thiol (-SH) group.

Hydroxyl-Containing Amino Acid

• Threonine contains a hydroxyl (-OH) group.

Nonpolar Aliphatic Amino Acid

• Leucine is a nonpolar, aliphatic amino acid.

Cyclic Side Chain Amino Acid

• Proline has a cyclic side chain.

α-Amino Acid Classification

• α-amino acids (except glycine) are classified as D or L based on the orientation of the amino group relative to the chiral carbon in a Fischer projection.

L-Amino Acid Designation

• An amino acid is classified as L if the amino group is on the left side of the chiral carbon in a Fischer projection (excluding glycine).

Excitatory Neurotransmitters

• Glutamic acid and aspartic acid are primarily excitatory neurotransmitters in the central nervous system.

Serine and Glycine in Lipid Metabolism

• Serine and glycine are precursors in the synthesis of phospholipids.

Amino Acids Involved in Lipid Synthesis

• Serine and glycine are involved in the synthesis of lipids and their derivatives.

Glutamic Acid in Neuronal Signaling

• Glutamic acid is a primary excitatory neurotransmitter in neuron signaling.

Tyrosine as Hormone Precursor

• Tyrosine is a precursor for hormones like catecholamines and thyroid hormones.

Tyrosine and Hormonal Signaling

• Tyrosine-derived hormone precursors regulate hormonal signal transduction.

Ornithine and Citrulline Role

• Ornithine and citrulline are intermediate metabolites in the urea cycle.

Inhibitory Neurotransmitter

• γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter.

Peptide Bond Formation Byproduct

• Water is a byproduct of peptide bond formation.

Oligosaccharide Attachment in Glycoproteins

• Oligosaccharide chains are covalently attached to specific amino acid residues in glycoproteins via glycosidic bonds.

Common Phosphorylated Amino Acids

• Serine and threonine are commonly phosphorylated amino acids.

Vitamin Essentials

• Vitamins are essential as organic coenzymes or prosthetic groups in biochemical reactions.

Cell Cycle Checkpoint for Chromosome Attachment

• The M checkpoint ensures all chromosomes are properly attached to spindle fibers before separation.

Initiating tRNA in Eukaryotes

• Met-tRNAᵢMet is the initiating tRNA in eukaryotes.

DNA Polymerase Primer Requirement

• DNA polymerase requires a primer because it can only add nucleotides to an existing strand.