Bio - 2024 eksamen

Proteins are the main executive molecules in prokaryotic cells. They perform various crucial functions like catalyzing metabolic reactions, transporting molecules, providing structural support, and regulating cellular processes.

DNA polymerase is responsible for the synthesis of new DNA strands during replication. It analyzes each nucleotide for errors and adds nucleotides according to base complementarity, forming phosphodiester bonds. However, initiation of replication is a separate process involving other proteins.

Defects in proteins involved in DNA repair and regulation can lead to various issues. These include increased susceptibility to cancer due to uncontrolled cell growth, decreased immunity because repair mechanisms are compromised, and accelerated aging due to DNA damage accumulation.

Chromosomes are condensed structures made of DNA and proteins. They are only visible individually during the metaphase of cell division when they are highly compacted. This stage is crucial for proper chromosome separation during cell division.

A karyotype represents the complete set of chromosomes in a cell. It includes information like the number of chromosomes, their length, and any irregularities. These details provide insight into an individual's genetic makeup and potential health issues.

Mitochondria are organelles that function as cellular powerhouses. They are believed to have originated from bacteria absorbed by a eukaryotic proto-cell. This is evident in their double membrane structure and their own DNA.

A 46XY karyotype indicates a male individual with the normal number of chromosomes. The presence of the Y chromosome determines maleness.

Anaerobic organisms lack mitochondria. They obtain energy through fermentation processes, which do not require oxygen. Examples include certain bacteria and yeasts that thrive in oxygen-deprived environments.

The primary structure of DNA refers to the linear arrangement of individual nucleotides in a DNA strand. These nucleotides consist of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).

Both the cell nucleus and mitochondria have two membranes surrounding them. The nucleus contains the cell's genetic material, and the mitochondria are responsible for energy production.

Peripheral blood lymphocytes are used in cytogenetic tests because they are easily accessible and readily divide. Their rapid division allows for analysis of their chromosomes, which provides information on an individual's genetic make-up.

Homologous autosomal chromosomes are pairs of chromosomes numbered 1 through 22 in a normal human cell. They have the same shape, length, and carry genes for the same traits. This pairing ensures proper chromosome segregation during cell division.

Gyrase is an enzyme that attaches to the DNA strand ahead of the replication fork. It helps unravel DNA, reducing its supercoiled structure, and facilitating the replication process.

Cholesterol plays a vital role in regulating the cell membrane's properties. It influences its stiffness and permeability, acting as a molecular buffer. This helps maintain the cell's integrity and ensures efficient transport of molecules across the membrane.

Intermediate filaments provide structural support and mechanical strength to cells. They act as a network of fibers that hold organelles in place, resist mechanical stress, and contribute to cell shape and integrity.

The large ribosomal subunit in eukaryotes contains three rRNA molecules: 28S, 5.8S, and 5S. These rRNAs bind to the mRNA and tRNAs, facilitating protein synthesis by coordinating the assembly of amino acids into a polypeptide chain.

Stem cells have the unique ability to self-renew and divide without differentiating. This allows them to maintain a pool of undifferentiated cells that can give rise to specialized daughter cells when needed.

Transition mutations involve replacing one purine base (adenine or guanine) with another purine base. In this case, adenine (A) is replaced with guanine (G). This type of mutation can alter the amino acid sequence of a protein, potentially affecting its function.

Histone H1, and exceptionally H5 in erythrocytes, stabilizes the histone octamer. This octamer forms the core around which DNA wraps to form nucleosomes, the basic unit of chromatin.

Polyacrylamide gel electrophoresis (PAGE) is a technique primarily used for separating proteins based on their size and charge. The proteins are separated based on their migration through a porous gel under the influence of an electric field.

Human development in the female direction occurs in the absence of a Y chromosome. This is because the Y chromosome carries the SRY gene, which is responsible for male development. The presence of two X chromosomes and the absence of the Y chromosome lead to a female phenotype.

The cell nucleus is the control center of the cell, containing DNA, nucleoli, and the nuclear matrix. It is not considered a component of the Golgi apparatus, which is responsible for packaging and modifying proteins.

A protein made from the combination of peptide subunits has a quaternary structure. This involves multiple polypeptide chains interacting with each other, forming a functional protein complex.

Routine chromosome staining methods can detect numerical chromosomal aberrations, such as aneuploidy (extra or missing chromosomes). However, they are not sensitive enough to detect subtle structural abnormalities like microdeletions.

Ligase plays a crucial role in DNA replication by gluing Okazaki fragments together. These fragments are short segments of DNA synthesized discontinuously on the lagging strand during replication.

RNA interference (RNAi) is a biological process that silences gene expression. Small RNA molecules, such as microRNAs (miRNAs), bind to complementary regions of mRNA, preventing its translation into protein.

Apoptotic bodies are cell fragments that form during apoptosis, a process of programmed cell death. These fragments contain condensed chromatin debris, cytoplasm, and cell organelles. They are engulfed by macrophages, which remove them from the body.

Adding ethyl alcohol to a DNA solution causes DNA precipitation. This is because alcohol reduces the solubility of DNA in water, causing it to clump together and settle out of solution. This property is used in DNA extraction procedures.

Regeneration is a process of asexual reproduction where an organism can regrow lost or damaged parts. This is distinct from sexual reproduction, which involves the fusion of gametes.

Glycolysis, the first step in cellular respiration, occurs in the cytoplasm of a cell. It involves the breakdown of glucose into pyruvate, producing a small amount of ATP.

Epigenetic modifications, such as DNA methylation, regulate gene expression without altering the underlying DNA sequence. Methylation can silence genes by affecting the binding of transcription factors.

Water molecules make up approximately 70 percent of the total mass of a cell. This reflects the importance of water in cell functions, such as providing a medium for biochemical reactions and maintaining osmotic balance.

Smooth endoplasmic reticulum (SER) predominates in cells that synthesize non-protein organic products. These products can include lipids, steroids, and hormones. Cells with a high rate of protein synthesis rely on rough endoplasmic reticulum (RER), which is studded with ribosomes.

Liposomes are spherical vesicles composed of lipids. They can encapsulate DNA and deliver it into cells, acting as synthetic vectors for gene delivery. Liposomes are used in gene therapy to treat genetic disorders.

The sodium-potassium pump is a vital protein in maintaining the cell's osmotic balance. If it stops working, sodium ions accumulate inside the cell, causing water to rush in, leading to cell rupture. This highlights the importance of the pump in regulating cell volume and preventing swelling.

Epigenetics refers to changes in gene function or expression that do not involve alterations in the DNA sequence itself. These modifications, such as DNA methylation and histone modifications, influence gene accessibility and activity.

Small nuclear RNA (snRNA) functions in the splicing of pre-mRNA molecules. It participates in removing introns, non-coding regions, and connecting exons, coding regions, to generate mature mRNA that can be translated into proteins

Complementation occurs when the products of different genes interact to produce a specific trait. For example, if two genes are required for a particular function, mutations in either gene can lead to a loss of that function. However, if an individual inherits a mutation in one gene and a wild-type copy of the other gene, the wild-type gene can complement the mutation in the first gene.

The mitochondrial genome has its own DNA and its own system for translation. The AUU codon, which is typically a stop codon in nuclear DNA, serves as the initiation codon in mitochondrial DNA, signaling the start of translation.

The quaternary structure of proteins refers to the arrangement of multiple polypeptide chains (subunits) into a functional protein complex. These interactions can involve various forces, like hydrogen bonds, hydrophobic interactions, and disulfide bonds, which stabilize the complex's three-dimensional structure and enable its biological activity.

Enhancers are DNA sequences that can boost the rate of transcription initiation. They can bind to transcription factors, which then interact with the promoter region of a gene, increasing the chances of transcription.

Peripheral blood lymphocytes are the most common cell type used for chromosome analysis. They are readily accessible and readily divide, making it easier to obtain and analyze their chromosomes.

The quaternary structure of protein macromolecules is stabilized by various interactions, including hydrogen bonds, disulfide bonds, hydrophobic interactions, and electrostatic interactions. These interactions help maintain the protein's three-dimensional structure and support its biological activity.

The cell membrane serves as a protective barrier, controlling the movement of substances into and out of the cell. It is selectively permeable, allowing only certain molecules to pass through, while others are blocked. The membrane also plays a role in cell signaling by detecting stimuli from the environment.

Telomeres are protective caps found at the ends of chromosomes. They consist of repetitive DNA sequences and help prevent the loss of genetic information during DNA replication. Telomeres shorten with each cell division, contributing to cellular aging.

A genome is the complete set of genetic information of an organism. It includes both protein-coding genes and non-coding genes. The information is encoded in the sequence of nucleotides in DNA or RNA for viruses.

Apoptosis is characterized by a series of biochemical events that lead to programmed cell death. It is a crucial process in development, tissue homeostasis, and eliminating damaged or unwanted cells. It involves a series of steps, ultimately leading to the dismantling of the cell.

Necrosis is a form of uncontrolled cell death that occurs due to external factors like injury or infection. It involves the unregulated breakdown of cell components, leading to inflammation and tissue damage. In contrast to apoptosis, necrosis is harmful and can trigger a cascade of damaging events.

Cytokinesis is the final stage of cell division. It involves the division of the cytoplasm, creating two daughter cells, each with a complete set of chromosomes. It ensures that the duplicated genetic material is properly distributed to the newly formed cells.

A eukaryotic organism's genetic information is encoded in the DNA double helix, which is found within the nucleus. The nucleotide sequence of DNA contains all the genetic instructions necessary for replication, transcription, and ultimately protein synthesis.

Endoplasmic reticulum (ER) is a network of interconnected membranes that form a system of compartments within the cytoplasm. There are two types: smooth ER (SER) and rough ER (RER). SER is involved in lipid and steroid synthesis as well as detoxification, while RER is involved in protein synthesis and modification. This network plays a crucial role in the cell's ability to synthesize and transport molecules. It works like an internal transport system and an assembly line for various molecules.

P53 is a tumor suppressor gene that plays a critical role in preventing cancer development. It acts as a guardian by responding to DNA damage, triggering cell cycle arrest for repair or apoptosis if damage is irreparable. Without P53's watchful presence, cells with genetic errors can proliferate uncontrolled, leading to cancer formation.

Restriction enzymes, also known as restriction endonucleases, can produce both sticky and blunt ends. Sticky ends are short single-stranded overhangs that can base pair with complementary overhangs on other DNA molecules, facilitating cloning and DNA manipulations. Blunt ends lack these overhangs, requiring different ligation strategies to join DNA fragments. These enzymes are valuable tools in molecular biology research for DNA manipulation.

Introns are non-coding regions of DNA that are removed from pre-mRNA during splicing. Exons are the coding regions that are spliced together to form mature mRNA. The splicing process removes introns and joins exons, creating a continuous coding sequence that can be translated into a protein. Introns are like extra sections of the mRNA blueprint.

The transcriptome is a complete set of RNA molecules, including mRNA, that are expressed in a cell or organism. The transcriptome reflects the genes that are actively being transcribed, giving insight into cellular function and responses to stimuli. The transcriptome is like a snapshot of a cell's active genes and their messages.

Transcription and translation are inhibited during mitosis. These processes are essential for gene expression. Mitosis requires the cell to concentrate its energy and resources on dividing the chromosomes and cytoplasm. Transcription and translation can resume after the cell division is complete.

Heat shock proteins (HSPs) are produced by cells in response to various stresses like viral infection, heavy metal poisoning, and alcohol poisoning. They act like molecular chaperones, assisting in protein folding, assembly, and transport, helping the cell cope with stress conditions. HSPs are like the cell's stress responders.

DNA polymerase is responsible for synthesizing new DNA strands during replication. It meticulously analyzes each nucleotide for any errors and adds new nucleotides based on the complementary base pairing rule, forming strong phosphodiester bonds between them. However, the initiation of replication is a separate process requiring a specific group of proteins.

A karyotype is a complete representation of an organism's chromosomes, including their number, length, and any irregularities. It provides valuable insights into an individual's genetic makeup and can be used to detect potential health issues.

RNA interference (RNAi) is a natural process that silences gene expression. Small RNA molecules bind to complementary regions of mRNA, preventing it from being translated into protein, resulting in the silencing of a gene's instructions.

The mitochondrial genome has its own distinct DNA and a separate system for translation. Remarkably, the AUU codon, which typically functions as a stop codon in nuclear DNA, acts as the initiation codon in mitochondrial DNA, signaling the start of translation.

Telomeres, protective caps found at the ends of chromosomes, consist of repetitive DNA sequences. They help prevent the loss of genetic information during DNA replication. They shorten with each cell division, contributing to the process of cellular aging.

A genome is the complete set of genetic information of an organism, including both protein-coding genes and non-coding genes. It is encoded in the sequence of nucleotides in DNA, or RNA for RNA viruses, providing the blueprint for an organism's traits and functions.

The genetic information of a eukaryotic organism is stored in the DNA double helix, located within the nucleus. This DNA sequence contains all the necessary instructions for replication, transcription, and ultimately protein synthesis, making it the basis of an organism's functional characteristics.

Endoplasmic reticulum (ER) is a network of interconnected membranes within the cytoplasm, forming a system of compartments. There are two types: smooth ER (SER) and rough ER (RER). SER is involved in lipid and steroid synthesis as well as detoxification, while RER is involved in protein synthesis and modification. This network serves as a sophisticated internal transport system and molecular factory for the cell.

P53 is a crucial tumor suppressor gene often referred to as the ‘guardian of the genome’. It plays a vital role in preventing cancer by responding to DNA damage. If the damage is repairable, it triggers cell cycle arrest to allow for repair. If the damage is irreparable, it triggers apoptosis to eliminate the damaged cell before it can become cancerous.

Restriction enzymes can produce both sticky and blunt ends. Sticky ends are short single-stranded overhangs on DNA, allowing for easy joining with complementary overhangs on other DNA fragments. Blunt ends lack these overhangs, requiring different techniques to join DNA fragments. These enzymes are valuable tools for manipulating DNA in labs, like molecular scissors with specific targets.

Introns are non-coding regions of DNA that are removed from pre-mRNA during splicing. Exons are the coding regions that are spliced together to form mature mRNA. The splicing process removes introns and joins exons, creating a continuous coding sequence that can be translated into a protein. Introns are like extra sections of the mRNA ‘blueprint’.

The transcriptome represents the complete set of RNA molecules, including mRNA encoding proteins, expressed in a cell or organism. It is a snapshot of the cell's active genes, providing insights into cellular function and responses to stimuli. Consider it like a comprehensive catalog of all the active messages generated from genes in a cell.

Heat shock proteins (HSPs) are produced by cells in response to various stresses, including viral infection, heavy metal poisoning, and alcohol poisoning. Their role is like a molecular chaperone, assisting with protein folding, assembly, and transport, enabling the cell to cope with these challenging situations. It's like the cell's stress response, a molecular helper during difficult conditions.