Untitled Quiz

Sexual reproduction increases genetic diversity within a population. The greater diversity within the population allows for greater adaptation to changing environments. Some offspring might have variations that enable them to survive in a changing environment, while some might not survive, resulting in natural selection. This can help a species as a whole adapt to changes that would make it more difficult to survive in otherwise constant conditions.

False

It is thought that the Y chromosome evolved from an ancient autosome (a non-sex chromosome). Over time, the Y chromosome gained traits that allowed for the development of sex determination in males. It is thought that this gene, known as the SRY gene, was swapped to the Y chromosome during a translocation event.

<p>False</p> Signup and view all the answers

<p>50%</p> Signup and view all the answers

<p>1/16</p> Signup and view all the answers

<p>The mother's genotype must be IAi and the father must be IBi. This is due to their offspring. The mother passed on the recessive ii genotype to Marie, and the father passed on the recessive ii genotype to Marie's sister. The father must have a B allele, due to Marie's sister having the AB blood type. Marie's sister has both alleles of A and B, so she must have received one from each parent.</p> Signup and view all the answers

<p>C and D</p> Signup and view all the answers

<p>Nucleotides are bonded together to make a double-stranded DNA molecule through phosphodiester bonds, where the phosphate group of one nucleotide is linked to the sugar group of the next nucleotide by a covalent bond.</p> Signup and view all the answers

<p>The energy comes from breaking high-energy phosphate bonds within the triphosphate group of the incoming dNTP. During DNA replication, the energy needed to form the phosphodiester bond is provided by the hydrolysis of the two outermost phosphates of the incoming dNTP (deoxyribonucleoside triphosphate). This process releases pyrophosphate (PPi) and provides energy for the formation of the bond between the nucleotide and the existing DNA chain.</p> Signup and view all the answers

<p>DNA replication is called semi-conservative because each new DNA molecule consists of one original strand and one newly synthesized strand. The original DNA molecule is separated into two strands, and each strand acts as a template for the synthesis of a new complementary strand. The process preserves one-half of the original DNA molecule in each new molecule.</p> Signup and view all the answers

<p>Tautomeric shifts can affect hydrogen bonds in DNA. A tautomeric shift can cause a temporary change in the structure of a nucleotide, altering its base pairing properties. This can lead to mispairing during DNA replication, resulting in mutations.</p> Signup and view all the answers

<p>Errors in DNA replication can lead to mutations, which are permanent changes in the DNA sequence. Mutations can have various effects, ranging from no effect to lethal consequences. They can cause various problems in a variety of areas such as development, health, reproduction, and longevity.</p> Signup and view all the answers

<p>Single-stranded binding proteins (SSBs) bind to the separated DNA strands during DNA replication to prevent them from re-annealing together. This keeps the strands accessible for replication and helps to prevent unwanted base pairings.</p> Signup and view all the answers

<p>Helicase unwinds the double-stranded DNA molecule, separating the two strands. This unwinding creates a replication fork. Primase synthesizes a short RNA primer on the lagging strand, providing a starting point for DNA polymerase III to begin DNA synthesis.</p> Signup and view all the answers

<p>The mRNA segment that would be transcribed is: 5' UAAAUAGGCAUAAUGCUA 3' This would result in the amino acids: UAA - stop codon AUG - methionine GCA - alanine UAA - stop codon UGU - cysteine UA - no codon If there was a tautomeric shift causing a point mutation resulting in an adenine in position 7, the resulting mRNA would be UAAAUAAGCAUAAUGCUA. This would change the amino acid sequence to: UAA - stop codon UAA - stop codon GCA - alanine UAA - stop codon UGU - cysteine UA - no codon If there were a deletion of the nucleotide in position 8, the resulting mRNA would be UAAAUAGGCAUAAUGCUA. This would change the amino acid sequence to: UAA - stop codon AUG - methionine GCA - alanine UAA - stop codon UGU - cysteine UA - no codon</p> Signup and view all the answers

<p>DNA polymerase can only add nucleotides to a polynucleotide chain in the 5' to 3' direction. This means that a new nucleotide is always added to the 3' hydroxyl group of the last nucleotide in the growing chain.</p> Signup and view all the answers

<p>RNA polymerase can only add nucleotides to the 3' end of a growing mRNA strand. RNA polymerase has a preference for adding nucleotides to the 3' hydroxyl group of the previously added nucleotide.</p> Signup and view all the answers

<p>The template strand of DNA is the strand that is read by RNA polymerase to synthesize a new mRNA molecule. The template strand is complementary to the newly synthesized mRNA molecule. It's often considered the 'non-coding' strand, opposite to the coding strand that the RNA polymerase does not directly use as a template.</p> Signup and view all the answers

<p>The purpose of DNA replication is to duplicate the entire genome before cell division. This ensures that each daughter cell receives a complete copy of the genetic material.</p> Signup and view all the answers

<p>Transcription is the process of copying genetic information from DNA into mRNA. Translation is the process of converting the mRNA code into a protein. Transcription and translation are two essential processes that allow cells to express their genes and produce proteins.</p> Signup and view all the answers

<p>The replication bubble is formed during DNA replication. It is a region where the DNA strands are separated and replication occurs. - Leading strand: The leading strand is synthesized continuously in the 5' to 3' direction. - Lagging strand: The lagging strand is synthesized discontinuously in the 5' to 3' direction. - Okazaki fragments: Short DNA segments synthesized on the lagging strand. - Origin of replication: The specific site on the DNA where replication begins. - RNA primer: A short RNA sequence that provides a starting point for DNA polymerase. - Topoisomerase: An enzyme that relieves the tension in the DNA ahead of the replication fork. - DNA polymerase: An enzyme that adds nucleotides to the growing DNA chain. - Ligase: An enzyme that joins together the Okazaki fragments on the lagging strand.</p> Signup and view all the answers

<p>The environment of the island caused certain changes in the DNA of the lizards.</p> Signup and view all the answers

<p>The Central Dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein. DNA is transcribed into RNA, and then RNA is translated into protein.<br /> DNA -&gt; RNA -&gt; Protein DNA contains the genetic code. During transcription, the DNA sequence is copied into a messenger RNA (mRNA) molecule. The mRNA molecule then travels out of the nucleus and into the cytoplasm, where it is translated into a protein molecule by ribosomes. The order of the nucleotides in the mRNA molecule determines the order of the amino acids in the protein. The protein then folds into a three-dimensional structure. This process is called protein synthesis. The final folded protein performs a specific function in the cell.</p> Signup and view all the answers

<p>mRNA (messenger RNA) carries the genetic information from DNA to the ribosomes where proteins are made. tRNA (transfer RNA) carries amino acids to the ribosomes for protein synthesis. Both RNA molecules are involved in protein synthesis and have a unique structure but perform different roles.</p> Signup and view all the answers

<p>Transcription is the process of copying the genetic information from DNA into mRNA. It can be broken down into several steps: 1. Initiation: RNA polymerase binds to the promoter region at the beginning of a gene on the DNA template. 2. Elongation: RNA polymerase moves along the DNA template, adding nucleotides to the growing mRNA strand. 3. Termination: RNA polymerase reaches a termination sequence at the end of a gene. RNA polymerase detaches from the DNA template, and the mRNA molecule is released. There are also termination sequences. Here is a visual example of the process:</p> <p>**Initiation: **RNA polymerase binds to the promoter region. **Elongation: **RNA polymerase moves along the DNA template, adding nucleotides to the growing mRNA strand. **Termination: **RNA polymerase reaches a terminator sequence and releases the mRNA transcript.</p> Signup and view all the answers

<p>Before mRNA leaves the nucleus, it undergoes several post-transcriptional modifications that are important for the stability, processing, and translation of the mRNA molecule. 1. 5' capping: a modified guanine nucleotide is added to the 5' end of the mRNA molecule. This protects the mRNA from degradation and helps the ribosome to bind to the mRNA. 2. 3' polyadenylation: A poly-A tail, a string of adenine nucleotides, is added to the 3' end of the mRNA molecule. This protects the mRNA from degradation and helps the mRNA to be exported from the nucleus. 3 Splicing: Non-coding regions known as introns are removed from the pre-mRNA molecule, while the coding regions known as exons are joined together.</p> Signup and view all the answers

<p>Translation occurs in the cytoplasm, on ribosomes.</p> Signup and view all the answers

<p>The lac operon is present in bacteria, specifically in Escherichia coli.</p> Signup and view all the answers

<p>The default state of the lac operon is off because it is repressed by the lac repressor protein, which binds to the operator region, preventing RNA polymerase from transcribing the lac genes.</p> Signup and view all the answers

<p>The lac operon is a group of genes in bacteria that allows the bacteria to metabolize lactose, a sugar. It is a classic example of gene regulation, which is the process of controlling which genes are expressed in a cell. The lac operon consists of three genes: lacZ, lacY, and lacA. These genes encode the enzymes required for lactose metabolism. The lac operon is regulated by a regulatory gene called lacI, which encodes a protein called the lac repressor. The lac repressor binds to the operator region of the lac operon, preventing RNA polymerase from transcribing the lac genes. In the presence of lactose, the lac repressor is inactivated, and RNA polymerase can transcribe the lac genes.</p> <p>Here is a more detailed explanation of each term:</p> <ul> <li> <strong>Lactose:</strong> A type of sugar that bacteria can use as an energy source.</li> <li> <strong>Regulatory genes:</strong> Genes that control the expression of other genes. The lacI gene is a regulatory gene.</li> <li> <strong>Operator:</strong> A sequence of DNA that the repressor protein binds to.</li> <li> <strong>Repressor:</strong> A protein that binds to the operator region and prevents RNA polymerase from transcribing the lac genes.</li> <li> <strong>Promoter:</strong> A sequence of DNA that RNA polymerase binds to.</li> <li> <strong>RNA polymerase:</strong> An enzyme that transcribes DNA into RNA.</li> <li> <strong>Lactose-utilization genes:</strong> Genes that encode the enzymes required for lactose metabolism, lacZ, lacY, and lacA.</li> <li> <strong>Transcription factor:</strong> A protein that helps to regulate gene expression. The lac repressor is a transcription factor.</li> <li> <strong>Glucose:</strong> A type of sugar that bacteria prefer to use as an energy source. If glucose is present, the lac operon is not expressed.</li> </ul> Signup and view all the answers

<p>Gene expression can be regulated in many ways. Here are seven: 1. <strong>Transcriptional regulation:</strong> The initiation of transcription can be controlled by proteins that bind to DNA and either promote or inhibit the binding of RNA polymerase. 2. <strong>Post-transcriptional regulation:</strong> After transcription, mRNA can be modified or degraded, which can affect the amount of protein that is produced. 3. <strong>Translational regulation:</strong> The initiation of translation can be controlled by proteins that bind to mRNA and either promote or inhibit the binding of ribosomes. 4. <strong>Post-translational regulation:</strong> After translation, proteins can be modified or degraded, which can affect the protein's activity or longevity. 5. <strong>Epigenetic regulation:</strong> Chemical modifications of DNA or histones can affect gene expression. 6. <strong>Hormonal regulation:</strong> Hormones can bind to receptors on cells and trigger changes in gene expression. 7. <strong>Environmental regulation:</strong> Environmental factors, such as temperature or nutrient availability, can affect gene expression.</p> Signup and view all the answers

<p>Dogs begin life as a single cell with 78 chromosomes. This zygote will make copies of its DNA and divide many times to form a dog with many cells. Despite having the same DNA, the cells differentiate. They begin to express certain genes while suppressing the expression of other genes. This process is called cell differentiation. Differentiated cells such as intestinal and retinal cells have different functions and structures.</p> Signup and view all the answers

<p>Cell differentiation is the process by which a cell becomes specialized to perform a specific function. This occurs during development, where the cells in an organism become specialized to form different organs and tissues.</p> Signup and view all the answers

<p>Embryonic stem cells (ESCs) are pluripotent, meaning they can differentiate into any type of cell in the body. Adult stem cells are multipotent, meaning they can differentiate into a limited number of cell types. Embryonic stem cells are derived from embryos, and adult stem cells are found in specific tissues in the body. Embryonic stem cells are more versatile than adult stem cells.</p> Signup and view all the answers

<p>Induced pluripotent stem cells (iPSCs) are adult cells that have been reprogrammed to become pluripotent. They are generated by introducing specific genes into adult cells. iPSCs have the potential to be used for regenerative medicine, cell therapy, and disease modeling.</p> Signup and view all the answers

<p>CRISPR-Cas9 technology is a powerful tool for editing genes. It originated from a natural defense mechanism found in bacteria. Bacteria use CRISPR to defend themselves against invading viruses. CRISPR-Cas9 technology uses a protein called Cas9, which acts like a pair of molecular scissors to cut DNA at a specific location. A guide RNA molecule is used to direct Cas9 to the target site. CRISPR-Cas9 technology can be used to: 1) insert genes, knock out/silence genes, and repair mutations. It has the potential to be used to treat genetic diseases, improve crops, and develop new disease models.</p> Signup and view all the answers

<p>Protein hormones such as insulin and human growth hormone can be produced using gene technology through recombinant DNA, which is a technique that uses bacterial cells or yeast as a factory to produce the proteins. The gene for the desired protein is inserted into the bacterial cell or yeast, This allows the bacteria or yeast to produce the protein in large quantities for therapeutic use.</p> Signup and view all the answers

<p>Antibiotic resistance is a serious threat to global health. It occurs when bacteria evolve mechanisms that allow them to survive in the presence of antibiotics. This poses a significant threat to human health because it can lead to difficult-to-treat infections.</p> <p>Bacteria can acquire antibiotic resistance genes many ways, contributing to the problem of antibiotic resistance: 1) Mutation: Mutations occur randomly in bacterial DNA. Some mutations can change the target protein of an antibiotic or reduce its effectiveness. 2) Horizontal gene transfer: Bacteria can transfer genes to each other, even if they are not related. This is called horizontal gene transfer, and it occurs through three mechanisms: a) Transformation: Bacteria can take up DNA from their environment. b) Transduction: Bacteria can transfer DNA through viruses. c) Conjugation: Bacteria can directly transfer DNA from one bacteria to another. Genes for antibiotic resistance are often located on plasmids, small circular pieces of DNA that can be easily transferred between bacteria. 3) Overuse and Misuse of antibiotics: The use of antibiotics provides a selective pressure on bacteria. Overuse and misuse of antibiotics can lead to the development of resistance. This is because antibiotics kill off susceptible bacteria, but they do not kill off resistant bacteria. The resistant bacteria can then reproduce and spread, leading to an increase in the number of resistant bacteria in the population.</p> Signup and view all the answers

<p>Unlike humans, bacteria have additional mechanisms for transferring genes, which play a significant role in the evolution of antibiotic resistance. These mechanisms are known as horizontal gene transfer. 1. Transformation: Bacteria can take up free DNA from their environment released by other bacteria, often during lysis of the other bacteria. They incorporate this DNA into their own genome, acquiring new genes, including those for antibiotic resistance. 2. Transduction: Viruses can transfer DNA from one bacteria to another. Bacteriophages (viruses that infect bacteria) can sometimes package fragments of bacterial DNA into their capsids. When these bacteriophages infect new bacteria, they can inject the acquired bacterial DNA. 3. Conjugation: One bacterium can directly transfer a copy of a plasmid (a small circle of DNA) to another bacterium. This transfer occurs through a pilus that connects the two bacteria. Horizontal gene transfer allows bacteria to share genes rapidly, accelerating the spread of antibiotic resistance. When bacteria acquire antibiotic resistance genes through these mechanisms, they can quickly become resistant to the antibiotics that would normally kill them. This makes the battle against antibiotic resistance very difficult, and highlights the need to use antibiotics responsibly to prevent the spread of resistant bacteria.</p> Signup and view all the answers

<p>The Kirby-Bauer disk diffusion test is a standard method for determining the susceptibility or resistance of bacteria to antibiotics.</p> <p>Here is a breakdown of the procedure:</p> <ol> <li>Agar Plate Preparation: A standardized agar plate is prepared with a specific type of media suitable for the growth of the bacteria being tested.</li> <li>Bacterial Inoculation: A standardized amount of bacteria is uniformly spread across the agar plate using a swab.</li> <li>Disk Application: Disks impregnated with different antibiotics are placed onto the surface of the agar plate. Each disk contains a known concentration of antibiotic.</li> <li>Incubation: The inoculated plates are incubated for a specific duration at a controlled temperature (typically 35°C) to allow the bacteria to grow.</li> <li>Zone of Inhibition: During incubation, if the bacteria are susceptible to the antibiotic, there will be formation of a zone of inhibition, an area around the disk where the bacteria do not grow. The size of the zone of inhibition is related to the bacteria's susceptibility to the antibiotic: a) Larger zone = more sensitive to the antibiotic. b) Smaller zone = less sensitive to the antibiotic. c) No zone = resistant to the antibiotic.</li> <li>Interpretation: The diameter of the zone of inhibition is measured for each disk, and this information can be compared to a standard reference table. This table indicates whether the bacteria are susceptible, intermediate, or resistant to each antibiotic based on the zone size.</li> </ol> Signup and view all the answers

<p>Vaccines work by exposing the body to weakened or inactivated forms of a pathogen, without causing illness. This allows the immune system to learn to fight off the pathogen by producing antibodies. When the body is exposed to the actual pathogen, it is able to quickly recognize and fight it off, preventing severe illness. Vaccines are a safe and effective way to prevent diseases.</p> Signup and view all the answers

<p>Vaccinating healthy individuals protects immunocompromised individuals by building herd immunity. Herd immunity works by reducing the number of susceptible individuals in a population. This makes it less likely for a pathogen to spread, and it protects those who cannot be vaccinated or who have weaker immune systems (immunocompromised). When a large proportion of the population is vaccinated, the pathogen has a harder time finding a suitable host to infect.</p> Signup and view all the answers

<p>Innate immunity, also known as natural immunity, is the first line of defense against pathogens. It involves many different components that are always present in the body. Here are examples: 1. Physical Barriers: Skin, mucus membranes, respiratory cilia, and digestive enzymes. 2. Cellular Defenses: Phagocytes (e.g., macrophages, neutrophils) - engulf and destroy pathogens. 3. Chemical Defenses: Antimicrobial peptides, interferons, and complement proteins. 4. Inflammatory response: Inflammation is a process that brings immune cells and other factors to the site of infection.</p> Signup and view all the answers

<p>Adaptive immunity, also known as acquired immunity, is a more specific type of immunity that is tailored to fight off particular pathogens. Here are the cells involved:</p> <ul> <li>B cells: B cells produce antibodies, which are proteins that bind to specific antigens on pathogens, neutralizing the pathogen or marking it for destruction by other immune cells.</li> <li>T cells: T cells are a type of white blood cell that directly attacks infected cells or cancer cells. There are two main types of T cells: a) Helper T cells: Help to activate other immune cells, including B cells and cytotoxic T cells. b) Cytotoxic T cells: Destroy infected cells or cancer cells by releasing toxic chemicals.</li> </ul> <p>Here is a summary of the process of adaptive immunity involves:</p> <ol> <li>Antigen Recognition: Immune system cells called antigen-presenting cells (APCs) engulf pathogens and display pieces of the pathogen (antigens) on their surface.</li> <li>Helper T cell Activation: Helper T cells recognize the antigens on the APCs and become activated.</li> <li>T cell Differentiation: Activated helper T cells differentiate into different types of T cells, such as cytotoxic T cells or memory T cells.</li> <li>B cell Activation: Activated helper T cells also activate B cells.</li> <li>Antibody Production: Activated B cells differentiate into plasma cells, which produce antibodies specific to the antigen.</li> <li>Destruction of Pathogens: Antibodies bind to pathogens and neutralize them or mark them for destruction by other immune cells, such as macrophages or natural killer cells.</li> <li>Memory Cell Formation: Memory T and B cells remain in the body and can quickly activate and fight off the pathogen if they encounter it again.</li> </ol> Signup and view all the answers