Topic 2 - Genes and Health Flashcards
What causes cystic fibrosis?
Cystic fibrosis is caused by a mutated gene.
How can mutations happen during DNA replication?
Mutations can occur during DNA replication due to rare errors when DNA polymerase adds free nucleotides to the DNA strand, leading to incorrect pairing.
What is the role of DNA helicase in DNA replication?
DNA helicase unzips the DNA double helix, separating the two strands.
What does DNA polymerase do during replication on the leading strand?
DNA polymerase adds free nucleotides in complementary pairs to the exposed DNA template strand, forming weak hydrogen bonds.
How does DNA replication occur on the lagging strand?
On the lagging strand, DNA polymerase adds nucleotides in small sections called Okazaki fragments, which are then joined together by DNA ligase.
What joins the aligned bases in the DNA strands?
Phosphodiester bonds join the aligned bases, connecting the phosphate and sugar molecules.
What is an isotope?
An isotope is the same atom with a different number of neutrons, which changes its mass.
How can isotopes be used in DNA research?
Isotopes, such as Nitrogen-15, can be used as labels to track processes like protein and DNA synthesis in bacteria.
What are the three main theories of DNA replication?
The three main theories are:
Conservative replication
Semi-conservative replication
Dispersive replication
What is the function of the cell membrane?
The cell membrane creates a ‘compartment’ for the cell and controls what goes in and out.
What is the main structural component of the cell membrane?
The cell membrane is primarily made of a phospholipid bilayer.
What other components are found in the cell membrane besides phospholipids?
The cell membrane also contains proteins, cholesterol, and carbohydrates.
How does the cell membrane appear under a light microscope versus an electron microscope?
Under a light microscope, the cell membrane appears as a thin line. Under an electron microscope, it appears as two lines.
What is the structure of a phospholipid molecule?
A phospholipid has a structure similar to a triglyceride, but one of the fatty acid tails is replaced by a phosphate group.
What is the nature of the head and tail of a phospholipid molecule?
The head is hydrophilic (polar) and the tail is hydrophobic (nonpolar).
Why are the hydrophilic heads of phospholipids on the outside of the bilayer?
The hydrophilic heads are on the outside because the environment outside the cell and inside the cytoplasm is water-based.
What is the Fluid Mosaic Model of the cell membrane?
The Fluid Mosaic Model describes the cell membrane as a dynamic structure with a phospholipid bilayer, proteins, cholesterol, and carbohydrates that can move and rearrange within the membrane.
How does the unsaturated-to-saturated ratio of fatty acid tails affect the membrane?
A higher unsaturated-to-saturated ratio in the phospholipid tails leads to a more fluid structure, as the kinks in the unsaturated tails prevent the phospholipids from packing closely together.
What happens in the lungs of someone with cystic fibrosis?
In cystic fibrosis, sticky mucus builds up in the lungs, making it difficult to clear the airways and impairing gas exchange.
How do goblet cells normally work to keep mucus fluid?
Goblet cells move chlorine ions out via active transport, creating a concentration gradient that draws water out, resulting in runny mucus that can be moved by cilia.
What happens in goblet cells of someone with cystic fibrosis?
In cystic fibrosis, chloride ions cannot leave the goblet cells, causing water to move into the cells. This results in thicker, stickier mucus that cannot be wafted by cilia.
What is the function of the trachea and its structure?
The trachea is made of C-shaped rings of cartilage, which provide strength and flexibility. The shape allows it to expand around the oesophagus.
What is chest physiotherapy and how does it help in cystic fibrosis?
Chest physiotherapy helps dislodge thick mucus in the lungs, improving mucus clearance and enabling better gas exchange.
What type of molecule is DNA?
It is a polynucleotide
How do nucleotides join together to form a polynucleotide chain?
Nucleotides join through condensation reactions, forming phosphodiester bonds between the phosphate group and the deoxyribose sugar.
What types of bonds are found between complementary base pairs in DNA?
DNA bases form weak hydrogen bonds:
Adenine (A) and Thymine (T) have 2 hydrogen bonds
Cytosine (C) and Guanine (G) have 3 hydrogen bonds
How does RNA differ from DNA in terms of structure?
RNA has ribose sugar instead of deoxyribose, uses the base uracil (U) instead of thymine (T), and is single-stranded, whereas DNA is double-stranded.
What is the role of phosphodiester bonds in both DNA and RNA?
Phosphodiester bonds connect the nucleotides in both DNA and RNA, linking the phosphate group of one nucleotide to the sugar of the next.
What is the overall structure of a DNA molecule?
DNA consists of two long polynucleotide chains that form a double helix. Each chain is made up of nucleotides connected by phosphodiester bonds, with complementary base pairs (A-T and C-G) held together by hydrogen bonds. The two strands run in opposite directions and are coiled into a double helix shape.
What is the structure of a nucleotide?
A nucleotide consists of three components:
A phosphate group
A deoxyribose sugar (in DNA) or ribose sugar (in RNA)
A nitrogenous base (Adenine, Thymine, Cytosine, or Guanine in DNA; Adenine, Uracil, Cytosine, or Guanine in RNA).
What causes cystic fibrosis?
Cystic fibrosis is caused by a mutation in the gene for the CFTR protein, which normally allows chloride ions (Cl-) to move out of cells.
What happens in a healthy person to maintain water balance in the mucus?
In a healthy person:
Na+ is pumped across the basal membrane.
Na+ diffuses through the apical membrane, then is pumped back.
Cl- diffuses to balance the charge.
Water is drawn into the cell by osmosis.
Water is drawn out of the mucus, keeping it thin and fluid.
What happens in a healthy person to make mucus runny when there is too little water?
In a healthy person with too little water in the mucus:
Cl- pump is activated to pump Cl- into the cell.
Cl- diffuses through the CFTR channels.
Na+ diffuses into the mucus to balance the charge.
Increased salt concentration draws water out of the cell by osmosis, making the mucus runny.
How does cystic fibrosis affect the movement of water and mucus in the body?
In cystic fibrosis:
The CFTR channel is absent or not functional.
The Na+ channel remains open.
Water is continually removed from mucus by osmosis, causing the mucus to become thick and sticky.
What are the effects of cystic fibrosis on the pancreas and reproductive system?
Pancreas: Blocked pancreatic duct prevents enzyme release, leading to reduced digestion, weight loss, enzyme damage to tissues, and possible diabetes.
Reproductive system: Mucus buildup in the vas deferens (male) and oviducts (female) causes infertility due to blockages.
What are the key characteristics of enzymes?
Enzymes are large globular proteins that act as biological catalysts. They have a specific 3D shape with an active site that binds to a complementary substrate, facilitating chemical reactions.
What is the “induced fit model” of enzyme action?
The induced fit model states that when a substrate binds to an enzyme’s active site, the enzyme’s shape changes slightly to better fit the substrate, increasing the reaction’s efficiency.
What factors can affect the rate of an enzyme-catalyzed reaction?
The rate of an enzyme-catalyzed reaction can be affected by:
Temperature
Substrate concentration
Enzyme concentration
pH
Presence of inhibitors
How do enzymes lower activation energy?
Enzymes lower activation energy by orienting molecules properly and increasing the frequency of successful collisions, which results in more enzyme-substrate complexes and faster reactions.
What are the two types of enzyme inhibitors and how do they work?
Competitive inhibitors: Bind to the active site, preventing the substrate from binding.
Non-competitive inhibitors: Bind to a site other than the active site, causing a change in the enzyme’s shape, which alters the active site and prevents substrate binding.
How does temperature affect the rate of an enzyme reaction?
As temperature increases, the rate of enzyme-catalyzed reactions typically increases, as molecules move faster, increasing the frequency of collisions. However, if the temperature is too high, enzymes may denature, causing a decrease in reaction rate.
What is Down’s syndrome, and what causes it?
Down’s syndrome is caused by an extra copy of chromosome 21, resulting in 47 chromosomes instead of the typical 46.
What is Non-Invasive Prenatal Testing (NIPT), and why is it beneficial?
NIPT is a non-invasive method to screen for Down’s syndrome, with 99% accuracy and no risk of miscarriage, as it involves analyzing fetal DNA from a blood sample.
What are the potential positives and negatives of genetic screening for Down’s syndrome?
Positives: No risk of miscarriage, offers valuable information for parents.
Negatives: Could lead to increased abortion rates if parents decide it’s “best for the baby.”
What is Preimplantation Genetic Diagnosis (PIGD), and how is it used?
PIGD involves collecting cells from embryos created via in vitro fertilization (IVF), then analyzing them for genetic disorders like cystic fibrosis or chromosomal conditions.
What are some advantages and disadvantages of PIGD?
Advantages: No pregnancy to terminate, peace of mind for parents.
Disadvantages: Risk of embryo damage, high costs, IVF can be unreliable, and false negatives could lead to emotional/financial issues.
What is the difference between prenatal testing and prenatal screening?
Prenatal testing (like amniocentesis and CVS) is diagnostic and involves sampling fetal cells to test for genetic conditions.
Prenatal screening is a non-invasive initial test (e.g., blood test or ultrasound) to assess the risk of genetic disorders.
What does “homologous pair” mean in genetics?
A homologous pair refers to two chromosomes that carry the same genes at the same location (locus), but they may have different versions (alleles) of these genes.
What is monohybrid inheritance, and what is an example?
Monohybrid inheritance is the inheritance of a single gene that determines a phenotype. An example is Cystic Fibrosis, which is caused by the inheritance of a recessive allele.
What are proteins made of, and what is their role in the body?
Proteins are made of chains of amino acids (polypeptides) folded into complex shapes. They play various roles, including acting as enzymes, transport molecules, structural molecules, and messengers.
How many types of amino acids are there, and what elements make up proteins?
There are 20 types of amino acids, and proteins are made up of carbon, hydrogen, oxygen, nitrogen, and sulfur.
What is the primary structure of a protein?
The primary structure of a protein is the sequence of amino acids in a polypeptide chain.
What is secondary protein structure, and what causes it?
Secondary structure refers to the folding of the polypeptide chain into structures like alpha helices or beta-pleated sheets, caused by hydrogen bonds between the amino acids.
What occurs during the tertiary structure of a protein?
In tertiary structure, the polypeptide chain folds into a complex 3D shape due to interactions between the R groups, including disulfide bridges, ionic bonds, hydrogen bonds, hydrophobic interactions, and hydrophilic interactions.
What is quaternary protein structure?
Quaternary structure occurs when multiple folded polypeptide chains come together to form the final protein structure. These chains may also interact with other functional groups, such as carbohydrates.
What are the key differences between globular and fibrous proteins?
Globular proteins: Compact, spherical shape, soluble, involved in biochemical roles (e.g., enzymes, insulin, hemoglobin).
Fibrous proteins: Long, tough fibers, insoluble, provide structural roles (e.g., keratin, collagen).
What are the key features of hemoglobin and collagen?
Hemoglobin: Globular protein, 4 polypeptide chains, complex quaternary structure, hydrophilic R groups on the outside.
Collagen: Fibrous protein, primary and secondary structures, three polypeptide chains, provides tensile strength, hydrophobic R groups on the outside, insoluble in water.
What is a gene, and how is it related to protein synthesis?
A gene is a sequence of bases on DNA that codes for a specific polypeptide, ultimately determining the sequence of amino acids in a protein.
How do RNA polymerase and the promoter region contribute to transcription?
RNA polymerase binds to the promoter region upstream of the gene, initiating transcription by unzipping the DNA and copying the non-coding strand into mRNA.
What are the steps involved in transcription?
RNA polymerase binds to the promoter region.
DNA is unzipped, exposing the bases.
Free RNA nucleotides bind to the template DNA strand (U instead of T).
mRNA is formed with phosphodiester bonds between RNA bases.
What happens to mRNA after transcription?
mRNA leaves the nucleus through the nuclear pores and travels to the ribosomes for translation, where it will be used to synthesize proteins.
What is the process of translation, and how does it relate to mRNA and tRNA?
In translation, mRNA moves through the ribosome, where each codon (triplet) on the mRNA binds to a complementary anticodon on a tRNA molecule. This process assembles amino acids in the correct sequence to form a polypeptide.
What is a codon and an anticodon in protein synthesis?
A codon is a triplet of bases on mRNA that codes for a specific amino acid. An anticodon is a complementary triplet on a tRNA molecule that binds to the mRNA codon during translation.
How are amino acids bonded together during translation?
Amino acids are joined by peptide bonds, which are formed between the amino group of one amino acid and the carboxyl group of the next, creating a polypeptide chain.
What is the role of tRNA in protein synthesis?
tRNA carries specific amino acids to the ribosome and has an anticodon that binds to the complementary codon on mRNA, ensuring the correct amino acid is added to the polypeptide chain.
What is the nature of the genetic code?
Triplet code: Each amino acid is coded by a sequence of three DNA bases.
Non-overlapping: The triplets do not overlap; each is read independently.
Degenerate: More triplet codes (64) than amino acids (20), meaning some mutations do not change the amino acid.
Why do most mutations have no effect on gene expression?
They occur in non-coding regions of DNA.
They do not change the amino acid sequence due to the degeneracy of the genetic code.
They do not alter protein function, even if the amino acid sequence changes.
How can mutations change gene expression and be damaging?
Altering the amino acid sequence can change the protein’s tertiary structure, affecting its function.
A mutation in the promoter region may prevent RNA polymerase from binding, stopping transcription.
A stop codon appearing prematurely may produce a non-functional, truncated protein.
What is a point mutation and its effect?
A point mutation involves a change in one base, either by substitution (base flipped or replaced) or inversion (base order reversed). It can lead to a change in the amino acid sequence, altering the protein.
What is a frame shift mutation and why is it problematic?
A frame shift mutation occurs when bases are inserted or deleted. This shifts the reading frame, changing all subsequent triplets, which usually results in a non-functional protein.
Give an example of a point mutation and its effect on the amino acid sequence.
Original sequence: C A G T C A G G C (Val Ser Pro).
Point mutation (substitution): C A G T C C G G C (Val Arg Pro).
This mutation changes the amino acid from Serine to Arginine, altering protein function.
What happens in frame shift deletion and insertion mutations?
Frame shift deletion: A base is deleted, shifting the reading frame (e.g., C A G C A G G C becomes G U C G U C C G, leading to different amino acids).
Frame shift insertion: A base is added, altering the triplet groupings and amino acids (e.g., C A G T C C A G G C becomes G U C A G G U C C G).
Can mutations ever be beneficial?
Yes, mutations can occasionally be beneficial. They are the only source of new alleles, creating genetic variation in populations, which may be advantageous in changing environments.
What is diffusion, and what types of molecules can pass through the membrane by this method?
Diffusion is the passive movement of molecules from a high to low concentration gradient. Small, uncharged, non-polar molecules like O₂, CO₂, and lipid-soluble vitamins (A, D, E, K) can diffuse directly through the phospholipid bilayer.
What is facilitated diffusion, and how does it differ from regular diffusion?
Facilitated diffusion is passive transport from high to low concentration but involves channel proteins or carrier proteins. It helps transport larger or charged molecules (like Na⁺, K⁺, glucose) that can’t pass freely through the phospholipid bilayer.
What is the role of channel proteins in facilitated diffusion?
Channel proteins move ions (e.g., Na⁺, K⁺) across the membrane. These proteins prevent charged ions from interacting with the hydrophobic interior of the phospholipids, and some can be gated, opening or closing in response to signals like hormones or changes in voltage.
What is osmosis, and how does it occur in cells?
Osmosis is the passive movement of water from an area of high to low concentration. Water can pass through the phospholipid bilayer directly or via aquaporins, which are water-specific channels. When water concentration is balanced, the solution is isotonic.
What is active transport, and how is it different from passive transport?
Active transport requires ATP energy to move molecules from a low to high concentration gradient, against the natural direction. This occurs through carrier proteins (also called protein pumps) and is essential for processes like nutrient absorption and ion balance.
What are endocytosis and exocytosis, and what types of molecules do they move?
Endocytosis: Active process that moves large molecules or multiple molecules into the cell in a vesicle (e.g., cholesterol uptake, phagocytosis).
Exocytosis: Active process that moves large molecules or multiple molecules out of the cell by fusing a vesicle with the plasma membrane (e.g., neurotransmitter release).
