Topic 2 - Genes and Health

Question 1

What causes cystic fibrosis?

Answer 1

Cystic fibrosis is caused by a mutated gene.

Question 2

How can mutations happen during DNA replication?

Answer 2

Mutations can occur during DNA replication due to rare errors when DNA polymerase adds free nucleotides to the DNA strand, leading to incorrect pairing.

Question 3

What is the role of DNA helicase in DNA replication?

Answer 3

DNA helicase unzips the DNA double helix, separating the two strands.

Question 4

What does DNA polymerase do during replication on the leading strand?

Answer 4

DNA polymerase adds free nucleotides in complementary pairs to the exposed DNA template strand, forming weak hydrogen bonds.

Question 5

How does DNA replication occur on the lagging strand?

Answer 5

On the lagging strand, DNA polymerase adds nucleotides in small sections called Okazaki fragments, which are then joined together by DNA ligase.

Question 6

What joins the aligned bases in the DNA strands?

Answer 6

Phosphodiester bonds join the aligned bases, connecting the phosphate and sugar molecules.

Question 7

What is an isotope?

Answer 7

An isotope is the same atom with a different number of neutrons, which changes its mass.

Question 8

How can isotopes be used in DNA research?

Answer 8

Isotopes, such as Nitrogen-15, can be used as labels to track processes like protein and DNA synthesis in bacteria.

Question 9

What are the three main theories of DNA replication?

Answer 9

The three main theories are:

Conservative replication
Semi-conservative replication
Dispersive replication

Question 10

What is the function of the cell membrane?

Answer 10

The cell membrane creates a ‘compartment’ for the cell and controls what goes in and out.

Question 11

What is the main structural component of the cell membrane?

Answer 11

The cell membrane is primarily made of a phospholipid bilayer.

Question 12

What other components are found in the cell membrane besides phospholipids?

Answer 12

The cell membrane also contains proteins, cholesterol, and carbohydrates.

Question 13

How does the cell membrane appear under a light microscope versus an electron microscope?

Answer 13

Under a light microscope, the cell membrane appears as a thin line. Under an electron microscope, it appears as two lines.

Question 14

What is the structure of a phospholipid molecule?

Answer 14

A phospholipid has a structure similar to a triglyceride, but one of the fatty acid tails is replaced by a phosphate group.

Question 15

What is the nature of the head and tail of a phospholipid molecule?

Answer 15

The head is hydrophilic (polar) and the tail is hydrophobic (nonpolar).

Question 16

Why are the hydrophilic heads of phospholipids on the outside of the bilayer?

Answer 16

The hydrophilic heads are on the outside because the environment outside the cell and inside the cytoplasm is water-based.

Question 17

What is the Fluid Mosaic Model of the cell membrane?

Answer 17

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.

Question 18

How does the unsaturated-to-saturated ratio of fatty acid tails affect the membrane?

Answer 18

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.

Question 19

What happens in the lungs of someone with cystic fibrosis?

Answer 19

In cystic fibrosis, sticky mucus builds up in the lungs, making it difficult to clear the airways and impairing gas exchange.

Question 20

How do goblet cells normally work to keep mucus fluid?

Answer 20

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.

Question 21

What happens in goblet cells of someone with cystic fibrosis?

Answer 21

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.

Question 22

What is the function of the trachea and its structure?

Answer 22

The trachea is made of C-shaped rings of cartilage, which provide strength and flexibility. The shape allows it to expand around the oesophagus.

Question 23

What is chest physiotherapy and how does it help in cystic fibrosis?

Answer 23

Chest physiotherapy helps dislodge thick mucus in the lungs, improving mucus clearance and enabling better gas exchange.

Question 24

What type of molecule is DNA?

Answer 24

It is a polynucleotide

Question 25

How do nucleotides join together to form a polynucleotide chain?

Answer 25

Nucleotides join through condensation reactions, forming phosphodiester bonds between the phosphate group and the deoxyribose sugar.

Question 26

What types of bonds are found between complementary base pairs in DNA?

Answer 26

DNA bases form weak hydrogen bonds: Adenine (A) and Thymine (T) have 2 hydrogen bonds Cytosine (C) and Guanine (G) have 3 hydrogen bonds

Question 27

How does RNA differ from DNA in terms of structure?

Answer 27

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.

Question 28

What is the role of phosphodiester bonds in both DNA and RNA?

Answer 28

Phosphodiester bonds connect the nucleotides in both DNA and RNA, linking the phosphate group of one nucleotide to the sugar of the next.

Question 29

What is the overall structure of a DNA molecule?

Answer 29

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.

Question 30

What is the structure of a nucleotide?

Answer 30

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).

Question 31

What causes cystic fibrosis?

Answer 31

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.

Question 32

What happens in a healthy person to maintain water balance in the mucus?

Answer 32

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.

Question 33

What happens in a healthy person to make mucus runny when there is too little water?

Answer 33

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.

Question 34

How does cystic fibrosis affect the movement of water and mucus in the body?

Answer 34

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.

Question 35

What are the effects of cystic fibrosis on the pancreas and reproductive system?

Answer 35

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.

Question 36

What are the key characteristics of enzymes?

Answer 36

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.

Question 37

What is the "induced fit model" of enzyme action?

Answer 37

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.

Question 38

What factors can affect the rate of an enzyme-catalyzed reaction?

Answer 38

The rate of an enzyme-catalyzed reaction can be affected by: Temperature Substrate concentration Enzyme concentration pH Presence of inhibitors

Question 39

How do enzymes lower activation energy?

Answer 39

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.

Question 40

What are the two types of enzyme inhibitors and how do they work?

Answer 40

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.

Question 41

How does temperature affect the rate of an enzyme reaction?

Answer 41

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.

Question 42

What is Down's syndrome, and what causes it?

Answer 42

Down's syndrome is caused by an extra copy of chromosome 21, resulting in 47 chromosomes instead of the typical 46.

Question 43

What is Non-Invasive Prenatal Testing (NIPT), and why is it beneficial?

Answer 43

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.

Question 44

What are the potential positives and negatives of genetic screening for Down's syndrome?

Answer 44

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.”

Question 45

What is Preimplantation Genetic Diagnosis (PIGD), and how is it used?

Answer 45

PIGD involves collecting cells from embryos created via in vitro fertilization (IVF), then analyzing them for genetic disorders like cystic fibrosis or chromosomal conditions.

Question 46

What are some advantages and disadvantages of PIGD?

Answer 46

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.

Question 47

What is the difference between prenatal testing and prenatal screening?

Answer 47

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.

Question 48

What does "homologous pair" mean in genetics?

Answer 48

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.

Question 49

What is monohybrid inheritance, and what is an example?

Answer 49

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.

Question 50

What are proteins made of, and what is their role in the body?

Answer 50

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.

Question 51

How many types of amino acids are there, and what elements make up proteins?

Answer 51

There are 20 types of amino acids, and proteins are made up of carbon, hydrogen, oxygen, nitrogen, and sulfur.

Question 52

What is the primary structure of a protein?

Answer 52

The primary structure of a protein is the sequence of amino acids in a polypeptide chain.

Question 53

What is secondary protein structure, and what causes it?

Answer 53

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.

Question 54

What occurs during the tertiary structure of a protein?

Answer 54

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.

Question 55

What is quaternary protein structure?

Answer 55

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.

Question 56

What are the key differences between globular and fibrous proteins?

Answer 56

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).

Question 57

What are the key features of hemoglobin and collagen?

Answer 57

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.

Question 58

What is a gene, and how is it related to protein synthesis?

Answer 58

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.

Question 59

How do RNA polymerase and the promoter region contribute to transcription?

Answer 59

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.

Question 60

What are the steps involved in transcription?

Answer 60

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.

Question 61

What happens to mRNA after transcription?

Answer 61

mRNA leaves the nucleus through the nuclear pores and travels to the ribosomes for translation, where it will be used to synthesize proteins.

Question 62

What is the process of translation, and how does it relate to mRNA and tRNA?

Answer 62

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.

Question 63

What is a codon and an anticodon in protein synthesis?

Answer 63

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.

Question 64

How are amino acids bonded together during translation?

Answer 64

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.

Question 65

What is the role of tRNA in protein synthesis?

Answer 65

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.

Question 66

What is the nature of the genetic code?

Answer 66

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.

Question 67

Why do most mutations have no effect on gene expression?

Answer 67

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.

Question 68

How can mutations change gene expression and be damaging?

Answer 68

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.

Question 69

What is a point mutation and its effect?

Answer 69

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.

Question 70

What is a frame shift mutation and why is it problematic?

Answer 70

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.

Question 71

Give an example of a point mutation and its effect on the amino acid sequence.

Answer 71

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.

Question 72

What happens in frame shift deletion and insertion mutations?

Answer 72

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).

Question 73

Can mutations ever be beneficial?

Answer 73

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.

Question 74

What is diffusion, and what types of molecules can pass through the membrane by this method?

Answer 74

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.

Question 75

What is facilitated diffusion, and how does it differ from regular diffusion?

Answer 75

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.

Question 76

What is the role of channel proteins in facilitated diffusion?

Answer 76

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.

Question 77

What is osmosis, and how does it occur in cells?

Answer 77

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.

Question 78

What is active transport, and how is it different from passive transport?

Answer 78

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.

Question 79

What are endocytosis and exocytosis, and what types of molecules do they move?

Answer 79

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).