Which of the following characteristics of the structure of DNA allows it to carry a large amount of hereditary information?
different five-carbon sugars
the sequence of bases
phosphate-sugar backbones
complementary pairing of bases
Answer
- complementary pairing of bases
Explanation:
DNA is usually double stranded, each strand has a sequence of bases joined together. Bases in DNA can be divided into pyrimidines and purines. DNA winds into a double helix. The bases are joined together by hydrogen bonds which forms a ladder-like structure. This complimentary base pairing enables the structure to coil and lots of information can be stored in a small space.
When the substrate of a metabolic pathway is present in a bacterial cell, which of the following processes will occur?
deactivation of the promoter for an operon
allosteric regulation of an inducer
transcription of the genes in a repressible operon
transcription of the genes in an inducible operon
Answer
- transcription of the genes in an inducible operon
Explanation:
The lac operon in bacteria is a classic example of an inducible operon. In presence of lactose in the cell, it is converted ti allolactose which then acts as an inducer. The inducer’s role is to bind to the repressor and preventing it from binding the operator. After the inducer binds to the repressor, transcription of structural genes begins.
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. What function is impaired in their cells?
They cannot replicate DNA.
They cannot undergo mitosis.
They cannot exchange DNA with other cells.
They cannot repair thymine dimers.
Answer
- They cannot repair thymine dimers.
Explanation:
In xeroderma pigmentosum, the cells have decreased ability to repair DNA damage caused by UV light. The pathway that is affected in such individuals is the excision repair pathway which is responsible in repairing thymine dimers and other forms of UV damage. This lack of repair causes increased chances of growth of tumor.
The three classification of joints are?
Answer
- There are three classifications of joints: fibrous, cartilaginous, and synovial.
Fibrous – Fibrous tissue connects bones
Cartilaginous – bones connected by cartilage.
Synovial – articulating surfaces within synovial cavity
Explanation:
Joints are categorized into three types depending on the type of tissue involved in the joint. Fibrous joints are connected by dense, tough connective tissue, rich in collagen example is the periodontal ligament. Cartilaginous joints are connected by a fibrocartilage and allows more movement than the fibrous joints example, intervertebral discs. Synovial joints are most common and movable joints with synovial cavity. Examples are knees and elbows
What is the main component of blood that determines osmotic pressure?
thromboplastin
heart rate
erythrocytes
albumins
Answer
- albumins
Explanation:
Osmotic pressure is caused by differences in concentration gradient between solutions separated by a semi-permeable membrane. Blood osmotic pressure is determined by albumin, which displaces water molecules in blood vessel’s plasma creating a deficit of solvent molecules. Its impact on osmotic pressure is explained by Gibbs-Donnan effect of attracting other active positive ions, further enhancing its water-retaining effect
Can an ecosystem support an infinite number of moose
Answer
- No. An ecosystem cannot support infinite number of organisms with limited resources, unless if the available resources are infinite as well. Once the carrying capacity of the ecosystem is reached, moose will consume more resources and eventually lead to competition and eventually death.
Explanation:
Every ecosystem has a carrying capacity, which refers to the maximum number of organisms the ecosystem can support with the available resources. An infinite number of moose implies that organisms will be more than the resources can support and hence the population will start dying off due to lack of food.
What is the Hardy Weinberg principle?
Answer
- The Hardy Weinberg Equilibrium principle states that the genetic variation in a population remains constant from one generation to the next if there is no disturbing factors.
Explanation:
Mating in a large population with no external disturbances, the same genotype and phenotype will be retained because of equilibrium. There are several factors that can cause disturbance to a Hardy-Equilibrium including genetic drift, gene flow, natural selection, and nonrandom mutations. When a population is in Hardy-Equilibrium, it is not evolving and allele frequencies will remain the same over many generations.
A typical neuron’s membrane potential is -66 mV. A researcher team developed a novel drug which can be used to block the movement of K+ through the neuron cell membrane. If the drug is applied to this neuron, what would happen to the value of its resting potential?
A. It will decrease because K+ will no longer exit the cell
B. It will increase because K+ will no longer enter the cell
C. It will increase because K+ will no longer exit the cell
D. It will decrease because K+ will no longer enter the cell
E. It will not change because no K+ moves across the membrane at rest.
Answer
- E. It will not change because no K+ moves across the membrane at rest.
Explanation:
The resting membrane potential is mainly due to the movement of potassium ions out of the cell, because of the difference in concentration gradient between the inside and outside. As the potassium ions move out of the cell, the membrane potential falls and starts to approach the resting potential. To change the resting membrane potential, potassium ions diffuse out of the cell to make the interior more negative. However, since potassium ions can not longer exit or enter the cell, the resting membrane potential remains the same.
Why is fish farming an issue for wild populations genetically?
a. Genetically weaker fish may escape and mix with wild populations
b. Wild fish may get into pens, breed with hatchery fish and take those poor genes to wild populations
c. Wild fish become dependent on genetically inferior feed that falls out of the submersible pens
d. Prey items for wild populations become genetically enhanced due to fewer predators
Answer
- a. Genetically weaker fish may escape and mix with wild populations
Explanation:
Domesticated fish face less competition and live in favorable conditions compared to the wild populations. Domesticated fish have abundant food and there are no predators, which induces the loss of their ability to find food and avoid predators on their own. This weakens their gene pool and if these fish escape and breed with the wild populations, their genes may pollute the wild gene pool and cause decreased fitness of the entire population (Lynch & O’Hely, 2001).
Reference
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1299107/
Which of the following is true regarding bisphosphonates?
A. they include ibandronate and calcitrol
B. they can only be administered orally once or twice a year
C. they reverse hypocalcemia
D. they promote osteoporosis
E. they should be combined with calcium supplements and vitamin D for optimal effect
Answer
- E. they should be combined with calcium supplements and vitamin D for optimal effect
Explanation:
Biphosphonates are a class of drugs used to prevent bone density loss, treating osteoporosis and related diseases. They can be administered orally, or through injection. bisphosphonates combined with calcium plus vitamin D are more effective compared to when administered alone. It is also indicated that as the concentration of calcium and vitamin D increases, the drug is more effective. Calcium helps in increasing bone density while Vitamin D helps in absorbing calcium and promoting bone strength.
f an aerobic organism is exposed to oxygen that contains a radioactive oxygen isotope, which of the molecules listed below is likely to be radio labeled
A. water is a correct answer be
b. pyruvate I choose this answer because
C. NADH and FADH2
D. CO2
Explain why the correct answer is correct and the other answers are wrong
Answer
- A. water
Explanation:
- Aerobic respiration involves three stages. The glycolysis in which glucose is converted to two pyruvate molecules, TCA cycle which forms electron carriers and ATP, and lastly, oxidative phosphorylation which has electron transport chain and chemiosmosis. Oxygen is important because it acts as the final electron acceptor. Electrons are passed from one molecule to another, and energy is released and in chemiosmosis, the energy stored in the gradient is used to make ATP. Oxygen sits at the end of ETC, picking up protons to form water. Thus, if oxygen is radiolabelled, we will see the label in water molecule.
- Pyruvate does not use oxygen; it is formed by splitting glucose molecule
- NADH and FADH are not formed with the use of oxygen, there they cannot contain the radiolabelled oxygen as well
- Carbon dioxide is produced by decarboxylation of molecules in TCA cycle, which means it is not formed by use of oxygen either.
What anterior arm muscle can you observe when you flex a heavy object?
Answer
- Flexor muscle
Explanation:
The muscles in the posterior compartment of the forearm are extensor muscles while the anterior muscles are the flexor muscles. When flexing the arm, the muscle on the anterior part that is visible is the flexor muscle. biceps is one type of flexor muscle that is visible when lifting a heavy object as they bulge upwards.
