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Ageing is defined as a series of biological phenomena that follow a natural course from birth through maturity to old age and ultimately death. It begins at conception and continues until death. Hair thinning and greying, loss of muscle mass and strength, skin wrinkling, and other signs of ageing are typical manifestations of the process. Genetics plays a part in the occurrences of old age and mortality. Cells in the body tend to become inefficient as they age, resulting in the inability to conduct basic tasks such as breathing and digestion. As a result, in addition to slowing down reactions, the body’s immune system is compromised as well as its lung capacity and heart’s ability to pump blood.
- Human immunodeficiency virus (HIV) has a protein coat and a genetic material which is
(a) double-stranded RNA
(b) double-stranded DNA
(c) single-stranded DNA
(d) single-stranded RNA.
Answer
(d): HIV is a retrovirus with single-stranded RNA genetic material enveloped by a protein coat (core-shell). AIDS-causing. HIV is not like other retroviruses. It’s about 120 nm in diameter (60 times smaller than a red blood cell) and spherical.
- What does “growth” signify in developmental biology?
a) Cell size rises throughout growth.
b) Cell proliferation causes growth.
c) Increases in extracellular matrix volume between cells might cause growth.
d) Cell death affects overall growth.
e) All of the above
Answer: e) Growth is defined as the increase in the size and quantity of cells that occurs throughout an organism’s life history.
- The amount of DNA in the nucleus determines the cell’s size. What can doubling DNA (tetraploidy in salamanders) tell us about growth control?
a) The creatures grow to normal size, but contain half the number of cells, demonstrating that size is regulated rather than cell number.
b) The animals double in size, demonstrating that cell count regulates growth.
c) As a result, the animals are half their normal size. This indicates that the number of cells is the primary factor of growth.
d) The animals develop to normal size, but contain half the number of cells, demonstrating that DNA content regulates growth.
Answer: a) The balance between cell growth (the increase in mass or volume) and the timing of cell division determines the size of the cell at the time of cell division. It is interesting to note that quicker growth rates in bacteria and eukaryotes result in greater cell sizes.
- Adult human bone:
a) just at the extremities (epiphysis)
b) just in the middle (diaphysis)
c) solely between the epiphysis and diaphysis
d) expands continuously
Answer: c) In a process analogous to endochondral ossification, the epiphyseal plate of the bone grows in length, increasing the length of the bone. Mitosis is responsible for the continued growth of cartilage in the region of the epiphyseal plate next to the epiphysis. Specifically, the chondrocytes in the zone next to the diaphysis grow old and degenerate.
- Cancer is thought to emerge from stem cells rather than mature cells. Which of the following is true?
a)In order to become a cancer cell, stem cells must experience fewer alterations than fully differentiated cells.
b) Mutations require DNA replication, which stem cells do but differentiated cells do not.
c) Teratocarcinomas are cancers that develop from germ cells or embryonic stem cells, proving that tumours can develop from stem cells without mutation.
d) Wnt-like genes are required for stem cell maintenance, and many of these genes are oncogenes.
Answer: a,b,c and d) These are all reasons why cancer cells may arise from stem cells rather than fully differentiated cells.
- What does it mean that cells from various species can only divide a certain number of times in culture, and that number indicates the organism’s relative lifespan?
a) These species’ cells aren’t all equally suited to culturing.
b) Each creature appears to have a genetically defined number of cell divisions before senescence and death.
c)This indicates a genetically set life span.
d) The conditions in which cells are grown cause oxidative damage, which causes ageing in the organism.
Answer: b)Each organism appears to have a genetically set number of cell divisions before senescence and death.
- According to an ageing model, stress causes DNA damage, causing senescence and ageing.
a) The C. elegans DAF-16 protein is involved in stress response activation.
b) Dietary restriction lowers DNA-damaging free radical generation in mitochondria.
c) Werner’s syndrome is an ageing disorder caused by a DNA repair deficiency.
d) The all above fits with an ageing model based on DNA damage.
Answer: d)
In the course of everyday life, DNA damage happens as a result of a variety of causes including intracellular metabolism, replication, and exposure to genotoxic chemicals, which include ionising radiation and chemotherapy. It is possible that if this damage is not corrected, it will cause changes or mutations in the genomic material of the cell.
- What processes must occur in the blastema after amputation of a newt limb for regeneration to occur?
a) Regeneration occurs when cells begin to divide.
b) To regenerate, the cells must simply dedifferentiate.
c) AER-like function creation requires dedifferentiation, cell division and transdifferentiation.
d) After amputation, some blastema cells transdifferentiate, allowing regeneration.
Answer: c) During the creation of an artificial limb, cells from a more distal region in the limb generate blastema cells, which are responsible for acquiring the positional information of the missing distal components.
- How can cutting the nerve supply to a newt limb influence regeneration?
a)No effect because regeneration involves new muscle, bone, and connective tissue growth.
b) Normal tissue regeneration occurs, but nerve regeneration does not.
c) Outgrowth occurs, but the limb loses identity and typical proximo-distal patterning is lost.
d)A blastema forms but does not develop; regeneration fails.
Answer: d) During the process of developing and regenerating the peripheral nervous system, the mechanisms of epimorphic regeneration are interacted with. Following amputation of a leg, blastemal cells, which are the progenitor cells of the regeneration, appear at the site of the amputation and spread outward.
- Intercalary growth in a regenerating amphibian limb means:
a) the distal blastema regenerates proximal elements, then distal structures.
b)In order to produce positional values of the blastema, the stump regenerates proximal structures until the distal blastema takes over and completes distal structure outgrowth.
c)This leaves a limb devoid of intermediate structures as the distal blastema matures.
d)In this case, the regenerate lacks distal components and grows proximally, intercalating intermediate structures between it and the stump.
Answer: b) In order to regenerate proximal structures, the stump extends out until the positional values of the blastema are produced, at which point the distal blastema takes over and completes the outgrowth of distal structures.
- What excites you about zebrafish regeneration research?
a)In the absence of anatomical resemblance, the two structures are evolutionarily homologous.
b) Since zebrafish and humans have extremely similar eyes, this research may lead to new remedies for eye injuries in humans.
c) Zebrafish have limited regeneration of heart muscle, thus studying them genetically will help us understand the genetic basis of regeneration.
d)There are mutations that increase the healing abilities of zebrafish that may be used to boost human regeneration.
Answer: c) A limited amount of heart muscle regeneration can occur in zebrafish, and the capacity to study zebrafish genetically will improve our ability to understand how the genetic basis of regeneration is established.
- Pulse release of ____________ causes puberty (hormone)
a) somatostatin
b) Growth hormone
c) Gonadotropin-releasing hormone
d) Insulin-like growth factors
e) Growth hormone-releasing hormone
Answer: c) the first endocrine event associated with puberty is an increase in the amplitude of gonadotropin pulses during the night, which is caused by an increase in the pulsatile release of hypothalamic gonadotropin-releasing hormone (GnRH) into the hypothalamic-pituitary portal system.
