Smart Pedigree Analyisis Tips and Tricks: Part 1
Digestive System Practice Questions
Q1. A gap between teeth is called:
a) Diastema b) Peristoma c) Dentosa d) Geostema
a) Diastema b) Peristoma c) Dentosa d) Geostema
Q2. Peristalsis occurs in:
a) Stomach b) Esophagus c) Ileum d) Jejunum
Q3. Gastro-esophageal sphincter is present between:
a) Esophagus and stomach b) Stomach and duodenum
c) Duodenum and pancreas d) between duodenum and jejunum
Q4. Zymogen cells secrete:
a) Mucus b) Pepsinogen c) Pepsin d) Rennin
Q5. Which is the largest part of the intestine
a) Duodenum b) Jejunum c) Ileum d) Caecum
Q6. Which of the following is not secreted by Crypts of Leiberkuhn:
a) Lipase b) Maltase c) Aminopeptidase d) Nucleases
Q7. Myenteric nerve plexus is present in:
a) Serosa b) Muscularis c) Submucosa d) Mucosa
Q8. Auerbach’s plexus is present between:
a) Longitudinal and circular muscle
b) Submucosa and mucosa
c) Serosa and muscular is
d) Muscularis and sub mucosa
Q9. Which of the following ions are responsible for the activation of ptyalin:
a) Na+ b) Cl- c) HCO3- d) SCN-
Q10. How much saliva is secreted per day:
a) 1000 - 1200 ml per day
b) 800 - 1000 ml per day
c) 600 - 800 ml per day
d) 900 - 1200 ml per day
Q11. Which of the following is correct about mucus:
a) It is alkaline and proteinaceous
b) It is acidic and proteinaceous
c) It is neutral and fatty in nature
d) It is neutral and proteinaceous
Q12. Intrinsic factor malsecretion may lead to:
a) Pernicious anemia
b) Rickets
c) Scurvy
d) Dermatitis
Q13, All of the following glands are present in mucosa except:
a) Oxyntic cells
b) Zymogen cells
c) Peptic cells
d) Brunner’s gland
Q14. Intestinal juice is secreted by:
a) Crypts of Leiberkuhn
b) Brunner’s gland
c) Both a and b
d) Gall bladder
Q15. Glisson’s capsule is present in:
a) Liver b) Gall bladder c) Small intesine d) Large intestine
Q16. Which of the following cells are associated with Liver:
a) Kuffer cells b) Paneth cells c) Both a and b d) Argentiffin cells
Q17. The pH of hepatic bile and gall bladder bile are:
a) 8.6 and 7.4 b) 7.4 and 8.6 c) 6.8 and 7.4 d) 7.4 and 6.8
Q18. The main pancreatic duct is also known as:
a) Duct of Wirsung
b) Duct of Santorini
c) Sphincter of Boyden
d) Sphincter of Oddi
Q19. The disease gall stone in the gall bladder is known as:
a) Cholethisasis
b) Cholelithiasis
c) Biliary duskiness
d) Sclerosing cholangitis
Q20. Which of the following pancreatic cells secrete pancreatic polypeptide
a) Alpha cells b) Beta cells c) Delta cells d PP cells
Q21. Pancreatic amylase is also known as:
a) Pancreatic acini b) Steapsin c) Proteolase d) Tryptase
Q22. Which of the following cells secrete somatostatin hormone responsible for inhibiting insulin and glucagon
a) Alpha cells b) Beta cells c) Delta cells d PP cells
Q23. Salivary amylase and pancreatic amylase work on pH:
a) 6.8 and 7.5 b) 6.8 and 7.0 c) 7.2 and 7.9 d) 7.2 and 6.8
Q24. Food in the buccal cavity and stomach are respectively called as:
a) Bolus and chyme b) Chyme and bolus c) Chile and bolus d) Bolus and chile
Q25. Lingual lipase is secreted by:
a) Ebner’s gland
b) Brunner’s gland
c) G-cells
d) Paneth cells
Q26. GIP (Gastric Inhibitory hormone) is secreted by:
a) Epithelium of duodenum
b) Epithelium of stomach
c) Epithelium of Jejunum
d) Epithelium of Ileum
Q27. CCK (cholecystokinin) is responsible for the secretion of:
a) Bicarbonate ions from pancreas
b) Bile from the gall bladder
c) Mucus from the sub mucosa of duodenum
d) Pancreatic juice from the pancreas
Q28. The pH of succus entericcus is:
a) 1.8
b) 6.8
c) 7.8
d) 7.0
Q29. Absorption of water occurs through
a) Osmosis b) Secondary active transport c) Both d) None
Q30. Gross calorific value of fat is:
a) 4.6 Kcal / gm of food
b) 5.65 Kcal/ gm of food
c) 9.45 Kcal / gm of food
d) 9.1 Kcal /gm of food
Q31. Physiological calorific value of fat is:
a) 9.1 Kcal / gm of food
b) 9.45 Kcal / gm of food
c) 9.6 Kcal / gm of food
d) 8.1 Kcal / gm of food
Q32. Choose the correct statement among the following:
a) Intestinal mucosal epithelium has enzymatic cells
b) Ptylin converts protein into proteoses and peptones
c) Crypts of Leiberkuhn are seen between bases of villi in intestine
d) Sphincter of Oddi is present at the junction of esophagus and cardiac stomach
e) Goblet cells secrete hydrochloric acid in stomach
Q33. Enzyme not present in pancreatic juice is:
a) Amylase b) Chymotrypsinogen c) Lipase d) Enterokinase
Q34. The enzymes are location ‘X’ and ‘Y’ are respectively:
Proteins___X____ Ã Proteoses + Peptones ___Y___Ã Dipeptide
a) Chymotrypsinogen and Pepsin
b) Pepsin and trypsin
c) Ptylin and pepsin
d) Trypsin and dipeptidase
Q35. Chilomicrons are:
a) small fat globules coated with protein
b) protein molecules coated with fat
c) small granules found in gastric juice
d) aerobic microbes
Q36 Which one does not produce any digestive enzymes:
a) Salivary glands b) Pancreas c) Gall bladder d) Stomach
Q37. Which is component of Waldeyer’s ring:
a) Pharynx b) Tonsils c) Ileum d) Esophagus
Q38. Which is not correct:
a) Human saliva is near neutral
b) An adult secretes 1.0 - 1.5 L of saliva per day
c) Saliva is secreted by six pairs of glands
d) Ptylin breaks down cooked starch into maltose
Q39. Which gastric secretion is correctly matched with its source:
a) Pepsin -- Chief cells
b) Chemotropism -- Parietal cells
c) Hcl -- goblet cells
d) Mucus -- Oxyntic cells
Q40. Which enzymes are likely to act on the baked potatoes eaten by a man, starting from mouth and as it moves down the alimentary canal:
a) Disaccharidase like maltase à Lipases à Nucleases
b) Salivary amylase à Pancreatic amylase à Diasaccharidases
c) Salivary maltase à carboxypeptidase à Trypsinogen
d) Pancreatic amylase à Salivary amylase à Lipases
Q41. Absence of enzyme in small intestine will severely affect digestion of proteins:
a) Maltase b) Lipase c) Enterokinase d) Pancreatic amylase
Q42. Which process helps in maintaining blood glucose level under fasting:
a) Glycogenesis b) Glycogenolysis c) Lipogenesis d) Glycolysis
Q43. Aggregates of lymphoid tissue present in distal part of the small intestine are known as:
a) Villi b) Rugae c) Choroid plexus d) Payer’s patches
Q44. Back flow of faecal matter from large intestine is prevented by:
a) Epiglottis
b) Sphincter of Oddi
c) Ieocaecal valve
d) Gastro-esophageal sphincter
e) Pyloric sphincter
Q45. Special feature of bile juice is that it
a) has no enzyme b) has amylase c) contains lipase d) contains Hcl
Q46. Bilirubin is formed by breakdown product of:
a) Haempglobin b) Haemocyanin c) Haemoprotein d) Haematin
Q47. In the absence of which of the duodenal enzyme, digestion of chyme proteins not possible:
a) Dil HCl b) Enterokinase c) Gastrin d) All of the above
Q48. Common passage for bile and pancreatic juice is:
a) Ampulla of Vater
b) Duct of Wirsung
c) Ductus coledochus
d) Duct of Santorini
Q49. Which pair reaches the stomach totally undigested:
a) Fat, cellulose b) Starch, cellulose c) Protein, starch d) Starch, fat
Q50. Which is not a gastrointestinal hormone:
a) CCK b) Gastrin c) Secretin d) Cortisol
ANSWER KEY:
1. a 11. a 21. b 31. a 41. c
2. b 12. a 22. c 32. c 42. b
3. a 13. d 23. a 33. d 43. d
4. b 14. c 24. a 34. b 44. c
5. c 15. a 25. a 35. a 45. a
6. c 16. a 26. a 36. c 46. a
7. b 17. a 27. b 37. b 47. b
8. a 18. a 28. c 38. c 48. a
9. b 19. b 29. a 39. a 49. a
10. a 20. d 30. c 40. b 50. d
What is Apomixis and Polyembryony?
In a normal sexual cycle (amphimixis), the megaspore mother cell (2n) of ovule is converted to haploid gametophytic cells (embryo sac) through meiosis (reductional division). This results in the formation of an egg cell, synergids, antipodal cells and polar nuclei cell. Egg fertilizes with the male gamete to form an embryo. This process occurs in almost all angiospermic plants. However, in some plants, meiotic division and fertilization are eliminated still a functional embryo is formed. The formation of embryo without fertilization (by asexual means) is called Apomixis (Apo = not, mixis = act of mixing) and the seed formed is called Apomictic seed. In other words, apomixis is a type of asexual reproduction that does not involve meiosis and syngamy (fusion of male and female gametes) for the formation of an embryo.
Apomixis occurs in about 300 species of angioperms that comprises of at least 35 plant species. It is most common in families such as Asteraceae, Graminaceae, Rosaceae and Rutaceae. Some of the most common examples of apomixis include citrus and mango.
Types of Apomixis:
1. Gametophytic:
a) Diplospory
b) Apospory
2. Sporophytic
a) Adventive embryony
DIPLOSPORY:
Megapore mother cell does not go through meiosis. Besides, egg sac organizes normally but the cells are diploid. It is important to note that the embryo develops without being fertilized. This occues because the egg is already growing. Endosperm development may or may not involve fertilization.
Diplospory is common in grasses and asteraceae family.
APOSPORY:
In this case, the MMC (megspore mother cell) undergoes meiosis, but the resulting cells degenerate before forming a functional embryo sac. Additional cells present in the nucellus become cytoplasmic and function as apomictic initials. These cells do not undergo meiosis and form their own embryo sac inside the same ovule.
Apospory condition is found in families such as Rosaceae, Asteraceae and Grasses.
Advantages of Apomixis:
Seeds and plants produced through apomixis are genetically similar to their parent. This technique is can be used in hybrid seed production. We know that hybrid seeds formed in F1 generation is always superior than its pureline parents. However, the same hybrid seeds cannot be used every year due to segregation of characters. And therefore, farmers need to buy hybrid seeds every year for cultivation. However, forming hybrid seeds is a tough task. Using apomictic technique, hybrid seeds can be easily produced in large amounts.
Seed formation through the apomictic process does not require any pollinating agent.
Advantages of Apomixis:
Seeds and plants produced through apomixis are genetically similar to their parent. This technique is can be used in hybrid seed production. We know that hybrid seeds formed in F1 generation is always superior than its pureline parents. However, the same hybrid seeds cannot be used every year due to segregation of characters. And therefore, farmers need to buy hybrid seeds every year for cultivation. However, forming hybrid seeds is a tough task. Using apomictic technique, hybrid seeds can be easily produced in large amounts.
Seed formation through the apomictic process does not require any pollinating agent.
ADVENTIVE EMBRYONY (POLYEMBRYONY):
In adventive embryony, the megaspore mother cells (MMC) undergoes normal meiotic division and forms a normal embryo sac. Besides, these cells are fertilized normally with male gametes just like normal embryogenesis. What happens is that the cells in the nucellus become embryogenic and form multiple embryos in the micropylar region of the ovule. The resulting asexual embryos do not form their own embryos rather they grow inside the sexual embryo. This is common in tropical fruit trees such as citrus and mango.
THE LIVING WORLD
Characteristics of Living Organisms:
1. Cellular Structure
2. Metabolism
3. Growth
4. Reproduction
5. Consciousness
Other characteristics of living beings include:
- Adaptation
- Lifespan
- Homeostasis
- Healing and repair
- Movement and variation
Q. What is a defining feature?
A. A feature is said to be defining if it fulfills two criteria:
a) If it is unexceptionally present in all organisms.
b) It should not be part of non-living objects.
1. Cellular Structure: It is the structural and functional unit of life. Cells are present in all living objects. Cells are not present in non-living objects. Therefore, it can be said that cellular structure is a defining feature.
2. Metabolism: (Gk: metabole = change / conversion)
All the organisms are made of chemicals -- these chemicals are constantly being made. These changes are called chemical reactions. All chemical reactions occurring inside our body constitute metabolism.
Metabolism comprises of two events: Anabolism and Catabolism
=> These metabolic reactions can occur in vivo or in vitro.
- Metabolism is a characteristic feature of all living organisms and it is absent in non-living objects. It can, therefore, be said that metabolism is a defining feature.
3. Growth:
Growth is defined as an irreversible increase in mass or overall size of our cell / organ or the whole organism. In other words, growth is an increase in body mass.
Growth occurs due to net results of two components of metabolism:
If anabolism > catabolism --- It leads to growth
If anabolism = catabolism --- no growth will occur
If anabolism < catabolism --- it leads to negative growth
Q. Compare plants and animals + growth in living and non-living with respect to growth?
=> Since growth is a characteristic of both living and nonliving objects. Growth is, therefore, a non-defining feature.
4. Reproduction:
It is a process of formation / production of offspring having features more or less similar to parents.
Asexual Reproduction: It involves single parent, it is therefore, uniparental. Besides, it does not involve fertilization of gametes.
Types of asexual reproduction:
Fish -- Fission (eg: binary fission in bacteria)
Fry -- Fragmentation (eg: in filamentous algae)
Really -- Regeneration (eg: Planaria)
Very -- Vegetative reproduction
Spicy: sporulation (eg: algae, fungi, bacteria)
Buddy -- Budding (eg: yeast, unicellular fungi, hydra)
Sexual reproduction: It involves two parents = biparental. Besides, it involves the formation of gametes and their fusion.
=> In unicellular organisms, growth and reproduction are synonymous. For instance in bacteria and amoeba -- increase in cell number is associated with the growth. On the other hand, in higher plants and animals, growth and reproduction are mutually exclusive events. A Mutually Exclusive term is used to describe a situation where the occurrence of one event is not influenced or caused by another. Mutually exclusive events never occur at the same time.
- Reproduction is not present universally. For instance Mule (a cross between male donkey [Jack] and female horse [Mare]) and worker bee. Both mule and worker bees are sterile.
=> Since reproduction is somewhere associated with growth in unicellular organisms and since reproduction is not present universally -- it can be considered as a non-defining feature.
5. Consciousness:
It is the ability to sense stimulus / environment and response to it. External stimulus can be physical, chemical or biological. It is unexceptionally shown by all living organisms. It can, therefore, be considered as a defining feature.
1. Cellular Structure
2. Metabolism
3. Growth
4. Reproduction
5. Consciousness
Other characteristics of living beings include:
- Adaptation
- Lifespan
- Homeostasis
- Healing and repair
- Movement and variation
Q. What is a defining feature?
A. A feature is said to be defining if it fulfills two criteria:
a) If it is unexceptionally present in all organisms.
b) It should not be part of non-living objects.
1. Cellular Structure: It is the structural and functional unit of life. Cells are present in all living objects. Cells are not present in non-living objects. Therefore, it can be said that cellular structure is a defining feature.
2. Metabolism: (Gk: metabole = change / conversion)
All the organisms are made of chemicals -- these chemicals are constantly being made. These changes are called chemical reactions. All chemical reactions occurring inside our body constitute metabolism.
Metabolism comprises of two events: Anabolism and Catabolism
=> These metabolic reactions can occur in vivo or in vitro.
- Metabolism is a characteristic feature of all living organisms and it is absent in non-living objects. It can, therefore, be said that metabolism is a defining feature.
3. Growth:
Growth is defined as an irreversible increase in mass or overall size of our cell / organ or the whole organism. In other words, growth is an increase in body mass.
Growth occurs due to net results of two components of metabolism:
If anabolism > catabolism --- It leads to growth
If anabolism = catabolism --- no growth will occur
If anabolism < catabolism --- it leads to negative growth
Q. Compare plants and animals + growth in living and non-living with respect to growth?
=> Since growth is a characteristic of both living and nonliving objects. Growth is, therefore, a non-defining feature.
4. Reproduction:
It is a process of formation / production of offspring having features more or less similar to parents.
Asexual Reproduction: It involves single parent, it is therefore, uniparental. Besides, it does not involve fertilization of gametes.
Types of asexual reproduction:
Fish -- Fission (eg: binary fission in bacteria)
Fry -- Fragmentation (eg: in filamentous algae)
Really -- Regeneration (eg: Planaria)
Very -- Vegetative reproduction
Spicy: sporulation (eg: algae, fungi, bacteria)
Buddy -- Budding (eg: yeast, unicellular fungi, hydra)
Sexual reproduction: It involves two parents = biparental. Besides, it involves the formation of gametes and their fusion.
=> In unicellular organisms, growth and reproduction are synonymous. For instance in bacteria and amoeba -- increase in cell number is associated with the growth. On the other hand, in higher plants and animals, growth and reproduction are mutually exclusive events. A Mutually Exclusive term is used to describe a situation where the occurrence of one event is not influenced or caused by another. Mutually exclusive events never occur at the same time.
- Reproduction is not present universally. For instance Mule (a cross between male donkey [Jack] and female horse [Mare]) and worker bee. Both mule and worker bees are sterile.
=> Since reproduction is somewhere associated with growth in unicellular organisms and since reproduction is not present universally -- it can be considered as a non-defining feature.
5. Consciousness:
It is the ability to sense stimulus / environment and response to it. External stimulus can be physical, chemical or biological. It is unexceptionally shown by all living organisms. It can, therefore, be considered as a defining feature.
What is Amitosis and Where Does it Occur?
Amitosis is a method of asexual reproduction, which occurs in acellular organisms such as bacteria, protozoans, diseased cells, old cells, mammalian cartilage cells and in fetal membranes, yeast budding, etc. It was first discovered by the scientist, REMAK.
Mechanisms:
-- Nucleus of the cell elongates.
-- Constriction appears in the nucleus, which gradually deepens and divides the nucleus into two daughter nuclei.
-- A constriction appears in the cytoplasm, which divides the cytoplasm and the nuclei into two daughter cells each with a nucleus.
-- In direct division, no spindle formation and no direct chromosome formation occurs.
Q. What is the minimum number of meiotic divisions required to produce 100 wheat grains?
a) 100 b) 125 c) 150 d) 200
Ans (b)
Explanation: Usually, one meiotic division forms 4 pollen grains
One meiotic division forms 1 egg cells
So, to produce 100 wheat grains, we need 100 pollen grains and 100 eggs
To produce 100 pollen, only 25 meiotic divisions are required and to produce 100 eggs, 100 meiotic divisions are required. Therefore, a total of 125 meiotic divisions are required to produce 100 wheat grains.
Shortcut:
No of meiotic divisions required to produce 'n' number of seeds / grains
No. of grains = n + n / 4
= Egg + Pollen
= 100 + 100 /4
= 125
Q. Number of mitotic divisions required for the formation of 100 cells:
a) 100 b) 50 c) 25 d) 99
Ans: (d)
Explanation:
Number of mitotic divisions for the formation of ‘n’ number of cellls = (n - 1)
Mechanisms:
-- Nucleus of the cell elongates.
-- Constriction appears in the nucleus, which gradually deepens and divides the nucleus into two daughter nuclei.
-- A constriction appears in the cytoplasm, which divides the cytoplasm and the nuclei into two daughter cells each with a nucleus.
-- In direct division, no spindle formation and no direct chromosome formation occurs.
Q. What is the minimum number of meiotic divisions required to produce 100 wheat grains?
a) 100 b) 125 c) 150 d) 200
Ans (b)
Explanation: Usually, one meiotic division forms 4 pollen grains
One meiotic division forms 1 egg cells
So, to produce 100 wheat grains, we need 100 pollen grains and 100 eggs
To produce 100 pollen, only 25 meiotic divisions are required and to produce 100 eggs, 100 meiotic divisions are required. Therefore, a total of 125 meiotic divisions are required to produce 100 wheat grains.
Shortcut:
No of meiotic divisions required to produce 'n' number of seeds / grains
No. of grains = n + n / 4
= Egg + Pollen
= 100 + 100 /4
= 125
Q. Number of mitotic divisions required for the formation of 100 cells:
a) 100 b) 50 c) 25 d) 99
Ans: (d)
Explanation:
Number of mitotic divisions for the formation of ‘n’ number of cellls = (n - 1)
Multiple Choice Questions on Cell Cycle
Q1. Which of the following choice is incorrect in relation to the interphase stage?
a) Period of great metabolic activity
b) It covers over 95% of the total duration of cell cycle
c) Absence of replication of DNA
d) Also called as preparatory phase
Q2. Duplication of DNA occurs in:
a) G1 phase
b) S phase
c) G2 phase
d) M phase
Q3. If cell division is restricted in G1 phase of a cell cycle, the condition is known as:
a) G1 phase
b) G2 phase
c) G0 phase
d) M phase
Q4. Go-phase of cell denotes:
a) Check point before entering the next phase
b) Death of cell
c) Temporary pause
d) Exit of cell from cell cycle
Q5. The sequence of cell cycle is:
a) S, M, G1 and G2
b) G1, G2, S and M
c) S, M, G2 and G1
d) G1, S, G2 and M
Q6. The synthesis of spindle proteins occur during:
a) G1-phase
b) S-phase
c) G2-phase
d) M-phase
Q7. Histone protein synthesis occurs during:
a) G1 phase
b) G2 phase
c) M phase
d) S phase
Q8. During cell cycle, DNA replicates:
a) Once
b) Twice
c) Many times
d) Not at all
Q9. Which of the following doubles during S phase:
a) Mitochondria
b) Chloroplast
c) Golgi body
d) All of the above
Q10. Which of the following phase of a cell cycle is called invisible phase:
a) G1 phase
b) S phase
c) G2 phase
d) M phase
Q11. If the DNA content in a cell at G1 phase is 2C, what will be the DNA content at S phase?
a) 2C
b) 4C
c) 1C
d) None
Q12. If the DNA content of a cell at G1 phase is 2C what will be the DNA content of its daughter cells after mitotic division?
a) 2C
b) 4C
c) 1C
d) None
Q13. The DNA content of a cell at G1 phase is 2C, what will be the DNA content of its daughter cells after meiosis II?
a) 2C
b) 1C
c) 4C
d) All of the above
Answer Key:
1. c 4. d 7. d 10. b 13. b
2. b 5. b 8. a 11. b
3. c 6. c 9. d 12. a
a) Period of great metabolic activity
b) It covers over 95% of the total duration of cell cycle
c) Absence of replication of DNA
d) Also called as preparatory phase
Q2. Duplication of DNA occurs in:
a) G1 phase
b) S phase
c) G2 phase
d) M phase
Q3. If cell division is restricted in G1 phase of a cell cycle, the condition is known as:
a) G1 phase
b) G2 phase
c) G0 phase
d) M phase
Q4. Go-phase of cell denotes:
a) Check point before entering the next phase
b) Death of cell
c) Temporary pause
d) Exit of cell from cell cycle
Q5. The sequence of cell cycle is:
a) S, M, G1 and G2
b) G1, G2, S and M
c) S, M, G2 and G1
d) G1, S, G2 and M
Q6. The synthesis of spindle proteins occur during:
a) G1-phase
b) S-phase
c) G2-phase
d) M-phase
Q7. Histone protein synthesis occurs during:
a) G1 phase
b) G2 phase
c) M phase
d) S phase
Q8. During cell cycle, DNA replicates:
a) Once
b) Twice
c) Many times
d) Not at all
Q9. Which of the following doubles during S phase:
a) Mitochondria
b) Chloroplast
c) Golgi body
d) All of the above
Q10. Which of the following phase of a cell cycle is called invisible phase:
a) G1 phase
b) S phase
c) G2 phase
d) M phase
Q11. If the DNA content in a cell at G1 phase is 2C, what will be the DNA content at S phase?
a) 2C
b) 4C
c) 1C
d) None
Q12. If the DNA content of a cell at G1 phase is 2C what will be the DNA content of its daughter cells after mitotic division?
a) 2C
b) 4C
c) 1C
d) None
Q13. The DNA content of a cell at G1 phase is 2C, what will be the DNA content of its daughter cells after meiosis II?
a) 2C
b) 1C
c) 4C
d) All of the above
Answer Key:
1. c 4. d 7. d 10. b 13. b
2. b 5. b 8. a 11. b
3. c 6. c 9. d 12. a
How the Cell Cycle is Controlled?
Cell cycle is run by a group of special proteins, called Cyclins and Cdks (cyclin dependent kinases). A cell reproduces by performing an orderly set sequences of irreversible events in which it duplicates its contents and then divide into two. These events are collectively called as cell cycle.
Molecular biologists have made a remarkable progress in identifying the biomolecules that control the cell cycle. Scientists working on frog eggs and yeast cell concluded that the activity of enzymes such as cyclin dependent kinases (Cdk‘s) regulate the cell cycle.
Kinase is a type of enzyme that is responsible for removing a phosphate group from ATP and add to another protein. The kinases involved in the cell cycle are called Cdks because they are activated when they combine with the key protein, cyclin.
At some check-point in the cell cycle (G1 Ã S and G2 Ã M), a kinase enzyme combines with cyclin and this moves the cell cycle forward. G1 or S-kinase is capable of initiating the replication of DNA once it combines with S-cyclin. After some time, S-cyclin is destroyed and S-kinase is no longer active. M-kinase, on the other hand, is capable of turning on mitosis once it combines with M-cyclin.
G1 to S transition is carried out by G1 or S cyclin + cdc 2 kinase
G2 to M transition is triggered by maturation promoting factor (MPF) formed by mitotic cyclin + cdc 2 kinase
Molecular biologists have made a remarkable progress in identifying the biomolecules that control the cell cycle. Scientists working on frog eggs and yeast cell concluded that the activity of enzymes such as cyclin dependent kinases (Cdk‘s) regulate the cell cycle.
Kinase is a type of enzyme that is responsible for removing a phosphate group from ATP and add to another protein. The kinases involved in the cell cycle are called Cdks because they are activated when they combine with the key protein, cyclin.
At some check-point in the cell cycle (G1 Ã S and G2 Ã M), a kinase enzyme combines with cyclin and this moves the cell cycle forward. G1 or S-kinase is capable of initiating the replication of DNA once it combines with S-cyclin. After some time, S-cyclin is destroyed and S-kinase is no longer active. M-kinase, on the other hand, is capable of turning on mitosis once it combines with M-cyclin.
G1 to S transition is carried out by G1 or S cyclin + cdc 2 kinase
G2 to M transition is triggered by maturation promoting factor (MPF) formed by mitotic cyclin + cdc 2 kinase