Class 12 Biology - Chapter Human Health and Disease NCERT Solutions | What is the mechanism by which the AIDS
What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human immunodeficiency virus (HIV) via sexual or blood-blood contact. After entering the human body, the HIV virus attacks and enters the macrophages. Inside the macrophages, the RNA of the virus replicates with the help of enzyme reverse transcriptase and gives rise to viral DNA. Then, this viral DNA incorporates into the host DNA and directs the synthesis of virus particles. At the same time, HIV enters helper T- lymphocytes. It replicates and produces viral progeny there. These newly formed progeny viruses get released into the blood, attacking other healthy helper T-lymphocytes in the body. As a result, the number of T-lymphocytes in the body of an infected person decreases progressively, thereby decreasing the immunity of a person.
More Questions From Class 12 Biology - Chapter Human Health and Diseas
- Q:- How does the transmission of each of the following diseases take place?
(a) Amoebiasis
(b) Malaria
(c) Ascariasis
(d) Pneumonia - Q:- Draw a well-labelled diagram of an antibody molecule.
- Q:- What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q:- In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
- Q:- List the harmful effects caused by alcohol/drug abuse.
- Q:- Name the primary and secondary lymphoid organs.
- Q:- Differentiate the following and give examples of each:
(a) Innate and acquired immunity
(b) Active and passive immunity - Q:- How is a cancerous cell different from a normal cell?
- Q:- In which way has the study of biology helped us to control infectious diseases?
- Q:- Discuss with your teacher what does a suitable gene means, in the context of DNA vaccines.
Popular Questions of Class 12 Biology
- Q:- Why is reproduction essential for organisms? Answer
- Q:- Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
- Q:-
Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
(b) Humans are__________. (oviparous/viviparous/ovoviviparous)
(c) Fertilization is __________ in humans. (external/internal)
(d) Male and female gametes are __________. (diploid/haploid)
(e) Zygote is __________. (diploid/haploid)
(f) The process of release of the ovum from a mature follicle is called__________.
(g) Ovulation is induced by a hormone called the __________.
(h) The fusion of male and female gametes is called _____________.
(i) Fertilisation takes place in _____________.
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between fetus and uterus is called ____________. - Q:- What do you think is the significance of reproductive health in a society?
- Q:- Mention the advantages of selecting pea plant for experiment by Mendel.
- Q:- Group the following as nitrogenous bases and nucleosides:
Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine. - Q:- Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
- Q:- Explain in brief the role of animal husbandry in human welfare.
- Q:- Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
- Q:- Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
Recently Viewed Questions of Class 12 Biology
- Q:- Define spermiogenesis and spermiation.
- Q:- Explain why meiosis and gametogenesis are always interlinked?
- Q:- Identify True/False statements. Correct each false statement to make it true.
(a) Androgens are produced by Sertoli cells. (True/False)
(b) Spermatozoa get nutrition from Sertoli cells. (True/False)
(c) Leydig cells are found in ovary. (True/False)
(d) Leydig cells synthesise androgens. (True/False)
(e) Oogenesis takes place in corpus luteum. (True/False)
(f) Menstrual cycle ceases during pregnancy. (True/False)
(g) Presence or absence of hymen is not a reliable indicator of virginity or sexual experience. (True/False) - Q:- What is meant by emasculation? When and why does a plant breeder employ this technique?
- Q:- Define phenotypic adaptation. Give one example.
- Q:- State True/False with explanation
(a) Abortions could happen spontaneously too. (True/False)
(b) Infertility is defined as the inability to produce a viable offspring and is always due to abnormalities/defects in the female partner. (True/False)
(c) Complete lactation could help as a natural method of contraception. (True/False)
(d) Creating awareness about sex related aspects is an effective method to improve reproductive health of the people. (True/False) - Q:- The second trophic level in a lake is-
(a) Phytoplankton
(b) Zooplankton
(c) Benthos
(d) Fishes - Q:- Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
- Q:- Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
- Q:- Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
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