| Class XII |
Biology |
Biology |
3 |
risk factors involved in illegal abortions aswellasprovidingmorehealthcarefacilitiescouldreversethementioned unhealthy trend. 3.4 S EXUALLY T RANSM... |
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| Class XII |
Biology |
Biology |
3 |
the simple principles given below: (i) Avoid sex with unknown partners/multiple partners. (ii) Always try to use condoms during coitus. (iii) In ca... |
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| Class XII |
Biology |
Biology |
3 |
another method attempted. Intra cytoplasmic sperm injection(ICSI)isanotherspecialisedproceduretoformanembryo in the laboratory in which a sperm is ... |
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| Class XII |
Biology |
Biology |
3 |
Health Care programmes. An overall improvement in reproductive health has taken place in our country as indicated by reduced maternal and infant mo... |
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| Class XII |
Biology |
Biology |
3 |
schools? Why? 4. Do you think that reproductive health in our country has improved in the past 50 years? If yes, mention some such areas of improve... |
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| Class XII |
Biology |
Biology |
4 |
Chapter 4 The work of Mendel and others who followed him gave us an Principles of Inheritance ideaofinheritancepatterns.Howeverthenatureofthose‘fac... |
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| Class XII |
Biology |
Biology |
4 |
with J. D. Watson, then a young man of 23, leading in 1953 to the proposal of the double-helical structure for DNA and the replication scheme. Cric... |
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| Class XII |
Biology |
Biology |
4 |
wild cows, we have well-known Indian breeds, e.g., Sahiwal cows in Punjab. We must, however, recognise that though our ancestors knew about the inh... |
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| Class XII |
Biology |
Biology |
4 |
Reprint 2026-27 PRINCIPLES OF INHERITANCE AND VARIATION Table 4.1: Contrasting Traits Studied by Mendel in Pea S.No. Characters Contrasting Traits ... |
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| Class XII |
Biotechnology |
Biotechnology |
1 |
are true and the reason is the correct explanation of the assertion. (b) Both assertion and reason are true but the reason is not the correct expla... |
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| Class XII |
Biology |
Biology |
4 |
the F g1neration while at the F 2tage both the traits were expressed in the proportion 3:1. The contrasting traits did not show any blending at eit... |
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| Class XII |
Biology |
Biology |
4 |
is convenient (and logical) to use the capital and lower case of an alphabetical symbol to remember this concept of dominance and recessiveness. (D... |
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| Class XII |
Biology |
Biology |
4 |
possible gametes are written on two sides, usually the top row and left columns. All possible combinations are represented in boxes below in the sq... |
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| Class XII |
Biology |
Biology |
4 |
to dominate over the other allele t or ‘dwarf’ character. It is thus due to this dominance of one character over the other that all the F are tall ... |
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| Class XII |
Biology |
Biology |
4 |
can easily be analysed to predict the genotype of the test organism. Figure 4.5 shows the results of typical test cross where violet colour flower ... |
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| Class XII |
Biology |
Biology |
4 |
or was in-between (incomplete dominance). But, in the case of co-dominance the F genera1ion resembles both parents. A good example is different typ... |
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| Class XII |
Biology |
Biology |
4 |
the example of ABO blood grouping also provides a good example of multiple alleles? Here you can see that there are more than two, i.e., three alle... |
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| Class XII |
Biology |
Biology |
4 |
shaped seeds. Here can you tell which of the characters in the pairs yellow/ green colour and round/wrinkled shape was dominant? Thus, yellow colou... |
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| Class XII |
Biology |
Biology |
4 |
Green) = 9 Round, Yellow : 3 Wrinkled, Yellow: 3 Round, Green : 1 Wrinkled, Green Based upon such observations on dihybrid crosses (crosses between... |
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| Class XII |
Biology |
Biology |
4 |
different types of genotypes and phenotypes are formed? Note them down in the format given. Can you, using the Punnett square data work out the gen... |
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| Class XII |
Biology |
Biology |
4 |
the pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried. Sutton united the knowledge of... |
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| Class XII |
Biology |
Biology |
4 |
generation of non-parental gene combinations (Figure 4.11). Morgan and his group also found that even when genes were grouped on the same chromosom... |
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| Class XII |
Biology |
Biology |
4 |
into account the influence of environment. Human skin colour is another classic example for this. In a polygenic trait the phenotype reflects the c... |
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| Class XII |
Biology |
Biology |
4 |
could trace a specific nuclear 69 structure all through spermatogenesis in a few insects, and it was also observed by him that 50 per cent of the s... |
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| Class XII |
Biology |
Biology |
4 |
(heterogametic) composition; Among the males an X-chromosome is (c) In many birds, female has a pair present but its counter part is distinctly dis... |
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