How is the sex of the child determined in human beings?
In organisms, a specific pair of chromosomes determine the sex of the individual called sex chromosome. In human beings, sex is determined by the XX-XY chromosomes. Females contain XX chromosomes and males contain XY chromosomes.
So, if the male gamete X chromosome fuses with the female X chromosome then the child will be female or when male gamete Y fuses with the female X chromosome then it will be the male child.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
Give an example of a metal which
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.
What is meant by saying that the potential difference between two points is 1 V?
A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
How is oxygen and carbon dioxide transported in human beings?
Describe double circulation of blood in human beings. Why is it necessary?
Name two safety measures commonly used in electric circuits and appliances.
Which of the following terms does not represent electrical power in a circuit?
(a) I2R (b) IR2 (c) VI (d) V2/R
The refractive index of diamond is 2.42. What is the meaning of this statement?
How is the process of pollination different from fertilisation?
Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.