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.
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Five solutions A,B,C,D and E when tested with universal indicator showed pH as 4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
How many structural isomers can you draw for pentane?
Find the focal length of a lens of power – 2.0 D. What type of lens is this?
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
What does an electric circuit mean?
What is the role of the brain in reflex action?
People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
What type of oxides are formed when non-metals combine with oxygen?
What are the components of the transport system in highly organised plants?