Assertion: Polytene chromosomes have a high amount of DNA.
Reason: Polytene chromosomes are formed by repeated replication of chromosomal DNA without separation of chromatids.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
A.
If both assertion and reason are true and reason is the correct explanation of assertion
Polytene chromosomes are quite common in salivary glands of insects and so are called salivary chromosomes. These chromosomes have high amount of DNA of almost I 000 times in Drosophila as compared to ordinary somatic chromosomes. These chromosomes are multistranded. They are in permanent prophase stage. These chromosomes& are formed by somatic pairing between homologous chromosomes and repeated replication pf their chromonemata without separation of chromatids. All the chromosomes may remain attached to one another at a common point called chromocentre.
In which one of the following sets of three items each belong to the category mentioned against them
Lysine, glycine, thiamine - amino acids
Myosin, oxytocin and gastrin - hormones
Rennin, helicase and hyaluronidase - enzymes
Optic nerve, oculomotor, vagus - sensory nerves
The "cri-du-chat" syndrome is caused by change in chromosome structure involving
deletion
duplication
inversion
translocation
Which one of the following pairs of features is a good example of polygenic inheritance
Human height and skin colour
ABO blood group in humans and flower colour of Mirabilis jalapa
Hair pigment of mouse and tongue rolling in humans
Human eye colour and sickle cell anaemia
Grain colour in wheat is determined by three pairs of polygenes. Following the cross AABBCC (dark colour) x aabbcc (light colour), in F2 generation what proportion of the progeny is likely to resemble either parent?
None
Less than 5 percent
One third
Half
Given below is a highly simplified representation of the human sex chromosomes from a karyotype
The gene a and b could be of
colour blindness and body height
attached ear lobe and Rhesus blood group
haemophilia and red-green colour blindness
phenylketonuria and haemophilia
Mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called
reciprocal cross
dihybrid crossn
test cross
back cross
Given below is a pedigree chart showing the inheritance ofa certain sex-linked trait in humans
The trait traced in the above pedigree chart is
dominant X- linked
recessive X- linked
dominant Y- linked
recessive Y- linked
Genes present in the cytoplasm of eukaryotic cells are found in
mitochondria and inherited via egg cytoplasm
lysosomes and peroxisomes
Golgi bodies and smooth endoplasmic reticulum
plastids and inherited via male gamete
