Biology:2010:CBSE: [All India ]:Set-I

In amphibians, syngamy occurs in the external medium (water), ie., outside the body of the organism and hence, is known as external fertilisation.
In reptiles, syngamy occurs inside the body of the organism and hence, called as internal fertilisation.

Snow blindness in humans is caused due to temporary loss of vision and inflammation of the conjunctiva and cornea, caused by exposure of the eyes to bright sunlight and ultraviolet rays reflected from snow.

An autosomal dominant disorder is Myotonic dystrophy.An autosomal recessive disorder is Sickle cell anaemia.

Exonucleases remove nucleotides from the ends of the DNA whereas endonucleases make cuts at specific positions within the DNA.

It represents Genetic Diversity.

The health workers are able to estimate the amount of organic matter in sewage water by measuring the BOD of a water body.

The enzyme involved in the continuous replication of the DNA strand is DNA dependent DNA polymerase.
The polarity of the template strand is 3’ 5’.

Offsprings derived from asexual reproduction are called clones because:
1.  They are genetically and morphologically similar to their parents.
2. A single individual is capable of producing the offspring; hence, no genetic recombination occurs.

• Ribosome is the organelle within which the formation of peptide bond occurs. The P and A sites in the larger subunit of the ribosome remain close enough to each other for the formation of the peptide bond.
• The charging of amino acids in the initial stage occurs due to ATP’s.

Copper and hormone releasing IUD’s act as contraceptives as they increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilising capacity of sperms. Moreover, they make the uterus unsuitable for implantation and the cervix hostile to the sperms.