Trisomy-2l or Down's syndrome.
Symptoms - Mental retardation, malformed ears, protruded tongue, mouth is constantly open, etc.

The wall of the uterus has three layers of tissues. The outermost thin membranous serous layer called the perimetrium, the middle thick muscular layer called myometrium and the inner glandular layer called endometrium. The endometrium undergoes cyclic changes during the menstrual cycle while myometrium exhibits strong contractions during parturition.

Dr. Sheela will be be arrested under PCPNDT Act - preconception and prenatal diagnostic technique Act-1994.

A - Neisseria Gonorrhoea
B - AIDS
C - Jaundice

Queen Bee, Worker Bee - Diploid (2n)
Drones (Male Bee), Egg, sperm - Haploid (n)

In Ovoviviparous animals, the embryo develops inside the egg and remains in the mother's body until they are ready to hatch. This method of reproduction is similar to viviparity but the embryos have no placental connection with the mother and receive their nourishment from the egg yolk. Ovoviviparity is seen in fishes like shark

(a) Arrhenotoky: In this type, only males are produced by parthenogenesis. eg: honey bees
(b) Thelytoky: In this type of parthenogenesis only females are produced by parthenogenesis. e.g: Solenobia
(c) Amphitoky: In this type parthenogenetic egg may develop into individuals of any sex. e.g: Aphis.

The transfer of an embryo with more than 8 blastomeres stage into uterus is called embryo transfer technique.

(a) Human Sperm
(b) 1- Acrosome 2 - Nucleus 3 - Neck

PCOS is a complex endocrine system disorder that affects women in their reproductive years. Polycystic means 'many cysts'. It refers to many partially formed follicles on the ovaries, which contain an egg each. But they do not grow to maturity or produce eggs that can be fertilized. Women with PCOS may experience irregular menstrual cycles, increased androgen levels, excessive facial or body hair growth (hirsutism), acne, obesity, reduced fertility and increased risk of diabetes. Treatment for PCOS includes a healthy lifestyle,weight loss and targeted hormone therapy.

(i) Sertoli cells are elongated and pyramidal and provide nourishment to the sperms till maturation.
(ii) They also secrete inhibin, a hormone which is involved in the negative feedback control of sperm production.

During replication in DNA, in the template strand, replication is continuous and is called the leading strand. In the coding strand with polarity 5' ➝ 3', replication is discontinuous and DNA is synthesized in fragments called okazaki fragments which are joined by the enzyme DNA ligase. This is called the lagging strand.

The RNase is an enzyme that destroys protein. Therefore DNA, RNA and proteins from heat killed S-strand of bacteria when added to 'R'strain changed surface character and also made them pathogenic. The DNA is the transforming principle and not the proteins.

(i) Aurelia
(ii) The Significance is that Aurelia reproduces asexually by a special type of transverse fission called strobilation.

Organisms have three phases in its life cycle.
(i) Juvenile phase/ vegetative phase is the period of growth between the birth of the individual upto reproductive maturity.
(ii) Reproductive phase/maturity phase the organisms reproduce and their offsprings reach maturity period.
(iii) Senescent phase begins at the end of reproductive phase when degeneration sets in the structure and functioning of the body.

(i) Buds are formed on the outer surface of the parent body, it is known as exogenous budding e.g. Hydra.
(ii) In Hydra when food is plenty, the ectoderm cells increase and form a small elevation on the body surface.
(iii) Ectoderm and endoderm are pushed out to form the bud. The bud contains an interior lumen in continuation with parent's gastrovascular cavity.
(iv) The bud enlarges, develops a mouth and a circle of tentacles at its free end.
(v) When fully grown, the bud constricts at the base and finally separates from the parent body and leads an independent life.

(i) Alteration or mutation in a single gene causes Mendelian disorders. These disorders are transmitted to the offsprings on the same line as the Mendelian pattern of inheritance.
(ii) Some examples for Mendelian disorders are Thalassemia, albinism, phenylketonuria, etc. These disorders may be dominant or recessive and autosomal or sex linked.

(i) A dominant X - linked gene is necessary for the formation of colour sensitive cells, the cones. which helps to distinguish colours.
(ii) A recessive form of the gene is incapable of producing the cones. Hence the affected person is unable to distinguish red and green colour.

(i) In Drosophila the sex is determined by the balance between the genes'for femaleness located on the 'X' chromosome and those for maleness located on the 'auto somes' (A).
(ii) Hence the sex of an individual is determined by the ratio of its X chromosome to that of the autosome A sets. This ratio is termed as sex index and is expressed as
Sex Index \(=\frac{Number\ of\ X\ chromosomes(X)}{Number\ of\ X\ automosome}\)
change in this ratio leads to a changed sex phenotype Eg: Drosophila

In ABO blood group, each allele (I^A and I^B) produces a transferase enzyme. I^A allele produces N-acetyl galactose transferase and can add N-acetyl galactosamine (NAG) and Ballele encodes for the enzyme galactose transferase that adds galactose to the precursor (i.e. H substances) In the case of I^o/I^o allele no terminal transferase enzyme is produced and therefore called "null" allele arid hence cannot add NAG or galactose to the precursor.