Causes of variations in clones.
Clones have the same genetic makeup but variations appear in clones due to following reasons:
(i) Effect of environment termed acquired variations are not inherited.
(ii) Mutations. These are sudden stable abrupt changes and they are discontinuous inheritable as produced due to changes in genetic makeup.
(iii) Identical twins arising from one fertilized egg are clones of each other though they are offspring of their parents and have the same genetic set up.

(i) Human placenta is called haemochorial type because the maternal blood and foetal blood are separated by only foetal placental tissues while all the maternal placental tissues have been digested.
(ii) During parturition, placenta releases relaxin hormone which softens the pubic symphysis present between the pubic symphysis present between the pubic bones of two pelvic girdles so widens the pelvis for easy childbirth.

Evolutionary features of mammals:
(i) Mammals become viviparous and protected their unborn young ones inside the mothers body.
(ii) They are more intelligent (with increased brain size) in sensing and avoiding danger.

1. Periodic abstinence and coitus interruptus (withdrawal method) are the natural methods of birth control.
2. Periodic abstinence is the method in which the couples avoid or abstain from sexual intercourse from day 10 to 17 of the menstrual cycle, when chances of fertilisation are high.
3.Coitus interruptus or withdrawal is a method in which the male partner withdraws his penis from the vagina just before ejaculation.

Yes, sex education is necessary in schools because 
(i) The children should know about sex-related issues and problems like adolescence changes, menstrual cycle, menstrual problems, unwanted pregnancy, unsafe abortion, reproductive tract infections, STDs and cancer.
(ii)They should be aware of changes happening in their body and should be taught about healthy habits including personal cleanliness and hygiene.
(iii) Counselling and awareness regarding reproductive organs, safe and hygienic sexual practices will play an important role in making people reproductively healthy.

(i) Pollen release and stigma receptivity is not synchronised.
(ii) Anther and stigma are placed at different position.
(ill) Self-incompatibility.
(iv) Production of unisexual flowers
Three outbreeding devices are:
(i) Dichogamy: Stamens and carpels do not mature at the same time. Therefore stigma is not receptive at the time of pollen release or vice-versa.
(ii) Dicliny: The flowers are unisexual
(iii) Herkogamy: There is a physical barrier present between anther and stigma e.g. in calotropis or the anther and stigma are placed in different positions.

(a) Genetic RNA-Double stranded RNA of mammalian reovirus
Non-genetic RNA-Ribosomal RNA, messenger RNA or transfer RNA
(b)Prolaryotic mRNA is short lived and hardly undergoes processing(capping, methylation and polyadenylation)to from comparatively stable mRNA.

(i)differences,offsprings
(ii)germ,somatic
(iii)charles Darwin,pangenes,
(iv)Hugo devries,Karl Correns,T-shermak
(v)Garden pea
(vi)3:1 ; 1: 2 : 1.

Reptilian characters: 
1. Presence of similar teeth in jaws.
2. Each finger ending into a claw.
3. A long tail with free caudal vertebrae.
4. Presence of weak and keelless sternum.
Avian characters: 
1. Presence of feathers on body.
2. Rounded cranium.
3. Forelimbs modified into wings and have three figures.
4. Presence of four toes.
5. Presence of furcula or wish bone.

(a) Promoter
This is the sequence of DNA/gene, that provides place for binding of RNA polymerase.
(b) tRNA
It acts as an adapter molecule, that reads the code on the mRNA on one hand and binds to a specific amino acid on the other hand.
By its anticodon, it recognises the codon of the amino acid it carries, and transports the amino acid to the site of protein synthesis.
(c) Exons
These are the regions of eukaryotic gene/DNA, which form parts of RNA and code for different regions in the proteins.

The plants must be crossed with a white flowered (homozygous recessive) plant, i.e. a test cross is conducted.
Garden Pea
1.If the plant is homozygous dominant, all the plants in the progeny would bear red flowers (heterozygous) and if the plant is heterozygous, the progeny would consist of red-flowered plants and white-flowered plants in the ratio of 1 : 1.


2.In snapdragon, when a red-flowered plant is crossed to a white-flowered plant, the progeny would consist of pink-flowered plants.
3.So, red-flowered plants are homozygous dominant, while heterozygous condition produces pink-flowered plants.
4.The cross is as follows:

5.It is because of incomplete dominance, where neither of the two alleles is completely dominant over the other and the hybrid is intermediate between the two i.e. pink-flowered.

Microsporogenesis :
(i)When the anther develops, each cell of sporogenous tissue functions as microspore mother cell (MMC) or pollen mother cell (PMC) and undergoes is meiotic divisions to form microspore tetrads.
(ii) The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis.
(iii) The microspores get arranged in a cluster of four cells and hence are microspore tetrad.
(iv) As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains
(v) In each microsporangium, thousands of pollen grains are formed and released with the dehiscence of anther.

a) Structure of ovum. Most animal eggs are spherical or oval, non-motile but on close examination

it is noted that one pole is different from the other. The pole from which polar bodies are given off is called animal pole while the opposite is termed as vegetal pole. Thus it is said to have polarity. Thus various
cytoplasmic substances are distributed along the axis in unequal manner. The nucleus also called (germinal vesicle) having chromatin network is surrounded by nuclear membrane. It also contains prominent nucleolus. All animal eggs contain some reserve material to provide food called yolk. The cytoplasm of ovum is called ooplasm. It lacks centrosome but contains cortical granules derived from Golgi bodies in its outer region termed cortex.
(b) Function of Zona pellucida. During fertilisation as a result of cortical reaction, zona pellucida hardens and prevents the entry of additional sperms (polyspermy).

(i) (b) : MTP is comparatively safe upto 12 weeks (the first trimester) of pregnancy. It becomes more risky after the first trimester period of pregnancy as the fetus becomes intimately associated with the maternal tissues.
(ii) (c) : MTP helps to get rid of unwanted pregnancies due to casual unprotected intercourse, or where pregnancy can be harmful to either mother or fetus.
(iii) (d) : Child detected with congenital heart disease can be aborted upto 28th week of pregnancy under the guidance of family physician and the gynaecologist.
(iv) (a) : Government ofIndia legalised MTP in 1971 with some strict conditions to avoid its misuse.
(v) (a) : MTP is comparatively safe upto 12 weeks (the first trimester) of pregnancy. It becomes more risky after the first trimester period of pregnancy as the fetus becomes intimately associated with the maternal tissues.

(i) (d): DNA is the genetic material in E. coli. RNA is the genetic material in Tobacco Mosaic virus and Q\(\beta\) bacteriophage.
(ii) (a): The presence of thymine in DNA at the place of uracil which is present in RNA provides additional stability to DNA.
(iii) (d)
(iv) (a)
(v) (b): Purines present in DNA and RNA are adenine and guanine, while pyrimidines present in DNA are cytosine and thymine and pyrimidines present in RNA are cytosine and uracil.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
Explanation:
Reusable contraceptives do not guarantee prevention from accidental pregnancy.

(c) If A is true, but R is false

(a) Both A and R are true and R is the correct explanation of A.
A single stranded DNA or RNA, tagged with a radioactive molecule called probe is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography.

(c) : Monohybrid cross is a cross between two organisms of a species which, is made to study the inheritance of a single pair of alleles or factors of a character. Dominant character is one of a pair of alleles which can express itself whether present in homozygous or heterozygous state. In F₁ generation, (the generation of hybrids produced from a cross between the genetically different homozygous individuals called parents the progenies are heterozygous dominant.