( A n s w e r) Homogamy : Anthers and stigma of the bisexual flowers of some plants mature at the same time. They are brought close to each other by growth, bending or folding to ensure self pollination. This condition is called homogamy. e.g., Mirabilis (Four O, clock), Catharanthus (= Vinca), Potato, Sunflower, Wheat, Rice, etc.

Translation is the process in which mRNA produced by transcription is decoded by the ribosomes to produce a specific amino acid chain.

 Protein synthesis occurs in the following steps: 

Activation of tRNA: This step occurs before the process of translation and is an essential step as it loads the amino acids on their respective tRNA. Only activated tRNA are required to form peptide bond between two amino acids.

Initiation - It involves binding of small ribosomal subunits to mRNA and then is joined by the 50S subunit. It includes steps of formation of the peptide bond between the first two amino acids. Protein synthesis is initiated with the amino acid methionine because the AUG translation initiation codon of mRNAs is recognized by the anticodon (UAC) of initiator methionine transfer RNA.

Elongation - It includes all the reactions from the synthesis of the first peptide bond to the addition of the last amino acid. 

Termination-  In the termination step, the completed polypeptide chain is released and the ribosome dissociates from mRNA. The tRNA recognises a stop codon and stops the synthesis of proteins.

Three codons on mRNA which are not recognized by tRNA are UAG (amber), UGA (opal), UAA (ochre). These codons are collectively known as nonsense codons or terminator codons. They are significant since their presence bring the termination of protein synthesis (translation).

The process of removal of anthers from the flower is called as emasculation. It is done before dehiscence to prevent contamination of stigma with any undesired pollen and to ensure cross-pollination by desired pollens. Emasculation is useful in artificial hybridization to pollinate stigma with selected emasculated pollens only.  Emasculation is performed by plant breeders in bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain. To remove the anthers, the flowers are covered with a bag before they open. This ensures that the flower is pollinated by pollen grains obtained from desirable varieties only. Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.

A genetically modified organism (GMO) is an organism (plant, animal, bacteria or virus) whose genetic makeup has been modified for a partic- ular purpose. The organism does not occur naturally in this modified state.

In biology, a part of the cell cycle in which cells divide (mitosis) and/or reproduce (meiosis). In eukaryotes, the cell cycle consists of four discrete phases: G1, S, G2, and M. The S or synthesis phase is when DNA replication occurs, and the M or mitosis phase is when the cell actually divides. Mitosis is the process in which the nucleus of a eukaryotic cell divides. During this process, sister chromatids separate from each other and move to opposite poles of the cell. This happens in four phases, called prophase, metaphase, anaphase, and telophase.

Process of Translation

The protein synthesis occurs in two steps, namely transcription and translation. During transcription, the information from DNA is encoded into mRNA. During translation, the mRNA works with a ribosome and tRNA to synthesize proteins. 

Transcription takes place in the nucleus. During transcription, DNA partially unwinds by the enzyme helicase. This results in the single nucleotide chain to be copied. RNA polymerase reads the DNA strand from the 3' to 5' direction and synthesizes the complementary strand of messenger RNA in the 5' to 3' direction. The DNA strand which is transcribed is called as the template strand. The nucleotides on the RNA strand are complementary to the nucleotides on the DNA strand. DNA cytosine pairs with RNA guanine, DNA guanine pairs with RNA cytosine, DNA thymine pairs with RNA adenine and DNA adenine pairs with RNA uracil. After mRNA is synthesized, it is transported to the cytoplasm where it binds with ribosomes. Ribosomes are the sites of protein synthesis. Ribosomes have three important binding sites, one for mRNA and two (A site and P site) for tRNA. The start codon methionine occupies the P site and the second codon occupies the A site. The tRNA molecule whose anticodon is complementary to the mRNA forms a base pair with the mRNA in the A site. A peptide bond is formed between the amino acid attached to the tRNA in the A site and the methionine in the P site. The ribosome then slides down the mRNA in such a way that the tRNA in the A site moves to the P site and a new codon occupies the A site. This process continues until one of the three stop codons occupies the A site. At that point, the protein chain connected to the tRNA in the P site is released and the translation is complete.

Transcription

Transcription is the process of synthesis of RNA from DNA template. A segment of DNA gets copied into mRNA during the process. The process of transcription starts at the promoter region of the template DNA and terminates at the terminator region. The segment of DNA between these two regions is known as transcription unit. The transcription requires RNA polymerase enzyme, a DNA template, four types of ribonucleotides, and certain cofactors such as Mg2+.

The three important events that occur during the process of transcription are as follows.

(i) Initiation

(ii) Elongation

(iii) Termination

The DNA-dependent RNA polymerase and certain initiation factors (σ) bind at the double stranded DNA at the promoter region of the template strand and initiate the process of transcription. RNA polymerase moves along the DNA and leads to the unwinding of DNA duplex into two separate strands. Then, one of the strands, called sense strand, acts as template for mRNA synthesis. The enzyme, RNA polymerase, utilizes nucleoside triphosphates (dNTPs) as raw material and polymerizes them to form mRNA according to the complementary bases present on the template DNA. This process of opening of helix and elongation of polynucleotide chain continues until the enzyme reaches the terminator region. As RNA polymerase reaches the terminator region, the newly synthesized mRNA transcripted along with enzyme is released. Another factor called terminator factor (ρ) is required for the termination of the transcription.

Amniocentesis is a foetal *** determination test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo. Amniocentesis is used for *** determination which most people get done to kill the female foetus. Therefore, it has been banned. 

The main bonding in DNA which renders the double helix structure so stable is that of hydrogen bonds. Between the complementary base pairs, hydrogen bonds connect the two strands of the helix. There are 3 H bonds between Guanine and Cytosine and 2 between Adenine and Thymine. Due to its deoxyribose sugar, which contains one less oxygen-containing hydroxyl group, DNA is a more stable molecule than RNA, which is useful for a molecule which has the task of keeping genetic information safe. RNA, containing a ribose sugar, is more reactive than DNA and is not stable in alkaline conditions.

Water hyacinth has single spike of 8-15 conspicuous attractive flowers which attract bees and other insects. These insects pollinate them. This plant is an aquatic weed. 

Water lily is also an aquatic plant with large conspicuous coloured flowers. Most of the species are bee pollinated except few species where wind pollination occurs. Insect pollinated flowers have coloured petals, big size and they offer fragrance and nectar to attract insects which bring about pollination in them.

Causes of Dengue fever

This Infectious Disease is mainly caused by the female Aedes mosquitoes. These mosquitoes carry the dengue virus and infect a healthy person with dengue fever.

Symptoms for dengue fever include:

• Fatigue.
• Vomiting.
• Tiredness.
• Headache.
• Skin Rash
• High Fever.
• Low blood pressure.
• Pain behind the eyes.

Sometimes, for certain ecological investigations, there is no need to the absolute population densities. Relative densities serve the  purpose equally well. In this case, population size is indirectly estimated without actually counting them. For example, the number of fishes caught per trap is good enough measure of its total population density in the lake. The tiger census in our National park and tiger reserves is often based on pug marks (animal's ft print ) and fecal pellets. 

Ans : Streptococcus pneumoniae bacteria.

Explanation:

Griffith experimented with Streptococcus pneumoniae bacteria. This bacteria causes Pneumonia.Two strains of this bacteria were used R-strain & S-strain.

• S strain
  • Smooth mucous polysaccharide coat
  • Resistant to immune system
  • Virulent
• R strain
  • Lacks the coat
  • Destroyed by immune system of the host
  • Non-virulent

i. Streptococcus pneumoniae (pneumococcus) bacteria were grown on a culture plate, some produces smooth shiny colonies (S) while others produces rough colonies (R). This was because the S strain bacteria has a mucous (polysaccharide) coat, while R strain does not.
Mice infected with the S strain (virulent) die from pneumonia infection but mice infected with the R strain do not develop pneumonia.
S strain ---> Inject into mice ----> Mice die
R strain ----> Inject into mice ----> Mice live

The virulet S strain bacteria were killed by heating them. It was observed that heat killed S strain bacteria injected into mice did not kill them.
S strain (heat-killed) ----> Inject into mice ----> Mice live

When a mixture of heat-killed S and live R bacteria was injected, the mice died.
S strain (heat-killed) + R strain (live) ----> Inject into mice ----> Mice died. Moreover, living S bacteria was recovered from the dead mice.

The experment concluded that the R strain bacteria had somehow been transformed by the heat-killed S strain bacteria and that some ‘transforming principle’, transferred from the heat-killed S strain, had enabled the R strain to become virulent. It was thought that this must be due to the transfer of the genetic material.
 

T.aquaticus or Thermus aquaticus is a bacterium that lives in hot springs and hydrothermal vents, and Taq polymerase was identified as an enzyme able to withstand the protein-denaturing conditions like high temperature required during PCR. Therefore is the source of the DNA polymerase used in PCR technique.

• Animals that have had their DNA manipulated to possess and express a foreign gene are known as transgenic animals. Example- Transgenic rats, rabbits, pigs, sheep etc.
• Transgenic animals are created-
• To study how genes are regulated, and how they affect the normal functions of the body and its development. Example- study of complex factors involved in growth such as insulin-like growth factor.
• to study how genes contribute to the development of disease.

The number of linkage group(s) present in Escherishia coli is 4.

The number of linkage groups equals the number of chromosomes in the basic set. The number of linkage groups in an organism is equal to the haploid number of its chromosomes. Example - In Drosophila, the haploid number is n = 4, so linkage group is 4. But the number of linkage group is prokaryotes (bacteria, like E. coli) is one. This is because bacteria being prokaryotes have only a single circular chromosome.

Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development. e.g., wheat, maize, barley, castor, sunflower. 

When remnants of nucellus are persistent it is said to have a perisperm. Example; biack pepper, beat.

Mendel's work remained unrecognized from 1865 to 1900 because of the following reasons:

1. He was a monk and not a scientist.
2. The people (scientists) in the rest of the world were engrossed in Darwin's work and his theory of evolution.
3. Mendel's theories of inheritance and heredity were in opposition to Darwin's theories.
4. His work and results on inheritance were mostly accidental.