In a polynucleotide chain, the dotted line (‘-----’) indicates the bond between the nitrogenous base (B) and the sugar (S). This bond is referred to as an N-glycosidic linkage. It connects the nitrogen atom of the nitrogenous base to the 1' carbon of the pentose sugar, linking the two components.

Other bonds present in the structure of a polynucleotide include:

Phosphodiester bond: This bond links the sugar molecules of adjacent nucleotides, forming the backbone of the polynucleotide chain.

Hydrogen bond: This bond forms between complementary nitrogenous bases in double-stranded DNA, holding the two strands together.

Peptide bond: Found in proteins, not in polynucleotides, peptide bonds join amino acids to form polypeptides. Quick Tip: Identify bonds in biomolecules:
N-glycosidic linkage: Connects sugar and base in nucleotides.
Phosphodiester bond: Forms the backbone of DNA/RNA.
Hydrogen bond: Holds the strands of DNA together.
Peptide bond: Found in proteins.

The human female reproductive cycle is regulated by a series of hormonal events. The correct sequence of events is as follows:

1. Secretion of FSH (Follicle-Stimulating Hormone):
- The cycle begins with the secretion of FSH by the anterior pituitary gland. FSH promotes the growth and maturation of ovarian follicles, marking the first step of the cycle.

2. Follicular growth and oogenesis:
- As FSH is released, the ovarian follicles begin to grow, and oogenesis occurs. During this process, the primary oocyte undergoes maturation, transforming into a secondary oocyte within the developing follicle.

3. Surge in LH (Luteinizing Hormone):
- Just before ovulation, a surge in LH occurs, triggered by elevated estrogen levels from the growing follicles. This LH surge is the critical signal for ovulation.

4. Ovulation:
- The sharp increase in LH causes the mature follicle to rupture, releasing the secondary oocyte. This event, known as ovulation, typically occurs in the middle of the menstrual cycle.

5. Formation of corpus luteum:
- After ovulation, the ruptured follicle changes into the corpus luteum, which secretes progesterone. This hormone prepares the uterine lining for the possibility of pregnancy.

The correct order of events is:
Secretion of FSH (i)

Follicular growth and oogenesis (iv)

Surge in LH (v)

Ovulation (ii)

Formation of corpus luteum (iii)


Therefore, the correct sequence is \( i \to iv \to v \to ii \to iii \), corresponding to option (B). Quick Tip: The cycle begins with FSH secretion, which stimulates follicular growth and oogenesis. The LH surge triggers ovulation, followed by the formation of the corpus luteum.

Lactobacillus is a type of heterotrophic bacterium that ferments lactose present in milk to produce lactic acid.
This fermentation process causes the milk to coagulate, transforming it into curd.
Heterotrophic bacteria obtain their energy by consuming organic substances. Quick Tip: Recall the classification of bacteria:
Cyanobacteria: Capable of photosynthesis.
Chemosynthetic bacteria: Use inorganic substances for energy.
Heterotrophic bacteria: Rely on organic matter for energy.

Bt toxin genes (Cry-I Ac and Cry-II Ab) are sourced from the bacterium \textit{Bacillus thuringiensis.
These genes are incorporated into cotton plants, enabling them to produce insecticidal proteins that defend against bollworm infestations. Quick Tip: Learn key Bt genes:
Cry-I Ac: Specifically targets bollworms.
Cry-II Ab: Effective against cotton pests.

To determine the DNA sequence that encodes the specified polypeptide, follow these steps:


The mRNA codon for Alanine is \( GCA \), so the corresponding DNA coding strand will have \( CGT \).
The mRNA codon for Arginine is \( CGA \), which corresponds to the DNA codon \( GCT \).
The mRNA codon for Lysine is \( AAG \), and its matching DNA codon is \( TTC \).
The mRNA codon for Phenylalanine is \( UUU \), which corresponds to the DNA codon \( AAA \).

Therefore, the correct DNA sequence is \( CGT GCT TTC AAA \). Quick Tip: To solve DNA coding problems, follow these simple guidelines: DNA coding strand sequences mirror mRNA sequences, with T replacing U. The complementary DNA strand follows the base-pairing rules (A-T, G-C). Carefully check each codon to ensure correct pairing with the amino acids.

Maize is a monoecious plant, meaning it has both male and female flowers on the same plant.
Geitonogamy occurs when pollination takes place between flowers on the same plant, while xenogamy happens between flowers from different plants.
Papaya and Date Palm are dioecious plants, meaning their male and female flowers are on separate plants. Spinach does not fit into this context. Quick Tip: Remember:
Monoecious plants have male and female flowers on the same plant.
Dioecious plants have male and female flowers on different plants.

Transgenic mice are genetically modified to carry human genes that make them vulnerable to polio infection.
These mice are utilized to evaluate the safety and efficacy of the polio vaccine prior to human clinical trials. Quick Tip: Transgenic animals play a crucial role in research:
Mice: Used for vaccine testing and genetic studies.
Sheep and Goats: Engineered to produce therapeutic proteins.

Mast cells play a crucial role in allergic reactions by releasing histamines when exposed to allergens.
Histamines cause symptoms like inflammation, itching, and increased vascular permeability. Quick Tip: Key points:
Mast cells release histamine in allergic reactions.
Allergy: Caused by hypersensitivity to specific antigens.

Periodic abstinence involves avoiding intercourse during the fertile window.
In a 28-day cycle, ovulation usually occurs around day 14. The fertile window is days 10 to 17 when conception chances are high. Quick Tip: Remember:
Fertile window: Days 10–17 in a 28-day cycle.
Ovulation occurs around day 14.

The karyotype 45 + XX does not exist. The correct condition for a broad palm with characteristic palm crease is 47 + XXY (Klinefelter syndrome) or other related conditions. Quick Tip: Focus on karyotypes:
Turner Syndrome: 45 + XO.
Klinefelter Syndrome: 47 + XXY.

In Polymerase Chain Reaction (PCR), the DNA amplification follows a process of exponential growth. In each cycle, the amount of DNA doubles. Therefore, after each cycle, the number of DNA molecules increases by a factor of 2.

If we start with one DNA molecule, the number of DNA molecules after \( n \) cycles of amplification can be calculated using the formula:
\[ Number of DNA molecules = 2^n \]

where \( n \) is the number of cycles.

Given that the question asks about 10 cycles:
\[ Number of DNA molecules after 10 cycles = 2^{10} = 1024 \]

Therefore, after 10 cycles of PCR amplification, the number of DNA molecules generated will be 1024.

Option (A): 512 is incorrect. It represents the number of DNA molecules after 9 cycles (\(2^9 = 512\)).
Option (B): 1024 is the correct answer. After 10 cycles, \( 2^{10} = 1024 \) DNA molecules are generated.
Option (C): 2048 is incorrect. It represents the number of DNA molecules after 11 cycles (\(2^{11} = 2048\)).
Option (D): 256 is incorrect. It represents the number of DNA molecules after 8 cycles (\(2^8 = 256\)). Quick Tip: In PCR, the number of DNA molecules increases exponentially, and after each cycle, the DNA count doubles. The formula \( 2^n \) gives the total number of DNA molecules after \( n \) cycles.

Statement (i) is correct because both the lion (a carnivore) and the sparrow (a herbivore) are consumers in the ecological food chain.
Statement (ii) is correct as the starfish \textit{Pisaster acts as a keystone predator, preventing the dominance of certain species and thus maintaining species diversity.
Statement (iii) is incorrect because predators usually regulate prey populations rather than leading to their extinction.
Statement (iv) is incorrect as the production of secondary metabolites like nicotine and strychnine in plants are defensive mechanisms, not metabolic disorders. Quick Tip: When answering ecological questions, consider: Consumers can include both herbivores and carnivores. Keystone species play a critical role in maintaining ecosystem balance. Predators regulate rather than eliminate prey populations. Secondary metabolites in plants serve protective functions.

Agrobacterium tumefaciens is primarily a pathogen of dicot plants, not monocots. However, the statement about T-DNA is correct, as this bacterium transfers T-DNA into plant cells, causing crown gall disease. Quick Tip: \textit{Agrobacterium tumefaciens is widely used in genetic engineering for dicot plants due to its natural ability to transfer genes.

Legal adoption is indeed permitted by Indian law and encouraged for childless couples. However, emotional and social factors are not absolute deterrents to adoption, as awareness and government initiatives have addressed these concerns. Quick Tip: Understanding the legal framework of adoption can help eliminate misconceptions regarding social and emotional barriers.

Linked genes are present on the same chromosome and tend to be inherited together. As a result, they do not assort independently according to Mendel’s law of independent assortment, and thus, the expected dihybrid ratio of 9:3:3:1 is not observed. Quick Tip: Remember, genes located close to each other on the same chromosome tend to be inherited together, leading to deviations from expected Mendelian ratios.

Adenosine deaminase (ADA) deficiency is treated by introducing functional ADA genes into the lymphocytes of the patient. However, this does not necessarily have to be done at the early embryonic stage; it can also be done later.

The statement that embryonic cells are immortal, differentiated, and easy to manipulate is incorrect. Embryonic cells are actually undifferentiated and have the potential to develop into various cell types, but they are not necessarily easy to manipulate. Quick Tip: Gene therapy for ADA deficiency typically involves introducing the gene into lymphocytes or bone marrow cells, not necessarily at the embryonic stage.

Apomixis can be compared to asexual reproduction because it leads to the formation of offspring without fertilization. In apomixis, seeds are produced without the fusion of gametes, resulting in progeny that are genetically identical to the parent plant.

Benefits of apomixis to farmers:

Ensures the production of hybrid seeds without segregation of traits.
Reduces the cost of hybrid seed production.
Provides disease-resistant and high-yielding crops. Quick Tip: Apomixis helps in maintaining hybrid vigor for successive generations, benefiting farmers economically and ensuring uniform crop traits.

The naturalist who provided the explanation for this example is Jean-Baptiste Lamarck.

According to Lamarck's theory of evolution, the long necks of giraffes evolved over generations due to the following explanation:


Giraffes originally had shorter necks and fed on lower vegetation.
Due to competition and environmental changes, they stretched their necks to reach higher leaves.
This continuous use of neck muscles led to gradual elongation over generations.
The acquired trait of a longer neck was passed on to the offspring.


This idea is known as the Theory of Inheritance of Acquired Characteristics. Quick Tip: Lamarck's theory suggested that characteristics acquired during an organism's lifetime could be inherited, but modern genetics has shown that traits are passed through genes, not by use or disuse.

The basic steps followed in the Assisted Reproductive Technologies (ART) programme are:


Step 1: Hormonal stimulation is provided to the female to induce the production of multiple ova.
Step 2: The eggs (ova) are retrieved from the ovaries and fertilized with sperm in a laboratory setting.
Step 3: The fertilized egg (zygote) undergoes early embryonic development in vitro (outside the body).
Step 4: The resulting embryo is then implanted into the uterus for further development.


It is known as the test tube baby programme because fertilization and early embryonic development occur outside the female body in a laboratory setting, commonly in a petri dish or test tube. Quick Tip: Assisted Reproductive Technology (ART) techniques like IVF help couples conceive by fertilizing the egg outside the body, and successful embryos are transferred back into the uterus.

Transgenic animals are those that have had foreign genes deliberately inserted
into their genome. These genes are introduced to study gene functions, improve livestock
traits, or produce biologically important substances.

The first transgenic cow is Rosie.
 Importance: Rosie produced milk enriched with the human protein alpha-lactalbumin, making it nutritionally more balanced for infants. Quick Tip: Remember: - Transgenic animals = Genetic modification for improved traits or study. - Rosie = First transgenic cow producing enriched milk.

 EcoRI: 1. ”E” = Genus (Escherichia).
2. ”co” = Species (coli).
3. ”R” = Strain (RY13).
4. ”I” = First identified enzyme from this strain.

\[ 5'-GAATTC-3' \quad (Cleavage Site) \]
EcoRI cuts between G/AATTC, resulting in sticky ends. Quick Tip: Learn enzyme conventions: - Genus + Species + Strain + Number (e.g., EcoRI = Escherichia coli RY13, 1st enzyme). - Remember: EcoRI creates sticky ends.

 Pneumonia symptoms: \( A \) include breathing difficulty, cough, and chest pain.

 Typhoid causative organism: \( B \) is \textit{Salmonella typhi.

 Common cold symptoms: \( C \) include nasal congestion, sore throat, and cough.
 Ringworm causative organism: \( D \) is \textit{Trichophyton.

 Ascariasis symptoms: \( E \) include internal bleeding, muscular pain, and anemia.

 \( F \): Disease caused by \textit{Entamoeba histolytica is Amoebiasis.
Quick Tip: For disease tables:
 Learn causative agents and symptoms.
 Focus on common examples like typhoid, pneumonia, and ringworm.

 Mode of Action
1. Contraceptive pills contain synthetic hormones (estrogen and progesterone) that prevent ovulation by inhibiting the secretion of FSH and LH from the pituitary gland.

2. They thicken cervical mucus, making it difficult for sperm to enter the uterus.

3. They alter the endometrial lining, preventing implantation of a fertilized egg.

 Schedule for Effective Outcome:
 Pills should be taken daily for 21 days starting from the 5th day of the menstrual cycle, followed by a 7-day gap during which withdrawal bleeding occurs.
Quick Tip: Key to effectiveness: - Start pills on the 5th day of the cycle. - Maintain daily intake for 21 days without missing a dose.

 Type of DNA: Short Tandem Repeats (STRs) or Variable Number Tandem Repeats (VNTRs).

 Characteristics:

1. They are non-coding, repetitive sequences of DNA.

2. They show high polymorphism, making them unique to each individual (except identical twins).
Quick Tip: Focus on VNTRs:
 Found in non-coding regions.
 Highly variable among individuals, forming the basis for unique identification.

1. Forensic Science: Used for identification in criminal investigations.

2. Paternity Testing: Determines biological relationships.
Quick Tip: DNA fingerprinting:
 Solve crimes (forensics).
 Establish paternity or ancestry.

 Significance of Miller’s Experiment:
 Demonstrated that organic molecules like amino acids could be synthesized abiotically under conditions resembling early Earth's atmosphere.
 Supported the theory that life originated from simple organic compounds.
 Scientists: The experiment was based on the hypothesis of Alexander Oparin and J.B.S. Haldane. Quick Tip: Remember: - Miller simulated early Earth conditions. - Key outcome: Abiotic synthesis of amino acids.

 Meteorite analysis revealed the presence of simple organic compounds, such as amino acids, on extraterrestrial objects. This suggests that organic molecules can form naturally, supporting the idea of abiotic synthesis. Quick Tip: Meteorite evidence:
 Presence of amino acids supports the theory of abiotic synthesis and the origin of life from organic molecules.

Four patterns of inheritance that deviate from Mendelian genetics are:

Incomplete dominance: Neither allele is completely dominant, resulting in an intermediate phenotype. Example: In snapdragons, red (\(RR\)) and white (\(rr\)) flowers produce pink (\(Rr\)) flowers in the heterozygous condition.
Codominance: Both alleles are equally expressed in the heterozygous condition. Example: Blood group AB in humans, where both \(IA\) and \(IB\) alleles are expressed.
Multiple alleles: A gene has more than two alleles. Example: ABO blood group in humans, controlled by three alleles (\(IA, IB, i\)).
Polygenic inheritance: Traits are controlled by multiple genes. Example: Human skin color, which is determined by several gene pairs.


Explanation:

Incomplete dominance: The pink color in snapdragons arises as the red allele cannot completely mask the effect of the white allele.
Codominance: In blood group AB, both \(IA\) and \(IB\) alleles are expressed, showing traits of both A and B blood groups.
Multiple alleles: The ABO blood group system shows that more than two alleles can govern a trait, where \(IA\) and \(IB\) are codominant, and \(i\) is recessive. Quick Tip: Mendelian inheritance explains basic patterns, but deviations like incomplete dominance and codominance occur due to variations in allele interactions.

The transcription unit includes:
• Promoter: Located upstream of the transcription start site.
• Coding region: Contains the sequence to be transcribed.
• Terminator: Signals the end of transcription.

The coding strand does not become the template strand. Instead, the
complementary strand (non-coding strand) acts as the template strand during transcription.

Transcription produces a single-stranded RNA because:

RNA polymerase synthesizes RNA complementary to only one strand (the template strand).
The resulting RNA strand does not pair with the DNA template, ensuring a single-stranded molecule for translation. Quick Tip: Transcription involves RNA polymerase reading only the template strand, leading to the formation of single-stranded RNA.

The formation of the male gametophyte in an angiosperm occurs through the following steps:


The male gametophyte is represented by the pollen grain, also known as the microspore.
Inside the pollen grain, the nucleus undergoes mitotic division to form two distinct cells:

A larger vegetative cell (also called the tube cell) that is responsible for guiding the growth of the pollen tube.
A smaller generative cell that divides mitotically to produce two male gametes.

Once the pollen grain reaches the three-celled stage, it is fully prepared for fertilization. Quick Tip: Key points in male gametophyte development:
Pollen grain = Male gametophyte.
Vegetative cell: Controls pollen tube growth.
Generative cell: Forms two male gametes.

The diagram should include the following components:


The vegetative cell (tube cell) along with its nucleus.
Two male gametes produced by the generative cell.
The outer structure of the pollen grain.


Quick Tip: The male gametophyte develops inside the pollen grain and matures into a three-celled structure consisting of one vegetative cell and two male gametes.

The diagram should depict the following elements:


The outer ovarian wall.
Several follicles in various stages of development, such as primary and tertiary follicles.
The ovum located within the mature Graafian follicle.
Blood vessels that supply the ovary.



Quick Tip: When illustrating the ovary, remember to include follicles at different stages and show the mature Graafian follicle containing the ovum.

Primary follicles are formed during the fetal stage in the ovary of a developing female fetus. Quick Tip: Primary follicles are the earliest stage of follicular development and are formed during fetal development. After birth, they remain dormant until puberty.

The events include:

Ovulation:

Triggered by a surge in luteinizing hormone (LH) around the 14th day of the menstrual cycle.
The mature Graafian follicle ruptures, releasing the ovum.

Post-ovulation:

The ruptured follicle transforms into the corpus luteum, secreting progesterone.
Progesterone maintains the uterine lining for potential implantation.

If fertilization does not occur:

The corpus luteum degenerates, leading to a drop in progesterone levels.
The uterine lining is shed, resulting in menstruation. Quick Tip: The menstrual cycle is regulated by hormonal interplay (FSH, LH, estrogen, and progesterone). Ovulation marks the midpoint of the cycle, driven by an LH surge.