SAU Tandojam Entrance Test Preparation

• Organelle - A specialized structure inside a cell that performs a particular function. - Enzyme - A biological catalyst, usually a protein, that speeds up a chemical reaction. - Gene - A section of DNA that carries information for a specific trait or protein. - Allele - An alternative form of a gene. - Mitosis - Cell division producing two genetically identical cells. - Meiosis - Cell division producing four genetically different haploid cells. - Mutation - A change in the DNA base sequence.

Active Recall

• Organelle ________________________________________________ ________________________________________________

• Enzyme ________________________________________________ ________________________________________________

• Gene ________________________________________________ ________________________________________________

• Allele ________________________________________________ ________________________________________________

• Mitosis ________________________________________________ ________________________________________________

• Meiosis ________________________________________________ ________________________________________________

Worked Examples

1. Identifying an organelle

Question: A cell produces large amounts of ATP. Which organelle is especially active?

1. ATP is the main usable energy molecule in cells. 2. Mitochondria release energy during aerobic respiration. 3. Therefore, the mitochondria are especially active.

Answer: Mitochondria.

Now you try: Which organelle makes proteins?

________________________________________________ ______________________________________________ ________________________________________________

2. Genetic cross

Question: In a cross between Tt and Tt, where T is dominant, what percentage of offspring show the recessive trait?

1. Possible combinations are TT, Tt, Tt, and tt. 2. Only tt shows the recessive trait. 3. One out of four offspring is tt. 4. Percentage = 25%.

Answer: 25%.

Now you try: In a cross between Bb and bb, what percentage show the dominant trait?

________________________________________________ ______________________________________________ ________________________________________________

Practice Questions

1. (Easy) Which organelle controls most cell activities? ________________________________________________ ______________________________________________ ________________________________________________

2. (Easy) Name the sugar found in DNA. ________________________________________________ ______________________________________________ ________________________________________________

3. (Medium) State two differences between DNA and RNA. ________________________________________________ ______________________________________________ ________________________________________________

4. (Medium) Why does high temperature reduce enzyme activity? ________________________________________________ ______________________________________________ ________________________________________________

5. (Medium) What is the main result of mitosis? ________________________________________________ ______________________________________________ ________________________________________________

6. (Hard) Explain why meiosis increases genetic variation. ________________________________________________ ______________________________________________ ________________________________________________

Answer Key

1. Nucleus. 2. Deoxyribose. 3. DNA is usually double-stranded and contains thymine; RNA is usually single-stranded and contains uracil. 4. High temperature changes the enzyme’s shape, so the active site no longer fits the substrate. 5. Two genetically identical diploid daughter cells. 6. Crossing over and independent assortment create new combinations of alleles.

Exam Tips & Common Mistakes

• Do not confuse ribosomes with mitochondria: ribosomes make proteins, while mitochondria release energy. - Remember that dominant does not mean more common; it only means expressed when present. - Do not state that meiosis produces identical cells. It produces genetically different haploid cells. - In enzyme questions, mention both the active site and denaturation when temperature or pH is extreme. - Examiners reward comparisons using clear terms such as “double-stranded,” “haploid,” and “genetically identical.” - For genetic crosses, write all possible allele combinations before calculating percentages. - Use correct symbols and show working in inheritance questions.

Quick Reference

| Topic | Essential fact | |---|---| | Nucleus | Contains chromosomes and DNA | | Ribosome | Protein synthesis | | Mitochondrion | Aerobic respiration and ATP production | | Chloroplast | Photosynthesis | | DNA bases | A, T, C, G | | RNA bases | A, U, C, G | | Mitosis | 2 identical diploid cells | | Meiosis | 4 different haploid cells |

Enzyme rule: Extreme temperature or pH can denature an enzyme.

Mnemonic: “Mitosis Makes Matching; Meiosis Makes Many.”

• DNA stores hereditary information. - Genes are sections of DNA; alleles are alternative forms. - Proteins are made from amino acids. - Carbohydrates contain simple sugars joined together. - Complementary DNA bases pair as A-T

, C-G. - RNA uses uracil instead of thymine. - Mitosis supports growth, repair, and replacement of cells. - Meiosis forms gametes and reduces chromosome number by half. - A genotype is the allele combination; a phenotype is the observable characteristic.

Remember: Cell structure, biomolecules, enzymes, DNA base pairing, inheritance, and cell division are frequent entrance-test areas.

End of chapter one. 4 more chapters in the full book.