Year 10 Biology Exam Revision Notes

Total Magnification Calculation: Determined by multiplying the power of the objective lens ( $4x$ , $10x$ , or $40x$ ) by the power of the eyepiece lens (usually $10x$ ).
Cell Components and Functions:
- Mitochondria: Generate energy for the cell in the form of ATP (adenosine triphosphate).
- Nucleus: Responsible for managing DNA and containing genetic material.
- Golgi apparatus: Processes, packages, and helps export proteins from the cell.
- Ribosome: Site of protein synthesis.
Scientific Drawing Standards: Must use a sharp pencil and plain A4 paper. Drawings require solid outlines without shading, horizontal or vertical label lines without arrowheads, and the inclusion of total magnification (e.g., $400x$ ). Cells are measured in micrometres ( $\mu m$ ).

Blood Components:
- Red blood cells: Carry oxygen using haemoglobin.
- White blood cells: Defend the body against infection.
- Platelets: Assist with blood clotting at wounds.
- Plasma: Transports nutrients, hormones, waste, and contains antibodies.
ABO Blood Types: Controlled by the ABO gene with three alleles ( $A$ , $B$ , and $O$ ).
- $A$ and $B$ are co-dominant and both are dominant over $O$ (recessive).
- Genotypes and Phenotypes:
  - Blood Type A: Genotypes $AA$ or $AO$ .
  - Blood Type B: Genotypes $BB$ or $BO$ .
  - Blood Type AB: Genotype $AB$ .
  - Blood Type O: Genotype $OO$ (Universal donor).
Kastle-Meyer Test: A presumptive test for blood using phenolphthalein and hydrogen peroxide. It turns pink in the presence of hemoglobin. False positives can be caused by bleach, tomato, meat, and red onion.

DNA (Deoxyribonucleic Acid): A double helix structure located in the nucleus. It is composed of a sugar-phosphate backbone and base pairs.
Base Pairing Rules: Adenine pairs with Thymine ( $A-T$ ) and Cytosine pairs with Guanine ( $C-G$ ).
Genetic Structures:
- Chromosomes: Structures made of DNA containing many genes. Humans have $46$ chromosomes in body cells and $23$ in sex cells (gametes).
- Genes: Sections of DNA that code for specific traits.
Cell Division:
- Mitosis: For growth and repair; produces identical daughter cells.
- Meiosis: For producing gametes; introduces genetic variation.
Inheritance Patterns:
- Co-dominance: Two alleles are equally dominant ( $AB$ blood type).
- Incomplete Dominance: Alleles blend to show a middle trait (e.g., red and white flowers creating pink).
- Autosomal Dominant/Recessive: Traits located on non-sex chromosomes.
- Sex-linked: Genes found on $X$ or $Y$ chromosomes.

Meaning: The study of ethical issues arising from biology and medicine.
Ethical Principles:
- Integrity: Honesty in reporting and action.
- Justice: Fair distribution of benefits and burdens.
- Beneficence: Acting in the best interest of others.
- Non-maleficence: Avoiding the causation of harm.
- Respect (Autonomy): Considering the welfare and liberty of individuals.
Moral Approaches:
- Consequence-based: Focuses on the outcome (the ends justify the means).
- Deontology: Focuses on the nature of the action itself, regardless of consequences.

Natural Selection: The process where individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation.
Mutation: Changes in DNA that introduce new variations or alleles into a population.
Genetic Drift: Random changes in allele frequencies, which have a more significant effect on small populations.
Gene Flow: The movement of genes between populations due to migration.

Question: What is the difference between genotype and phenotype?
Response: Genotype is the genetic makeup (e.g., $AO$ ), while phenotype is the physical expression (e.g., Blood Type A).
Question: Predict the genotype of offspring if Parent 1 is $AB$ and Parent 2 is $AO$ .
Punnett Square Calculation:
- $A \times A = AA$ ( $25\%$
- $A \times O = AO$ ( $25\%$
- $B \times A = AB$ ( $25\%$
- $B \times O = BO$ ( $25\%$
Question: What is a key ethical concern with DIY home genetic testing?
Response: Major concerns include privacy issues, emotional distress, and the potential for discrimination based on the results.