ACT SSC Biology · Unit 3
ACT SSC Biology Unit 3: Heredity and Continuity of Life — Flashcards & Quiz
ACT SSC Biology Unit 3 explores heredity and the continuity of life within the BSSS framework. This unit covers DNA structure and replication, gene expression, Mendelian genetics, pedigree analysis, mutations and biotechnology. These flashcards and quiz questions help you master the molecular and inheritance concepts tested in ACT assessments.
Key Terms
- Allele
- An alternative form of a gene that arises by mutation and occupies the same locus on a chromosome; understanding dominant and recessive alleles is essential for BSSS genetics problems involving Punnett squares.
- Meiosis
- A type of cell division that produces four genetically unique haploid gametes from one diploid cell, introducing genetic variation through crossing over and independent assortment as assessed in ACT SSC Biology.
- DNA Replication
- The semi-conservative process by which a cell copies its DNA before division, ensuring each daughter cell receives a complete set of genetic instructions; a core process in BSSS heredity assessments.
- Protein Synthesis
- The two-stage process of transcription (DNA to mRNA in the nucleus) and translation (mRNA to polypeptide at ribosomes) that converts genetic information into functional proteins.
- Mutation
- A permanent change in the nucleotide sequence of DNA that may alter gene function; BSSS unit score tasks often ask students to evaluate mutations as sources of genetic variation and potential disease.
- Genotype
- The genetic makeup of an organism for a particular trait, expressed as a combination of alleles; distinguished from phenotype in ACT Board of Senior Secondary Studies assessment criteria.
- Pedigree Analysis
- A method of tracing the inheritance pattern of a trait through generations using a standardised family tree diagram; a key skill assessed in BSSS Biology Unit 3 genetics tasks.
- Biotechnology
- The application of biological knowledge and techniques to develop products and processes, including genetic engineering and gene therapy; evaluated in BSSS assessments for both scientific merit and ethical implications.
Sample Flashcards
Q1: Outline Darwin's theory of natural selection.
Individuals in a population show variation. Those with traits better suited to the environment are more likely to survive and reproduce (survival of the fittest). These advantageous traits are passed to offspring, gradually changing the population over generations.
Q2: List four types of evidence for evolution.
1) Fossil record — transitional forms. 2) Comparative anatomy — homologous structures. 3) Molecular biology — DNA/protein sequence similarity. 4) Biogeography — species distribution patterns.
Q3: What are homologous and analogous structures?
Homologous structures have a common evolutionary origin but may serve different functions (e.g. bat wing, whale flipper). Analogous structures have similar functions but different origins (e.g. bird wing, insect wing).
Q4: What is speciation?
Speciation is the formation of new species. It occurs when populations become reproductively isolated and evolve independently through natural selection, genetic drift and mutation until they can no longer interbreed.
Q5: Distinguish allopatric from sympatric speciation.
Allopatric: a geographic barrier physically separates populations. Sympatric: new species arise within the same geographic area through polyploidy, habitat differentiation or behavioural isolation.
Q6: What is a phylogenetic tree (cladogram)?
A phylogenetic tree is a branching diagram showing evolutionary relationships among species based on shared derived characteristics or molecular data. Branch points (nodes) represent common ancestors.
Q7: What is genetic drift?
Genetic drift is random change in allele frequencies in a population due to chance events. It has a stronger effect in small populations and can lead to fixation or loss of alleles.
Q8: What is gene flow?
Gene flow is the transfer of alleles between populations through migration or dispersal. It increases genetic diversity within populations and reduces differences between populations.
Sample Quiz Questions
Q1: Natural selection acts on phenotypes, not directly on genotypes.
Answer: TRUE
Selection acts on observable traits (phenotype). Genotypes are inherited indirectly.
Q2: Natural selection always leads to the evolution of new species.
Answer: FALSE
Natural selection can maintain traits (stabilising) without creating new species.
Q3: Homologous structures indicate a common ancestor.
Answer: TRUE
Homologous structures share a common evolutionary origin, indicating descent from a common ancestor.
Q4: Analogous structures indicate close evolutionary relationship.
Answer: FALSE
Analogous structures result from convergent evolution in unrelated species, not close common ancestry.
Q5: Allopatric speciation requires a geographic barrier.
Answer: TRUE
A physical barrier separates populations, preventing gene flow and allowing independent evolution.
Why It Matters
Heredity and Continuity of Life in ACT SSC Biology Unit 3 explores how biological information is stored, copied and transmitted across generations. BSSS assessments test your ability to explain DNA structure and replication, trace gene expression from transcription to translation, and solve inheritance problems using Punnett squares and pedigrees. This unit connects molecular biology to observable traits, requiring you to move fluently between different scales of biological organisation. Strong performance in heredity concepts directly supports your understanding of evolution, biotechnology and the internal environment in Unit 4. Gene expression concepts feed into the internal environment unit, where hormones regulate gene activity to maintain homeostasis. BSSS exam questions on heredity frequently require you to trace a trait through three generations using a pedigree diagram, so practise identifying inheritance patterns and calculating genotype probabilities for autosomal and sex-linked traits.
Key Concepts
DNA Structure and Replication
The double helix structure of DNA enables accurate replication through complementary base pairing. Understanding the roles of key enzymes, the semiconservative nature of replication, and how errors can lead to mutations provides the molecular foundation for all heredity topics.
Gene Expression
Transcription converts DNA to mRNA, and translation converts mRNA to protein at ribosomes. Tracing this central dogma pathway and understanding how mutations at different stages affect protein function is a core BSSS assessment requirement.
Mendelian Inheritance
Mendel's laws of segregation and independent assortment explain predictable inheritance patterns. Solving problems involving dominance, codominance, sex linkage and multiple alleles through Punnett squares and pedigree analysis builds essential problem-solving skills.
Mutations and Biotechnology
Gene and chromosomal mutations alter DNA sequences with varying consequences for organisms. Modern biotechnology techniques including PCR, gel electrophoresis and genetic engineering build on heredity knowledge, and BSSS assessments increasingly ask you to evaluate their ethical and social implications.
Common Mistakes to Avoid
- Using genotype and phenotype interchangeably in BSSS responses — genotype refers to the allele combination while phenotype is the observable characteristic expressed; always define both clearly.
- Forgetting that meiosis produces four haploid cells while mitosis produces two diploid cells — ACT SSC examiners frequently test this distinction in comparison questions.
- Writing incomplete Punnett squares by not showing all possible gamete combinations — BSSS marking guides require the full cross with parental genotypes, gametes and offspring ratios clearly displayed.
- Neglecting to address ethical considerations when discussing biotechnology applications — ACT Senior Secondary Certificate evaluation criteria explicitly require balanced analysis of benefits and concerns.
Study Tips
- Practise Punnett square problems daily, starting with monohybrid crosses and progressing to dihybrid and sex-linked scenarios for exam readiness.
- Build a flashcard deck for genetics vocabulary, ensuring you can distinguish between easily confused terms like gene, allele and locus using spaced repetition.
- Draw the process of protein synthesis as a flowchart, including all key molecules and their roles at each stage of transcription and translation.
- Work through pedigree analysis problems by first identifying the inheritance pattern before attempting to assign genotypes.
- Summarise one biotechnology application per study session, noting both its benefits and ethical considerations for evaluation questions.
- Before your exam, work through the practice questions in this set at least twice using spaced repetition. Testing yourself repeatedly is the most effective revision strategy for long-term retention.
Related Topics
Frequently Asked Questions
What does ACT SSC Biology Unit 3 cover?
Unit 3 covers DNA structure and replication, transcription and translation, Mendelian genetics, pedigree analysis, mutations, meiosis and biotechnology applications.
How many flashcards are in this set?
This free set contains 20 flashcards and 20 true/false quiz questions covering heredity and continuity of life, aligned to the BSSS Biology framework.
Are these aligned to the ACT curriculum?
Yes — every flashcard and quiz question is mapped to the BSSS Science Framework for ACT SSC Biology Unit 3.
Last updated: March 2026 · 20 flashcards · 20 quiz questions · Content aligned to the BSSS Framework