§-Section

DNA, genetics and cell division (Modules 2 and 3)

8 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

How is DNA structured, and how is it copied accurately before a cell divides?

DNA structure and replication: DNA is a double-stranded molecule in the nucleus of eukaryotic cells; nucleotide composition and complementary base pairing (A-T, C-G); the process of DNA replication including the enzymes helicase, primase, DNA polymerase and ligase; the significance of semi-conservative replication; genome sequencing

TASC Biology Level 3 (BIO315124, criterion 5): nucleotide structure, the double helix and complementary base pairing, the roles of helicase, primase, DNA polymerase and ligase in replication, why replication is semi-conservative, and a general understanding of genome sequencing.

8 min read →

How does the sequence of DNA direct the synthesis of proteins?

Protein synthesis: proteins are a diverse group of molecules, including enzymes; genes include coding (exons) and non-coding (introns and regulatory) components of DNA; transcription of a gene into messenger RNA in the nucleus; translation of mRNA into an amino acid sequence at the ribosome, using transfer RNA, codons and anticodons

TASC Biology Level 3 (BIO315124, criterion 5): how the base sequence of a gene directs protein synthesis, exons and introns, transcription of a gene into mRNA in the nucleus, translation at the ribosome using codons, tRNA and anticodons, and differential gene expression.

8 min read →

How do bacteria switch genes on and off in response to their environment?

Gene expression and regulation: prokaryotic cells only, using the lac operon example; the phenotypic expression of genes depends on factors controlling transcription and translation, the products of other genes and the environment; differential gene expression controls cell differentiation

TASC Biology Level 3 (BIO315124, criterion 5): the structure of the lac operon in E. coli (regulator gene, promoter, operator, lacZ and lacY), how the repressor switches the operon off without lactose and on with lactose, what happens when glucose is available, and differential gene expression.

8 min read →

How do mutations arise, and how do they affect proteins?

Mutations: models of how mutations in genes and chromosomes result from errors in DNA (point and block mutations, including substitutions, deletions, additions and inversions), errors in cell division (types of chromosomal mutation) and damage by mutagens (physical, UV radiation, ionising radiation, heat and chemical); the impact of mutation on the final gene product, specifically protein

TASC Biology Level 3 (BIO315124, criterion 5): point mutations (substitution, deletion, addition, inversion), chromosomal mutations from errors in cell division, physical and chemical mutagens, and how each type of mutation can change, shorten or leave unchanged the protein a gene codes for.

8 min read →

How do cells divide and how does meiosis create genetic variation?

Reproduction and cell division: chromosomes package DNA; all eukaryotic cells come from pre-existing cells through the cell cycle (G1, S, G2, M and C phases); the sub-phases of mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis in animal cells; meiosis I and II, the role of homologous chromosomes in independent assortment and crossing over; random fertilisation and the significance of genetic variation

TASC Biology Level 3 (BIO315124, criterion 8): asexual and sexual reproduction, chromosomes, the cell cycle (G1, S, G2, M and C), mitosis and cytokinesis, meiosis I and II, and how crossing over, independent assortment and random fertilisation generate genetic variation.

7 min read →

How are characteristics passed from parents to offspring and why do offspring vary?

Genetics: monohybrid crosses; use models such as Punnett squares to predict frequencies of genotypes and phenotypes for autosomal dominant or recessive, sex-linked dominant or recessive, incomplete dominance, codominance and multiple alleles (ABO blood groups only, with alleles i, IA and IB); use pedigree charts to analyse inheritance

TASC Biology Level 3 (BIO315124, criterion 8): genetics vocabulary, monohybrid crosses and Punnett squares for autosomal and sex-linked dominant and recessive alleles, incomplete dominance, codominance and ABO multiple alleles, and the sources of variation between offspring.

8 min read →

How can a family pedigree be used to work out how a trait is inherited?

Use pedigree charts to describe and analyse the inheritance of genetic disorders and disease: identify and justify the likely mode of inheritance (dominant or recessive, autosomal or X-linked) and the likely genotypes of individuals

TASC Biology Level 3 (BIO315124, criterion 8): reading pedigree symbols, the key evidence that proves a trait is dominant or recessive and autosomal or X-linked, how to assign genotypes, and how to justify a mode of inheritance with named individuals as TASC markers expect.

8 min read →

How do we manipulate and analyse DNA, and what are the implications?

Demonstrate and apply the use of enzymes to manipulate DNA, including polymerase to synthesise DNA, ligase to join DNA and endonucleases to cut DNA; investigate genome sequencing

TASC Biology Level 3 (BIO315124): how polymerase, ligase and restriction endonucleases are used to synthesise, join and cut DNA, and genome sequencing, with background on PCR, gel electrophoresis, recombinant DNA and CRISPR and which parts are examined.

8 min read →