Biology module 5

Inquiry Question 1: How does reproduction ensure the continuity of a species?

How do cell division and reproduction ensure the continuity of genetic information between generations?

Heredity

The transmission of genetic information from parents to offspring.

Genetics

The study of genes, inheritance and genetic variation.

DNA (Deoxyribonucleic acid)

The hereditary molecule that stores the genetic information of an organism.

Gene

A section of DNA that codes for a functional protein or RNA molecule.

Genome

The complete set of genetic material in an organism.

Chromosome

A thread-like structure composed of DNA and proteins that carries genetic information.

Chromatin

The uncoiled form of DNA and associated proteins found within the nucleus.

Histone

A protein around which DNA is wound to form chromatin.

Nucleotide

The basic building block of nucleic acids consisting of a phosphate group, a pentose sugar and a nitrogenous base.

Deoxyribose

A five-carbon sugar found in DNA.

Phosphate group

A component of nucleotides that forms part of the sugar-phosphate backbone of DNA.

Nitrogenous base

A nitrogen-containing molecule that forms part of a nucleotide.

Purine

A nitrogenous base with a double-ring structure, including adenine and guanine.

Pyrimidine

A nitrogenous base with a single-ring structure, including cytosine and thymine.

Adenine (A)

A purine base that pairs with thymine in DNA.

Thymine (T)

A pyrimidine base that pairs with adenine in DNA.

Cytosine (C)

A pyrimidine base that pairs with guanine in DNA.

Guanine (G)

A purine base that pairs with cytosine in DNA.

Complementary base pairing

The specific pairing of nitrogenous bases where adenine pairs with thymine and cytosine pairs with guanine.

Hydrogen bond

A weak chemical bond that holds complementary nitrogenous bases together.

Sugar-phosphate backbone

The alternating chain of sugars and phosphate groups forming the sides of the DNA molecule.

Double helix

The twisted ladder-shaped structure of DNA consisting of two complementary strands.

Semi-conservative replication

The process in which each new DNA molecule contains one original strand and one newly synthesised strand.

DNA replication

The process of producing two identical DNA molecules before cell division.

Helicase

An enzyme that unwinds and separates the two strands of DNA during replication.

DNA polymerase

An enzyme that synthesises a new DNA strand by adding complementary nucleotides.

Ligase

An enzyme that joins Okazaki fragments on the lagging strand during DNA replication.

Replication fork

The Y-shaped region where DNA strands separate during replication.

Leading strand

The DNA strand synthesised continuously towards the replication fork.

Lagging strand

The DNA strand synthesised discontinuously away from the replication fork.

Okazaki fragments

Short DNA fragments synthesised on the lagging strand that are joined by DNA ligase.

Cell cycle

The sequence of events involving cell growth, DNA replication and cell division.

Interphase

The stage of the cell cycle during which the cell grows, carries out normal functions and replicates its DNA.

Mitosis

The process of nuclear division producing two genetically identical daughter cells.

Cytokinesis

The division of the cytoplasm following nuclear division.

Daughter cell

A cell produced by the division of a parent cell.

Somatic cell

Any body cell that is not involved in reproduction.

Gamete

A specialised haploid reproductive cell such as a sperm or egg.

Diploid (2n)

A cell containing two complete sets of chromosomes.

Haploid (n)

A cell containing one complete set of chromosomes.

Homologous chromosomes

A pair of chromosomes with the same genes at the same loci, one inherited from each parent.

Sister chromatids

Identical copies of a chromosome joined at the centromere.

Centromere

The region of a chromosome where sister chromatids are joined.

Spindle fibres

Microtubules that separate chromosomes during cell division.

Prophase

The first stage of mitosis during which chromosomes condense and the nuclear membrane breaks down.

Metaphase

The stage of mitosis where chromosomes align at the cell equator.

Anaphase

The stage of mitosis during which sister chromatids separate and move to opposite poles.

Telophase

The final stage of mitosis where nuclear membranes reform around each set of chromosomes.

Meiosis

A specialised type of cell division producing four genetically different haploid cells.

Crossing over

The exchange of DNA between homologous chromosomes during prophase I of meiosis.

Independent assortment

The random orientation of homologous chromosome pairs during metaphase I, producing genetic variation.

Genetic variation

Differences in DNA sequences between individuals within a population.

Sexual reproduction

The production of offspring through the fusion of two genetically different gametes.

Asexual reproduction

The production of genetically identical offspring from a single parent without gamete fusion.

Fertilisation

The fusion of male and female gametes to form a diploid zygote.

Zygote

The diploid cell formed following fertilisation.

Continuity of species

The maintenance of a species through successful reproduction and inheritance of genetic information.

Inquiry Question 2: How does the environment affect the expression of genes?

How do genes direct the production of proteins, and how can environmental factors influence gene expression?

Gene expression

The process by which the information in a gene is used to produce a functional protein or RNA molecule.

Protein synthesis

The process by which proteins are produced through transcription and translation.

RNA (Ribonucleic acid)

A single-stranded nucleic acid involved in protein synthesis.

Messenger RNA (mRNA)

RNA that carries genetic information from DNA to the ribosome.

Transfer RNA (tRNA)

RNA that carries specific amino acids to the ribosome during translation.

Ribosomal RNA (rRNA)

RNA that forms part of the structure of ribosomes and catalyses protein synthesis.

Transcription

The process by which a complementary mRNA strand is synthesised from a DNA template.

Translation

The process in which ribosomes read mRNA codons to assemble amino acids into a polypeptide.

Codon

A sequence of three nucleotides on mRNA that codes for a specific amino acid or stop signal.

Anticodon

A sequence of three complementary nucleotides on tRNA that pairs with an mRNA codon.

Genetic code

The set of rules by which codons specify particular amino acids.

Start codon

The codon AUG that signals the beginning of translation and codes for methionine.

Stop codon

A codon that signals the end of protein synthesis and does not code for an amino acid.

Ribosome

The organelle where translation and protein synthesis occur.

Amino acid

The basic building block of proteins.

Polypeptide

A chain of amino acids joined by peptide bonds.

Protein

A biological macromolecule composed of one or more polypeptide chains that performs specific cellular functions.

Peptide bond

A covalent bond joining adjacent amino acids in a polypeptide.

Template strand

The DNA strand used during transcription to synthesise complementary mRNA.

Coding strand

The DNA strand with the same base sequence as mRNA except thymine is replaced by uracil.

Uracil (U)

A pyrimidine base found in RNA that pairs with adenine.

RNA polymerase

The enzyme that synthesises mRNA during transcription.

Exon

A coding region of a gene that remains in mature mRNA after processing.

Intron

A non-coding region of a gene removed from pre-mRNA before translation.

Splicing

The removal of introns and joining of exons to produce mature mRNA.

Mutation

A permanent change in the nucleotide sequence of DNA.

Point mutation

A mutation affecting a single nucleotide.

Substitution mutation

A mutation in which one nucleotide is replaced by another.

Insertion mutation

A mutation in which one or more nucleotides are added to a DNA sequence.

Deletion mutation

A mutation in which one or more nucleotides are removed from a DNA sequence.

Frameshift mutation

A mutation caused by insertion or deletion that alters the reading frame of codons.

Silent mutation

A mutation that does not alter the amino acid sequence of a protein.

Missense mutation

A mutation that changes one amino acid in a protein.

Nonsense mutation

A mutation that introduces a premature stop codon.

Mutagen

An agent that increases the likelihood of mutations occurring.

Physical mutagen

A mutagen such as ultraviolet radiation or X-rays that damages DNA.

Chemical mutagen

A substance that causes changes to DNA through chemical interactions.

Beneficial mutation

A mutation that increases an organism's survival or reproductive success.

Neutral mutation

A mutation with no significant effect on phenotype or fitness.

Harmful mutation

A mutation that reduces survival, reproduction or normal function.

Gene regulation

The control of when, where and how much a gene is expressed.