GRADE 12 IEB LIFE SCIENCES
DEFINITIONS HANDBOOK
Table of Contents
Strand 1 – Life at the Molecular, Cellular and Tissue Level ....................................................................1
Strand 2 – Life Processes in Plants and Animals ...................................................................................... 13
Strand 3 – Environmental Studies .................................................................................................................. 23
Strand 4 – Diversity, Change and Continuity ............................................................................................. 28
Paper 3 – Investigations and Applications .................................................................................................. 38
Strand 1 – Life at the Molecular, Cellular and Tissue Level
Topic 1: Genes
DNA, RNA and Genetic Material
Term Definition
The branch of biology that studies inheritance and variation in
Genetics
organisms.
The hereditary information contained in DNA that is passed from
Genetic Material
one generation to the next.
Large biological molecules consisting of nucleotides; includes
Nucleic Acids
DNA and RNA.
A large molecule made up of repeating subunits called
Polymer
monomers.
The basic unit of DNA and RNA consisting of a phosphate group,
Nucleotide
sugar and nitrogenous base.
DNA (Deoxyribonucleic A double-stranded nucleic acid that carries hereditary
Acid) information and controls cell activities.
1
, Term Definition
RNA (Ribonucleic Acid) A single-stranded nucleic acid involved in protein synthesis.
Genome The complete genetic material of an organism.
Human Genome The complete mapping of all genes on all human chromosomes.
Gene A section of DNA that codes for a specific characteristic.
An alternative form of a gene found at the same locus on
Allele
homologous chromosomes.
Locus The specific position occupied by a gene on a chromosome.
A thread-like structure made of DNA that carries genetic
Chromosome
information.
Homologous A pair of chromosomes carrying the same genes at the same loci,
Chromosomes one inherited from each parent.
Chromatid One half of a duplicated chromosome.
Sister Chromatids Two identical chromatids joined by a centromere.
Centromere The region joining two chromatids together.
Diploid Cell (2n) A cell containing two sets of chromosomes.
Haploid Cell (n) A cell containing one set of chromosomes.
Somatic Cell A body cell containing the diploid number of chromosomes.
DNA Replication
Term Definition
The process by which DNA makes an exact copy of itself before
DNA Replication
cell division.
Template Strand The original DNA strand used to build a complementary strand.
Complementary Base
The pairing of specific nitrogenous bases (A-T and C-G in DNA).
Pairing
2
, Term Definition
Double Helix The twisted ladder shape of a DNA molecule.
Protein Synthesis
Term Definition
The process by which proteins are manufactured using genetic
Protein Synthesis
information.
A biological molecule composed of amino acids that performs
Protein
structural and functional roles.
Enzyme A protein that speeds up chemical reactions in living organisms.
A chemical messenger produced by cells and transported to target
Hormone
organs.
The process during protein synthesis in which mRNA is formed using
Transcription
a DNA template.
The process in which amino acids are assembled into proteins
Translation
according to the codon sequence on mRNA.
mRNA (Messenger
RNA that carries the genetic message from DNA to the ribosome.
RNA)
tRNA (Transfer RNA that transports amino acids to the ribosome during protein
RNA) synthesis.
rRNA (Ribosomal
RNA that forms part of the ribosome.
RNA)
Ribosome The organelle where proteins are assembled.
Codon A triplet of bases on mRNA coding for a specific amino acid.
Anticodon A triplet of bases on tRNA complementary to an mRNA codon.
Amino Acid The basic building block of proteins.
Peptide Bond The bond linking amino acids together.
3
, Term Definition
The sequence of bases that determines the amino acid sequence of a
Genetic Code
protein.
Mendel's Laws of Inheritance
Term Definition
During gamete formation, allele pairs separate so that each
Law of Segregation
gamete receives only one allele.
Law of Independent Alleles of different genes segregate independently during
Assortment gamete formation.
The passing of characteristics from parents to offspring through
Inheritance
genes.
Differences in characteristics among individuals of the same
Variation
species.
Topic 2: Inheritance and Variation
Genetic Terminology
Term Definition
Genotype The genetic make-up of an organism.
Phenotype The observable characteristics of an organism.
An allele expressed in both homozygous and heterozygous
Dominant Allele
conditions.
Recessive Allele An allele expressed only in the homozygous condition.
Homozygous Having two identical alleles for a characteristic.
Heterozygous Having two different alleles for a characteristic.
Homozygous
Having two dominant alleles for a characteristic.
Dominant
4
DEFINITIONS HANDBOOK
Table of Contents
Strand 1 – Life at the Molecular, Cellular and Tissue Level ....................................................................1
Strand 2 – Life Processes in Plants and Animals ...................................................................................... 13
Strand 3 – Environmental Studies .................................................................................................................. 23
Strand 4 – Diversity, Change and Continuity ............................................................................................. 28
Paper 3 – Investigations and Applications .................................................................................................. 38
Strand 1 – Life at the Molecular, Cellular and Tissue Level
Topic 1: Genes
DNA, RNA and Genetic Material
Term Definition
The branch of biology that studies inheritance and variation in
Genetics
organisms.
The hereditary information contained in DNA that is passed from
Genetic Material
one generation to the next.
Large biological molecules consisting of nucleotides; includes
Nucleic Acids
DNA and RNA.
A large molecule made up of repeating subunits called
Polymer
monomers.
The basic unit of DNA and RNA consisting of a phosphate group,
Nucleotide
sugar and nitrogenous base.
DNA (Deoxyribonucleic A double-stranded nucleic acid that carries hereditary
Acid) information and controls cell activities.
1
, Term Definition
RNA (Ribonucleic Acid) A single-stranded nucleic acid involved in protein synthesis.
Genome The complete genetic material of an organism.
Human Genome The complete mapping of all genes on all human chromosomes.
Gene A section of DNA that codes for a specific characteristic.
An alternative form of a gene found at the same locus on
Allele
homologous chromosomes.
Locus The specific position occupied by a gene on a chromosome.
A thread-like structure made of DNA that carries genetic
Chromosome
information.
Homologous A pair of chromosomes carrying the same genes at the same loci,
Chromosomes one inherited from each parent.
Chromatid One half of a duplicated chromosome.
Sister Chromatids Two identical chromatids joined by a centromere.
Centromere The region joining two chromatids together.
Diploid Cell (2n) A cell containing two sets of chromosomes.
Haploid Cell (n) A cell containing one set of chromosomes.
Somatic Cell A body cell containing the diploid number of chromosomes.
DNA Replication
Term Definition
The process by which DNA makes an exact copy of itself before
DNA Replication
cell division.
Template Strand The original DNA strand used to build a complementary strand.
Complementary Base
The pairing of specific nitrogenous bases (A-T and C-G in DNA).
Pairing
2
, Term Definition
Double Helix The twisted ladder shape of a DNA molecule.
Protein Synthesis
Term Definition
The process by which proteins are manufactured using genetic
Protein Synthesis
information.
A biological molecule composed of amino acids that performs
Protein
structural and functional roles.
Enzyme A protein that speeds up chemical reactions in living organisms.
A chemical messenger produced by cells and transported to target
Hormone
organs.
The process during protein synthesis in which mRNA is formed using
Transcription
a DNA template.
The process in which amino acids are assembled into proteins
Translation
according to the codon sequence on mRNA.
mRNA (Messenger
RNA that carries the genetic message from DNA to the ribosome.
RNA)
tRNA (Transfer RNA that transports amino acids to the ribosome during protein
RNA) synthesis.
rRNA (Ribosomal
RNA that forms part of the ribosome.
RNA)
Ribosome The organelle where proteins are assembled.
Codon A triplet of bases on mRNA coding for a specific amino acid.
Anticodon A triplet of bases on tRNA complementary to an mRNA codon.
Amino Acid The basic building block of proteins.
Peptide Bond The bond linking amino acids together.
3
, Term Definition
The sequence of bases that determines the amino acid sequence of a
Genetic Code
protein.
Mendel's Laws of Inheritance
Term Definition
During gamete formation, allele pairs separate so that each
Law of Segregation
gamete receives only one allele.
Law of Independent Alleles of different genes segregate independently during
Assortment gamete formation.
The passing of characteristics from parents to offspring through
Inheritance
genes.
Differences in characteristics among individuals of the same
Variation
species.
Topic 2: Inheritance and Variation
Genetic Terminology
Term Definition
Genotype The genetic make-up of an organism.
Phenotype The observable characteristics of an organism.
An allele expressed in both homozygous and heterozygous
Dominant Allele
conditions.
Recessive Allele An allele expressed only in the homozygous condition.
Homozygous Having two identical alleles for a characteristic.
Heterozygous Having two different alleles for a characteristic.
Homozygous
Having two dominant alleles for a characteristic.
Dominant
4
