Genetics and Genetic Engineering Review

Vocabulary-style flashcards covering the core concepts of Grade 12 Genetics and Genetic Engineering, emphasizing terminology, laws of inheritance, and modern biotechnological processes.

Variation

The state of being different from one another among human beings and all living organisms.

Discontinuous variation

Characteristics that fall into distinct, separate categories with no intermediate forms, usually controlled by one or a few genes and not significantly influenced by the environment (e.g., blood groups).

Continuous variation

Characteristics that show a range of values with many intermediate forms between extremes, typically controlled by many genes and often influenced by environmental factors (e.g., height).

Polygenic inheritance

A type of inheritance where a single characteristic is controlled by two or more genes ($polygenes$) that may be situated on different chromosomes.

Genetic traits

Human characteristics determined by genes inherited from parents, such as a widow’s peak, eye colour, or handedness.

Gregor Mendel

An Austrian monk ($1822$ – $1884$) regarded as the ‘father of genetics’ for his pioneering work using pea plants to study inheritance patterns.

Monohybrid cross

A genetic cross where only one pair of contrasting characteristics is considered.

Pure-breeding lines

Plants or organisms that always give rise to offspring similar to themselves after self-pollinating over many generations.

Phenotype

The observable physical and chemical characteristics of an organism, resulting from its genotype and environmental effects.

Genotype

The genetic information contained in a cell’s DNA.

Locus

The specific position on a particular pair of chromosomes where a gene coding for a particular characteristic is found.

Gene

A segment of DNA coding for a specific RNA molecule to give particular characteristics because of the protein produced.

Allele

One of two or more different forms of a gene, with each producing different alternative forms of a characteristic.

Homozygous

An organism that has two identical alleles for a specific gene on a pair of homologous chromosomes.

Heterozygous

An organism that has two different alleles for a specific gene on a pair of homologous chromosomes.

Dominant allele

An allele ($T$) whose effect is expressed in the phenotype even when only one copy is present.

Recessive allele

An allele ($t$) whose effect is only expressed in the phenotype when it is present in the homozygous condition ($tt$).

Law of Dominance

States that when two different alleles for a characteristic are present, one allele may mask the expression of the other.

Law of Segregation

States that allele pairs separate during the formation of gametes in meiosis so that each gamete carries only one allele for each gene.

Law of Independent Assortment

States that alleles of different genes assort independently of one another during gamete formation.

Gonosomes

The sex chromosomes ($X$ and $Y$) that determine the sex of an individual.

Sex-linked traits

Disorders or characteristics, such as haemophilia and red-green colour blindness, caused by genes located on the sex chromosomes.

Carrier

A phenotypically normal female who is heterozygous ($X^{N}X^{n}$) and can pass a recessive allele for a disorder to her offspring.

Human Genome Project

An investigative project completed in $2003$ that identified approximately $20\,000$ – $25\,000$ human genes and determined the sequence of $3$ billion chemical base pairs.

Pedigree tree

A diagram showing relationships between individuals across several generations used to trace the inheritance of genetic traits or disorders.

Genetic disorder

A condition resulting from mutations of genes or chromosomes that disrupts normal body functioning and may be inherited.

Gene therapy

A medical technique used to treat or prevent disease by replacing, repairing, or inserting functional genes into a patient's cells using a vector.

Mutation

A random change in the DNA sequence of a gene or chromosome which may result in new alleles.

Mutagens

Environmental factors such as UV radiation, mutagenic chemicals (e.g., benzene), or certain viruses that increase the rate of mutations.

Biotechnology

The use of plants, animals, and microbes to produce useful products for people.

Recombinant DNA technology

The process of combining DNA from different sources that would not normally occur together.

Genetically modified organism (GMO)

Also known as a transgenic organism; an organism that has had foreign DNA ($donor gene$) inserted into its genetic material.

Restriction enzymes

Enzymes that act as ‘molecular scissors’ to cut DNA at specific sequences, often producing ‘sticky ends’.

DNA ligase

An enzyme that acts as ‘molecular glue’ to join DNA fragments together by forming bonds between them.

Plasmid

A small, circular DNA molecule found in bacterial cells that is separate from chromosomal DNA and can replicate independently.

Vector

A plasmid, bacterium, or virus used to carry recombinant DNA into the cells of a recipient organism.

CRISPR

A precise gene-editing tool adapted from a bacterial immune defense system used to cut, remove, or replace specific sections of DNA.

Reproductive cloning

The process of producing genetically identical copies of whole organisms.

Somatic cell nuclear transfer (SCNT)

A technique used to produce clones by transferring the nucleus of a somatic cell into an egg cell which has had its own nucleus removed.

Stem cells

Cells found in bone marrow and embryos that have the ability to develop into any type of specialized cell in the body.

Artificial selection

The process by which humans choose organisms with desirable traits and breed them to produce specific offspring.

Hybrid vigour

Also known as heterosis; the phenomenon where cross-bred offspring show superior characteristics, such as increased resilience and productivity, compared to their parents.