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Genetics, DNA and Evolution | Definitions
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Genetics, DNA and Evolution | Definitions
Allele
Different forms of the same gene.
Acquired Variation
The differences between species that are not controlled by genes.
Chromosome Mutation
A large change in the structure or number of one or more chromosomes.
Codon
A sequence of three bases on an RNA or DNA molecule.
Cell Continuity
Life comes from pre-existing life and this is vital for growth and for life to continue.
Coding DNA
The length of DNA where a gene is located. It carries the code for the production of a specific protein.
Dihybrid Cross
Involves two characteristics being studied, e.g. height and flower colour in plants.
Diploid
An organism with two sets of chromosomes, e.g. 2n = 46 chromosomes in humans.
Dominant Allele
The allele that gets expressed. It prevents the expression of the recessive allele in the heterozygous condition.
DNA Profiling
The process of making a unique pattern of bands from the DNA of a person which can be used to distinguish that DNA from another person's DNA.
Evolution
An inheritable or genetic change within a population or species in response to a change in the environment over a long period of time.
F1 Generation
F1 refers to the first generation of offspring.
F2 Generation
F2 refers to the second generation of offspring.
Fertilisation
The fusion of the male gamete (sperm) and the female gamete (egg) to form a diploid zygote (n + n = 2n).
Fertility
The ability to produce offspring.
Gamete
A haploid sex cell formed from meiosis containing 1 set of chromosomes that is capable of fusing with another gamete of the opposite sex to form a diploid zygote.
Gene
A short section of DNA that contains a code for the production of a particular protein.
Gene Expression
The production of a particular protein using the gene's code.
Gene Mutation
A change in the DNA in a single gene.
Gene Therapy
Involves inserting new genes into the cells of a person to replace faulty genes.
Genetic Code
The precise sequences of bases along the DNA.
Genetic Engineering
The artificial alteration or manipulation of genes.
Genetic Screening
Testing a person's DNA for the presence or absence of a particular gene or altered gene.
Genotype
The genetic make-up of an organism.
Haploid
An organism with one set of chromosomes (n = 23 chromosomes in humans).
Heredity
The passing on of characteristics or traits using genes from one generation to the next.
Heterozygous
Two alleles that are different, e.g. Tt.
Homozygous
Homozygous is the term used for two alleles that are the same, e.g. TT or tt.
Incomplete Dominance
Where neither allele is dominant or recessive with respect to the other. Both alleles are expressed in the heterozygous genotype and an intermediate phenotype is produced.
Inherited Variations
The diffferences between species that are controlled by genes. They are caused by sexual reproduction and mutations.
Law of Independent Assortment
When gametes are formed, each member of a pair of alleles may combine randomly with either of another pair of alleles.
Law of Segregation
Inherited characteristics are controlled by pairs of factors (alleles). These factors separate from each other at gamete formation with only one member of each pair found in each gamete.
Linked Genes
When genes for two characteristics are on the same chromosome, they are passed on together in the gametes to the next generation.
Locus
The locus of a gene is its position on a chromosome.
Meiosis
A type of nuclear division where four daughter nuclei are produced, each containing half the number of chromosomes as the parent nucleus.
Monohybrid Crosses
A cross involving only one characteristic, e.g. height.
Mutagens
Agents that cause mutations.
Mutations
A change in the amount or in the structure of DNA.
Non-Nuclear DNA
This is DNA that is found outside the nucleus of a cell which is passed from one generation to the next, e.g. mitochondrial DNA.
Phenotype
The physical appearance of an organism.
Plasmid
A circular piece of DNA, sometimes found in bacteria, that can contain genes.
Population
Population refers to all the organisms of a particular species that occupy an ecosystem.
Progeny
Progeny means the offspring of a cross.
Protein Synthesis
A complex process that occurs in all cells involving transcription and translation to produce a new protein.
Punnett Square
A square diagram that is used to predict the genotypes and by extension, the phenotypes of a particular cross.
Recessive Allele
The allele that is not expressed. Its expression is prevented due to the presence of the dominant allele.
Recombinant DNA
The DNA that is composed of the DNA of two different species.
Sex Linkage
A characteristic is controlled by an allele located on the X chromosome.
Sex-Linked Genes
Genes found on the X chromosome without a corresponding gene on the Y chromosome.
Speciation
When one species gives rise to a new and distinctly different species.
Species
A group of similar organisms that are capable of interbreeding with one another to produce fertile offspring.
Transcription
The making of mRNA using DNA as a template.
Transgenic Organism
An organism that contains genes from another species. They can also be referred to as 'genetically-modified organisms' (GMOs).
Translation
The making of a protein using messenger RNA (mRNA) code in a ribosome.
Variation
The differences between members of the same species.
Chromosome
A thread-like structure made up of DNA and proteins called histones. Chromosomes contain genes and are found in the nucleus.
Homologous Chromosomes
Pairs of chromosomes that contain genes that control the same characteristics.
Sex Chromosomes
Pairs of chromosomes that determine the sex of the individual, e.g. XX = female or XY = male in humans.
Linkage
When genes are present on the same chromosome.
Autosomes
The 22 pairs of chromosomes that are not sex chromosomes.
Non-Coding DNA
Does not carry the information to make a protein.
Complementary Base Pairs
Each base has a corresponding base/pair, e.g. cytosine and guanine are complementary pairs.
DNA (Deoxyribonucleic Acid)
Located in the nucleus and makes up genes and chromosomes. It forms a double helix and its base sequence forms the genetic code.
Natural Selection
The process by which species become better adapted to their environment over time due to the advantages of genetic changes and mutations.
Cut dotted horizontal lines. Fold vertical line.
Allele
Different forms of the same gene.
Acquired Variation
The differences between species that are not controlled by genes.
Chromosome Mutation
A large change in the structure or number of one or more chromosomes.
Codon
A sequence of three bases on an RNA or DNA molecule.
Cell Continuity
Life comes from pre-existing life and this is vital for growth and for life to continue.
Coding DNA
The length of DNA where a gene is located. It carries the code for the production of a specific protein.
Dihybrid Cross
Involves two characteristics being studied, e.g. height and flower colour in plants.
Diploid
An organism with two sets of chromosomes, e.g. 2n = 46 chromosomes in humans.
Dominant Allele
The allele that gets expressed. It prevents the expression of the recessive allele in the heterozygous condition.
DNA Profiling
The process of making a unique pattern of bands from the DNA of a person which can be used to distinguish that DNA from another person's DNA.
Evolution
An inheritable or genetic change within a population or species in response to a change in the environment over a long period of time.
F1 Generation
F1 refers to the first generation of offspring.
F2 Generation
F2 refers to the second generation of offspring.
Fertilisation
The fusion of the male gamete (sperm) and the female gamete (egg) to form a diploid zygote (n + n = 2n).
Fertility
The ability to produce offspring.
Gamete
A haploid sex cell formed from meiosis containing 1 set of chromosomes that is capable of fusing with another gamete of the opposite sex to form a diploid zygote.
Gene
A short section of DNA that contains a code for the production of a particular protein.
Gene Expression
The production of a particular protein using the gene's code.
Gene Mutation
A change in the DNA in a single gene.
Gene Therapy
Involves inserting new genes into the cells of a person to replace faulty genes.
Genetic Code
The precise sequences of bases along the DNA.
Genetic Engineering
The artificial alteration or manipulation of genes.
Genetic Screening
Testing a person's DNA for the presence or absence of a particular gene or altered gene.
Genotype
The genetic make-up of an organism.
Haploid
An organism with one set of chromosomes (n = 23 chromosomes in humans).
Heredity
The passing on of characteristics or traits using genes from one generation to the next.
Heterozygous
Two alleles that are different, e.g. Tt.
Homozygous
Homozygous is the term used for two alleles that are the same, e.g. TT or tt.
Incomplete Dominance
Where neither allele is dominant or recessive with respect to the other. Both alleles are expressed in the heterozygous genotype and an intermediate phenotype is produced.
Inherited Variations
The diffferences between species that are controlled by genes. They are caused by sexual reproduction and mutations.
Law of Independent Assortment
When gametes are formed, each member of a pair of alleles may combine randomly with either of another pair of alleles.
Law of Segregation
Inherited characteristics are controlled by pairs of factors (alleles). These factors separate from each other at gamete formation with only one member of each pair found in each gamete.
Linked Genes
When genes for two characteristics are on the same chromosome, they are passed on together in the gametes to the next generation.
Locus
The locus of a gene is its position on a chromosome.
Meiosis
A type of nuclear division where four daughter nuclei are produced, each containing half the number of chromosomes as the parent nucleus.
Monohybrid Crosses
A cross involving only one characteristic, e.g. height.
Mutagens
Agents that cause mutations.
Mutations
A change in the amount or in the structure of DNA.
Non-Nuclear DNA
This is DNA that is found outside the nucleus of a cell which is passed from one generation to the next, e.g. mitochondrial DNA.
Phenotype
The physical appearance of an organism.
Plasmid
A circular piece of DNA, sometimes found in bacteria, that can contain genes.
Population
Population refers to all the organisms of a particular species that occupy an ecosystem.
Progeny
Progeny means the offspring of a cross.
Protein Synthesis
A complex process that occurs in all cells involving transcription and translation to produce a new protein.
Punnett Square
A square diagram that is used to predict the genotypes and by extension, the phenotypes of a particular cross.
Recessive Allele
The allele that is not expressed. Its expression is prevented due to the presence of the dominant allele.
Recombinant DNA
The DNA that is composed of the DNA of two different species.
Sex Linkage
A characteristic is controlled by an allele located on the X chromosome.
Sex-Linked Genes
Genes found on the X chromosome without a corresponding gene on the Y chromosome.
Speciation
When one species gives rise to a new and distinctly different species.
Species
A group of similar organisms that are capable of interbreeding with one another to produce fertile offspring.
Transcription
The making of mRNA using DNA as a template.
Transgenic Organism
An organism that contains genes from another species. They can also be referred to as 'genetically-modified organisms' (GMOs).
Translation
The making of a protein using messenger RNA (mRNA) code in a ribosome.
Variation
The differences between members of the same species.
Chromosome
A thread-like structure made up of DNA and proteins called histones. Chromosomes contain genes and are found in the nucleus.
Homologous Chromosomes
Pairs of chromosomes that contain genes that control the same characteristics.
Sex Chromosomes
Pairs of chromosomes that determine the sex of the individual, e.g. XX = female or XY = male in humans.
Linkage
When genes are present on the same chromosome.
Autosomes
The 22 pairs of chromosomes that are not sex chromosomes.
Non-Coding DNA
Does not carry the information to make a protein.
Complementary Base Pairs
Each base has a corresponding base/pair, e.g. cytosine and guanine are complementary pairs.
DNA (Deoxyribonucleic Acid)
Located in the nucleus and makes up genes and chromosomes. It forms a double helix and its base sequence forms the genetic code.
Natural Selection
The process by which species become better adapted to their environment over time due to the advantages of genetic changes and mutations.