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Unit 4 Outcome 1 Biology key terms

This is a guest post from former VCE student Olivia Anderson for VCE Biology. If you want to contribute your own VCE resources check out the guidelines here. Thanks Olivia!

Allele: a variation of a gene

Anaphase: the phase of cell division where the chromosomes more to the poles of the new cells

Aneuploidy: an abnormal number of chromosomes- eg. Too many or too few

Anticodon: a sequence of three nucleotides on a molecules of tRNA that is complementary to the base sequences on a codon of mRNA

Apoptosis: programmed cell death

Autosomal: relating to the autosome: any non-sex chromosome

Barr body: the inactive X chromosome in non-dividing nuclei of females

Binary fission: a type of cell reproduction of prokaryotes where two daughter cells are produced from the parent cell asexually

Centromeres: a point on a chromosome at which the two homologous chromosomes are seen to be attached during meiosis and mitosis

Chromatids: one half of a pair of genetically identical chromosomes formed in prophase of mitosis and in the first stage of meiosis

Chromosome: a structure containing DNA and proteins which carry genetic information (linear in eukaryotes, ring shaped in prokaryotes)

Codominance: the quality of two heterozygous alleles that are fully and equally expressed in the phenotype eg blood groups: AB: both Aa and B proteins are produced

Codon: a group of three nucleotides (triplet) of DNA or RNA

Continuous variation: variation of a characteristic in a population that is controlled by a number of genes, so multifactorial inheritance is shown.

Crossing over: the interchanging of sections between pairing homologous chromosomes during prophase of mitosis

Cytokinesis: the process of cytoplasmic division and enclosure of the cytoplasm of the new daughter cells by the plasma membrane during mitosis or meiosis

Deletion: the process of removal of one or more bases from DNA or of a section of a DNA molecule from a chromosome

Dihybrid cross: a cross of two individuals that are heterozygous at two loci

Diploid: a term that describes the number of chromosomes in the nucleus of a cell as two paired sets, or twice the number of the haploid set of chromosomes. (2n)

Discontinuous variation: variation of a characteristic in a population that is controlled by a single gene, that is, shows single factor inheritance

DNA ligase: the enzyme that synthesizes bongs between adjacent nucleotides

DNA polymerase: the enzyme that catalyzes the assembly of deoxyribonucleoside triphosphate building blocks onto the DNA in the 3’ to 5’ direction

DNA sequencing: sequencing methods for determining the specific base sequence in DNA

DNA template: the strand of DNA that acts as a ‘template’ for mRNA in the process of transcription

Dominant: an allele that is expressed in a phenotype masking the effect of a recessive trait, expressed whether organism is heterozygous or not

Eukaryotic: an organism that consists of cells containing distinct organelles, including a nucleus, many of which are bound by a membrane

Exon: a nucleotide sequence of a gene that codes for an amino acid sequence or a control sequence

Frameshift Mutation: a type of mutation caused by the deletion or addition of a single nucleotide in a codon that results in a change in the reading frame of the codons- shifts the whole sequence

Gamete: a mature sperm or ovum germ cell

Gene: an inherited unit of DNA molecules (chromosomes) that controls a structure or function of an organism

Gene expression: conversion of the information held in DNA to mRNA and then to a protein or other functional gene product

Gene linkage: traits that tend to be inherited together as they are located on the same chromosome

Genome: the total DNA of the haploid set of chromosomes in an organism

Genotype: the genetic profile of an individual- the range of alleles of each gene the organism possesses

Haploid: the condition of having one set of unpaired chromosomes

Hemizygous: having some single copies of genes in an otherwise diploid cell or organism

Heterozygous: a cell/organism in which the alleles of its genes for a particular trait are different

Homologous chromosomes: chromosomes that carry alleles of the same genes in the same order and have the same appearance

Homozygous: a cell/organism in which the alleles of its genes for a particular trait are identical

Incomplete dominance: the condition where both alleles of a gene are expressed in the phenotype- resulting in combined phenotype eg. Flower colour: red mixed with white = pink

Independent assortment: the process of random segregation and assortment of chromosomes during anaphase 1 of meiosis (they separate independently of other chromosomes)

Insertion: the addition of one or more nucleotides to a DNA sequence

Interphase: the period between successive cycles of mitosis in cells, normally cell growth occurs

Intron: a nucleotide sequence of a gene that doesn’t code for a gene product or control sequence and is thus taken out during transcription

Locus: the position of a gene on a chromosome

Meiosis: the process of cell division whereby the originating germ cell replicates once and divides twice, resulting in four new daughter cells each containing one copy of each homologous chromosome

Metaphase: a stage in the cell division process of mitosis and meiosis

Mode of inheritance: The manner in which a particular genetic trait or disorder is passed from one generation to the next. Autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, multifactorial, and mitochondrial inheritance are examples.

Monohybrid cross: a cross between organisms that involves only a single gene, usually with two different alleles

mRNA: the group of RNA molecules that transcribes the genetic information from the DNA in the nucleus

Multiple alleles: the existence of more than 2 alleles at a locus in a population

Mutagen: an environmental influence that is able to cause change in one or more nucleotide bases of the genetic material

Mutant: an organism that has characteristics resulting from chromosomal alteration

Mutation: a change in the sequence of nucleotide bases of the genetic material

Non-disjuction: a feature of the cellular processes of either mitosis or meiosis that results in cells that have an incorrect number of chromosomes

Nucleotide: a sub-unit of nucleic acids that has a distinct structure consisting of a 5-carbon sugar, a phosphate group and a nitrogenous base

PCR: a procedure in which the enzyme DNA polymerase is used to clone (copy exactly) a specific sequence of DNA without the need of a living cell

Pedigree: a graphic representation of the occurrence of a particular inherited trait over many generations of one family

Phenotype: the visible physical or non-visible physiological outcomes of gene expression

Plasmid: a piece of DNA found in bacteria and yeast that is able to replicate independently of the main chromosome/s of the cell

Point mutation: a mutation in the nucleotide sequence of a gene in which only one base is altered, either by being substituted for another nucleotide or by being deleted

Polygenic inheritance: a trait/feature the expression of which is controlled by a polygene- more than 1 gene.

Polypeptide: a molecule consisting of a single chain of many amino acids linked together by peptide bonds

Primers: a short fragment of RNA that is complementary to a region of single stranded DNA and is able to bind to it, stimulating the enzyme DNA polymerase to copy the nucleotide bases on the exposed section of DNA near the primer and create a double stranded molecule

Polyploidy: the possession of one or more complete extra sets of chromosomes in each cell

Prokaryotic: an organism that is usually unicellular, does not have its DNA enclosed in a distinct nucleus, lacks double-membrane bound organelle and employs alternative methods of cell division and movement

Prophase: the 1st stage in cell division processes of mitosis and meiosis, when chromosome condensation occurs

Recessive: a term used to describe a phenotype controlled by an allele which is only expressed in the phenotype of the organism when another allele is present (homozygous alleles)

Recognition site: a specific sequence of nucleotides in DNA that is recognised by restriction enzymes which then ‘cut’ the DNA at that particular sequence

Recombination: any process occurring in the cells of an organism that results in the organism having cells with a different genetic combination from any it inherited

Recombinant phenotype: a phenotype that doesn’t necessarily follow the parental phenotype due to events such as crossing over

Restriction endonuclease: a group of enzymes produced naturally by bacteria to combat bacteriophages, which cut DNA at specific recognition sites (base sequence sites) in precise and predictable ways and so destroy them

RNA polymerase: an enzyme that produces RNA

RFLP’s: variations in DNA fragments that result from point mutation, deletions, insertions or tandem repeats of sequences. These can be detected by using restriction enzymes

Semi-conservative: the replication of DNA that results in each new double stranded consisting of one strand from the original molecule and one newly synthesized strand

Sex-linked: a gene located on a sex-chromosome

Sexual reproduction: the methods of reproduction involving the fusion of the male and female haploid gametes

Silent mutation: DNA mutations that do not result in a change to the amino acid sequence of a protein

Stop codon: a sequence of 3 nucleotides that codes for the end of a gene

Telophase: a late stage of mitosis/meiosis where chromosomes regain original form, spindle fibres disappear and nuclear membrane is reformed.

Test cross: the cross of one organism with a homozygous recessive organism for a particular trait to determine if the organism under examination is heterozygous or homozygous

Thermophilic: organism living in high temperature

Transcription: the synthesis of mRNA from a template strand of DNA in the nucleus

Transgenic: an organism with one or more genes in its genome that have come from another organism

Translation: the process of protein synthesis that occurs in the cytoplasm of cells. The mRNA molecule is read by the ribosomes and amino acids are ordered to form a polypeptide

Translocation: the rearrangement of parts of a chromosome

Trisomy: having more than the normal number of chromosomes in a cell

tRNA: a molecule found in the cytoplasm of a cell which brings specific amino acids to the ribosome to be formed into a polypeptide

Vector: a DNA molecules found in bacterial cells that is used to carry foreign DNA into host cells; or, something that brings foreign DNA into host cells

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