Chapter 1

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Introduction to Genetics

homunculus

sex cells that contain a complete miniature adult, perfect in every form (idea)

cell theory

all organisms are composed of basic units called cells

epigenesis / preformation

The idea that an organism or organ arises through the sequential appearance and development of new structures

spontaneous generation

the creation of living organisms from nonliving components

fixity of species

animal and plant groups have remained unchanged in form since the moment of their appearance on Earth

natural selection

differential reproduction among members of a species owing to variable fitness conferred by genotypic differences

chromosomal theory of inheritance

the theory that heredity and development were dependent on genetic information residing in genes contained in chromosomes which were then contributed to each individual by gametes

genetics

the branch of biology concerned with the study of heredity and variation

diploid number (2n)

a condition in which each chromosome exists in paris; having two of each chromosome

homologous chromosomes

chromosomes that synapse or pair during meiosis and that are identical with respect to their loci and centromere placement

mitosis

a form of cellular reproduction producing two progeny cells, identical genetically to the progenitor cell, that is, the production of two cells from one, each with the same chromosome complement as the parent cell

meiosis

The process of cell division in gametogenesis or sporogenesis during which the diploid number of chromosomes is reduced to the haploid number

haploid (n) number

a cell or organism having one member of each pair of homologous chromosomes. Also, the gametic chromosome number

chromosome theory of inheritance

the idea put forward independently by Walter Sutton and Theodor Boveri that chromosomes are the carriers of genes and the basis for the Mendelian mechanisms of segregation and independent assortment

mutation

the process that produces an alteration in DNA or chromosome structure; in genes, the source of new alleles.

allele

any one of alternate forms of the same gene, often distinguished by alternate phenotypic expressions

phenotype

the overt appearance of a genetically controlled trait

genotype

the allelic or genetic constitution of an organism; often, the allelic composition of one or a limited number of genes under investigation

bacteriophages / phages

a virus that infects bacteria, using it as the host for reproduction

nucleotides

In nucleic acid chemical nomenclature, a nucleoside covalently linked to one or more phosphate groups. Nucleotides containing a single phosphate linked to the 5' carbon of the ribose or deoxyribose sugar are the building blocks of nucleic acids

transcription

transfer of genetic information from DNA by the synthesis of a complementary RNA molecule under the direction of RNA polymerase

messenger RNA / mRNA

An RNA molecule transcribed from DNA and translated into the amino acid sequence of a polypeptide

ribosome

a ribonucleoprotein organelle consisting of two subunits, each containing RNA and protein molecules. Ribosomes are the site of translation of mRNA codons into the amino acid sequence of a polypeptide chain.

translation

the derivation of the amino acid sequence of a polypeptide from the base sequence of an mRNA molecule association with a ribosome and dependent of tRNAs

genetic code

the deoxynucleotide triplets that encode the 20 amino acids or specify termination of translation

codon

a triplet of nucleotides that specifies a particular amino acid or a start or stop signal in the genetic code. Sixty-one codons specify the amino acids used in proteins, and three codons, called stop codons, signal termination of growth of the polypeptide chain.

transfer RNA / tRNA

a small ribonucleic acid molecule playing an essential role in translation, which adapts a triplet codon to tis prescribed amino acid

central dogma

the concept that genetic information flow progresses from DNA to RNA to proteins. Although expectations are known, this idea is central to an understanding of gene function.

restrictions enzymes

enzymes that cut viral DNA at specific sites; they are also used to cut any organism's DNA at specific nucleotide sequences producing a reproducible set of fragments

vectors

In recombinant DNA, an agent such as a phage or plasmid into which a foreign DNA segment will be inserted and utilized to transform host cells

recombinant DNA

A DNA molecule formed by joining two heterologous molecules. A term also applied to the technology associated with the use of DNA molecules produced by in vitro ligation of DNA from two different organisms

clones

Identical molecules, cells, or organisms derived from a single ancestor by asexual or parasexual methods; for example, a DNA segment that has be inserted into a plasmid or chromosome of a phage or a bacterium and replicated to produce many copies, or an organism of identical genetic composition to that used in its production

genome

the haploid set of hereditary information encoded in the DNA of an organism, including both the protein-coding and non-protein-coding sequences

biotechnology

commercial and/or industrial processes that utilize biological organisms or products

DNA microarrays / DN chips

an ordered arrangement of DNA sequences or oligonucleotides on a substrate (often glass). Microarrays are used in quantitative assays of DNA-DNA or DNA-RNA binding to measure profiles of gene expression (For example, during development or to compare the differences in gene expression between normal and cancer cells).

gene therapy

clinicians transfer normal genes into individuals affected with genetic disorders

genomics

a subdiscipline of the field of genetics generated by the union of classical and molecular biology with the goal of sequencing and understanding genes, gene interaction, genetic elements, and the structure of genomes

proteomics

the study of the expressed proteins present in a cell at a given time

bioinformatics

the design and application of software and computational methods for the storage, analysis, and management of biological information such as nucleotide or amino acid sequences

model organisms

an experimental organism conducive to efficiently conducted research whose genetics is intensively studied on the premise that the findings can be applied to other organisms

preformation

the development of an organisms or organ is the result of the assembly of structures already present in the egg.

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