Genetics, populations, evolutions and ecosystems Flashcards
Allele
An alternative form of a gene that occurs at the same locus on homologous chromosomes.
Anticodon
A sequence of three nitrogenous bases on a tRNA molecule that is complementary to a codon in mRNA. The anticodon enables tRNA to sequence amino acids in the order specified by mRNA.
Apoptosis
Programmed cell death. Cellular DNA is degraded and the nucleus is condensed, then the cell is devoured by phagocytes.
Carcinogen
Physical or chemical agent which induces cancer.
Chiasmata
Observable regions in which non sister chromatids of homologous chromosomes cross over each other.
Chromatid
One of the two side-by-side replicas produced by chromosome duplication.
Chromosome
Structures within the cell nucleus that carry genes encoded by DNA.
Clone
A group of cells or molecules that are identical by having arisen from a single ancestral cell or molecule.
Codon
A sequence of three nitrogenous bases in DNA or RNA which codes for a single amino acid. Enables specific proteins to be made by specific genes.
Crossing over
The exchange of genetic material between members of a pair of homologous chromosomes.
Denaturation
Disruption of the structure of any complex molecule without breaking the major bonds of its chain.
Dominance
Where an allele can cause a trait to be expressed in heterozygous or homozygous.
DNA
Deoxyribonucleic acid. Composed of nucleic acids: deoxyribose sugar, a phosphate group and a nitrogenous base. DNA encodes for the genes that allow genetic information to be passed onto offspring.
DNA polymerase
Enzymes that can synthesise new DNA strands using previously synthesised DNA or RNA as a template.
Exon
The protein-coding sequences of a gene. Exons are represented in the mature RNA product.
Gamete
Sex cells- sperm cells and egg cells.
Genome
The entire set of genes of a gamete, person, population or species.
Genetic code
The set of correspondences between base triplets in DNA and amino acids.
Genotype
All of the alleles present at the locus of a blood group system.
Haploid
A single set of chromosomes . Present in sperm cells, egg cells of animals, pollen cells of plants and yeast.
Hemizygous
Inheritance of an X-linked gene in males.
Heterozygous
The situation in which allelic genes are different.
Homologous chromosomes
A matched pair of chromosomes, with one coming from each parent.
Homozygous
The situation in which allelic genes are the same/ identical.
Introns
The DNA base sequences that interrupt the protein-coding sequences of a gene. The non-coding sections of DNA or RNA. These sequences are transcribed into RNA but are spliced out to form the mature mRNA before translation.
Karyotype
The entire chromosome complement of an individual or cell, as seen during mitotic metaphase.
Locus
A specific position on a chromosome.
Meiosis
The type of cell division that occurs in sex cells by which gametes having the haploid number of chromosomes are produced from diploid cells.
Messenger RNA
A type of RNA molecule that conveys genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression.
Mitosis
Cell division that results in two daughter cells with the same number of chromosomes as the parent cell. Cell division that forms all new cells except sex cells.
Mutagen
Any agent that is capable of increasing mutation rate.
Nucleic acid
Polymers of phosphorylated nucleosides. The building blocks (monomers) of DNA and RNA.
Nucleoside
The building blocks of DNA and RNA. Compounds consisting of a purine or pyrimidine attached to ribose or deoxyribose at the 11 carbon.
Oligonucleotides
Small single-stranded segments of DNA, typically 20-30 nucleotides in length, which are synthesised in vitro.
Oncogene
An allele of a normal gene, called a proton-oncogene, that causes a cell to become cancerous.
Phenotype
Observable characteristics of an organism.
Plasmid
Cytoplasmic, autonomously replicating extrachromosomal DNA molecules.
Recessive
Genes are recessive if the phenotype that they code for is only expressed when the genes are homozygous.
Recombination
The formation of a new combination of alleles as a result of independent segregation or crossing-over.
Ribosomes
Complexes of rRNA and protein in cytoplasm that serves as a platform for translation of mRNA into protein.
RNA
Ribonucleic acid. Nucleic acids formed using DNA as a template. Similar to DNA except it has ribose in place of deoxyribose, and it has uracil instead of thymine.
rRNA
Ribosomal RNA- the type of RNA found in ribosomes, the site of protein synthesis.
Somatic cells
All the cells of an organism except those of the germ line. Autosomes.
Nondisjunction
The failure of two members of a chromosome pair to disjoin during anaphase.
Reverse transcriptase
An RNA-dependent DNA polymerase enzyme that synthesises DNA from an RNA template.
Transcription
The synthesis of single stranded RNA by RNA transcriptase using DNA as a template. The process in the nucleus by which mRNA is transcribed from DNA.
tRNA
Transfer RNA- the type of RNA that facilitates the translation of mRNA into a sequence of amino acids. Contains anticodons that provide the molecular link between the codons of mRNA and the amino acid sequences of proteins.
Translation
The process in ribosomes by which the codon sequence of mRNA is translated into polypeptides with the help of tRNA molecules.
