science revision

• DNA (deoxyribonucleic acid)


  Genetic make-up that carries the instructions for life
• Double helix


  • Structure of DNA
• Nucleotide


  A subunit of DNA
• Deoxyribose


  A five-carbon sugar molecule found in DNA
• Nitrogenous bases


  • Adenine
  • Guanine
  • Cytosine
  • Thymine
• Phosphate group


  One of the three components of nucleotide
• Hydrogen bonds


  Chemical bonds that hold the two strands of DNA together
• Complementary pairing


  Adenine pair with Thymine; Cytosine pair with Guanine (in DNA) Adenine pair with Uracil; Cytosine pair with Guanine (in RNA)
• Purine


  Double-ring chemical structure, includes guanine and adenine
• Pyrimidine


  Single-ring chemical structure, includes cytosine and guanine
• Histone


  A protein that provides structural support for a chromosome
• Chromosome


  A structure of tightly wound DNA
• Gene


  A length of chromosome
• Triplet


  3 DNA bases that code for an amino acid
• Codon


  3 mRNA bases that code for an amino acid
• RNA (Ribonucleic acid)


  A nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins
• Single helix


  • Structure of RNA
• Ribose


  A five-carbon sugar molecule found in RNA
• Uracil


  One of the four nitrogenous bases in RNA
• Transcription


  The process of making an RNA copy (mRNA) of a gene's DNA sequence carrying the gene's protein information encoded in DNA
• Translation


  The process through which information encoded in messenger RNA (mRNA) directs the addition of amino acids during protein synthesis
• mRNA (messenger RNA)


  A type of single-stranded RNA involved in protein synthesis, the role of mRNA is to carry protein information from the DNA in a cell's nucleus to the cell's cytoplasm (watery interior), where the protein-making machinery reads the mRNA sequence and translates each three-base codon into its corresponding amino acid in a growing protein chain
• tRNA (transfer RNA)


  A small RNA molecule that plays a key role in protein synthesis. Transfer RNA serves as a link (or adaptor) between the messenger RNA (mRNA) molecule and the growing chain of amino acids that make up a protein. Each time an amino acid is added to the chain, a specific tRNA pairs with its complementary sequence on the mRNA molecule, ensuring that the appropriate amino acid is inserted into the protein being synthesized
• rRNA (ribosomal RNA)


  Molecule in cells that forms part of the protein-synthesizing organelle known as a ribosome
• Ribosome


  An intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell. The ribosome reads the messenger RNA (mRNA) sequence and translates that genetic code into a specified string of amino acids, which grow into long chains that fold to form proteins
• Organelles containing DNA


  • Nucleus
  • Mitochondria
  • Chloroplast
• Amino acid


  Molecules that combine to form protein
• Karyotype


  A pictorial representation of an organism's chromosome
• Homologous chromosomes


  Matching chromosomes
• Non-homologous chromosomes


  Non-matching chromosomes
• Autosomes


  In humans, chromosome pairs 1 to 22
• Sex chromosomes


  In human, the 23rd pair of chromosomes that determines the sex of a person
• Chromatid


  One of two molecules of DNA that makes up a chromosome
• Centromere


  Connects the two chromatids and is the location where fibres attach during cell division
• Telomere


  Protective molecular caps of repeating DNA located at the ends of the chromosomes
• P arm


  Short arm of chromosome
• Q arm


  Long arm of chromosome
• Sexual reproduction


  Reproduction involving sex cells
• Gametes


  Sex cells that combine to produce new offspring
• Gonads


  The sexual organs: tests in males and ovaries in females