Genetic information

• What is a sequence of 3 DNA bases called?

  A triplet
• What is a gene?


  A section of DNA in a chromosome
• How many bases does a gene consist of?

  153 bases
• What is a locus?


  The exact position of a gene on a chromosome
• What is a genome?


  The complete set of genes in a cell or organism
• What is the genetic code?

  A set of codons that specify which amino acids are coded for by which combination of bases
• What is a proteome?


  The full range if proteins that can be produced by a cell
• Why is the genetic code universal?

  The same codon makes the same amino acid in different organisms
• Why is the genetic code degenerate?

  More than one codon can code for the same amino acid
• Why is the genetic code non-overlapping?

  It is read as separate triplets
• What are mutagenic agents?

  Factors that increase the rate of gene mutation, such as gamma rays or smoking
• What are the three types of gene mutation?

  Addition, deletion, substitution
• What is a silent mutation?

  Where a base is substituted but it does not affect the amino acid coded for
• What mutations can result in a frameshift mutation?

  Additions or deletions
• What is a frameshift mutation?

  mutations, usually addition or deletion of a base, which change the subsequent triplets after
• What is an exon?

  A segment of DNA that codes for a polypeptide
• What is an intron?

  The non-coding regions of DNA
• Which strand of DNA is used as a template in transcription?

  The 3' to 5' strand, as RNA can only run in 5' to 3
• Describe the process of transcription

  - RNA polymerase binds itself to the promoter region, breaking the hydrogen bonds between bases

  - One strand acts as a template

  - Free RNA nucleotides move in and line up opposite the exposed bases on the template strand according to complementary base pair rules

  - ATP is hydrolysed and the nucleotides are phosphorylated

  - RNA polymerase forms phosphodiester bonds that link adjacent RNA nucleotides

  - RNA synthesis stops as soon as a stop codon is reached

  - The Pre-mRNA is spliced, removing introns
• Describe the process of translation

  - mRNA leaves the nucleus and attaches to a ribosome

  - A tRNA molecule with the complementary anticodon attaches to the mRNA codon, bringing the specific amino acid encoded for

  - The ribosome advances through the mRNA molecule's codons, one by one

  -The amino acids join by peptide bonds, forming a primary polypeptide chain

  - Once it reaches the stop codon the process is ended, resulting in a complete polypeptide chain
• What is a missense mutation?

  Where only one amino acid changes at the point of mutation, caused by substitution
• What is a nonsense mutation?

  When an amino acid changes to a stop codon, prematurely ending the polypeptide chain
• What are the three types of chromosome mutation?

  Non-disjunction, duplication, inversion
• What is chromosome non-disjunction?

  The failure of chromosomes separating properly during meiosis
• Aneuploidy


  The presence of an abnormal number of chromosomes in a cell
• Polysomy


  Where an organism has at least one less chromosome than expected
• How is a diploid cell represented in terms of number of chromosomes?

  2n
• What are homologous chromosomes?

  Two chromosomes that contain the same gene at the same loci
• What is the name of the chromosomal structure formed during prophase I?

  A chiasma
• What is the purpose of a chiasma?


  Crossing over causes genetic variation by exchanging genetic material between homologous chromosomes
• What forms as a result of a chiasma?

  Recombinant chromosomes
• What happens during metaphase I and II and anaphase I and II that are essential for the production of genetically different gametes?

  Random assortment - homologous chromosomes are positioned randomly on the equator

  Independent segregation - each set of chromosomes are pulled to opposite poles of the cells
• What is an allele?

  A different version of a gene
• What is co-dominance?

  When two dominant alleles are expressed together
• What is the process of natural selection?

  -Genetic variation, selection pressures,
• What is a species?

  A group of similar organisms that can mate and produce fertile offspring
• Binomial naming


  System by which organisms are classified by their genus and species
• Rules of binomial naming system

  Genus initial is capitalised and italicised
• Phylogeny


  Shows the evolutionary history of a species
• 5 types of courtship behaviours


  - Singing

  - Dancing

  - Gift giving

  - Home building

  - Visual signalling