Genetics, Biodiversity & Classification

The process by which a gene in a strand of DNA is copied into a new molecule, mRNA by the enzyme RNA polymerase

The process in which ribosomes in the cytoplasm or RER synthesise proteins, mRNA decoded by RNA to produce a specific polypeptide

A section of DNA that contains a code for making a polypeptide and functional RNA, found on a locus on a chromosome

Exactly the same size and genes, but may have different alleles

In eukaryotic cells, the DNA double helix is tightly coiled around histone proteins in a chromosome, prokaryotic DNA is not histone bound

• Degenerate - there is more than one triplet of bases that codes for the same amino acids • Universal - the same triplet of bases codes for the same amino acid in all organisms • Non-overlapping - each base in a gene is only part of one triplet of bases that codes for one amino acid (each codon is a discrete unit)

Introns - sections of DNA that do not code for amino acids and therefore polypeptide chains, these are spliced out of mRNA molecules (not found in prokaryotic DNA) Exons - the sections of DNA that do code for amino acids

Genome - an organisms complete set of DNA in one cell, should never change Proteome - the full range of proteins in one cell, constantly changing depending on proteins needed

mRNA (messenger) - carries the copy of the genetic code of one gene to a ribosome in the cytoplasm tRNA (transfer) - each molecule attaches to one amino acid and transfers it to the ribosome to create the polypeptide chain rRNA (ribosomal) - makes up the bulk of ribosomes

• H bonds between DNA bases break, causing DNA double helix to separate and expose template strand • Only 1 DNA strand acts as a template for the formation of RNA • Free RNA nucleotides align by CBP to the exposed bases on the DNA template strand • In RNA, uracil base pairs with adenine on DNA • RNA polymerase catalyses the condensation reaction of joining adjacent RNA nucleotides together • Phosphodiester bonds form between adjacent RNA nucleotides creating backbone

• One modified mRNA has left the nucleus, mRNA attaches to a ribosome • Ribosome reads sequence of codons on mRNA • tRNA molecule with complementary anticodon binds by CBP • Each tRNA molecule carries a specific amino acid • Ribosome joins amino acids carried by tRNA molecule using peptide bond (ATP required) • Ribosomes move along mRNA to next codon + process repeats • Continues until stop codon is reached

Meiosis produces daughter cells that are genetically different from each other and involves to nuclear divisions creating 4 haploid daughter cells from a single diploid parent cell

Independent segregation/assortment of homologous chromosomes - it is random which side of the equator the paternal + maternal chromosomes lie Crossing over between homologous chromosomes - part of the chromatids can become twisted around each other, causing them to break and they recombine with another chromatid Both occur in meiosis 1 Random fertilisation

• All living things produce more offspring than survive to adulthood • In spite of this, population sizes remain roughly constant • Variation exists among species • Characteristics can be passed on from one generation to the next

Disruptive - pressure toward the extremes creates 2 modal values Stabilising - pressure toward the centre increases the number of individuals at the modal value Directional - pressure toward one extreme moves the mode in this direction

• Formation of a new species • Requires 2 populations of the same species to become reproductively isolated • Isolation can be geographical (allopatric) • Isolation can be due to changes in reproductive mechanisms (sympatric)

• isolation involves mechanism acting before fertilisation (pre) and after fertilisation (post) to prevent successful reproduction • Natural selection reinforces reproductive barriers, strengthening isolation and promoting species divergence over time

• Occurs when cell division errors double chromosome sets, creating offspring with extra chromosomes • Reproductively isolated from diploids due to incompatible chromosome numbers • Often show increased size, stress tolerance, and altered flowering times, aiding survival and diversification • Can create new species within a single generation without geographic isolation, driving fast speciation

The study of principles behind the classification of organisms, according to their observable features or genetic characteristics A hierarchal grouping system, where each group is subdivided into smaller groups

Domain - Bacteria, archae, eukarya Kingdom Phylum Class Order Family Genus Species