Chapter 11 Flashcards
(8 cards)
Origin of mitochondria and their features
Mitochondria are believed to have existed as aerobic bacterium which were engulfed by eukaryotic unicells
Mitochondria have their own circular DNA which replicate independently, have their own mitochondria, divide by binary fission, and a double-membrane
mtDNA passes from mother to children, generation after generation (not affected by recombination in meiosis)
D-loop
D-loop is a non-coding region which has two hypervariable region (undergo mutations at a higher rate) HVR1 HRV2
Haplotype/ haplogroup
A person’s haplotype is determined by the sequence of the D-loop
A group of haplotypes= haplogroup
Comparing proteins
Comparing proteins
All organisms’ proteins are composed from the same 20 amino acids, meaning that the genetic code that carries the information for making these proteins is essentially the same in all organisms
Species that are more closely related have less differences in amino acid sequences than if compared to a species that is more distantly related (the more time available for changes to occur in protein)
Examples: haemoglobin beta chain and cytochrome c (ETC)
Comparing DNA
Comparing DNA
Sequences: those most closely related will show more similarities in the base sequences of common genes
Gene conservation doesn’t mean that the DNA sequence of the genes in related species will be identical, however very similar
Whole genomes: compare different genomes to clarify evolutionary history, similarity
DNA hybridisation: DNA is taken from two species, heated so they become single stranded and re-paired, the temperature at which the double stranded DNA shows similarity between two species, for every 1 degree Celsius lower means a 1% difference in DNA sequence (94)
The fewer the mispairings the more closely related (mispairings require less heat to break)
Comparing chromosomes
Chromosome banding (bands compared, homologous) and chromosome painting (FISH binds to specific gene sequences, used for comparison, homologous regions)
Molecular clock
changes in amino acid sequence happen at a steady rate, thus enabling us to determine how long ago two species had shared a common ancestor
But different proteins change at a different rate, rate of change also depends on the different species (e.g. may be slower in plants than in animals)
Phylogenetic trees and cladograms
Phylogenetic trees- show inferred evolutionary relationships (shows where extinction occurs)
Useful for organising information about diversity, classification and evolutionary history
Cladogram- organisms organised based on the presence of novel features of ancestors (shows extinct groups)
