CH 23 (CH 4) Flashcards
genome
- an organisms full set of genes as well as any non-coding regions of DNA (for some viruses it is RNA)
The study of Molecular evolution
investigates the mechanisms and consequences of the evolution of macromolecules
Ways in which genes evolve:
- Nucleotide substitutions which can result in amino acid replacements in
proteins - Changes in amino acids can result in changes in secondary and tertiary
structures of proteins - the longer two sequences have been evolving separately., the more differences they accumulate
structure of protein
just the chain
Alpha helix or beta pleated sheet (based on the interactions of amino acids. Proline causes kinks!)
Alpha helix and beta pleated sheet together (basically, the final folding of the proteins based on r groups, charges, polarity and hydro attractions)
Multiple proteins together like hemoglobin (4 units)
to find homologous chromosomes
(same series of genes in multiple organisms)
- use sequence alignment (line up the chromosomes essentially)
similarity matrix
counting the number of nucleotides or amino acids that differ between two sequences
LOOK AT THE IMAGE
multiple substitutions:
more than one genetic change at a given position
Coincident substitutions
at a given position different substitutions occur between ancestor and each descendant
Parallel substitutions
the same substitution occurs independently between the ancestor and both descendants
Back substitutions
is where the ancestral form changed at a point, then changed back
SEE DIAGRAM OF EVOLUTION OF GENES
PLEASE
synonymous or silent substitution
unlikely to be influenced by natural selection
Occur 5x more often in proteins encoding regions than non-synonymous mutations
when amino acid isn’t changed but nucleotide is
Non-synonymous substitution
nucleotide changes causes codon change
Likely to be deleterious to organism
Does not always alter protein shape and size
much of evolution is
neutral
mutations can be
good or bad
- if bad, they are removed through natural selection
- if good, they are fixed so no population varies
mechanisms of molecular evolution?
non coding DNA, gene duplication, gene family, concerted evolution via 2 mechanisms,
non coding DNA
They hold space open that can be important for the timing of genes, where things bind (transcription factors). There needs to be an amount of space between genes to activate them
Also can sometimes regulate how and when genes become active. How much unravelling of DNA occurs for transcription and translation
Adds to evolutionary potential when natural selection happens, there might be a mutation or something that can be transcribed leading to a new trait
gene duplication
Two of the same gene, will yield two copies of the same protein is gene duplication
Usually, two new coding sections can evolve on their own (won’t stay identical and make the same two protein each time gene is activated)
1. both retain function
2. One gets made in neurons vs. Muscles or Time wise, one can be in development vs the other in adult years
3. You don’t need both so body deactivates it
4. Proteins both do different thing
At first, it usually does only 1 but as they evolve, it will fall into one of the three categories
several successful rounds of duplication and mutation may result in
a gene family
gene family
group of homologous genes with related functions
Concerted evolution
multiple copies of genes within a species evolve together
happens through unequal crossing over in meiosis resulting in more copies of genes on chromosome and
biased gene conversion (damage is repaired using another homologous sequence resulting in resulting in two copies of the same chromosome.
SEE DIAGRAM
gene tree
shows the evolutionary relationships of a single gene in different species or of the members of a gene family
Homologs
genes that are similar as a result of a common ancestry
Orthologs
genes found in different species, and whose divergence can be traced back to the speciation event that gave rise to various species
Paralogs
genes in the same or different species that are related through duplication events
Bioprospecting
the search for naturally occurring compounds that can be used for pharmaceutical, agricultural, or industrial purposes
In vitro evolution
new molecules are produced in the laboratory to perform novel and useful functions
To study and combat disease
understanding how and when viruses and bacteria have evolved and mutated
how can genome be diverse
-Mistakes in DNA replication (mutations) provide material for evolutionary
change
- Genes of an organism can be looked at as interacting members of a group (different dependencies, expressions locations)
- The positions of genes and their sequences are subject to evolutionary change
GENE FAMILY
group of homologous genes with a similar function
