Molecular Homology (11.1) Flashcards
State what evidence was used prior to molecular techniques to determine relatedness between species
Morphological and functional similarities
Describe homologous features
Features that are similar because the organisms share a common ancestor
Describe analogous feautres
Features that have similar structures and functions bu t have evolved independently and do not share a recent common ancestor
State what analogous features are a result of
Convergent evolution
State what homologous features are retain through
Divergent evolution
Describe divergent evolution
The evolution of two or more different species from a common ancestral species
Describe convergent evolution
The evolution of similar features in unrelated groups of organisms (which do not share a common ancestors)
State what 2 things similar features can result from
- Shared ancestry (homologous)
2. Independent evolutionary paths (analogous)
State what a similar set of what three things provides evidence of a common ancestor
- Proteins
- Chromosomes
- DNA sequences
State what all organisms on Earth once shared
A common ancestor
State what would occur if two populations become isolated from each other
They will accumulate different mutations in their DNA
State what occurs to the sequences of nucleotides in the DNA of organisms in isolated populations
It becomes more different and what was once similar DNA gradually diverges
State what the more mutations that accumulate in DNA sequences between two species is evidence of
The greater the time that has passed since the two species diverged from their common ancestor
State what changes in nucleotide sequences are caused by
Mutations
State what may occur when a cell copies its’ DNA
Errors may occur
State what generally occurs to errors that are made by cell DNA is copies
Repair of these errors prior to mitosis
State what occurs occasionally when errors in copied DNA are not repaired prior to mitosis
Errors become a permanent part of the genome
State what errors in copied DNA that become a permanent part of the genome are referred to as
Mutations
State what will occur if mutations occur within the germ line cells of an organisms
The mutations will be passed on to the next generation
State whether or not mutations occur regularly
Yes. Mutations occur regularly as a species evolves
State an alternative term to describe the regular occurrence of mutations in the germline cells of an organism
‘molecular clockwork’
State what occurs in relation to mutations as time passes
Mutations accumulate in genetic differentiation and divergence of species
State what will occur when two species diverge from a common ancestor
They accumulate different mutations in their DNA
State what occurs when two species accumulate different mutations in their DNA
They start accumulating differences in the amino acid sequences of their proteins
Describe the trend that follows an increase in time passed and differences in the amino acid sequences of species
The greater the time that has passed, the more differences there are between their amino acid sequences of species which have diverged from a common ancestor
State whether or not point mutations, in the DNA sequences always cause a difference in the amino acid sequence
No. Point mutations in the DNA sequence may not cause a difference in the amino acid sequence.
State why point mutations in the DNA sequence may not always cause a difference in the amino acid sequence
The genetic code is degenerate
State whether or not a point mutation that leads to a change in an amino acid may lead to a change in phenotype
No. Changes in the amino acid structure do not always cause a change in phenotypical structure.
State what the effect an amino acid substitution has on the function and structure of a protein is dependent on
How biochemically similar the substituted amino acid is to the original amino acid in properties such as size, hydrophobicity and charge
State what an amino acid when it is substituted for another with biochemically similar properties is called
A conservative substitution
Describe conservative substitution
A change in the nucleotide sequence of DNA or RNA that leads to the replacement of one amino acid with a functionally similar one
State whether or not a conservative substitution causes a change in the protein
A conservative substitution does not cause a change in the protein produced
Describe a semi-conservative substitution
A replacement of an amino acid with one that has a similar shape but different biochemical properties
State what a semi-conservative substitution leads to
Possible change in protein structure and function
Describe a non-conservative substitution
A substitution of one amino acid with another that has different biochemical properties
State what a non-conservative substitution leads to
Major changes in protein structure and function
State what the order of nucleotides in the DNA indicates
Evolutionary relationship between species
State whether or not it is more accurate to determine the evolutionary relationship between species by analysing the order of nucleotides in DNA
Yes. Compared to the amino acid sequence.
Describe homology
Similarity in structure between parts of different organisms due to evolutionary differentiation from a corresponding part in a common ancestor
