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Evolution Lecture 3
Terms in this set (19)
What is blending inheritance and why does it cause a problem?
Blending inheritance is literally a combination of both the parents' characteristics (Tall man with short woman) will reproduce medium height child; this poses a problem because it eliminates variation
*Note that resemblance of parents and their offspring is an important observation but it's important for natural selection.
Who was Gregor Mendel?
He proposed that determinants of inheritance are units that retain their identity over generations rather than breaking up or blending (B, b)
Dominant Allele: B <----- These will always be manifested
Recessive Allele: b
Why was Mendelian genetics a problem for natural selection?
Mendel's genes were discontinuous; it seemed as if new variants could arise only by discontinuous jumps
If new species were formed in a sudden jump, what role could natural selection play?
There's little opportunity for natural selection to play a role in speciation; no natural selection meant no Darwinism
How do we distinguish continuous variation/traits from discontinuous variation/traits?
Continuous variation like height was a combination of many separate genes but each of those genes might behave in mendelian fashion
Each gene only add to a small amount to the overall height or any character state; many genes contribute to characters; each genes can be mendelian but you have everything working together (in this way, it's continuous without mendel's discontinuous genes & you maintain variability & natural selection)
If variation and natural selection are working which leads to an accumulation of small changes over time then what might occur?
Adaptation and possible speciation
When was the structure of DNA known?
What genetic material relays information from parents to offspring?
The sequence of nucleotides (ATGC)
If there's a change in DNA leading to changes in proteins what happens?
Changes in function occur
How did Dobzhansky define evolution?
A change in the frequency of an allele within a gene pool
*Changes of an allele in the gene pool meant there's evolution
What can change the genetic composition of a population?
What is assortative mating?
Alleles are paired non-randomly
What is non-assortative mating?
Alleles are paired randomly
Is the composition of a finite population subject to change and why?
Yes, because it is finite.
True or False: Changes in allele frequencies are subject to chance even when the probabilities of change are constant.
TRUE! Why? because allele frequencies are not set in stone. They can change at any given moment.
Also know that in smaller populations, there is a stronger effect of chance.
In Hardy-Weinberg, nothing is evolving; thus, what is necessary for a population not to evolve? (Hint: there's 5 assumptions)
No natural selection
Infinitely large population
*If a population is not @ Hardy-Weinberg Equilibrium, then some evolutionary process must be occurring
Where do rare alleles mostly occur?
In Heterozygotes; heterozygotes carry the lethal genes though it's not present phenotypically
Where do common alleles mostly occur?
In Homozygotes; dominant alleles are usually manifested in homozygotes
Note to remember:
Chance plays an important role in small populations
Advantageous genes don't really get passed on in small populations especially when they are rare
Small populations lose genetic variation easily
The loss of variation reduces their ability to respond to natural selection
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