1. 1. Unequal Crossing-Over a. process: If homologs line up askew:
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
1. Unequal Crossing-Over
a. process:
If homologs line up askew: A B a b

2. 1. Unequal Crossing-Over a. process: If homologs line up askew
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
1. Unequal Crossing-Over
a. process:
If homologs line up askew
And a cross-over occurs A a b B

3. 1. Unequal Crossing-Over a. process: If homologs line up askew
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
1. Unequal Crossing-Over
a. process:
If homologs line up askew
And a cross-over occurs
Unequal pieces of DNA will be exchanged… the A locus has been duplicated on the lower chromosome and deleted from the upper chromosome A a b B

4. 1. Unequal Crossing-Over a. process: b. effects: - can be bad:
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
1. Unequal Crossing-Over
a. process:
b. effects:
- can be bad:
deletions are usually bad – reveal deleterious recessives
additions can be bad – change protein concentration

5. 1. Unequal Crossing-Over a. process: b. effects: - can be bad:
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
1. Unequal Crossing-Over
a. process:
b. effects:
- can be bad:
deletions are usually bad – reveal deleterious recessives
additions can be bad – change protein concentration
- can be good:
more of a single protein could be advantageous
(r-RNA genes, melanin genes, etc.)

6. 1. Unequal Crossing-Over a. process: b. effects: - can be bad:
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
1. Unequal Crossing-Over
a. process:
b. effects:
- can be bad:
deletions are usually bad – reveal deleterious recessives
additions can be bad – change protein concentration
- can be good:
more of a single protein could be advantageous
(r-RNA genes, melanin genes, etc.)
source of evolutionary novelty (Ohno hypothesis )
where do new genes (new genetic information) come from?

7. Gene A
Duplicated A
generations
Mutation – may even render the protein
non-functional
But this organism is not selected against, relative to others in the population that lack the duplication, because it still has the original, functional, gene.

8. Gene A
Duplicated A
generations
Mutation – may even render the protein
non-functional
Mutation – other mutations may render the protein functional in a new way
So, now we have a genome that can do all the ‘old stuff’ (with the original gene), but it can now do something NEW. Selection may favor these organisms.

9. If so, then we’d expect many different neighboring genes to have similar sequences. And non-functional pseudogenes (duplicates that had been turned off by mutation).
These occur – Gene Families

10. And, if we can measure the rate of mutation in these genes, then we can determine how much time must have elapsed since the duplication event…
Gene family trees…

11. Mechanism #1: Exon Shuffling
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
E. Change in Gene Structure
Mechanism #1: Exon Shuffling
Crossing over WITHIN a gene, in introns, can recombine exons within a gene, producing new alleles.
Allele “a”
EXON 1a
EXON 2a
EXON 3a
Allele “A”
EXON 1A
EXON 2A
EXON 3A

12. Mechanism #1: Exon Shuffling
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
E. Change in Gene Structure
Mechanism #1: Exon Shuffling
Crossing over WITHIN a gene, in introns, can recombine exons within a gene, producing new alleles.
EXON 1a
EXON 2a
EXON 3a
Allele “a”
EXON 1A
EXON 2A
EXON 3A
Allele “A”
Allele “α”
Allele “ά”

13. 1. Mechanism #1: Exon Shuffling 2. Mechanism #2: Point Mutations
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
E. Change in Gene Structure
1. Mechanism #1: Exon Shuffling
2. Mechanism #2: Point Mutations
a. addition/deletion: “frameshift” mutations
…T C C G T A C G T ….
Normal
…A G G C A U G C A …
ARG
HIS
ALA
Mutant: A inserted
…T C C A G T A C G T ….
…A G G U C A U G C A …
SER
CYS
DNA
m-RNA
Throws off every 3-base codon from mutation point onward

14. 1. Mechanism #1: Exon Shuffling 2. Mechanism #2: Point Mutations
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
E. Change in Gene Structure
1. Mechanism #1: Exon Shuffling
2. Mechanism #2: Point Mutations
a. addition/deletion: “frameshift” mutations
b. substitution
… T C C G T A C G T ….
Normal
…A G G C A U G C A …
DNA
m-RNA
ARG
HIS
ALA
Mutant: A for G
…T C C A T A C G T ….
…A G G U A U G C A …
TYR
At most, only changes one AA (and may not change it…)

15. Sources of Variation Causes of Evolutionary Change
VI. Mutation
Overview
Changes in Ploidy
Changes in ‘Aneuploidy’ (changes in chromosome number)
D. Change in Gene Number/Arrangement
E. Change in Gene Structure
F. Summary
Sources of Variation Causes of Evolutionary Change
MUTATION: Natural Selection
-New Genes: 
point mutation  Mutation (polyploidy can make new
exon shuffling  species)
RECOMBINATION:
- New Genes:
crossing over
-New Genotypes:
independent assortment
VARIATION