1. Variation in chromosome structure and number

2. Short arm; For the French, petite
Long arm
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3. Genetic variation refers to differences between members of the same species or those of different species
Allelic variations are due to mutations in particular genes
Chromosomal aberrations are substantial changes in chromosome structure or number
These typically affect more than one gene
They are quite common, which is surprising
Cytogenetics -The field of genetics that involves the microscopic examination of chromosomes
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5. Human chromosome 1
Human chromosome 21

6. Deficiencies/ Deletion
A chromosomal deficiency occurs when a chromosome breaks and a fragment is lost
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7. Duplications
A chromosomal duplication is usually caused by abnormal events during recombination
A repetitive sequence contained multiple times can cause alignment where the alleles don’t actually match.
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8. Genes derived from a single ancestral gene
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9. Inversions
A chromosomal inversion is a segment that has been flipped to the opposite orientation
Centromere lies within inverted region
Centromere lies outside inverted region

10. Translocation

11. VARIATION IN CHROMOSOME NUMBER
Chromosome numbers can vary in two main ways
Euploidy
Variation in the number of complete sets of chromosome
Aneuploidy
Variation in the number of particular chromosomes within a set
Euploid variations occur occasionally in animals and frequently in plants
Aneuploid variations, on the other hand, are regarded as abnormal conditions
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12. Polyploid organisms have three or more sets of chromosomes
Individual is said to be trisomic
Individual is said to be monosomic

13. In most cases, these effects are detrimental
They produce individuals that are less likely to survive than a euploid individual
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14. Trisomics for individual chromosomes Datura stramonium

16. Genetic variation is a result of various types of changes at the molecular level
Changes in chromosome number
•Single chromosomes may be lost or gained
•A whole set of chromosomes may be inherited

17. Some human aneuploidies are influenced by the age of the parents
Older parents more likely to produce abnormal offspring
Example: Down syndrome (Trisomy 21)
Incidence rises with the age of either parent, especially mothers

18. Familial down Syndrome

19. Complete nondisjunction can produce an individual with one or more sets of chromosomes
This condition is termed autopolyploidy
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20. Interspecies Crosses
A much more common mechanism for changes in the number of sets of chromosomes is alloploidy
It is the result of interspecies crosses
Most likely occurs between closely related species
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21. An allodiploid has one set of chromosomes from two different species
An allopolyploid contains a combination of both autopolyploidy and alloploidy
An allotetraploid: Contains two complete sets of chromosomes from two different species
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22. AnaaAanand two copies of other chromosomes
Polyploids having an odd number of chromosome sets are usually sterile
These plants produce highly aneuploid gametes
Example: In a triploid organism there is an unequal separation of homologous chromosomes (three each) during anaphase I
Anaphase I of meiosis
AnaaAanand two copies of other chromosomes

23. All four gametes are abnormal
During fertilization, these gametes produce an individual that is trisomic for the missing chromosome
During fertilization, these gametes produce an individual that is monosomic for the missing chromosome
All four gametes are abnormal
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24. 50 % Abnormal gametes 50 % Normal gametes
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25. This cell will be trisomic This cell will be monosomic
This cell will be normal
Will be degraded if left outside of the nucleus when nuclear envelope reforms

26. No synapsis between the 9 radish and 9 cabbage chromosomes
Proper synapsis between the 18 radish chromosomes
and the 18 cabbage chromosomes
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27. Octoploid strawberries

28. Hexaploid wheat

29. Triploid seedless fruits

30. Asian carp is a polyploid, a mix of four species, the bighead carp, the black carp, the grass carp, and the silver carp.

31. Mule is a result of a cross between a male donkey (Chr# 62) & a female horse (Chr# 64)