Genetics: Chromosome Changes In Number And Structure

Front 1

Euploid

Back 1

Multiples of complete genomes or chromosome sets.
2n = diploid
3n = triploid

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Trisomy

Back 2

Having three of one chromosome.
(2n + 1)

Front 3

Aneuploidy

Back 3

Deviations not multiples of the normal haploid number, too much or too little of some genetic info.
Ex:
Nullisomic: (2N-2)
Monosomic: (2N-1)
Doubly Monosomic: (2N-1-1)
Trisomic: (2N+1)
Tetrasomic: (2N+2)
Doubly Tetrasomic: (2N+2+2)
Autosomal: 13, 18, 21
and Sex chromosomes

Front 4

Autopolyploids

Back 4

Karyotype is comprised of chromosomes from one species.

Front 5

Allopolyploids

Back 5

Karyotype is comprised of chromosomes from more than one species.

Front 6

Chromosome Doubling

Back 6

Results from nondisjunction of sex stem cells in mitosis and then is divided by meiosis to give gametes with 2x as much alleles.

Front 7

Acentric Fragment

Back 7

Without a centromere, lacks a kinetochore and is unable to attach to spindle fibers during cell division, lost during division.

Front 8

Terminal Deletion

Back 8

Chromosome break that detaches one arm of the chromosome.
Ex: Cri-Du-Chat Syndrome

Front 9

Interstitial Deletion

Back 9

Loss of an internal segment of a chromosome that results from two chromosome breaks.
Ex: WAGR Syndrome

Front 10

Psuedodominance

Back 10

Genetic phenomenon that occurs when the recessive allele is expressed because the dominant allele on the homologous chromosome has been deleted.

Front 11

Duplication

Back 11

Result from unequal cross-over, 2x the amount of genetic info.

Front 12

Paracentric Inversion

Back 12

An inversion of a segment on a chromosome that does not involve the centromere.

Front 13

Pericentric Inversion

Back 13

An inversion of a segment on a chromosome that involves the centromere and reorients it.

Front 14

Dicentric Bridge

Back 14

During meiosis, an inverted heterozygote produces an abnormal dicentric chromosome with 2 centromeres. Eventually splits at a random break point from tension, losing an acentric fragment, and produces 2 normal chromosomes and 2 nonviable deletion products.

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Inversion Heterozygote

Back 15

An individual with one normal chromosome and one inverted chromosome.

Observations about Recombination:
1. Probability of cross over = size of inversion loop
2.Inversion suppresses the production of recombinant chromosomes (viable vs. nonviable)
3.Fertility may be altered if an inversion heterozygote carries a very large inversion.

Front 16

Crossover Suppression

Back 16

Absence of recombinants from inversion heterozygotes because of deletions and duplications produce nonviable chromosomes.

Front 17

Translocation Heterozygote

Back 17

An individual with a chromosome break that attached to a nonhomologous chromosome.Two homologous pairs with one normal chromosome and one altered chromosome. Has same amount of DNA info, no effect to phenotype.

Front 18

Semisterility

Back 18

Individuals with abnormal chromosomes may be affected by semisterility, because of the production of viable and nonviable chromosomes.

Front 19

Unbalanced Translocation

Back 19

One chromosome segment breaks off and is attached to a nonhomologous chromosome.

Front 20

Reciprocal Translocation

Back 20

When two chromosome segments break and are attached to each other's nonhomologous chromosome.
No loss of DNA and same size.

Front 21

Robertsonian Translocation

Back 21

-Fused chromosome
One chromosome breaks at the centromere and attaches to the end of a nonhomologous chromosome. The small p arm and centromere are lost.

Front 22

Adjacent-1 Segregation

Back 22

Tetravalent complex in metaphase 1 pairs horizontally, ~50%, all nonviable

Front 23

Alternate Segregation

Back 23

Tetravalent complex in metaphase 1 pairs kiddy corner to each other, ~50%, all viable