Chromosome Aberrations

Question 1

deletion

Answer 1

missing part of a chromosome

Question 2

Cri du chat

Answer 2

human disorder due to missing part of the short arm of one copy of chromosome 5

Question 3

terminal deletion

Answer 3

single break in the chromosome so the end is separated from the rest
an acentric fragment will be produced

Question 4

acentric fragment

Answer 4

piece of chromosome that does not have a centromere
resulting from deletion
these will be lost during cell division

Question 5

insterstitial deletion

Answer 5

a segment of the chromosome that is not at the end is deleted
requires 2 breaks and then the chromosome is resealed
an acentric fragment will be produced

Question 6

compensation loop

Answer 6

created during synapsis in meiosis in heterozygous individuals (those with one normal chromosome and one chromosome with a deletion)
one of the chromosomes pokes out (the one without deletion) as this region doesn’t have a homologous region to synapse to

Question 7

haploinsufficiency

Answer 7

single copy of gene is not enough to allow the wild-type phenotype to occur

Question 8

pseudodominance

Answer 8

expression of normally recessive phenotype because their is no homologous allele due to deletion

Question 9

effects of deltions

Answer 9

• acentric fragments are lost
• imbalance in the amount of gene products produced
• deletion of normal allele on one chromosome may allow the recessive allele on the homolog to be visible causing mutant

Question 10

Normal: AB.CDEFG
Duplication: AB.CDEFDEF

Answer 10

Tandem

Question 11

Normal: AB.CDEFG
Duplication: AB.CDEFFEDG

Answer 11

Reverse Tandem

Question 12

Normal: AB.CDEFG
Duplication: AB.CDEFGDEF

Answer 12

Homobrachial Displaced

Question 13

Normal: AB.CDEFG
Duplication: DEFAB.CDEFG

Answer 13

Heterobrachial Displaced

Question 14

duplication

Answer 14

extra copies of a part of a chromosome

Question 15

tandem duplication

Answer 15

the duplicated copy is next to the original with the same gene order

will form compensation loop

Question 16

reverse tandem duplication

Answer 16

the duplicated segment is next to the original but in backwards order

Question 17

displaced homobrachial

Answer 17

same arm

the duplicated segment is on the same arm of the chromosome but not next to the original

Question 18

displaced heterobrachial

Answer 18

not adjacent to the original and on the other arm

Question 19

unbalanced gene dosage

Answer 19

changes phenotype

ex. Bar eye mutation in drosophila - duplication leads to fewer eye facets and narrower shape

Question 20

Susumu Ohno

Answer 20

duplications are essential to origin of new genes in a species

• one copy of each gene is essential to survival and therefore cannot accumulate mutation
• however the duplicated can and may develop a different function overtime which may become essential to the species as it evolves

Question 21

inversions

Answer 21

segment of chromosome is removed, turned 180 degrees, and reinserted into chromosome

Question 22

paracentric inversion

Answer 22

• inverted area does not include centromere

- doe not change arm ratio of chromosome

Question 23

pericentric inversion

Answer 23

• inverted area does include centromere

- can alter arm ratio

Question 24

synapsis of homolog when one has an inversion create a…

Answer 24

inversion loop

Question 25

Does crossing over occur in inversion?

Answer 25

crossing over still occurs in an inversion lopp, but recombinant products are inviable
duplication and deletion result

Question 26

dicentric bridges

Answer 26

• common in anaphase I when crossover occurs in a paracentric inversion loop
• occur when a chromosome has 2 centromeres

Question 27

What leads to speciation?

Answer 27

Inversions

• individuals who are homozygous for either the original or the inverted produce more viable gametes than the heterozygote.
• this favors both extremes leading to disruptive selection

Question 28

Evoutionary significance of inversion

Answer 28

• suppress crossover as the result are often not viable

- may lead to speciation

Question 29

reciprocal translocation

Answer 29

two nonhomologous chromosome exchange are or parts of arms

there is no gain or loss of DNA

Question 30

non-reciprocal translocation

Answer 30

a segment from one chromosome is moved to a nonhomologous chromosome

no overt gain or loss of DNA

Question 31

Robertsonian translocations

Answer 31

two telocentric/nearly telocentric chomosomes combine to make one large, more metacentric chromosome

lose a bit of DNA that is not usually noticeable

Question 32

isochromosome

Answer 32

two chromosomes joined are homologs

Question 33

An individual who is a translocation carrier produces…

Answer 33

half viable gametes

half non-viable gametes

Question 34

An example of robertsonian translocation

Answer 34

familial down syndrome

joining of chromosome 14 and 21 or compound chromosome of 21

Question 35

The individual with familial down syndrome has…

Answer 35

46 chromosomes

3 copies of information from chromosome 21

Question 36

The parent with robertsonian translocation has…

Answer 36

45 chromsomes
normal phenotype
2 copies of chromosome 21

Question 37

Chronic Myelogenous Leukemia

Answer 37

fatal, uncontrolled replication of myeloid stem cells

reciprocal translocation involving chromosome 9 and 22 results in fusion of 2 oncogenes whose protein product causes uncontrolled replication

ex of impact of reciprocal translocation

Question 38

Burkitt’s Lymphoma

Answer 38

abnormal function of B cells

reciprocal translocation between 8 and 14 places c-myc next to an enhancer which normally stimulates production of immunoglobin

Question 39

position effect

Answer 39

same genes are present but chromosomal location alters the phenotype