Variations In Chromosome Structure 34-38 Flashcards

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1
Q

What does 1 or more breaks in the chromosome do (possibly by unequal recombination)?

A
  • free ends of DNA unstable
    —-> can be degraded by exonuclease
    —-> can bond with other free ends (sometimes telomeres)
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2
Q

What is a Deletion?

A

-loss of segment
-break, then degredation

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3
Q

What is Intercalary Deletion?
What is Terminal Deletion?

A

ABC.DEFG —> ABC.DG
ABD.DEFG —> ABC.DE

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4
Q

What happens if you delete dominant allele?
What happens if gene dosage occurs?
What happens during meiosis prophase I?

A

expression of recessive allele
haploinsufficiency
looped out structure

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5
Q

What is a Duplication?

A

-2 copies of chromosomal segment

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6
Q

What is Tandem Duplication?
What is Reverse Tandem Duplication?
What is Displaced Duplication?

A

ABC.DEFG —> ABCBC.DEFG
ABC.DEFG —> ABC.DEFFEG
ABC.DEFG —> ABC.DEFGBC

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7
Q

What causes phenotypic changes in Duplication?

A

-gene dosage effects
-break in the middle destroys function
-looped structure during meiosis prophase I (loop in mutant only)

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8
Q

What is an Inversion?

A

-chromosomal segment turns around

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9
Q

What is a Paracentric Inversion?
What is a Pericentric Inversion?

A

ABC.DEFG —> ABC.DGFE
ABC.DEFG —> ABD.CEFG
AB.CDEFGH —> AEDC.BFGH

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10
Q

What causes phenotypic changes in Inversions?

A

-gene expression altered —> position effect
-break in the middle destroys function
-inversion loop during meiosis prophase I
-Hets for gametes usually have gamete issues

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11
Q

What is crossing over in Inversions?

A

-abnormal gametes
–> dicentric + acentric if PARA
–> duplicates + deletion if PERI

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12
Q

What is Translocation?

A

-movement of DNA between non-homologous chromosomes

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13
Q

What are Reciprocal Translocations?
What are Simple Translocations?

A

ABC.DEFG
HI.JK
—>
ABC.DEK
HI.JFG

ABC.DEFG
HI.JK
—>
A.DEFG
HBCI.JK

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14
Q

What causes phenotype changes in Translocations?

A

-gene expression may be altered –> position effect
-break in the middle of gene destroys function
-can lead to deletions

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15
Q

What type of deletions can Translocations cause?

A

unbalanced - DNA deleted after break & before translocation
balanced - no DNA deleted after break & before translation (normal phenotype likely)

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16
Q

What are Robertsonian Translocations?

A

-result from fusion of 2
- do not usually produce abnormal phenotypes
-p arms contain many copies of rRNA genes only

17
Q

What are the acrocentric chromosomes in Humans?

A

13,14,15,21,22