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Genetics HW Chapter 8

What is the difference between a paracentric and pericentric inversion?

Paracentric inversion does not include the centromere; pericentric does.

How do translocations produce phenotypic defects?

Like inversions, translocations can produce phenotypic effects if the translocation breakpoint disrupts the gene or if the gene near the breakpoint is altered in its expression because of relocation to a different chromosomal environment (position effect).

What is the difference between primary and familial Down syndrome? How does each type arise?

Primary Down syndrome is caused by spontaneous, random nondisjunction of chromosome 21, leading to Trisomy 21. Familial DS arises from Robertsonian translocation between chromosome 21 and 14. Translocation carriers do not have DS, but their children have an increased incidence of it. If the translocated chromosome segregates with a normal 21, the gametes will have two copies of chromosome 21 and result in DS

Why do extra copies of genes sometimes cause drastic phenotypic effects?

The expression of some genes is balanced with the expression of other genes. The ratio of different gene products should be maintained within a range to ensure proper cellular function. Extra copies of one of the genes results in over expression of the gene product and throws off the balance

What type of Chromosome mutation increase the amount of genetic material in a particular chromosome?

duplication

What type of Chromosome mutation increase the genetic material in all chromosomes?

polyploidy

What type of Chromosome mutation decrease the amount of genetic material in a particular chromosome?

deletion

What type of Chromosome mutation change the position of DNA sequence without changing the amount of genetic material?

inversion

What type of Chromosome mutation move DNA from one chromosome to a non-homologous chromosome?

translocation

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B E * F G

deletion

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A E D C B * F G

segment BCDE is inverted 180 degrees; but as the centromere has not changed position it is PARACENTRIC INVERSION.

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B A B C D * F G

tandem duplication of segment AB

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B * E D C B G

PERICENTRIC INVERSION, as the gene order and centromere position have changed

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B C D E E D C * F G

duplication and paracentric inversion

A chromosome has the following sequence where * represents the position of the centromere;
A B * C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B A B * C D E F G

tandem duplication of AB

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B * C D E A B F G

displaced duplication of AB

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B * C F E D G

paracentric inversion of DEF

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A * C D E F G

deletion of B

A chromosome has the following sequence where represents the position of the centromere; A B C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B * C D E

deletion of FG

A chromosome has the following sequence where * represents the position of the centromere;
A B * C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B * E D C F G

paracentric inversion of CDE

A chromosome has the following sequence where * represents the position of the centromere;
A B * C D E F G.
What types of mutation is necessary to change this chromosome into the following?

C * B A D E F G

pericentric inversion of ABC

A chromosome has the following sequence where * represents the position of the centromere;
A B * C D E F G.
What types of mutation is necessary to change this chromosome into the following?

A B * C F E D F E D G

duplication and inversion of DEF

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