Chromosomal Mutations

Question 1

What are the major types of chromosomal rearrangements? (5)

Answer 1

DDITT

deletions
duplications
inversions
translocation
transpositions

Question 2

DELETIONS

What are chromosomal deletions?

Answer 2

Chromosomal deletions involve deletion of more than one gene.

Question 3

Drosophila geneticists refer to deletions as ______ and use the abbreviation ____.

Answer 3

Drosophila geneticists refer to deletions as deficiencies and use the abbreviation Df.

Question 4

DELETIONS

What are causes of deletions?

Answer 4

• Incorrect repair of broken DNA
• incorrect reciprocal genetic exchange
• secondary consequences of chromosomal rearrangements

Question 5

DELETIONS

Chromosomal deletions also can occur from faulty meiotic crossing over, if the reciprocal exchange is __________.

Answer 5

Chromosomal deletions also can occur from faulty meiotic crossing over, if the reciprocal exchange is NOT reciprocal.

Question 6

DELETIONS

What are interstitial deletions?

Answer 6

Deletions that are in the interior.

Question 7

DELETIONS

Deletions can be _____ or _____.

Answer 7

Deletions can be terminal or interstitial.

Question 8

DELETIONS

All stable deletions are _______.

Answer 8

All stable deletions are interstitial with at least the telomere on the other side.

Question 9

DELETIONS

T or F: Different organisms tolerate deletions (deficiencies) to the same extent.

Answer 9

Different organisms tolerate deletions (deficiencies) to different extents.

In general, the more sophisticated the body of the adult, the MORE tolerant is the species of deletions (and duplications).

Question 10

DELETIONS

In general, the more sophisticated the body of the adult, the _____ tolerant is the species of deletions (and duplications).

Answer 10

In general, the more sophisticated the body of the adult, the MORE tolerant is the species of deletions (and duplications).

Question 11

DELETIONS

Between higher animals (vertabrates) and lower animals and plants, which tolerates deletions well?

Answer 11

Lower animals and plants tolerate deletions better than higher animals.

Question 12

DELETIONS

In general, the bigger the deletion, the more ______ the consequence.

Answer 12

In general, the bigger the deletion, the more serious the consequence.

Question 13

DELETIONS

Under what circumstance would a deletion homozygote survive?

Answer 13

In rare cases, when the deleted sequence contains no essential genes, a deletion homozygote may survive.

Question 14

DELETIONS

Most of the time, homozygosity for a deletion (Del/Del) is _____ in all eukaryotes.

Answer 14

Most of the time, homozygosity for a deletion (Del/Del) is LETHAL in all eukaryotes.

Question 15

DELETIONS

Individuals who are heterozygous for chromosomal deletion are essentially _____ for deleted genes.

Answer 15

Individuals who are heterozygous for chromosomal deletion are essentially hemizygous for deleted genes.

Question 16

DELETIONS

What are the consequences of hemizygosity for deletions?

Answer 16

Phenotype problems/consequences

Question 17

DELETIONS

The only way a diploid organism can survive a deletion of essential genes is if _____

Answer 17

The only way a diploid organism can survive a deletion of essential genes is if it carries a non-deleted wild type version on the homologous chromosome

*still can’t be too large deletion in heterozygote Del/+ (otherwise, lethal)

Question 18

DELETIONS

What is pseudo-dominance?

Answer 18

Pseudo-dominance is the unmasking of a recessive mutation

*Can be used to map genes that are v close together

Question 19

DELETIONS

What are some examples of humans who are heterozygous for chromosomal deletions?

Answer 19

• Cri du chat syndrome (cat-like cry in infants) due to deletion in chrosome 5
• microencephaly (small head)
• moon-like face
• mental retardation
• DeGeorge’s syndrome - a genetic disease that accounts for 5% of congenital heart defects

Question 20

DUPLICATIONS

Duplications are symbolized by ____.

Answer 20

Duplications are symbolized by Dp.

Question 21

DUPLICATIONS

What is a chromosome duplication?

Answer 21

Chromosome duplications - an extra copy of a region of a chromosome is present.

Question 22

DUPLICATIONS

How are duplications generated?

Answer 22

Same reasons as deletions:

• incorrect repair of double strand breaks in the DNA
• errors during meiosis for crossing over
• duplications created as a secondary consequence of chromosome rearrangements

Question 23

Which is usually more damaging: deletions or duplications?

Answer 23

Deletions are more damaging that duplications, but duplications still have negative effects.

Question 24

DUPLICATIONS

Small duplications do not have strong negative effects. There is then an extra, non-essential copy of the gene. If this extra copy does not have a negative effect on the organism, it often persists.

What is an example of a the evolutionary impact of gene duplication?

Answer 24

Vision proteins are a good example.

Question 25

INVERSIONS

What are inversions?

Answer 25

Inversions - a type of chromosome rearrangement in which no DNA is lost/gained but the order of some of the chromosome’s genes is reversed

Question 26

INVERSIONS

True or False: It is unusual to have a heterozygote for inversions.

Answer 26

False - It is unusual to have a HOMOZYGOTE for inversions.

This is because inversions are rare events and being homozygous for the same very rare inversion is highly unlikely.

Question 27

INVERSIONS

What are two types of inversions?

Answer 27

Pericentric inversion

Paracentric inversion

Question 28

INVERSIONS

What is a pericentric inversion?

Answer 28

Pericentric inversion - centromere is included in inverted region

Question 29

INVERSIONS

What is a paracentric inversion?

Answer 29

Paracentric inversion - an inversion in which the centromere is not in the inverted region

Question 30

INVERSIONS

When talking about paracentric inversions, why is crossover suppression an incorrect term?

Answer 30

Crossing over is not suppressed - the recovery of the crossover products are suppressed (RT offspring due to a lack of viability)

Even thought there may be a normal amount of crossing over, there is a reduced recombination freq in offspring bc the RTs are typically nonviable.

Question 31

INVERSIONS

What is the type of duplication that is generated by the crossing over of pericentric inversions?

Answer 31

Non-tandem duplication - the type of duplication that is generated by pericentric inveresions

Question 32

INVERSIONS

What is the acentric fragment?

Answer 32

It is…

Question 33

TRANSLOCATION

What are translocations?

Answer 33

Translocation - when broken piece of one chromosome is attached to a diff chromosome