Sex Chromosome/Structural Abnormalities

Question 1

How is gender determined in mammals

Answer 1

Presence of the Y chromosome, specifically the SRY region

Question 2

What are Barr bodies

Answer 2

An inactive highly condensed X chromosome

Question 3

of chromosomes=?

Answer 3

of Barr bodies plus 1

Question 4

How are Y bodies detected

Answer 4

Quinacrine staining

WBC or Buccaneers mucosa

Question 5

What is the Lyon Hypothesis and when does it occur

Answer 5

Condensed X chromosomes are inactive with the exception of a few genes.

Inactivation occurs at the blastocyst stage of the being and the choice is random

Question 6

Unfavorable Lyonization

Answer 6

When a large majority of either parental or maternal X chromosomes are inactive rather than even deactivation

Question 7

Who does Klinefelter Syndrome Affect

Answer 7

Males

1/1000

Question 8

What is the Karotype of Klinefelter Syndrome

Answer 8

XXY/XXXY/XXXXY/

Also have mosaics 46XY/47XXY

The more X chromosomes, the more normal the individual

Question 9

Are no mosaic Klinefelter patients reproductively viable

Answer 9

No

Question 10

Who is affected in 47XXY syndrome and when does the error occur

Answer 10

Males (1/1000) and paternal NDJ in MII

Question 11

Who does trisomy X affect and what are its characteristics

Answer 11

.1% of all females
Normal fertility
Offspring typically normal
Maternal MI error

Question 12

Turner Syndrome, Karotype, and associated issues

Answer 12

45,X
Only Monosomic affiliated with life
Webbed neck and shield chest
No Barr bodies present

Question 13

What is significant about Turners syndrome

Answer 13

All XR alleles are expressed

Issues arise in paternal meiosis

Question 14

Why is high lethality seen in utero, but postnatal survival is close to normal in Turner Syndrome patients

Answer 14

Because only 1 X chromosome a active anyway

Question 15

What is the cause of structural chromosome rearrangements

Answer 15

Chromosome breakages with a reunion in a different configuration

Can be balanced or imbalanced

Question 16

A centric chromosome

Answer 16

A chromosome with out a centromere

These are typically lost

Question 17

Translocation

Answer 17

Transfer of genetic material from one chromosome to another

Question 18

Reciprocal translocations

Answer 18

Involve breakage of 2 no homologous chromosomes with the exchange of fragments

Question 19

Which balanced reciprocal translocations are relatively common

Answer 19

Ones involving chromosome 11 and 22

Question 20

What is the risk for reciprocal translocations of having an abnormal offspring

Answer 20

1-10%

Question 21

The Philadelphia Chromosome causes what disease

Answer 21

Chronic myelogenous leukeia

Example of a reciprocal translocation

Question 22

Robertsonian Translocation

Answer 22

Reciprocal translocations between Acrocentric chromosomes (13-15, 21,22) with the loss of the short arm from both participant

Question 23

What is the chromosome number after a Robertsonian translocation

Answer 23

45

Question 24

Why is a Robertsonian translocation still considered a balanced translocation

Answer 24

Because the loss includes genes that are present in multiple copies throughout the genome

Question 25

Short arms of the Acrocentric chromosomes contain what

Answer 25

Tandem repeats of rRNA

Question 26

Which chromosomes are most commonly associated with the Robertsonian translocation

Answer 26

The locus ion of the long arms of 13 and 14

Question 27

Translocation Down syndrome

Answer 27

Downs where the offspring inherits 2 copies of chromo 21 plus a translocation chromosome involving 21

Question 28

Balanced Reciprocal Translocations and offspring viability

Answer 28

1. Both normal progeny as well as balanced carriers are present
2. Carriers are asymptomatic, but produce unbalanced gametes that result in partial Monosomic and Trisomic zygotes

Question 29

Robertsonian Translocations and offspring viability

Answer 29

1. Normal as well as balanced carrier progeny

2. Carriers are asymptomatic but produce offspring that are full Monosomic or Trisomic

Question 30

Deletions of how much of the haploid genome are lethal

Answer 30

2%

Question 31

Terminal deletions

Answer 31

A deletion where the lost part of the chromosome includes the end of the chromosome

When this happens, the centric portion is lost while a telomere forms on the centric portion of the broken end

Question 32

Examples of diseases of terminal deletions 1

Answer 32

Wold-hirschborn syndrome (4p) severe mental retardation

Question 33

Examples of diseases of terminal deletions 2

Answer 33

Cri-du-chat syndrome (5p) distinctive “mewing” cry, microencephaly, severe mental retardation

Question 34

Interstitial deletions

Answer 34

Deletions resulting from two breaks on the Same chromosome. Larger fragments can rejoin without the middle piece

Question 35

Micro deletions

Answer 35

Regions of chromosomal loss that can not be detected by normal chromosome Banding

Question 36

Diseases associated with micro deletions

Answer 36

Di George syndrome=microdeletions on 22q11

Question 37

Ring chromosomes

Answer 37

Formed when a break occurs on each arm of a chromosome leavening 2 sticky ends on the central portion that reunites as a ring. 2 distal portions are lost

Question 38

Insertions

Answer 38

A segment from one chromosome becomes inserted into another and can be balanced or unbalanced

Question 39

Isochromosome

Answer 39

Shows loss f one arm with duplication of the other. Most common is isochromosome of the X=20% of ask Turner syndrome cases

Question 40

Duplication

Answer 40

Can arise by a breakage process or by misfiring following crossovers=partial trisomies

Question 41

Inversions.

Answer 41

Two break rearrangement involving a single chromosome in which a segment is reversed in position

Question 42

Peri centric inversion

Answer 42

Involves centromere

Question 43

Paracentric inversion

Answer 43

Does not involve the centromere