Chromosomes and Disease

Question 1

what are the origins of abnormal karyotypes?

Answer 1

Error in meiosis and maternal age

errors in mitosis ( anaphase lag)

Question 2

polyploidy

Answer 2

The heritable condition of possessing more than two complete sets of chromosomes.

Question 3

Euploidy

Answer 3

The state of a cell or organism having one or more than one set of the same set of chromosomes, possibly excluding the sex-determining chromosomes

Question 4

aneuploidy

Answer 4

a genetic disorder where the total number of chromosomes doesn’t equal 46

Question 5

non- disjunction

Answer 5

homologous chromosomes that fail to separate in anaphase

Question 6

what are the two classes of chromosome abnormalities?

Answer 6

Acquired (during embryogenesis in a subset of cells = mosaic

Constitutional (found in each cell of body)

Question 7

What are the five main causes of chromosome abnormalities

Answer 7

Anaphase lag
Chromsome missegregation
Meiotic/ mitotic failure
dispermy
incorrect DNA repair

Question 8

Anaphase Lag

Answer 8

One chromosome fails to migrate to pole of spindle

Lagging chromosome hence excluded from nuclei of daughter

Question 9

Trisomy in 10, 15 or 16 is:

Answer 9

early lethal
Gross generic imbalances prevent embryonic tissues from developing correctly

Question 10

Dosage compensation and an example

Answer 10

Evolutionary mechanism allowing altered gene doseage

genes on X-chromosome evolved so that normal development and cell function can take place with only one X per cell

Question 11

Barr Bodies

Answer 11

inactive X chromosome that has become hyper-condensed.

Area of heterochromatin representing X chromosome. One X chromosome is randomly and permanently inactive during embryogenesis.

Question 12

what are the four ways in which polyploidy can occur via meiotic/mitotic failure and Dispermy?

Answer 12

Complete non-disjunction

Error in gamete formation: Chromosome duplicated but cytoplasm and cell as whole fail to divide into daughter cells.

Error in early mitotic cell division: chromosomes duplicate but cytokinesis does not occur.

Errors at fertilization (dispermy): simultaneous fertilization of haploid egg by two haploid sperm = triploid.

Question 13

What are the two main types of chromsome inversion?

Answer 13

Pericentric and Paracentric

Question 14

what are the two types of translocations?

Answer 14

Reciprocal and insertion

Question 15

Philadelpiha Chromosome

Answer 15

90% of patients with Chronic Myelogenous Leukemia

BCR (from Ch-22) fuses with kinase ABL from (Ch-9) = uncontrolled division.

Question 16

Roberson Translocations

Answer 16

Centric fusion of Ch 13 and 14 = end – end fusion of acrocentric chromosomes (centromere not central).

Normal phenotype as no loss/gain of material

Increased Risk of abnormal child or spontaneous pregnancy loss.

Question 17

What is Uniparental Disomy and what two events are needed for it to occur?

Answer 17

Inheritance of 2 chromosomes or chromones parts from SAME parents

Due to simultaneous occurrence of two rare events:

Simultaneous non disjunction in sperm AND egg

Trisomy followed by chromosome loss.

Question 18

What are the symptoms of UPD Prader-Willi Syndrome and what chromosome is affeceted?

Answer 18

Low muscle tone, short stature, incomplete sexual development

Cognitive disabilities, behavioral problems, chronic feeling of hunger = excessive eating and life-threatening obesity

paternal Ch 15g11-q13 lost

Question 19

How can you tell if nondisjunction occurred in meiosis I or meiosis II?

Answer 19

I= three chromosomes, Non Identical
II- three chromosomes, 2 Identical

Question 20

Does Pericentric or Paracentric include the centromere in inversion?

Answer 20

Pericentric

Question 21

triploid vs trisomic?

Answer 21

Triploid= extra SET of chromosomes

Triploid = extra copy of ONE chromosome

Question 22

What does anaphase lag often result in?

Answer 22

euploidy and monomsy

Question 23

Describe the ouctome of meiosis I vs Meiosis II errors in Non-disjunction

Answer 23

Meiosis I errors
all gametes abnormal,
50% have trisomy and non-identical,
50% monosomy

Meiosis II errors
50% abnormal,
1 with trisomy, identical
1 monosomy

Question 24

dispermy

Answer 24

simultaneous fertilsation of haploid egg by 2 haploid sperm = triploidy