HRR: chromosomal abnormalities I

Question 1

What causes trisomy 13?

Answer 1

Usually nondisjunction during maternal meiosis, some from translocation

Question 2

What are facial features of trisomy 21?

Answer 2

Flat face, flat occiput, prominent tongue, up slanting eyes

Question 3

Having trisomy 21 increases risk for what diseases later in life?

Answer 3

Alzheimer’s and leukemia

Question 4

What age is more common to experience nondisjunction?

Answer 4

Older mothers due to a higher likelihood of premature loss of cohesion between homologous chromosomes

Question 5

What is the recurrence risk of trisomy 21 if it is a de novo nondisjunction event?

Answer 5

1% or age related

Question 6

What is the most common cause of aneuploidy?

Answer 6

Nondisjunction from maternal meiosis I

Question 7

What is trisomy?

Answer 7

Extra copy of a particular chromosome

Question 8

What is nondisjunction?

Answer 8

Abnormal segregation of chromosomes resulting in aneuploidy aka abnormal chromosome number (too few or too many, like monosomy or trisomy)

Question 9

Chromosome abnormalities are present in ___ live births

Answer 9

1 in 150

Question 10

What is patau syndrome?

Answer 10

Trisomy 13

Question 11

What are common features of trisomy 18?

Answer 11

Rocker bottom feet, clenched hands with overriding fingers, cardiac defects, small head w/ prominent occiput, small jaw, feeding issues, overall small

Question 12

What will the karyotype be in mosaicism?

Answer 12

One normal cell line and one aneuploid cell line

Question 13

What is digyny?

Answer 13

Extra chromosome of maternal origin. Results in small placenta without hydropic change and small baby.

Question 14

What is diandry/dispermy?

Answer 14

Extra chromosome of paternal origin; huge cause of triploidy

Question 15

What is the recurrence risk of trisomy 21 if there is a translocation between two 21 chromosomes?

Answer 15

100%; this is because it is inherited from the parent

Question 16

When does mosaicism occur?

Answer 16

AFTER fertilization, usually from mitotic errors

Question 17

What is true of chromosomes if there is nondisjunction in meiosis II?

Answer 17

The extra chromosome will be identical to one of the others

Question 18

What will be the ploidy of offspring if there is nondisjunction in meiosis II?

Answer 18

Half will be aneuploid and the other half will be euploid

Question 19

What is haploid?

Answer 19

One chromosome set; this is normal for sex cells in humans

Question 20

What is cutis aplasia?

Answer 20

A part of the scalp contains no skin or hair; often a result of trisomy 13

Question 21

What is trisomy 21?

Answer 21

Aka downs syndrome. An extra copy of chromosome 21

Question 22

What is euploid?

Answer 22

Chromosome number that is a multiple of the base haploid for a species; diploid aka 2n for humans

Question 23

What is disomy?

Answer 23

An organism having two copies of a particular chromosome; this is normal

Question 24

What is nullisomy?

Answer 24

Missing both copies of a particular chromosome

Question 25

How does trisomy 21 happen?

Answer 25

Nondisjunction during meiosis I, usually extra maternal

Question 26

What is a partial hydatiform mole?

Answer 26

A large placenta with hydropic changes (looks like bundle of grapes) due to diandry/dispermy. Results in a large baby.

Question 27

What is monosomy?

Answer 27

Missing copy of a particular chromosome

Question 28

What is true of chromosomes if there is nondisjunction in meiosis I?

Answer 28

All three of the chromosomes (if trisomy) will be unique

Question 29

What is polyploid?

Answer 29

More than two whole sets of chromosomes. ## Footnote Example is triploidy where we have 3 sets aka 69 chromosomes instead of 46.

Question 30

What is the recurrence rate of trisomy 13 if there is a translocation between two chromosome 13’s?

Answer 30

100%

Question 31

What will be the ploidy of offspring if there is nondisjunction in meiosis I?

Answer 31

All will be aneuploid, either monosomy or trisomy

Question 32

What is Edwards syndrome?

Answer 32

Trisomy 18

Question 33

What are causes of triploidy?

Answer 33

Diandry/dispermy, digyny

Question 34

What are features of trisomy 13?

Answer 34

A bunch of midline defects such as cleft lip/palate, brain defects, cardiac defects, polydactyly, and omphalocele

Question 35

What are presenting symptoms of trisomy 21?

Answer 35

AV canal heart defect, single palmar crease, GI anomalies, autoimmune disorders, hypotonia, brush field spots (spots in the eye)

Question 36

What is the outcome of a baby born with trisomy 18?

Answer 36

90% die in the first year of life

Question 37

What is the outcome of a baby born with trisomy 13?

Answer 37

90% die in the first year of life

Question 38

What is mosaicism?

Answer 38

Two or more cell lines in a single zygote; results in chromosome abnormalities or variants in certain parts of the body

Question 39

What can cause nondisjunction in meiosis II?

Answer 39

Premature loss of cohesion

Question 40

What are causes of nondisjunction during meiosis I?

Answer 40

Chiasmata not forming or premature loss of cohesion