Ploidy

Question 1

euploidy

Answer 1

• multiples of one complete chromosome compliment
• N, 2N, 3N, 4N
• haploid, diploid, triploid, tetraploid

Question 2

aneuploidy

Answer 2

• gain or loss of chromosomes equaling less than one complete complement
• trisomy 13- 47, XX, +13
• monosomy 8- 45, XY, -8
• sex chromosomes
• 45X, 47 XXY

Question 3

nomenclature

Answer 3

number of chromosomes, sex chromosomes

Question 4

mosaicism

Answer 4

• gain of trisomy if non-disjunction from zygote, or loss of trisomy
• presence of at least 2 different cell lines with at least one clear variation between them
• numerical changes 45, X and 46, XX
• structural change- one cell line with a translocation that doesn’t occur in the other
• mosaicism is acquired, can’t be inherited- because zygote is 1 cell

Question 5

chimera

Answer 5

• cells fuse and then keep diving

- vs one cell getting a mutation that is propagated in the organism

Question 6

viable autosomal trisomies

Answer 6

• 21,
• patau- 13
• edwards 18

Question 7

down syndrome

Answer 7

• multiple system defects
• heart, lung, brain, endocrine system, susceptibility to infectious disease, increased risk of leukemia
• high freq of AD
• more problems may arise as individual ages

Question 8

trisomy 13

Answer 8

• punched out scalp
• rocker bottom feet
• polydactyly

Question 9

trisomy 18

Answer 9

• grow, but don’t develop

- hand sign

Question 10

klinefelter syndrome

Answer 10

• 47, XXY
• 1/1000 male live births
• 50% due to meiosis I error in father
• tall
• interfility
• some female characteristics may develop
• learning deficit possible

Question 11

Turner syndrome

Answer 11

45, X

• half have that karyotype
• 15% have deletions or rearrangements of X
• 10 % mosaics- 45X/46,XX or 45X/46XY
• if have XY may be male or female phenotype
• male phenotype usually ok
• female- high probability of problem: increased risk of gonadoblastoma- recommendation to remove gonads
• diagnosis important
• cases can range from mild to severe, prenatal counseling can be difficult
• remove gonads if gonadoblastoma is an issue
• other problems may occur with time

Question 12

XXX female

Answer 12

• 1/1000 female live births
• usually due to maternal meiosis I error
• average to tall stature
• learning deficit possible
• some fertility problems possible

Question 13

XYY male

Answer 13

• 1/1000 live births
• failure of paternal meiosis
• tall stature
• normal intelligence
• normal fertility
• clinically indistinguishable from 46, XY

Question 14

Turner syndrome issues

Answer 14

• growth hormone
• monitor for heart malfunctions
• karyotype to check for Y chromosome
• counseling for probably infertility- donor egg

Question 15

XY female

Answer 15

1/ 20,000 live births

• androgen insensitive
• phenotypically normal female with testes
• infertility

Question 16

XX “male”

Answer 16

• congenital adrenal hyperplasia
• autosomal recessive condition
• mutation results in overproduction of androgens in female fetus
• in utero exposure causes virulization of fetus
• normal ovaries and internal genitalia
• ambiguous external genitalia
• can be due to CAH in mother or fetus

Question 17

XX male

Answer 17

• 1/20,000 live births
• X-Y recombination near pseudoautosomal region
• usually normal, possible klinefelter phenotype
• reciprocal translocation is replaced by Xp material which is transmitted to a child results in a turner female phenotype with and apparent 46, XY karyotype

Question 18

XY gonadal dysgenesis

Answer 18

• 46, XY disorder of sex development

- 46, XY complete gonadal dysgenesis

Question 19

46, XY disorder of sex development

Answer 19

male or female

• 46, XY karyotype
• ambiguous genitalia with mild to severe penoscrotal hypospadias with or without chordee
• dysgenetic testes
• reduced to no sperm production
• mullerian structures that range from absent to presence of a fully developed uterus and fallopian tubes

Question 20

46, XY complete gonadal dysgenesis

Answer 20

• 46 XY karyotype
• normal female external genitalia
• completely underdeveloped streak gonads
• no sperm or egg production
• presence of normal mullerian structures

Question 21

structural abnormalities

Answer 21

• deletion
• duplication
• translocation
• inversion

Question 22

balanced

Answer 22

• all material is present but rearranged

- some of the material is missing or duplicated

Question 23

deletion

Answer 23

• loss of a part of a chromosome
• leads to a partial monosomy
• terminal or interstitial
• loss of one or more genes usually leads to clinical abnormalities
• small deletions may be tolerated with minimal clinical abnormalities
• large deletions typically associated with developmental delay, mental retardation, abnormal features
• size is not as important as which genes and how many are missing

Question 24

wolf-hirschhorn syndrome

Answer 24

• 4p deletion
• short stature
• developmental delay
• greek helmut face

Question 25

karen

Answer 25

- 11 q deletion | - de novo interstitial

Question 26

duplication

Answer 26

- additional copy of a chromosome segment - partial trisomy - terminal or interstitial - cornelia de lange no longer duplication - 3q29 micro, 7q11.13, 16p11.2, 22q11.2 1q21. 1

Question 27

reciprocal translocation

Answer 27

- equal exchange involving two or more chromosomes | - can make balanced or unbalanced

Question 28

balanced translocation

Answer 28

- increased risk that another pregnancy will have an unbalanced chromosome complement - increased risk of infertility or spontaneous fetal loss - increased risk for an abnormal live born (10% per pregnancy) - relatively common, 1 in 500 - carriers are usually phenotypically normal - translocations can be inherited - other members of the family may have the rearrangement - can be de novo- if detected prenatally, may not be able to tell if it is balanced or not

Question 29

robertsonian translocation

Answer 29

- centromere to centromere involving acrocentric chromosomes | - can cause trisomy

Question 30

inverstion

Answer 30

- peri (involving centromere) or para centric - reversal of a chromosomal segment with respect to normal gene arragement - need a loop - para can lead to apparent suppression of recombination - pericentric need larger circle - larger inversion means more viable gametes because smaller inversion leads to a greater risk of unbalanced gametes

Question 31

paternity

Answer 31

- critical to know who the biological father is - interpretation of data may reveal that the husband is not the father of the child - if the data input is false, interpretation may be compromised