GENETICS

Question 1

Detects fetal Down Syndrome and other autosomal trisomies

Answer 1

Aneuploidy screening

Question 2

Clinically useful if the fetus is at risk for an X-linked disorder

Answer 2

Fetal sex determination

Question 3

May also be beneficial if the fetus is at risk for congenital adrenal hyperplasia because maternal corticosteroid therapy may be avoided if the fetus is male

Answer 3

Fetal sex determination

Question 4

Fetal cells are present in maternal blood at a _______ concentration

Answer 4

very low

Question 5

released from apopotic placental triphoblast—rather than actual fetal cells—and can be reliably detected in maternal blood after 7 weeks’ gestation

Answer 5

Cell free fetal DNA

Question 6

If a specific disease causing gene has not been identified, then _________ may be used to estimate the likelihood that an individual or fetus has inherited the abnormal trait

Answer 6

linkage analysis

Question 7

Uses the principles of PCR (polymerase chain reaction) and nucleic acid hybridization to screen DNA

Answer 7

Chromosomal Microarray Analysis

Question 8

For prenatal diagnosis for stillbirth evaluation

Answer 8

Chromosomal Microarray analysis

Question 9

allows identification of one or several DNA fragments of interest

Answer 9

Southern blotting

Question 10

Enables the rapid synthesis of large amounts of a specific DNA sequence or gene

Answer 10

PCR

Question 11

For any tissue containing dividing cells or cells that can be stimulated to divide

Answer 11

Cytogenic analysis

Question 12

Provides a rapid method for determining numerical changes of selected chromosomes and confirming the presence or absence of a specific gene or DNA sequence

Answer 12

Flourescence In Situ Hybridization (FISH)

Question 13

A recessive trait is expressed only when both copies of the gene function in the same way

Answer 13

Autosomal Recessive Inheritance

Question 14

When considering inheritance, it is the ________ that is dominant or recessive, not the genotype function in the same way

Answer 14

phenotype

Question 15

A __________ is caused by a mutation or alteration in a single locus or gene in one or both members of a gene pair

Answer 15

monogenic disorder

Question 16

Mechanism may be either mitotic nondisjunction or parental correction of a meiotic error

Answer 16

Confined placental mosaicism

Question 17

Likely arises from a mitotic error in cells destined to become the gonad and results in population of abnormal germ cells

Answer 17

Gonadal mosaicism

Question 18

A mosaic individual has two or more cytogenetically distinct cell lines that are derived from a single zygote

Answer 18

Chromosomal mosaicism

Question 19

Results when deletions occur at both ends of the same chromosome and the ends come together

Answer 19

Ring chromosomes

Question 20

Breaks in both p and q arms

Answer 20

Pericentric inversion

Question 21

Two breaks within one arm

Answer 21

Paracentric inversion

Question 22

These abnormal chromosomes are composed of either two q arms or two p arms of one chromosome fused together

Answer 22

Isochromosomes

Question 23

Can arise when the centromere breaks transversely instead of longitudinally during meiosis II or mitosis

Answer 23

Isochromosomes

Question 24

Can also result from a meiotic error in a chromosome with a robertsonian translocation

Answer 24

Isochromosomes

Question 25

Involves only acrocentric chromosomes which are chromosomes 13,14,15,21 and 22

Answer 25

Robertsonian translocation

Question 26

The q arms of two acrocentric chromosomes fuse at one centromere to form a derivative chromosome

Answer 26

Robertsonian translocation

Question 27

Develops when there are breaks in two different chromosomes and the broken fragments are exchanged, so that each affected chromosome contains a fragment of the other

Answer 27

Reciprocal translocation

Question 28

DNA arrangements in which a segment of DNA breaks away from one chromosome and attaches to another

Answer 28

Chromosomal Translocations

Question 29

The arranged chromosomes are called _________

Answer 29

derivative chromosomes

Question 30

2 types of derivative chromosomes are:

Answer 30

Reciprocal

Robertsonian

Question 31

Examples of Microduplication syndrome:

Answer 31

1. Velocardiofacial/DiGeorge
2. Smith-Magenis
3. Williams-Beuren

Question 32

Microdeletion syndrome are also known as:

Answer 32

DiGeorge Syndrome

Sphrintzen syndrome

Velocardiofacial syndrome

Question 33

45,X

Answer 33

Turner Syndrome (Monosomy X)

Question 34

47,XXY

Answer 34

Klinefelter Syndrome

Question 35

A lethal aneuploidy, more than 90% of fetuses with either a dandric or digynic form have multiple structural anomalies (CNS, heart, face and extremities, severe growth restriction)

Answer 35

Triploidy

Question 36

Extra chromosomal set is maternal, and the egg fails to undergo the first or second meiotic division before fertilization

Answer 36

Digynic triploidy (type II triploidy)

Question 37

Extra chromosomal set is paternal resulting from fertilization of one egg by two sperm or by a single diploid

Answer 37

Diandic triploidy (type I triploidy)

Question 38

Account for approximately 20% of spontaneous abortions

Answer 38

Polyploidy

Question 39

Abnormal number of complete haploid chromosomal sets

Answer 39

Polyploidy

Question 40

_________ is the most common trisomy found in the first-trimester losses

Answer 40

Trisomy 16