Chapter 13- Chromosomes

Question 1

Cytogenetics

Answer 1

Study of chromosomes and their abnormalities

Question 2

Karyotype

Answer 2

Displays chromosomes by their size and structure
Used for clinical diagnosis

Question 3

Telomeres

Answer 3

DNA Repeats on chromosome ends
Protects ends of DNA information
Shorten every cell division in absence of telomerase

Question 4

Centromere

Answer 4

Site of spindle fiber attachment
Specialized heterochromatin with DNA and proteins

Question 5

Telocentric chromosomes

Answer 5

Centromere at the tip of chromosomes

Question 6

Acrocentric chromosomes

Answer 6

Centromere close to the end

Question 7

Submetacentric chromosomes

Answer 7

Centromere off-center

Question 8

Metacentric chromosomes

Answer 8

Centromere in the center

Question 9

Amniocentesis

Answer 9

Collecting fetal cells from the amniotic fluid at 16-20 weeks to test for chromosomal and biochemical defects
Recommended for older women or history of chromosomal abnormalities

Question 10

Chorionic Villi Sampling (CVS)

Answer 10

Collect chorionic villi (placental projections) trans-vaginally
Earlier results but less accurate and higher chance of miscarriage

Question 11

Euploidy

Answer 11

Correct chromosome number

Question 12

Polyploidy

Answer 12

Cells with entire extra sets of chromosomes
Triploid- 69 chromosomes
Tetraploid- 92 chromosomes

Question 13

Aneuploidy

Answer 13

Gain or loss of individual chromosomes

Question 14

Non-disjunction

Answer 14

Failure of paired homologs to separate properly during segregation
Occurs in meiosis I or II
Causes aneuploidy

Question 15

Monosomy

Answer 15

2n-1 condition, loss of one chromosome
Lethal very early in embryogenesis

Question 16

Trisomy

Answer 16

2n+1 condition, gain of one chromosome
Varying lethality depending on chromosome repeated

Question 17

Trisomy 21- Down Syndrome

Answer 17

95% due to nondisjunction in meiosis I from ovum
Distinctive facial and physical problems
Predisposition for leukemia, alzheimer’s, and heart defects
Varying developmental disability

Question 18

Trisomy 18- Edward’s Syndrome

Answer 18

Survival less than 4 months
Most common in stillbirths
Associated with advanced maternal age

Question 19

Trisomy 13- Patau Syndrome

Answer 19

95% miscarry
Death within 3 months
Many growth, developmental, and anatomical defects

Question 20

XO- Turner Syndrome

Answer 20

Female phenotype
99% die in utero
Loss of one X chromosome from ovum or sperm
Short, infertile, many medical problems
Failure to develop secondary sex characteristics
Only viable monosomy in humans

Question 21

XXX- Triple X Syndrome

Answer 21

Little phenotypical change from normal females
Majority never diagnosed

Question 22

XXY- Klinefelter Syndrome

Answer 22

Many X with at least 1 Y chromosomes
Male phenotype
Tall, large limbs
Hypogonadism, sterile
Gynecomastia

Question 23

XYY- Jacob’s Syndrome

Answer 23

Male phenotype
96% normal development
Great height
Acne
Speech and reading disabilities

Question 24

Translocation of Chromosomes

Answer 24

Transfer a piece of chromosome to non-homologous chromosome
Balanced

Question 25

Robertsonian Translocation

Answer 25

Breakage of acrocentric chromosomes and fusion of two distinct long arms into hybrid chromosome No clinical significance for carrier Produce unbalanced gametes

Question 26

Reciprocal Translocation

Answer 26

Breakage of two non-homologous chromosomes with exchange of fragments Balanced Normal phenotype with risk for unbalanced gametes

Question 27

Burkitt Lymphoma

Answer 27

Translocation of pronto oncogeme c-myc into immunoglobulin heavy chain Leads to tumor development

Question 28

Chromosomal Deletions

Answer 28

Missing genetic segments Arise de novo from chromosome breaks Hemizygous expression- Only copy remaining will always be expressed

Question 29

Chromosomal Duplications

Answer 29

Part of chromosome is copied, leading to extra genetic material Occurs during meiosis due to unequal crossing over Tandem or dispersed repeats

Question 30

Chromosomal Inversions

Answer 30

Chromosome segment with flipped orientation May lead to health problems or reduced fertility Balanced- Both copies flip Unbalanced- Only one copy flips- Causes issues in crossing over

Question 31

Isochromosomes

Answer 31

Chromosome with two identical arms 2p arms- Short 2q arms- Long

Question 32

Tetrasomy 18

Answer 32

Isochromosomes of chromosome 18 lead to low birth weight and developmental abnormalities

Question 33

Ring Chromosomes

Answer 33

Chromosome ends break and fuse to one another, forming ring Arise with telomere loss Occur with or without disrupting genetic material

Question 34

Uniparental Disomy

Answer 34

One parent contributes both copies of a chromosome Loss during trisomy zygote Non-disjunction in both parents on same chromosome

Question 35

Robertsonian Down Syndrome

Answer 35

5% of cases Robertsonian translocation of chromosomes 21 and 14 Offspring has chance to inherit hybrid chromosome or normal copies from carrier Cause trisomy 21

Question 36

Cru du Chat Syndrome

Answer 36

De novo deletion on chromosome 5 Delete CTNND2 and HTERT gene Defects in telomerase and nerve cell development High pitched cry, intellectual and developmental impairment, low birth weight