Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MHG II > Cytogenetics I & II > Flashcards

Cytogenetics I & II Flashcards

1
Q

Euchromatin & Heterochromatin

A

Euchromatin: light bands; CG rich, early replication
Heterochromatin: dark bands; AT rich, late replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Centromere positions (3)

A
  1. Metacentric
  2. Submetacentric
  3. Acrocentric (p arm contains no unique sequence; same for: 13, 14, 15, 21, 22)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

prenatal diagnostic tissues for chromosome analysis (3)

A
  1. amniotic fluid
  2. chorionic villus sample
  3. percutaneous umbilical blood sample
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Adult tissues for chromosome analysis (4)

A

Any viable cell with nucleus

  1. peripheral blood: lymphocytes are in G0 (stimulated by mitogen pytohemagglutinin PHA)
  2. Bone marrow: typically for acquired abnormalities (leukemia, lymphoma)
  3. Skin: fibroblast culture from skin biopsy 1-3wks
  4. Internal organs: fetal death, autopsy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Chromosome Preparation procedure (6)

A
  1. “harvest” anc culture actively dividing cells (phytohemagglutinin ~3 days)
  2. Add COLCEMID, spindle fiber poison
  3. Hypotonic solution (low KCl molarity) –> swell
  4. Fixation: cell membrane brittle & fragile
  5. Slide preparation; proteolytic enzymes cleave bound proteins
  6. G-banding w/ Giemsa stain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Microscope analysis of chromosomes

A
  • Need 15-50 metaphases

- ID: individual chromosomes, missing/extra chromosomes, structural rearrangements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Recombination during meiosis

A
  1. At least one cross over (chiasmata) per chromosome arm
  2. number of cross overs correlates to length of arm
  3. decreased cross overs is associated with increased risk of nondisjunction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Male meiosis (3)

A
  1. 4 division products develop to sperm
  2. Begins during puberty
  3. After many mitotic divisions, develop into mature sperm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Female meiosis (3)

A
  1. 1 egg, 3 polar bodies
  2. cytoplasm unequally divided
  3. begins in fetal life (3-9 mos) –> prophase I at birth
    -ovulation: –> metaphase II
    stops until fertilized
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Constitutional cytogenetic abnormalities

A
  • present at conception

- associated with birth defects and miscarriages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Aneuploidy

A
  • most common type of human chromosome disorder (>3-4%)
    2. All monosomies lethal except X
    3. Caused by nondisjunction (most often in meiosis I)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Autosomal abnormalities

A
  1. Developmental delay/mental retardation
  2. facial features more characteristic of syndrome than of family members
  3. Growth delay
  4. Congenital malformations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Sex reversal

A

Results from aberrant cross-over btwn X and Y chromosomes

  • pseudo-autosomal region of homology can cross over
  • SRY (sex determination in males) is nearby and if moved to X chromosome –> XX male
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Robertsonian translocation

A

Whole arms ( q) of two acrocentric chromosomes
-break on p arm near centromere & two long arms join –> loss of P arm –> insignificant
-two centromeres in hybrid
Balanced: 45 (t13:14); unbalanced: 46 (t14:21)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Reciprocal translocation

A

Do not involve entire arm and centromere
-usually btwn two nonhomologous chromosomes
Balanced: 46, Unbalanced: 46 rarely 47
-Rearrangement of chromosomes (change sizes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Terminal deletions

A

Due to a break and loss of chromosome end

17
Q

Interstitial deletions

A

Two breaks; loss of middle portion

18
Q

Ring deletions

A

Two breaks; loss of P and Q terminus –> ends rejoin –> circular
-often lost or lead to abnormal phenotype

19
Q

Microdeletion syndromes

A

usually <5 megabases lost which can be missed by G-band studies
-Can be detected using high resolution chromosome analysis, FISH, array CGH
Ex: Prader-Willi/Angelman, Rb, William, DiGeorge/velocardiofacial

20
Q

Isochromosomes

A

Trasnverse division during meiosis at centromeres instead of longitudinal

  • results in chromosome with two P arms and one with 2 q arms
  • Turner syndrome phenotype: 46, X,i(Xq) 20%
21
Q

Pericentric inversion

A

Cut in both arms and middle region (containing centromere) is flipped

  • duplication of one, deletion of another
  • produce viable, abnormal offspring
22
Q

Peracentric inversion

A

-two breaks in same arm –> region in same arm is flipped, changing order of genes
-Results in chromosome with either two or no centromeres
Abnormal recombinant is almost never viable
-Viable offspring have normal offspring

23
Q

Complications with inversions (2)

A
  1. Carriers are at risk of having offspring with duplication AND deletion parts = recombinant chromosome
  2. problems in homologous alignment in meiosis –> abnormal chromosomes
24
Q

Indications for chromosome analysis (8)

A
  1. recognized cytogenic syndrome
  2. unrecognized syndrome with 2+ malformations
  3. ambiguous genitalia
  4. MR or developmental delay in children who are dysmorphic or have MCA
  5. 1st deg relative with structural chromosomal abnormalities
  6. Stillborn infants w/ malformations or no recognizable reason for fetal death
  7. Females with proportionate short stature and primary amenorrhea
  8. Males with small testes or significant gynecomastia
25
Q

Mosaicism (3)

A
  1. Presence in a tissue or individual with at least two cell lines
  2. Differ karyotypically, but are derived from a single zygote
  3. Severity of phenotype is dependent upon frequency of abnormal cell line and tissue distribution
26
Q

Chromosomal mosaicism

A

Most common way to generate mosaicism is via nondisjunction

  • trisomy can result –> anaphase lag can cause extra chromosome to be lost –> restore normal 46 in some cells
  • therefore, some cells will have 47, others 46
27
Q

Confined Placental mosaicism

A

Discrepancy btwn placental and fetal karyotype

  • more widely recognized after chorionic villus sampling (CVS)
  • 20% of pregnancies with idiopathic intrauterine growth retardation (IUGR) have confined placental mosaicism
  • potential for false positives (if placenta has trisomy, but fetus doesn’t) and negatives (if placenta doesn’t have trisomy, fetus does)
28
Q

Uniparental disomy (UPD)

A

Two chromosomes present, but both from one parent

-1/3 of corrected trisomies (as a result of nondisjunction) via trisomy rescue results in UPD

29
Q

Genomic Imprinting

A

Differential expression depending on parental source (maternal and paternal fxn differently and can influence expression of disorders)
2. Modification of DNA during critical period; Reversible change in the genetic material
3. Contrary to basic Mendelian principles
Occurs in certain parts and chromosomes (6 chromosomes where imprinting matters)

MHG II (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions