Chapters 5 & 11 Genetics Flashcards

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5: Clinical Cytogenetics & Genome Analysis 11: Molecular Basis of Genetic Disease
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1

Most accessible cells that are capable of proliferation in culture?

White Blood Cells (T lymphocytes)

2

Short term & long-term cultures are taken from samples of skin biopsy -->

cultures from cells produce fibroblasts, which can be used for biochemical, molecular studies, chromosome and genome analysis

3

WBCs can also be transformed in culture to form -->

Lymphoblastoid cell lines (HeLa cell is an immortal cell line. Oldest and most commonly used. Line derived from cervical cancer cells)

4

Fetal cells are derived from

amniotic fluid

5

Contributions HeLa Cells have made to science include (5):

1. Polio vaccine

2. Improved cell culture practices

3. Chromosome counting

4. Genome mapping

5. Human Papilloma Virus (HPV) vaccines

6

What does 46, XX, del(5)(q13) mean?

Female with terminal deletion of one chromosome 5 distal to band 5q13

7

What does 46, X, r(X) mean?

Female with ring X chromosome

8

What does 46, XX, t(2;8)(q22;p21) mean?

Female with balanced translocation between chromosomes 2 and 8, with breaks in bands 2q22 and 8p21

9

What does 47, XX, +21 mean?

Female with trisomy 21

10

What does 45, XY, -22 mean?

Male with monosomy 22

11

Dividing cells are arrested in .... by ......

Metaphase, destroying spindle fibers and shortening chromosomes

12

Clinical indications for chromosome and genome analysis (6):

  1. Problems of early growth & development
  2. Stillbirth & neonatal death
  3. Fertility problems
  4. Family History (abnormalities among relatives)
  5. Neoplasia (chromosome & genome evaluation in tumor or bone marrow)
  6. Pregnancy (women older than 35)

13

Base Substitution

mutation involving a base changing to a different base

14

Inversion

a stretch of DNA breaks off and reattaches in the opposite orientation

15

Insertion & Deletion

One/several bp added & deleted

16

Translocation

a stretch of DNA breaks off then reattaches somewhere else

17

Mispairing

A not pairing with T OR G not pairing with C

18

Aneuploidy

X & Y chromosomes

Autosomes

19

Structural abnormalities

Balanced & Unbalanced

20

Ring Chromosomes occur

in a mosaic state. 1 in 2500.

21

Molecular disorders: primary disease-causing even is an alternation either inherited or acquired -->

affecting a gene(s), its structure, and its expression

22

DNA sequencing alternations --> (2)

  1. amount or function of mRNA or protein --> diseases
  2. amount or function of noncoding RNAs (ncRNAs), including miRNA --> diseases

23

Mutations involving protein-coding genes -->

cause disease through one of four different effects on protein function

24

Four different effects are:

  1. Loss of Function (MOST COMMON)
  2. Gain of Function
  3. Novel Prperty Mutations
  4. Mutations associated with heterochronic or ectopic gene expression

25

Mutations involved in gene regulation are likely located in

Conserved or functional important

26

Mutations involved in RNA stability are likely located

at 5' or 3' UTRs

27

Other mutations include: (3)

  1. Silent: AA doesn't change
  2. Nonsense: AA changes to STOP
  3. Missense: conservative (AA has same property) & non-conservative (AA does not have same property)

28

Four mutations cause loss of function to the protein: (4)

  1. Missense
  2. Nonsense
  3. Frameshift
  4. Splice Site

29

Loss of Function Mutations: Deletion -->

Reduction in gene dosage

30

Gain of Function Mutations: Increase of one or more of protein functions -->

Increases gene dosage (gene duplication in amyloid precursor protein gene in AD)

31

Novel Property Mutations: Infrequent, amino acid sequence --> novel property on protein (sickle cell) -->

no effect on ability of sickle hemoglobin to transport oxygen

32

Mutations associated with Heterochronic or Ectopic Gene Expression: mutations --> inappropriate expression, regulatory regions -->

cell proliferation (oncogene) ex. cancer is due to abnormal expression

33

Any one of these 8 stages will disrupt normal productions of a protein

  1. Transcription
  2. Translation
  3. Polypeptide Folding
  4. Post-translational modification
  5. Assembly of monomers into a holomeric protein
  6. idk
  7. Cofactor or prosthetic group binding to the polypeptide
  8. Function of a correctly folded, assembled, and localized protein produced in normal amounts

34

Allelic Heterogeneity

multiple alleles at a single locus, ex CFTR

35

Locus Heterogeneity

mutations in more than two genes --> special clinical condition like thalassemia from either beta or alpha globin chain

36

Six types of human hemoglobin

  1. Hb Grower 1
  2. Hb Grower 2
  3. HB Portland
  4. Hb F (alpha2gamma2)
  5. HbA2 (aplha2delta2)
  6. HbA (alpha2beta2)

37

LCR

Locus Control Region

38

Expression of beta globin gene is only partly controlled by

the promoter and two enhancers

39

20 kb deletion upstream of LCR of beta goblin complex -->

disease since LCR is required for gene expression

40

Hemoglobin disorders: First Group

Structural Variants

ex. Sickle cells due to mutation --> deoxygenated beta goblin relatively insoluble --> changing shape of red cell

41

Hemoglobin disorders: Second Group

Thalassemias

structural variant --> destabilizes the chain --> decreases production of a globin chain --> decreases abundance of chains --> ratio of alpha to beta chains imbalance due to promoter mutations

42

Hemoglobin disorders: Third Group Hereditary persistence of fetal hemoglobin

benign conditions. impair perinatal switch from gamma globin to beta globin synthesis.

ex, deletion removes both delta and beta globin genes but leads to continued postnatal expression of the gamma globin genes to produce Hb F, an effective oxygen transporter

43

What kind of mutation causes sickle cell?

Base substitution mutation. GAG to GTG. Glutamate to Valine. Reduced oxygen carrying efficiency

44

Hemoglobin Structural Variants

400 abnormal hemoglobins, 50% are clinically significant.

Variants --> hemolytic anemia --> tetramer unstable

Variants with altered oxygen transport are due to ......

increased or decreased oxygen affinity or to formation of methemoglobin --> form of globin incapable of reversible oxygenation

45

Hb Kempsey

  1. Amino Acid substitution?
  2. Pathophysiological Effect?
  3. Inheritance?

1. Beta chain. Asp99Asn

2. Substitution keeps Hb in its high oxygen affinity structure --> less oxygen to tissues --> polycythemia

3. AD