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Flashcards in Trans - Basic Principles of Clinical Genetics Deck (79)
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1

Number of genes in humans

30,000

2

Number of base pairs in human genome

31,647 billion base pairs

3

Percentage of genes coding for proteins

less than 2%

4

Percentage of junk DNA in genome

as much as 90%

5

_____% of bases are exactly identical in all people

99.9%

6

Disease status is influenced by: ___ [2]

[1] genetic factors;
[2] environmental factors

7

Epigenetics

Study of heritable changes in gene expression caused by chemical modifications in a chromosome

8

3 interrelated mechanisms involved in epigenetics

[1] DNA methylation;
[2] histone modifications;
[3] activity of miRNA

9

Significance of miRNA activity in epigenetics

[1] miRNAs are encoded within the genome;
[2] miRNA expression is regulated by other epigenetic mechanisms;
[3] miRNAs bind to specific 3' UTR of an mRNA, and inhibits translation to protein

10

Characteristics of open chromatin

nonmethylated DNA, histones with acetylated tails

11

Mediates DNA methylation

DNA methyltransferase

12

What heavily influences an individual's adult health?

Early prenatal factors (exposure to certain substances, etc.)

13

Effect of foliate or choline deficiency in mother's diet

Undermethylation of certain portions of fetal DNA --> abnormalities

14

What is BPA and what is its effect on agouti mice?

Exposure to BPA (Bisphenol A) during early development causes decreased methylation of the agouti gene

15

The family pedigree is a tool for: [6]

[1] Making a medical diagnosis,
[2] deciding on testing strategies;
[3] establishing pattern of inheritance;
[4] identifying family members at risk;
[5] calculating risk;
[6] determining reproductive options

16

Often the most confusing aspect of pedigree interpretation

Non-paternity

17

Confounding factors in recognizing inheritance patterns [6]

[1] variable expressivity;
[2] clinical/genetic heterogeneity;
[3] sex influenced/limited gene expression;
[4] assortative mating (marrying the same looking person);
[5] small paternity size;
[6] lack of information

18

Usual patterns of inheritance [5]

[1] autosomal dominant;
[2] autosomal recessive;
[3] X linked recessive;
[4] X linked dominant;
[5] multifactorial

19

Unusual patterns of inheritance [3]

[1] mitochondrial DNA;
[2] triple repeat expansion;
[3] genomic imprinting

20

Affected genotypes of autosomal dominant inheritance

AA or Aa

21

Characteristics of autosomal dominant inheritance [3]

[1] no skipping of generations;
[2] both sexes affected in equal proportions;
[3] may be passed from male to male

22

If both parents are heterozygous for an autosomal dominant trait, what is the chance that the offspring will be severely affected?

25%

23

Achondroplasia - type of inheritance, site of mutation, characteristics

[1] autosomal dominant;
[2] FGF 3;
[3] short stature, skeletal dwarfism, midface hypoplasia, stenosis of spinal canal

24

Crouzon syndrome - type of inheritance, site of mutation, characteristics

[1] autosomal dominant,
[2] FGF 2,
[3] tower head skull (oxycephaly), supraorbital hypoplasia, eye proptosis/exopthalmos

25

Apert syndrome - type of inheritance, site of mutation, characteristics

[1] autosomal dominant;
[2] FGF;
[3] mental handicap, microcephaly, mitten hands

26

Marfan syndrome - type of inheritance, site of mutation, characteristics

[1] autosomal dominant;
[2] fibrillin 1 gene on chromosome 17;
[3] tall stature, scoliosis, arachnodactyly, positive thumb sign, positive wrist sign, dislocation of lens/myopia

27

Ehlers-Danlos syndrome - type of inheritance, nature of mutation, characteristics

[1] autosomal dominant;
[2] defect in collagen synthesis;
[3] cigarette-mark-like wounds on knees, stretchy skin

28

Affected genotypes of autosomal recessive inheritance

aa

29

Characteristics of autosomal recessive inheritance [3]

[1] both sexes affected in equal proportion;
[2] both parents must be carriers of a single copy of the gene for a child to he affected;
[3] risk is 25% per child of carrier parent

30

Harlequin syndrome - type of inheritance, site of mutation, characteristics, treatment

[1] autosomal recessive;
[2] keratin gene;
[3] ichthyosis, pseudo-amputation of digits, ectopion, eclabion;
[4] retinoin