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BPM DLA1 > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

Types of nuclear coding DNA (2)

A
  1. Unique Single copy genes
  2. Multigene familes
    2a) classic gene family
    2b) Gene superfamilies
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2
Q

Example of unique single copy genes

A

receptors, enzymes, hormone, structural cellular elements

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3
Q

What is multigene famil

A

genes with similar functions that have arisen by gene duplication (can be clustered or dispersed in different genomic location)

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4
Q

What is classic gene family

A

multicopy genes that show a high degree of homology such as HOX gene, globin gene, rRNA genes etc

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5
Q

What is gene superfamilies

A

multicopy genes with similar function but limited gene homolgy such as HLA genes, T-cell receptors (shows evolution)

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6
Q

Characteristics of extragenic DNA (6)

A
  1. Makes up majority of human genome
  2. transcriptionally inactive
  3. play a role in regulation of gene expression
  4. contain tandem repeated DNA seq where the shorter the repeat length, the more polymorphic that sequence is.
  5. Tandem repeat is inherited from each parent
  6. Simple sequence repeat variation used as the basis of DNA finger printing
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7
Q

4 types of DNA variation

A
  1. Single nucleotide polymorphism (SNP)
  2. Simple sequence repeat (SSR)
  3. VNTR
  4. Low copy repeat (LCR)
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8
Q

What is SNP?

A

The most common variation , but not associated phenotype.

Used for evolutionary research

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9
Q

Advantage of SSR

A

Useful in forensics and paternity testing

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10
Q

Application of SSR analysis of CA repeat linked to an autosomal-dominant disease

A

Tandem CA repeat is linked to mutation, so by analyzing CA repeat of family using PCR, we can find out to which allele is disease linked to.

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11
Q

What is relationship between low copy repeat (LCR) and meiosis or mitosis.

A

LCR is big repeats that are lowly copied. Since the repeats are big and similar, there might be mispairing during mitosis or meiosis, leading to abberant recombination. As a result, gamete might have duplication of some gene leading to increased expression, and the other gamete might have missing gene leading human disease.

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12
Q

2 types of Highly repeated interspersed repetitive sequences

A
  1. Long interspersed nuclear element (LINE)

2. Short interspersed nuclear element (SINE)

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13
Q

What is LINE element?

A

There is only one type of LINE element that is active in human.
LINE 1 is transcribed and translated into protein which act as reverse transcriptase that reverse-transcribe mRNA into DNA which gets inserted back to random site of human genome. Thus LINE can copy themselves and enlarge the genome.
* It can also lead to mutation by leading to unequal crossover during meiosis just like Low copy repeats

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14
Q

What is SINE element?

A

Same as LINE except it is shorter than LINE. Also, during reverse transcription, SINE element hijack reverse transcriptase from LINE.

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15
Q

What is most common SINE?

A

Alu sequence, SINE contain a sequence that is recognized by Alu restriction enzyme.

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16
Q

What is pseudogenes

A

sequences that look like real genes but are not functional (no protein production) arisen during evolution.

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17
Q

Why are the pseudogenes? (3)

A

By gene duplication and subsequent mutation
by coping of RNA back to DNA and re insertion into genome
Or gene is just turned off for some reasons

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18
Q

Mt DNA is inherited from which parent?

A

Maternally inherited (from cytoplasm of oocyte)

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19
Q

What is the letter for short arms and long arm of chromosome?

A

p arm (short arm) q arm (long arm)

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20
Q

What is another name for 30nm coiling of DNA?

A

solenoid structure

21
Q

When is chromosome maximally condensed and visible?

A

metaphase

22
Q

3 types of chromosome nomenclature

A
  1. Metacentric chromosome : p and q arms are equal length
  2. Submetacentric chromosome : p arm is shorter than q arm or another way
  3. Acrocentric chromosome : p arm contains little genetic information or the other way (centromere at one end)
23
Q

What is another name for X-inactivation?

A

Lyonization

24
Q

What is X inactivation?

A

One of X chromosome is inactivated and condensed to form the Barr body in female. Determining which X to be inactivated (either from mom or dad) is random, mostly 50% chance. Once determined, the same X chromosome is inactivated in all the descendant of cell.

25
Q

When does X-inactivation occur?

A

Early stages of development of female embryos

26
Q

How is X-inactivation regulated?

A

It is regulated by X-inactivation center (Xic) which has the gene, XIST gene. XIST RNA coat one of the X-chromosome, that result in transcriptional interference. Methylation of cytosin bases and histone deacetylation results in transcriptional repression.

27
Q

What is difference between alleles?

A

Different versions of same gene that they have slight difference in the base pair DNA sequence.

28
Q

Familial hypercholesterolemia (LDL receptor deficiency)

A

Autosomal dominant disorder
Normally, LDL receptor is found on hepatocytes,
but for this disease, people have heterozygous for a loss of function mutation in one LDLR allele
- can be inherited

29
Q

Symptom of familial hypercholesterolemia

A

Have 2X the level of circulating LDL and high circulating cholesterol, leading to xanthomas (deposition of cholesterol) near elbow, ankle, wrists, palpebral area.
Also high risk for heart disease

30
Q

Huntington disease

A

Autosomal dominant disorder
Normal number of repeat : 20 times
Mutation of triplet (CAG) repeat expansion lead to gain of function of the protein, leading to protein accumulation in brain. This leads to degeneration of neurons in basal ganglia and cortex of the brain.

31
Q

Symptom of Huntington disease

A
  • chorea, cognitive decline, memory loss, sleep disorder
32
Q

Myotonic dystrophy

A

Autosomal dominant disorder
caused by a triplet repeat expansion in DMPK gene
Most pleiotropic phenotype of all unstabl triplet repeat disorder (meaning 1 mutation cause many unrelated effects)

33
Q

Symptom of Myotonic dystrophy

A

Wasting of muscle, cataracts, heart conduction defects, endocrine changes, myotonia, drooping face

34
Q

Achondroplasia

A

autosomal dominant disorder
due to FGFR3 (Fibroblast growth factor receptor 3) mutation,
FGFR3 is involved in differentiation of cartilage to bone.
Due to mutation in this gene, gain of function mutation leads to severe stunting of growth (shorter limbs with right size of head)

35
Q

What is special about FGFR3 gene?

A

It is a mutation hot spot which means new mutations are likely to occur de novo, so person could get mutation in this gene without family history.

36
Q

Symptom of achondroplasia

A

Severe stunting of growth (dwarfism, but not true dwarfism as head size is right)

37
Q

Neurofibromatosis (NF1)

A

Autosomal dominant disorder
due to mutations in NF-1 gene that codes for neurofibromin protein (a tumor suppressor protein)
- allelic heterogeneity(each person may have unique mutation in the gene)

38
Q

What does allelic heterogeneity mean?

A

The gene so large that there are many places where a new mutation may inactivate the gene, as a result disorder exhibit different mutations in the same gene, leading to variable expressivity.

39
Q

Symptom of neurofibromatosis

A

Cafe-au-lait spots (darkening of skin like mold)
Neurofibromas (swelling on the skin)
Lisch nodules in the iris of eye

40
Q

3 reasons why autosomal dominant mutations manifest in the heterozygous state

A
  1. Haplo-insufficiency
  2. Dominant-negative mutation
  3. Gain-of-function mutation
41
Q

Example of haplo-insufficiency of autosomal dominant mutation

A

familial hypercholesterolemia
Acute intermittent porphyria (heme is not produced fast enough)
Osteogenesis imperfecta type I (Half the amount of collagen cause brittle bone)

42
Q

What does dominant-negative mutation mean?

A

A mutant gene product interferes with function of normal gene product.
Eg. assembly of multimeric protein is affected by the presence of mutant protein.

43
Q

Example of dominant-negative mutation

A

Collagenopathies, Marfan syndrome

44
Q

What is gain-of-function mutation?

A

Result from increased levels of gene expression, or gene activity or the development of new function of the gene (Usually attainment of novel function)

45
Q

Example of gain-of-function mutation

A

Huntington’s disease, achondroplasia

46
Q

How is autosomal recessive disorders trasmitted?

A

Horizontal transmission (among siblings)
Parents are carriers
Male and female affected in equal frequency

47
Q

How consanguinity play a role in autosomal recessive disorder?

A

It can give rise to higher chance of having the disease.

48
Q

If siblings have autosomal recessive disorder, what is the probability of him being a carrier?

A

2/3 change

49
Q

Most enzyme deficiencies are autosomal dominant or autosomal recessive?

A

Autosomal recessive

BPM DLA1 (47 decks)

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