The Genetic Basis of Complex Inheritance - Non-Mendelian Inheritance Flashcards

1
Q

What are the three laws of Mendelian Inheritance?

A

The Law of Dominance.

The Law of Segregation.

The Law of Independent Assortment.

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2
Q

What is Non-mendelian Inheritance?

A

Does not fit in with Mendelian’s Law
e.g.
Gene conversion. Intermediate phenotype

Genetic material from only one parent?

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3
Q

What is the mechanism for the following Inheritance patterns : Incomplete Penetrance

Genomic Imprinting

Extranuclear Inheritance

Anticipation

A

Environmental factor
Genetic Modifiers

Variants from parents

e.g. Mitochondria mutations

e.g. Triplet repeat expansion

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4
Q

What is penetrance?

A

Penetrance is the frequency with which a trait is manifested by individuals carrying the gene.

Compares risk of the same disease between different mutations

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5
Q

What else apart from the CTFR mutation is responsible for the severity of CF in organs?

A

Genetic modifiers : Genes that have small quantitative effects on the level of expression of another gene.

May involve polymorphism.

Environment factors:
Lifestyle, Diet, Smoke, Alcohol, Drug,
Stress, Air pollution, Chemicals,
Infection, etc.

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6
Q

What are the effects of CF?

A

Sinusitis

Lungs - Sticky mucus build up, bacterial infection and widened airways

Skin - sweat glands produce salty sweat

Liver - blocked biliary ducts

Pancreas - Blocked pancreatic ducts

Intestines - Cannot fully absorb nutrients

Reproductive organs - complications

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7
Q

What is responsible for the rapid increase in prevalence of diabetes in the pacific region

A

Not merely genetic factors

obesity, unhealthy diets, and physical inactivity are also responsible

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8
Q

What is genomic imprinting?

A

When genes are altered / shut off during the production of gametes

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9
Q

What is Bi-allelic?

A

Same allele is turned on in both chromosomes from each parent?

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10
Q

What is mono-allelic?

A

Gene is only turned on from one of the parents chromosomes

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11
Q

What is the expression of genetic disease like in imprinted DNA?

A

Higher because there is only only copy of the gene

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12
Q

What are Epigenetic modifications?

A

Heritable changes in gene function that cannot be explained by changes in DNA sequences

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13
Q

What is Uniparental disomy?

A

Inheritance of a chromosome pair from one parental origin, because genes can be turned off there is a high risk of genetic mutation?

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14
Q

What are the three sources of UPD?

A

Trisomy rescue, Monosomy rescue, Mitotic error (non-disjunction or Duplication)

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15
Q

What is the result of uniparental diploidy?

A

Gynogenic
- 2 maternal genomes
- Mass of embryo
- Ovarian teratoma

Androgenic
- 2 paternal genomes
- Mass of placenta
- Hydatidiform mole

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16
Q

What is responsible for Angelman UPD?

A

Paternal UPD

17
Q

What is responsible for Prader - Willi syndrome?

A

Maternal UPD

18
Q

Describe the DNA of mitochondria

A

Circular form
Lack of efficient DNA repair system.
Lack of protective proteins, such as histones.
Damaged by reactive oxygen species (ROS), such as free radicals.

19
Q

Describe the incidence of mutations of Mitochondria

A

100-fold higher than the nuclear genome.

20
Q

What is polyploidy?

A

up to thousands mitochondria per cell.
2 - 10 copies per mitochondrion.

21
Q

What is Homoplasmy?

A

A eukaryotic cell whose copies of mitochondrial DNA are all identical. When in normal and healthy tissues, all cells are homoplasmic.

22
Q

What is Heteroplasmy?

A

(two or more mtDNA)

23
Q

What does mitochondrial Disease affect?

A

Tissues with high metabolic demand

24
Q

What is a three parent baby?

A

Nucleasr DNA from one woman, plus the mitochondrial DNA from another woman, plus the fertilisation by a male

25
Q

What are triplet repeat diseases?

A

Diseases whereby a triplet repeat is repeated moreso than normal, Hungtington’s disease

26
Q

Define anticipation

A

Anticipation:
Disease presents at earlier age and/or increasing severity in succeeding generations

27
Q

Give examples of diseases that are spotted in earlier generations and increase with severity in later ones

A

Hungtington’s disease
Myotonic dystrophy
Fragile X syndrome

28
Q

What is the source of mitochondrial disease?

A

Form of maternal inheritance - mitochondrial DNA comes from the mother

29
Q

What type of disorder is cystic fibrosis?

A

Autosomal recessive disorder

Caused by faulty 7q31 gene

30
Q

How does the affected CTFR gene result in the condition?

A

Chloride channel responsible for removing chlorine from the cell is absent

Sticky mucus build up on the outside of the cell because this protein is absent

31
Q

Describe the disorder of Myotonic dystrophy

A

Autosomal dominant disorder

32
Q

What is the effect of

A

Severe distal muscle weakness and learning disabilities

Age of onset decreases with successive generations

33
Q

Describe the disorder of duchenne’s muscular dystrophy

A

X-linked recessive

34
Q

Where is the mutation in duchennes musculr dystrophy?

A

In the dystrophin gene

35
Q

What is the effect of duchennes muscular dystrophy?

A

Weakness of proximal muscle (close to the trunk of the body)

Delay in walking
Death at around 20 years

36
Q

What are the three mechanisms for epigenetic modifications?

A

DNA methylation, histone modification and non-coding RNA (ncRNA)-associated gene silencing

37
Q

Why can’t the other copy of the gene compensate in the case of uniparental diploidy?

A

The same gene on the other chromosome can not compensate for the deletion because it has been turned off by methylation, an epigenetic modification.