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POM GENETICS > Modes Of Inheritance > Flashcards

Modes Of Inheritance Flashcards

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Biology 101 flashcards
1
Q

What is dominant autosomal?

A

A characteristic is dominant if it manifests in a heterozygote (ie 2 different alleles at a locus)
- dominance refers to the phenotype

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2
Q

What gene is responsible for brown eyes and how?

A

The gene responsible OCA-2 controls amount of melanin in melanocytes. Active OCA-2 means brown, inactive OCA-2 means blue.

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3
Q

What is an autosomal dominant condition?

A

A condition where only one faulty allele/ gene is needed for the condition to be expressed

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4
Q

Can the autosomal dominant disorder arise de novo?

A

Yes it may, possible mosaicism

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5
Q

Where do autosomal dominant conditions manifest in?

A

They mainfest in heterozygotes

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6
Q

What are the effects of autosomal dominant conditions?

A
  1. Gain of function
  2. Insufficient amounts of protein being produced (rare)
  3. Dominant negative effect
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7
Q

What is an example of an autosomal dominant condition?

A

Huntingtons

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8
Q

What type of pedigree pattern do autosomal dominant conditions show?

A

Vertical pedigree pattern

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9
Q

What causes Huntingtons disease?

A

mutation, expansion of a CAG (glutamine) repeat huntingtin
which results in abnormal intracellular huntington protein aggregates
It gains a pathological function and is toxic to neurons resulting in cell death

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10
Q

What are the symptoms of huntington’s disease?

A

Symptoms usually start 30-50 y/o
Difficulty concentrating, depression, stumbling, involuntary jerking, problems swallowing

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11
Q

What is meant by gain of function?

A

gene now makes a protein with a new function e.g., constitutively active, aggregates

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12
Q

What is meant by a dominant negative effect?

A

The mutated form interferes with the activity of proteins it binds e.g., dimers or multimers which reduces activity

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13
Q

How do autosomal dominant conditions effect men and women?

A

They affect men and women equally and they are equally likely to pass on the condition

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14
Q

Is osteogenesis imperfecta a recessive autosomal disease?

A

No, it is dominant autosomal

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15
Q

What is osteogenesis imperfecta?

A

Brittle bone disease
Group of genetic disorders mainly affecting bones
Bones break easily
Mild to severe

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16
Q

What are the symptoms of osteogenesis imperfecta? (4)

A

hearing loss, breathing problems, short height, blue tinge to white of eyes

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17
Q

What is Type I osteogenesis imperfecta?

A

insufficient quantities of collagen

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18
Q

What are type II, III, and IV osteogenesis imperfecta?

A

mutation of collagen results in an abnormal protein has an altered structure and interferes with the function of the normal protein (expressed from the normal gene)

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19
Q

What is the overall result of osteogenesis imperfecta?

A

Weakening connective tissue particularly bone

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20
Q

What are autosomal recessive conditions?

A

where carriers of recessive disease have lost a single copy of a gene but the normal one is sufficient to maintain normal function

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21
Q

What does recessive mean?

A

2 copies of the abnormal gene must be present in order for the disease or trait to develop

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22
Q

What are the usual effects of autosomal recessive conditions?

A

Loss of function - having both copies results in a completely malfunctioning protein e.g., deletions

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23
Q

Are children usually affected with recessive disorders?

A

No, normally unaffected, each subsequent sibling of an affected child has a 1 in 4 chance of being affected

24
Q

What type of pedigree pattern do autosomal recessive conditions show?

A

Horizontal pedigree

25
Q

What can increase the risk of autosomal recessive conditions?

A

Consangious marriages

26
Q

Why can autosomal recessive conditions skip generations?

A

Due to the high chance of being a carrier

27
Q

How are men and women affected with autosomal recessive conditions?

A

They are affected equally

28
Q

What type of chromosomes are autosomal recessive genes located on?

A

Non-sex chromosomes

29
Q

What percentage of DNA is shared between first cousins?

A

12.5%

30
Q

Is cystic fibrosis a recessive disorder?

A

Yes

31
Q

What are symptoms of cystic fibrosis? (4.5)

A

Failure to thrive
The defective chloride ion channel results in impaired Airway defense
Prone to respiratory infections
Digestive issues e.g., meconium ileus
Largest cohort of chronically infected patients

32
Q

What causes cystic fibrosis?

A

Mutation, various mutations in gene encoding chloride ion channel (CFTR gene on chromosome 7)

33
Q

What does the mutation in cystic fibrosis result in?

A

Defective chloride ion channel
Loss of function, degraded faster or present in inadequate amounts

34
Q

Who do X-linked recessive conditions mainly affect?

A

Men (as it is effectively dominant)

35
Q

How can females have an X linked recessive condition?

A

They have to be homozygous for the condition

36
Q

What is the chance of a daughter of an affected male being a carrier of an X Linked recessive condition?

A

100%

37
Q

What is an X linked recessive condition?

A

Where the alleles are located on the sex chromosomes, and since males have XY, a portion of their second chromosome is missing, meaning males have an increased risk of the condition as they only need the one recessive allele to have the condition

38
Q

What are the probabilities of X linked recessive disorders?

A

Brothers of affected son have 1 in 2 risk of having disorders
Sisters 1 in 2 chance of being a carrier

39
Q

What happens to the daughters and sons of an affected father and unaffected mother of an X linked dominant condition?

A

Daughters - They are all affected

Sons - none affected

40
Q

What is an X-linked dominant disorder?

A

Similar to autosomal dominant pattern (seen in both sexes)
Condition is often milder and more variable in females than in males
some diseases only present in female as males not viable

41
Q

what is the possible mechanism of a dominant x-linked disorder?

A

gene mutation
causes overproduction of protein
inhibit a function

42
Q

what is an example of an x-linked recessive disorder?

A

Haemophilia- more frequent or severe bleeds, different levels of severity, factors VIII or IX

43
Q

Can female carriers exhibit subtle signs of an x-linked recessive disorder?

A

yes

44
Q

Who do Y linked disorders affect?

A

Only men as females do not have Y chromosome

45
Q

What type of pedigree pattern do Y linked disorders show?

A

Vertical pattern with only males affected

46
Q

What can a y-linked disorder cause?

A

Mutation in gene cells to produce a defective protein

47
Q

What are mitchondria?

A

Specialized organelle of eukaryotes
Share an evolutionary past with bacteria
Have their own DNA
Majority mitochondrial proteins encoded by nuclear genes
- Mutations in these genes cause most mitochondrial disease
Some disease caused by mutations mitochondrial DNA

48
Q

Who are all your mitochondria inherited from?

A

Mother

49
Q

What type of pedigree pattern does mitochondrial inherited disorders show?

A

Vertical

50
Q

A mother has a mitochondrial condition. What happens to her children?

A

They are all affected

51
Q

Why do mitochondrial disease vary in general?

A

Mitochondria have multiple copies genome some normal, some mutant (heteroplasmy)
Only express the disease effects if above a threshold
Due to mitochondria endosymbiosis (bacterial origin) they replicate by binary fission
Can lose or gain mutated genes in the process

52
Q

What causes most mitochondrial diseases?

A

not all mitochondrial diseases are caused by mutations in mitochondrial DNA
Most are caused by mutations in cell genome and have medalian or sex chromosome linked inheritance

53
Q

Why do the expression of mitochondrial conditions vary massively in a family?

A

When the mitochondria replicate, genes can be lost or gained meaning there is an enormous amount of variation

54
Q

How does severity vary with mitochondrial diseases?

A

Random segregation
Number of affected mitochondria
Symptoms develop once threshold is reached
Cells different number of mutant mitochondria can change with time
Develops with age due to accumulation of mutant mitochondria

55
Q

What are normally affected with mitchondrial diseases?

A

Motor and nerve function
Can present as unrelated multi-system symptoms

56
Q

Are mitochondrial conditions variable within a family?

A

Yes

57
Q

What type of inheritance is it when children of unaffected parents are affected?

A

X Linked recessive

POM GENETICS (9 decks)

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