Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

EMS - GiM > (2) Categories and impact of genetic disease > Flashcards

(2) Categories and impact of genetic disease Flashcards

1
Q

What are the 3 points of the triangle representing aetiology of disease?

A

100% environmental

Single gene

Polygenic

For any condition, the balance of genetic and environmental factors can be represented by a point somewhere within the triangle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What type of condition is achondroplasia?

A

Single gene but different heights

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of condition is stroke?

A

Multifactorial with environment and polygenic factors - for some there may be single gene influence (Cadasil)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

On a scale from 100% genetic to 100% environmental, what are the characteristics of diseases nearer the 100% genetic end?

A
  • rare
  • simple genetics
  • unifactorial
  • high recurrence rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

On a scale from 100% genetic to 100% environmental, what are the characteristics of diseases nearer the 100% environmental end?

A
  • common
  • complex genetics
  • multifactorial
  • low recurrence rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Give an example of a 100% genetic disease

A

Duchenne muscular dystrophy (single gene - mutation in dystrophin gene)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Give an example of a 100% environmental disease

A

Scurvy

tuberculosis also near this end of the scale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Is osteogenesis imperfecta (OI) more genetic or environmental?

A

In the middle but nearer the 100% genetic end of the scale

Bone fragility caused by genes, expression different on environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Give 5 classifications of genetic disorders

A
  • multifactorial/complex
  • single gene
  • chromosomal
  • mitochondrial
  • somatic mutations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are multifactorial/complex genetic disorders?

A

The interaction of multiple genes (genetic predisposition) in combination with environmental factors eg. type II diabetes, ischaemic heart disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a single gene genetic disorder?

A

A mutation in a single gene = Mendelian inheritance - AD, AR, XL eg. cyctic fibrosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a chromosomal genetic disorder?

A

An imbalance or rearrangement in chromosome structure eg. aneuploidy, deletion, translocation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a mitochondrial genetic disorder?

A

A mutation in mitochondrial DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a somatic mutation genetic disorder?

A

Mutation(s) within a gene(s) in a defined population of cells that results in disease eg. breast cancer

Not born with the mutation, mutation not found in the blood but found in the tumour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 4 single gene modes of inheritance?

A
  • autosomal dominant
  • autosomal recessive
  • X-linked
  • mitochondrial
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the characteristics of autosomal dominant (AD) inheritance?

A
  • a trait or disease runs from one generation to the next
  • males and females equally affected
  • offspring of affected person has a 50% chance of inheriting the mutation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the chance of the offspring of an affected parent inheriting an AD disorder?

A

50% (1 in 2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Autosomal dominant disordes are usually related to what?

A
  • structural proteins
  • receptors
  • transcription factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Give some examples of autosomal dominant disorders that are caused by gene mutations

A
  • myotonic dystrophy
  • marfan syndrome
  • huntington disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Give an example of an autosomal dominant disorder that is cause by chromosomal deletion or duplication

A

22q11 deletion syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Are affected individuals of AD disorders homozygous or heterozygous?

A

They are heterozygous for the mutation (one copy of mutation/one normal gene)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does ‘penetrance’ mean?

A

The frequency with which a specific genotype is expressed by those individuals that possess the mutation, usually given as a percentage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is incomplete penetrance?

A

Not all relatives who inherit the mutation develop the disorder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Give an example of a mutation that has incomplete penetrance

A

BRCA1 mutations - 80% life time chance of developing breast cancer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Penetrance may alter with which factor?
Age - eg. Huntington disease by 80 years has 100% penetrance
26
What is 'expressivity'?
Variation in expression - the extent to which a heritable trait is manifested by an individual
27
Give 2 examples of genetic diseases that vary in expressivity
- Marfan syndrome = 100% penetrance but some have aortic dilatation, lens dislocation, stretch marks etc, others do not - BRCA1 mutation = some may have ovarian cancer, some may have breast cancer, some both and some not at all (as it is not 100% penetrant)
28
What is 'anticipation'?
The symptoms of a genetic disorder become apparent at an earlier age as it is passed from one generation to the next. In most cases, there is an increased in the severity of the symptoms too
29
Give 2 examples of genetic disorders that show anticipation
- myotonic dystrophy | - huntington's disease
30
What is a new dominant/ de novo mutation?
A new mutation that has occurred during gametogenesis or in early embryonic development
31
Are the parents of those with new dominant/ de novo mutations affected?
No The parents are not affected and the mutation is not detected in their blood cells. The child is the first to be affected in the family but can pass the mutation on to their own children
32
What are the characteristics of autosomal recessive (AR) inheritance?
- disease seen in one generation - does not tend to pass from one generation to the next and so parents usually unaffected - offspring of affected individuals has low risk of disease unless in consanguineous relationship - relatives may be asymptomatic carriers of the disease - affects males and females equally - gene mutations, not chromosomes
33
Are those with autosomal recessive disorders homozygous or heterozygous?
Affected individuals are homozygous or compound heterozygous (two different mutations but they work together to give the disease)
34
What is the risk of offspring being affected if both parents are carriers of an AR disease?
1/4 (25%)
35
What is the risk to unaffected offspring being a carrier? (when both parents are heterozygous carriers of AR disorder)
2/3
36
Give some examples of autosomal recessive disorders
- cystic fibrosis - many of the metabolic disorder - haemachromatosis - sickle cell disease
37
Who is affected by X-linked inheritance?
- males affected - females may be unaffected, mildly affected or fully affected - males usually more severely affected than females
38
Why is male to male transmission not possible in X-linked disorders?
Fathers pass on their Y chromosome to their son Daughters all carriers as they definitely get their dad's X chromosome
39
Give some examples of X-linked disorders
Gene mutations and chromosome deletions/duplications - duchenne muscular dystrophy - fragile X syndrome - red/green colour-blindness - haemophilia
40
What is the chance of a so having haemophilia given that the father is affected with haemophilia?
All sons are unaffected (no male to male transmission) All daughters are carriers
41
In XL carrier females, the phenotype is very variable. What are the 2 main factors influencing expression of phenotype?
- X inactivation | - XL dominant vs. XL recessive inheritance
42
What is another name for X-inactivation?
Lyonisation
43
What is X-inactivation/lyonisation?
The process of random inactivation of one of the X chromosomes in cells with more than one X chromosome Compensates for the presence of the double X gene dose
44
What is a Barr body?
The inactive X chromosome rendered inactive during lyonisation (the condensed X chromosome)
45
Is X inactivation normal?
It is normal and occurs when there is 2 or more X chromosomes Occurs in early embryogenesis
46
Which X is silenced during X-inactivation?
Random
47
Does the silenced X chromosome remain inactive?
Once inactivated, an X chromosome remains inactive throughout the lifetime of the cell and all its descendants
48
Which genes are switched off on the inactivated X chromosome?
Most, but not all genes are switched off on the inactivated X chromosome
49
What does skewed X-inactivation mean?
There is a random preference for the "normal" X chromosome to be inactivated - significant phenotype
50
What is tissue variability in terms of X-inactivation?
There is a random preference for the X chromosome with the mutation to be active in crucial tissue group eg. muscle in Duchenne muscular dystrophy
51
Are XL dominant or XL recessive disorders more common?
XL recessive XL dominant conditions are rare
52
Give an example of an XL dominant condition
Rett syndrome Lethal in males, phenotype only in females Females only need gene on one of their Xs to show phenotype
53
What type of inherited disorder is fragile X syndrome?
XL dominant Females can be asymptomatic to fully symptomatic (due to X-inactivation pattern)
54
Give 2 XL dominant disorders
- Rett syndrome | - Fragile X syndrome
55
Give examples of XL recessive disorders
- red-green colour blindness - haemophilia - duchenne muscular dystrophy
56
Are girls affected by XL recessive disorders?
Carrier girls usually unaffected BUT can have significant symptoms because of X-inactivation switching off the normal X Girls are fully affected if they inherit the mutation from mum and dad
57
Give examples of mitochondrial inheritance disorders
- maternally inherited diabetes and deafness
58
Where do we inherit mitochondrial DNA from?
All mitochondrial DNA comes from the egg The sperm head does not have any mitochondria All out mitochondria are inherited from our mother
59
Who is affected by mitochondrial inheritance disorders?
Males and females are affected equally Rare
60
How many genes are there within mitochondrial DNA?
27 genes Every mitochondrion has many copies of each gene
61
How are offspring affected by mitochondrial inheritance?
An affected mother will give all of her children the mutation All the children of an affected man will be unaffected Highly variable expressivity and therefore severity of phenotype between relatives
62
Why is family history taking important?
- helps make a diagnosis - helps clarify risk for the patient - helps understand the patient's point of view - helps identify who else may be at risk - helps understand the patient's support network
63
How are males and females represented in a family pedigree?
Female = circle Male = square
64
How do you show a person has died in a family pedigree?
Draw a line through the circle/square
65
What information should you record about each person on a family pedigree?
- name - maiden name - date of birth
66
What does a line through a line connecting two people mean?
The couple has split up
67
What are 2 questions you shouldn't forget to ask when taking a family pedigree? (concerning half siblings and step siblings)
- "do the children all have the same dad?" - half siblings | - " do either of you have any other children from other relationships?" - step siblings
68
What are 2 questions you shouldn't forget to ask when taking a family pedigree? (concerning miscarriages)
- "have you had any other pregnancies?" | - "do you know if anyone in the family has had any miscarriages?"
69
How should you represent a person affected by the condition in question?
Colour in the square/circle
70
How is a miscarriage (spontaneous abortion) represented in a family pedigree?
Triangle
71
How is a therapeutic abortion represented in a family pedigree?
Triangle with a line through it
72
How is a stillborn baby of unknown sex represented?
Diamond with a line through it
73
How is an asymptomatic carrier of a recessive gene mutation represented in a family pedigree?
A coloured in circle in the middle of the square/circle
74
What does a double line connecting 2 people mean in a family pedigree?
Consanguineous couple
75
What is consanguinity?
- couples who are "blood" relatives - potentially share recessive gene mutations - seen in all ethnic groups
76
How does consanguinity change the risk of congenital birth defects?
Risk of congenital birth defects = 5-6% compared to 2-3% in the general population Given that there is no family history of genetic condition
77
How is a person of unknown sex represented in a family tree?
A diamond
78
How are twins represented in a family tree?
(look at image of this slide 33)
79
What does EDD mean in a family pedigree?
Expected date of delivery

EMS - GiM (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions