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FPH exam > 2D public health genetics > Flashcards

2D public health genetics Flashcards

1
Q

What is public health genetics

A

The study- at population level- of genetics, genomics and their links to biomedicine

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2
Q

what is genetics?

A

The study of individual genes and how they are inherited

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3
Q

What is genomics?

A

The study of the entire genome of an organism, the interaction between genes and the effect if the environment on them

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4
Q

what are the 4 bases and which pairs with which

A

Adenine, thymine, guanine, cytosine

A–> T

C–>G

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5
Q

what is a codon

A

A triplet nucleotide sequence that encodes an amino acid.

Some codons encode the end of proteins

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6
Q

what are exons

A

Exons are part of the DNA which encode proteins

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7
Q

What percentage of the genome is made of exons

A

about 2 %

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8
Q

What is the function of non-protein coding DNA?

A
  • still being discovered
  • some is responsible for affecting how genes are expressed in different cells
  • ie skin and muscle cells contain the same DNA but the proteins are expressed differently in order to produce different cells with different function, non-coding DNA controls this
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9
Q

What is transcription

A

Transcription is when mRNA is produced from DNA

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10
Q

What is translation

A

Translation is when a protein is produced from mRNA

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11
Q

what is a peptide

A

A chain of amino acids

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12
Q

What percentage of DNA is the same between humans worldwide

A

99.9%

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13
Q

How does genetic material and phenotype differ between individuals

A
  • each individual is a combination of genes from their mother and father. During meiosis genes are shuffled resulting in gametes with different genetic material
  • random genetic changes occur during mitosis/meiosis, these may be repaired but some are not, they may have a impact on a protein leading to a mutation/polymorphism of they may have no impact
  • epigenetics: persistent heritable changes in how the genome is expressed can occur via DNA methylation etc which can affect a persons phenotype even if DNA is identical
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14
Q

What is a polymorphism and how does it differ from a mutation

A
  • A polymorphism is a variation in genetic sequence which is present in at least 1-2% of the population
  • typically not disease causing but they may confer a risk factor or a protective factor
  • the term mutation is generally reserved for harmful, disease causing changes in DNA
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15
Q

3 categories of inherited diseases

A
  1. Multifactorial diseases
  2. single gene disorders
  3. chromosomal disorders
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16
Q

Inherited diseases: multifactorial diseases

A
  • these diseases have multiple implicated genetic and environmental factors
  • whilst the presence of certain genes may increase/decrease risk they do not absolutely predict the risk of disease
  • Ie CHD, diabetes, many cancers
  • some genes may have a very small influence on the risk of subsequent disease whilst for others it’ll be greater (ie BRCA1 confers a 50-80% lifetime risk of breast cancer)
17
Q

Inherited diseases: single gene disorders

A
  • also known as mendelian disorders
    -ie CF
  • can be further classified as:
    Autosomal dominant (ie HD)
    Autosomal recessive (ie CF)
    X-linked dominant (ie coffin- lowry syndrome)
    X-linked recessive )ie haemophilia, DMD)
    Y-linked
18
Q

Inherited diseases: chromosomal disorders

A
  • affect whole chromosomes or large parts of chromosomes
    -can be subdivided into:
    1. Numerical disorders (ie trisomy 21)
    2. structural disorders (ie cri du chat where there is a deletion of the short arm of chromosome 5)
19
Q

what is a genotype

A

The set of alleles carried by an individual

20
Q

What is a phenotype

A

The observed characteristics resulting from expression of a persons genotype

21
Q

define homozygous

A

Carry 2 of the same alleles for a gene

22
Q

define heterozygous

A

carry 2 different alleles for a gene

the phenotype seen will depend on which allele is dominant

23
Q

What is penetrance

A

The proportion of people with a give genotype that express its phenotype

24
Q

What factors can result in different phenotypic appearances

A

VARIABLE PENETRANCE just because an allele is present does not mean it will be expressed

MORE THAN ONE GENE MUTATION ASSOCIATED WITH THE DISEASE
ie CF you can have nonsense mutations (no CFTR produced–> bad CF) and missense mutations (Faulty CFTR produced–> CF may not be so bad)

GENE ENVIRONMENT INTERACTIONS
- sometimes a gene is only expressed if certain environmental conditions are satisfied

EPIGENETIC CHANGES
This changes, which can be inherited across generations, can determine gene expression (ie DNA methylation)

25
Q

Give examples of non-mendelian inheritance

A
  • polygenic disorders
    -multifactorial disorders
  • mitochondrial inheritance
26
Q

Discuss mitochondrial inheritance

A
  • mitochonidria contain DNA
  • mitochondria are only found in the eggs and therefore mtDNA is inherited entirely from mothers
  • show a threshold effect where a child has to inherit above a proportion of faulty DNA to express the phenotype
    -inheritance is very unpredictable
  • eg Leighs disease
27
Q

Polygenic disorders

A

-some disorders, not usually considered genetic or inherited, show a strong generic component in family studies
- there are likely many genes implicated which interact with each other alongside the environment to confer risk
- identifying genes in polygenic disorders can help:
1. understand disease aetiology
2. predict who is at risk of illness
3. target health promotion to those most at risk
4. target treatment to those most likely to benefit
5. identify new disease targets

28
Q

Name 5 categories of environmental exposure that may increase disease risk and give examples

A
  1. Infection (ie HIV and burkitts lymphoma
  2. Chemical exposure (ie tobacco smoke and lung cancer)
  3. Physical hazards (ie radon gas and lung cancer)
  4. Nutritional (ie PKU and dietary phenylalanine
  5. Behavioural (ie obesity and inactivity)
29
Q

What is pharmacogenetics and give an example

A

Pharmacogenetics uses individuals genetic characteristics as the basis for understanding the relative effectiveness of different pharmaceuticals

ie Ivacaftor only works for certain CF gene mutations

30
Q

What is gene therapy and give an example

A

Gene therapy uses viruses, bacteriophages and plasmids to deliver healthy DNA into the cells of individuals with certain diseases

Has been used in severe combined immunodeficiency

31
Q

Two types of genetic testing in asymptomatic individuals with a family member who has a genetic disease

A
  1. PREDICTIVE GENETIC TESTING
    Testing for genetic diseases that have an adult onset. This can help them make decisions about strategies to mitigate risk and family planning Ie huntingtons disease and BRCA genes

2 INDIVIDUAL CARRIER SCREENING
Used for asymptomatic family members who have a relative with an AR or x linked disease. Helps inform decisions about children

32
Q

Predictive genetic testing for multifactorial disorders (what are the limitations and what would the advantages be)

A
  • could be used in the future
  • currently the predictive utility based on a single risk allele is poor
  • even using multiple alleles the the clinical utility of a polygenic test in predicting future disease is limited. This is because generally the risk is only slightly increased
  • nevertheless, with furthe refinement, testing for a combination of alleles may allow:
    1. risk stratification
    2. targeting interventions ie treatment/ screening
33
Q

When might genetic carrier screening programmes be used- give an example

A
  • may be used for commoner diseases
  • the UK antenatal screening programme tests pregnant women living in high risk areas for carrier status for thalassaemia and sickle cell
  • if the mother is a carrier the father is also tested
34
Q

Give examples of control measures that might be used for diseases with a genetic component (5)

A
  • preimplantation testing (in combination with IVF)
  • antenatal screening and testing (ie Edwards syndrome)
  • Earlier/ more frequent screening or prophylactic surgery (ie BRCA)
  • treatment to reduce disease risk (ie cholesterol lowering drugs in those with familial hypercholesterolaemia)
    -genetic counselling
35
Q

what is molecular biology

A

the study and manipulation of biological processes and structures at the molecular level

36
Q

Name 3 molecular biological techniques which have been developed to assist in studying DNA

A
  1. restriction enzymes to cleave DNA at certain points so a particular gene can be isolated and studied
  2. PCR so a gene or DNA sequence can be amplified for study
  3. DNA sequencing
37
Q

Give 5 uses for studying the genetics of pathogens with examples

A
  1. IDENTIFYING AN ORGANISM
    - looking at the genetic sequence can identify the organism causign disease
  2. ASSESSING VIRULENCE
    - some genes confer virulence to a pathogen such as antimicrobial resistance genes
  3. STRAIN IDENTIFICATION
    - looking at the genome can enable strain identification which can guide treatment ie in UK hep c genome 1 has greater treatment resistance
  4. CAN DETECT TRENDS IN NEW DISEASE STRAINS
    - ie a new COVID variant circulating
  5. OUTBREAK INVESTIGATON
    Linkage studies can assist in studying disease outbreaks

FPH exam (24 decks)

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