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POM Revision Cards > Genetics > Flashcards

Genetics Flashcards

1
Q

Heteroplasmy?

A

Heteroplasmy - mitochondria have multiple copies of the genome - some may be mutant, others normal.

Mitochondria - vertical pedigree.

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2
Q

Which 3 changes are caused by autosomal dominant diseases?

A

Gain of function
Dominant negative - interferes with activity of proteins it binds
Insufficient - mutant gene = half amount of protein, not enough for normal function

autosomal dominant can be de novo - possible mosaicism

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3
Q

Reasons for using pedigrees?

A

Calculate risk of passing on disease or being carrier
Explain pattern to patient
Identify potential carriers
Easy

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4
Q

Risk modifiers?

A

Which side of family disease is on
Ethnic background

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5
Q

Causes of phenotypic variability?

A

Environment
Sex
Modifiers
Mutation
Unstable

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6
Q

Unstable mutations?

A

Trinucleotide repeat disorders

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7
Q

Karyotype method?

A
  1. 5ml heparinised venous blood collected, white blood cells isolated
  2. Culture in phytohaemagglutinin which stimulates T lymphocyte growth
  3. 48 hours later, add colchicine (causing mitotic arrest)
  4. Place in hypotonic saline which bursts cell, and place on slide.
  5. Fix and stain with Gisema, cut out individual chromosomes and arrange.
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8
Q

DNA compaction?

A

DNA is compacted around histones and further condensed into chromatin - what we see in karyotype.

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9
Q

Ideogram?

A

Way of showing chromosome based on G banded architecture.

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10
Q

Band formation?

A

Formed by Giesma staining, darker if they take up more stain.

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11
Q

Prophase vs metaphase karyotype?

A

Often in prophase more than metaphase as chromosomes are less compact here

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12
Q

Aneuploidy and meiosis?

A

Aneuploidy - abnormal number of chromosomes

Meiosis- to reduce from diploid to haploid. Ensure genetic variation in gametes by random assortment of homologues and recombination.

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13
Q

Non disjunction?

A

When chromosomes aren’t split properly between daughter cells and can occur in meiosis I or II.
If in meiosis I, all daughter calls are affected.
If in meiosis II, half daughter cells are affected.
sex chromosome most common form

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14
Q

Heterochromatin vs euchromatin?

A

Heterochromatin - dark bands, more compact but fewer cells.

Euchromatin - more open and more genes.

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15
Q

Maternal vs paternal effects on Aneuploidy?

A

Trisomy 21 increases with maternal age due to non disjunction. Oogenesis vulnerability - degradation of factors which hold homologous chromatids together.

Paternal age has no effect, but smoking does. ‘Selfish spermatogonial selection’ can affect gene disorders.

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16
Q

Crossing over?

A

To increase genetic diversity. Pairs of chromosomes align, form chiasma, crossover.
Can go wrong if chromosomes not lined up - unequal crossover, leads to deletion in one chromosome and duplication in the other.

Can cause partial trisomy or monosomy.

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17
Q

Deletion vs duplication vs inversion?

A

Deletion - microscopic or microdeletion.
Duplication - usually milder phenotype than reciprocal deletion.
Inversion -

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18
Q

FISH?

A

Fluorescent in situ hybridisation - if deletion is too small to see using standard karyotyping.

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19
Q

Robertsonian translocation?

A

Occurs between acrocentric chromosomes.
Metacentric - short and long arms are of equal length and centromere in middle of chromosome.
Submetacentric - short arm is shorter than long arm.
Acrocentric - short arm has been shortened down to residual stump.
silent carriers, but can cause problems for offspring

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20
Q

Mosaicism?

A

Presence of 2 or more populations of cells with different genotypes.
X inactivation results in mosaicism
Can arise from non disjunction in early pregnancy or loss of extra chromosome in early development.

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21
Q

Paracentric vs pericentric?

A

Paracentric - inversion that does not include the centromere (away from the centre)
Pericentric - includes centromere, around centre

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22
Q

Nomenclature of ideogram?

A

17p12
1. Chromosome number
2. Which arm
3. Region on arm

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23
Q

Mendelian trait?

A

Controlled by a single gene

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24
Q

Complex trait?

A

Controlled by multiple genes and the effect of the environment

25
Q

Continuum from Mendelian to complex trait?

A

Not totally separate but depends on both. E.g. sickle cell anaemia.

26
Q

Heritability with causes?

A

How much our phenotype variability is due to genetics.
1. Genetic differences
2. Shared environment
3. Unique environment

27
Q

Single nucleotide polymorphism?

A

DNA sequence variations that occur when a single nucleotide is changed at a specific point in the genome that is present in a sufficiently large fraction of the population.

28
Q

Genome wide association studies?

A

Doing association analysis for the whole genome. Over 10 million SNPs.
Pros - can identify SNP variant associations
Cons - doesn’t identify causal variants, can’t identify all heritability.

29
Q

Missing heritability hypothesis?

A

In genome wide studies, SNPs cannot account for much of disease, heritability, and phenotype. Other factors must cause lots.

30
Q

Pharmacogenomics?

A

Study of variability in drug response due to genetic differences

31
Q

Pharmacokinetics?

A

What the body does to the drug

32
Q

Pathway for drug and SNP effects on this?

A

Absorption, activation, target, inactivation, excretion.
SNP can decrease P-gp levels which decreases absorption.
SNPs can change metabolism.
personalised medicine

33
Q

12 week ultrascan aim?

A

Normal nuchal scan
Dates pregnancy, diagnoses multiple pregnancies, diagnoses major foetal abnormalities, assesses risk of Down syndrome and other chromosomal abnormalities.
anomaly scan at 20 weeks if any issues

34
Q

Nuchal translucency test?

A

Done at 10-14 weeks.
Tests thickness if fluid at back of neck.
Screening, not diagnostic.
Increased thickness >3mm fluid at back of neck can indicate chromosomal abnormalities

35
Q

Invasive prenatal testing examples?

A

Chorionic villus sampling (11-14 weeks)
Amniocentesis (16+ weeks, sample of amniotic fluid)

36
Q

Prenatal non-invasive testing examples?

A

Maternal blood test
Cell free foetal DNA (cffDNA, 4-5 weeks gestation, cannot be detected on test until 9 weeks).

37
Q

3 tests done with foetal DNA?

A

Tests for genetic disorder
Karyotype
QF-PCR

38
Q

CGH array?

A

For concerns in 20 week scan, for micro deletions and duplications.

39
Q

Reproductive options?

A

Natural
Adoption
Egg and sperm donation
Pre-implantation genetic diagnosis

40
Q

Germline vs somatic mutations?

A

Germ line - germ cells produce sperm or eggs, undergo meiosis and mitosis, heritable

Somatic - in non-germline tissues, non-heritable.

41
Q

Hallmarks of cancer?

A

Evading apoptosis
Self sufficiency in growth signals
Insensitivity to anti-growth signals
Tissue invasion -p+ metastasis
Limitless replication potential
Sustained angiogenesis

42
Q

Benign vs malignent?

A

Benign - slower growth, well differentiated, capsulated, does not invade neighbouring tissue, does not metastasise.
Malignant - fast growth, poorly differentiated, non-capsulated, invades neighbouring tissue, invades basement membrane and metastasises.

43
Q

Passenger vs driver mutations?

A

Passenger - occur during cancer growth, don’t contribute to phenotype
Driver - contribute to cancer growth and can cause clonal expansion

44
Q

Two hit hypothesis?

A

Genetic damage isn’t sufficient to enable cancer to develop, second hit initiates it.

45
Q

PD-L1 and CAR-T therapy?

A

PD-L1 - downregulates T cells

CAR-T therapy -T cells removed and modified to recognise PD-L1 receptor on cancer cells, so can be broken down via apoptosis

46
Q

CML?

A

Reciprocal translocation between chromosome 9 and 22, fuses BCR and ABL. Elevated tyrosine kinase.

47
Q

Cancer mechanisms?

A

Oncogenes -
Tumour suppressors -
Viruses -

48
Q

Inborn errors of metabolism?

A

Substrate cannot be converted to product. Affect various pathways of metabolism. E.g. PKU.

49
Q

Pharmacological chaperones?

A

Fix misfolded proteins

50
Q

Pharmacological modulators?

A

Receptor agonist/antagonists. Ion channel activators or blockers.

51
Q

Combination therapy?

A

Chaperone and activator for CF

52
Q

Stop codon read through?

A

Treats diseases caused by non-sense mutation which prevents protein production

53
Q

Mitochondrially inherited disease therapy?

A

Requires IVF and normal mitochondria from donor.

54
Q

Viral gene therapy?

A

Engineering a virus to carry a therapeutic gene.

55
Q

Anti-sense oligonucleotides?

A

Targeted against the gene that cause the disease. Treat dominant diseases caused by gain of function.

56
Q

Exon skipping?

A

Treat deletions, only used for large proteins.

57
Q

Ex vivo gene therapy?

A

For diseases that affect haemopoietic cells.

58
Q

In vivo therapies?

A

Can insert genes in vivo to replace defective genes, useful for treating recessive diseases. For lack of copy of functional gene.

59
Q

Ras mutations?

A

Ras controls signalling cascade - mutation means that cancer cells can grow uncontrollably and evade death

POM Revision Cards (7 decks)

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