Genetics 5, 6, 7 - Modes of inheritance, cancer and clinical practice Flashcards Preview

1st Year - Principles > Genetics 5, 6, 7 - Modes of inheritance, cancer and clinical practice > Flashcards

Flashcards in Genetics 5, 6, 7 - Modes of inheritance, cancer and clinical practice Deck (33)
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1

What are the 4 non-mendelian modes of inheritance?

MultifactorialiMprinting (epigenetic modification of DNA)MitochondrialMosaicism

2

What are copy number variations? (CNV)

Extra or missing stretches of DNA

3

Penetrance of genetics in a mendelian disorder?

High

4

Pentrance of genetics in a multifactorial disease?

Genetic change is just another risk factor, therefore penetrance is low for any one mutation

5

How many genes do monozygotic and dizygotic twins share?

Monozygotic = allDizygotic = 50%

6

What does P

There is a 1 in 20 probability that the data you see has happened by chance

7

What are risk models?

Any equation that ties together different risk factors and gives you a risk prediction for your patient

8

What is epigenetic modification of DNA/ imprinting?

When only one working allele is inherited (either mum or dad allele has been silenced) due to heritable alterations that are not due to changes in DNA sequence. Rather, epigenetic modifications, or tags, such as DNA methylation and histone modification, alter DNA accessibility and chromatin structure, thereby regulating patterns of gene expression.

9

What is DNA methylation?

an epigenetic mechanism that occurs by the addition of a methyl (CH3) group to DNA, thereby often modifying the function of the genes

10

What is the name for DNA complexed with histones?

Nucleosomes

11

Difference between chromosomes, chromatin and chromatids?

Chromatin = double-stranded helical structure of DNANucleosome = DNA complexed with histonesChromataosome = nucleosome + H1 proteinChromosome = tightly coiled nucleososmes - made up of chromatid

12

Where does methylation of DNA usually occur?

On cytosine bases just before guanine bases

13

What does DNA methylation cause?

Modification of histones repressing transcription

14

What is an example of a disease that can occur due to abnormalities of methylation?

Cancer (methylation causes gene silencing - histone de-acetylation is a drug target)

15

What is an example by how environment affects methylation?

Starvation during pregnancy affects foetus - methylation allows your environment to affect your genome

16

How can methylation affect behaviour?

RETT syndrome - changes methylation pattern of the genes in brain to the point were certain functions of the brain stop working

17

What are the symptoms of angelman syndrome?

Neurogenetic disorder causing developmental delay, intellectual disability, ataxia, epilepsy, happy demeanour, frequent laughing and smiling

18

What causes Angelman's syndrome?

Not having the working copy of the UBE3A gene on chromosome 15It only works in the mother's copy - fathers copy is methylated

19

What does methyl cytosine mutate easily to?

Thymine

20

Apart from in the nucleus, where else is DNA kept in humans?

Mitochondria

21

What is heteroplasmy?

Different daughter cells contain different proportions of mutant mitochondria

22

What are symptoms of mitochondrial disease?

MyopathyDiabetesDeafnessOptic atrophyStroke like episodesEncephalitis(dependant on mutation type and level of heteroplasty in different tissues)

23

Are daughters affected more in mitochondria inheritance?

No - sons and daughters are affected equally

24

What are the 4 ways in which DNA can be damaged?

Inherited mutationsDNA strand breaksMistakes in DNA synthesisChemical damage e.g. UV, smoking

25

What are the main mechanisms by which genes are activated? (3)

Duplication of the geneActivation of the gene promotorChange in amino acid sequence

26

What is the fate of a cell that has accumulated DNA damage? (4)

RepairSenescenece (cessation of cell growth of potentially cancerous cells)ApoptosisTumour growth

27

Mechanisms of DNA repair?

Direct repairBase excisionNucleotide excisionMis-match repair complex

28

What is mis-match repair?

Mis-mathc e.g. A-C is recognised and excised by mis-mathc repair complex

29

What is an example of a condition caused by a mutation in a mis-match repair gene?

Hereditary non-polyposis colorectal cancer

30

What do BRCA1/2 carriers have in terms of cancer risk?

An 80% chance of developing breast or ovarian cancer