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Principles > Genetics > Flashcards

Genetics Flashcards

1
Q

what are the stages of the cell cycle and when does DNA replication occur

A

G1-S-G2-M

DNA replication occurs in S phase

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2
Q

what is mitosis

A

when one diploid parent forms 2 identical diploid daughter cells

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3
Q

what is meiosis

A

when one diploid parent forms 4 different haploid cells.

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4
Q

how does meiosis create genetically different cells

A

due to crossing over of the chromosomes

- essential for gamete formation

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5
Q

how does RNA differ from DNA

A
  • single stranded
  • uracil instead of thymine
  • ribose sugar
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6
Q

what do sequence variations within a gene cause

A

changes in promotor/exon sequences

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7
Q

what do sequence variations in-between genes cause

A
  • SNPs (single nucleotide polymorphisms)

- larger deletions/duplications

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8
Q

define polymorphisms

A

a sequence variation with a population frequency of >1%

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9
Q

do polymorphisms directly cause disease

A

NO. they do not cause disease in their own right but may predispose to common diseases

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10
Q

what is a mutation

A

a sequence variation that directly causes disease or any heritable change in human genome

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11
Q

define a classical genetic disease

A

one mutation sufficient to cause disease

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12
Q

define a multifactorial genetic disease

A

multiple polymorphisms cause risk of disease

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13
Q

normal female chromosome arrangement is…

A

46XX

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14
Q

what is a balanced chromosome arrangement

A

all chromosome material is present

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15
Q

what is an unbalanced chromosome arrangement

A

when there is missing or extra chromosome material

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16
Q

define aneuploidy

A

whole extra or missing chromosome

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17
Q

what is 47XY + 21

A

downs syndrome

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18
Q

what is 47XY + 14

A

miscarriage

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19
Q

what is 47XY + 18

A

Edward’s syndrome

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20
Q

what is 45X

A

Turner’s syndrome

21
Q

what is 47XXY

A

Klinefelter syndrome

22
Q

what is Robertsonain translocation

A

when two acrocentric chromosomes stick end-to-end

- increases risk of miscarriage

23
Q

what are acrocentric chromosomes

A

only have q arms. (long arms on bottom)

24
Q

what is microarray CGH

A

1st line chromosome test as picks up polymorphisms, deletions, duplications

25
Q

define mosaicism

A

different cells have different genetic make-up

26
Q

what is somatic mosaicism

A

all cells suffer mutations as they divide

27
Q

what genes are involved in cancer

A

oncogenes and tumour suppressors

28
Q

define penetrance of mutation

A

likelihood of getting disease if you have the mutation

29
Q

what does PCR allow you to do

A

select part of genome and amplify it

30
Q

what is a mendelian disorder

A

a disease that is caused by a change in a single gene

31
Q

what are the 3 mendelian disorders

A
  • Autosomal Dominant
  • Autosomal Recessive
  • X-linked (recessive)
32
Q

What is autosomal dominant

A
  • disease seen in all generations

- 50% risk of child being affected if parent is

33
Q

what is autosomal recessive

A
  • 2 faulty copies of gene required to cause disease
  • often only one generation affected
  • 25% risk of child being affected if parent is
34
Q

what is X-linked (recessive)

A
  • females need 2 copies to be affected
  • males need 1 copy to be affected
  • no male-to-male transmission
35
Q

what is X-inactivation

A

a cell only needs one working copy of X chromosome. In females, each cell has a random X chromosome inactivated

36
Q

what does mitochondrial DNA contain

A

genes for mitochondrial metabolic pathways and ribosomal RNA

37
Q

is mitochondrial DNA mainly maternal or paternal?

A

Maternal

38
Q

how do mutations cause disease

A
  • haploinsufficiency
  • dominant negative (abnormal protein interferes with normal protein)
  • loss of heterozygosity
  • mutation activates gene
39
Q

what is non-mendelian inheritance

A

DNA methylation leads to modification of histones which represses transcription

40
Q

what are the non-mendelian disorders

A

imprinting, angelman syndrome, heteroplasmy

41
Q

what is imprinting

A

differences in gene expression depending on whether gene is maternally or paternally inherited
- specific regions of chromosomes have imprinted genes (regions have both maternally and paternally imprinted genes)

42
Q

what is Angelman syndrome

A
  • a neuro-genetic disorder
  • causes developmental delay
  • causes intellectual disability
43
Q

what is heteroplasmy

A

different daughter cells contain different proportions of mutant mitochondria

44
Q

what are the characteristics gained by cells on progression to cancer

A
  • proliferation
  • evasion of immune system
  • avoid apoptosis
  • acquire vascular supply
  • metastasis
45
Q

what does FISH stand for and what is it

A
  • fluorescence in-situ hybridisation

- light up specific bit of chromosome

46
Q

breast cancer mutations

A

BRCA1

47
Q

what are the rare autosomal cancers

A
  • young age onset
  • many cancers
  • rare tumours
48
Q

what are the multifactorial predispositions of cancer

A
  • everyone at some risk

- anyone with family history

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