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Principles Collated Flashcards > Genetics > Flashcards

Genetics Flashcards

1
Q

2 factors of a disease?

A

Environment + genes

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2
Q

What processes occur in a 5’ -3’ direction?

A

Replication and reading of DNA structure

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3
Q

What is the DNA backbone composed of?

A

Sugar-phosphate

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4
Q

4 bases in DNA?

A

Thymine
Adenine
Cytosine
Guanine

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5
Q

What happens when DNA strand associates with proteins (name example of type of proteins)?

A

Histones

It is wound into a chromosome structure

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6
Q

Explain what can happen to DNA in replication and what it’s defect can result in?

A

Damaged during replication

-Repair mechanisms exist but when these have defects disease occurs

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7
Q

The stages of cell cycle?

A

G1, S, G2, M, G1

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8
Q

What stage of cell cycle does DNA synthesis take place in?

A

S phase

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9
Q

What unzips DNA molecule?

A

DNA Helicase

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10
Q

Which enzyme copies the 5’-3’ strand?

A

DNA polymerase

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11
Q

Interphase?

A

Cell is not dividing the stages of cell cycle included in this is S, G0, G1 & G2
Cell grows and is metabolically active

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12
Q

G2?

A

After DNA replication the cell continues to grow and produce proteins

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13
Q

M phase?

A

Mitosis checkpoint

Are chromosomes aligned on the spindle

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14
Q

G1?

A

Cell may increase in size, produce RNA and synthesize protein

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15
Q

S phase?

A

Period of DNA replication

Going from 2n- 4n in preparation for mitosis

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16
Q

How does DNA polymerase work with Okazaki fragments?

A

Copies the 3’-5’ strand which DNA ligase joins

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17
Q

Mitosis outcome?

A

One diploid cell becomes two identical daughter diploid cells

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18
Q

Meiosis outcome?

A

One diploid parent cell becomes 4 haploid daughter cells

  • crossing over occurs to produce variation
  • Gamete formation
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19
Q

Describe an RNA strand?

A
  • Single stranded
  • Ribose sugar
  • Uracil replaces thymine
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20
Q

Brief description of DNA-> protein?

A 
DNA
|                     Transcribing and splicing 
RNA
|                     Translation 
Protein
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21
Q

In detail transcription and translation?

A
  • DNA transcribed to pre-mRNA
  • Pre-mRNA pliced (removal of introns) to form mRNA
  • mRNA translated to protein (3 bases= 1 amino acid/stop codon)
  • Protein is modified and moved around cell
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22
Q

Types of sequence variations within a gene?

A

Changes in promoter sequence

Changes in exon sequence

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23
Q

Types of sequence changes in DNA between genes?

A

SNP’s

Larger deletions/duplications

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24
Q

What is a polymorphism?

A

Any variation in the human genome which has a population frequency of <1%

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25
Q

A polymorphism will cause disease. True or false?

A

FALSE

It can cause a disease but not in it’s own right, may predispose to a common disease

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26
Q

What is a mutation?

A

Gene changes that cause a genetic disorder

-any heritable change in the human genome

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27
Q

How many mutations required in a classical genetic disease?

A

One mutation sufficient to cause disease

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28
Q

Describe multifactorial disease and it’s relation to polymorphisms?

A

Multiple polymorphisms cause a risk of disease

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29
Q

Chromosome make up of a normal female?

A

46XX

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30
Q

What consists of an unbalanced chromosome rearrangement?

A
  • Extra or missing chromosomal material
  • Usually 1 or 3 copies of some of the genome
  • Concerning for development
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31
Q

Aneuploidy?

A

Whole extra or missing chromosome

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32
Q

Translocation?

A

Rearrangement of chromosomes

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33
Q

Describe genome defect of Down syndrome in a boy?

A

Trisomy 21

47XY + 21

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34
Q

What would happen if a genome was 47XY + 14? and what is the formula to describe this?

A

MIscarraige

Trisomy 14

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35
Q

What is the genome for Edward’s syndrome?

A

Trisomy 18

47 XY + 18

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36
Q

Which genetic condition is 45X?

A

Turner’s syndrome

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37
Q

What is 47 XXY?

A

Klinefelter syndrome

38
Q

What is a Robertsonian translocation?

A

2 acrocentric chromosomes stuck end to end

Most common ones are 13 &14, 14&21 and 14&15

39
Q

What does robertsonian translocation increase the risk of?

A

Trisomy in pregnancy (Down’s or miscarraige)

40
Q

Acrocentric?

A

Having centromere situated so that one chromosomal arm is much shorter than the other

41
Q

What is a first line chromosome test?

A

Microarray CGH

42
Q

What does a microarray CGH detect?

A

Any missing or duplicated piece of chromosome, finds polymorphisms.
It detects size of imbalances

43
Q

Gonadal mosaicism other term for it and explanation?

A

Germline mosaicism

-Causes recurrence risk fro autosomal dominant conditions even if parent unaffected

44
Q

Somatic mosaicism?

A

All cells suffer mutations as they divide

-Repair mechanisms exist for this

45
Q

What is mosaicism?

A

Different cells have a different genetic constitution

46
Q

How genes are analysed and how mutations are detected?

A

PCR
Sequencing
Filtering

47
Q

Types of mutation?

A 
Missense 
Premature stop
In frame 
Out of frame 
Splicing or promoters mutation 
Mutations that inactivate or activate a gene
48
Q

Missense?

A 
Base change causing amino acid change 
eg Instead of
The cat sat on the mat 
it would be 
The caR sat on the mat
49
Q

Premature stop?

A

Base change causing this **

50
Q

What causes an in frame or out of frame mutation?

A

Insertion or deletion of base

51
Q

What do we use to analyse deletions and duplications?

A

aCGH - for balanced rearrangements

52
Q

PCR is used for analysing?

A

For changes in small number of BP

53
Q

How does PCR work?

A

Allows us to select one small piece of human genome from a patient (100-10000 bases) and amplify it to make lots of copies

54
Q

Example of an insertion mutation in the sentence the cat sat on the mat?

A

The cat sPa to nth ema t

55
Q

Example of deletion out of frame and then in frame fro the cat sat on the mat?

A 
Out= The cas ato nt hem at 
In= The cat on the mat
56
Q

What are tumour suppresors?

A

Genes that stop cells dividing if switched on

57
Q

Oncogenes?

A

Genes that start cells dividing when switched on

58
Q

Penetrance?

A

The likelihood of having a disease if you have a genetic mutation

59
Q

Expression?

A

Variation in disease severity if you have a mutation

60
Q

Polymorphism?

A

Genetic variation that is prevalent in the population but is not in itself disease causing

61
Q

Promoter and splice site sequence changes?

A

Stop transcription or cause abnormal splicing

62
Q

What effect does a base change causing amino acid change have?

A

Change in protein sequence. May or may not reduce protein function

63
Q

What are mendelian disorders?

A

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

64
Q

Describe characteristic of an autosomal dominant disorder?

A
  • Seen in all generations
  • 50% risk of child being affected if parent is affected
  • Severity of disease is variable
  • Males and females equally likely to be affected
65
Q

Describe characteristics of an autosomal recessive disease?

A
  • 2 faulty copies of gene are required to cause disease
  • Affects only one generation
  • 1 in 4 chance of children having it if parents are carriers
  • Increased likelihood in incestuous families
  • Usually cause loss of function
66
Q

Fancy term for incestuous?

A

Consanguineous

67
Q

Describe characteristics of an X-linked recessive disease?

A

Recessive

  • Y chromosome irrelevant
  • Haemophilia
  • NO male-male transmission
68
Q

If a mother is a carrier of an x-linked recessive disease what is the chance her son or daughter is affected?

A

50% chance of daughter carrier

50% chance male is affected

69
Q

Describe characteristics of Mitochondrial disease?

A

Inherited almost exclusively maternally

-point mutations and deletions occur

70
Q

Symptoms of mitochondrial inherited disease?

A
  • Myopathy
  • Diabetes
  • Deafness
  • Optic atrophy
  • Stroke like episodes
  • Encephalitis
71
Q

Which disease is autosomal dominant?

A

Huntington’s disease

72
Q

Non-mendelian inheritence?

A

Methylation/imprinting
Mitochondrial inheritance
Mosaicism

73
Q

Which inheritance is common in incestuous families?

A

Autosomal recessive

74
Q

Why would a female carrier show mild features of an X-linked disease?

A

X-inactivation

in female cells only one X chromosome is active

75
Q

What is a CNV?

A

Copy number variation

They are extra or missing stretches of DNA

76
Q

How mendelian inheritence works with factors like environment?

A

High penetrance

Small environmental contribution

77
Q

Factors involved in multifactorial disease?

A

Genetic change is just another risk factor
penetrance for an one mutation is low
Individual genetic factors are treated the same as environmental risk factors

78
Q

What happens in DNA methylation?

A

Leads to modification of histones which represses transcription

79
Q

What is imprinting?

A

The differences in gene expression depending on whether a gene is maternally or paternally inherited

80
Q

What is angelman syndrome?

A

Neuro-genetic disorder caused by imprinting on chromosome 15

81
Q

Symptoms of angelman disorder?

A 
Developmental delay 
Intellectual disability 
Ataxia 
Epilepsy 
Happy demeanour 
Frequent laughing and smiling
82
Q

Heteroplasmy?

A

Different daughter cells contain different proportions of mutant mitochondria
-severity of phenotype depends on proportion and level of mitochondria/type of mutation

83
Q

Characteristics gained by cells on progression to cancer?

A 
Proliferation 
Evasion of immune response 
Acquire a vascular supply 
Avoid apoptosis 
Metastasis
84
Q

Genes involved in cancer?

A

Oncogenes
Tumour suppressors
DNA repair genes
Drug metabolism

85
Q

What are drug metabolism cells?

A

Genes that metabolise carcinogens

86
Q

Mechanisms of gene activation?

A

Duplication of the gene
Activation of the gene promoter
Change into amino acid sequence

87
Q

What does FISH stand for?

A

Fluorescence in situ hybrid

88
Q

What can FISH do?

A

Light up specific bits of chromosome

89
Q

What type of mutation causes a small proportion of familial breast cancer?

A

BRCA 1

90
Q

What is BRCA 1 gene involved in ?

A

DNA strand repair

91
Q

What is multifactorial predisposition?

A

Everyone is at some risk

Anyone with family history is at increased risk

Principles Collated Flashcards (13 decks)

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