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JL Principles > Genetics > Flashcards

Genetics Flashcards

0
Q

How is DNA always replicated and read?

A

In the 5’ to 3’ direction

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1
Q

How do strands of DNA pair up?

A

In an antiparallel fashion

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2
Q

What is the DNA sugar backbone composed of?

A

2-deoxyribose (ribose in RNA)

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3
Q

What are the bases in DNA and what are the bases in RNA?

A

DNA - ACGT

RNA - ACGU

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4
Q

Where is the information in DNA held?

A

In the sequence of the bases which are held on a sugar/phosphate backbone

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5
Q

In the DNA molecule what base pairs with what?

A

Thymine with Adenine

Guanine with Cytosine

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6
Q

Where are chromosomes found?

A

Within the nucleus

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7
Q

What is the DNA strand associated with and what structure is it wound into?

A

Associated with proteins (histones) and is wound into a structure called a chromosome

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8
Q

What is the order of the cell cycle starting from G1?

A 
G1
GO
Synthesis
G2
Mitosis
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9
Q

What are the three stages in DNA damage and repair?

A

DNA strand breaks
Chemical cross-linking
Mismatched base

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10
Q

At what stage of the cell cycle does DNA replication happen?

A

During S phase

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11
Q

What does mitosis start with and finish with?

A

Starts with one diploid parent cell

Ends with two identical diploid daughter cells

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12
Q

What does meiosis start with and finish with?

A

Starts with one diploid parent

Ends with 4 haploid daughter cells

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13
Q

Does crossing over occur in meiosis?

A

Yes i.e. genes segregate independently, even if on the same chromosome

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14
Q

Does meiosis occur in gamete formation?

A

Yes

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15
Q

What 3 changes does Ribonucleic acid (RNA) have compared to DNA?

A
  1. Single stranded
  2. Ribose in backbone not deoxyribose
  3. Uracil is used instead of Thymine
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16
Q

What are promotor, exon, intron, exon and stop all in?

A

DNA

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17
Q

What is exon, exon, stop in?

A

mRNA

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18
Q

What 4 things determine the amount of protein produced?

A
  1. Rate of transcription (manufacture of Pre-mRNA)
  2. Rate of splicing to mRNA
  3. Half life of mRNA
  4. Rate of processing of polypeptide
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19
Q

What does DNA get transcribed into?

A

pre-mRNA

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20
Q

What does pre-mRNA get spliced into?

A

mRNA

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21
Q

What is mRNA translated into?

A

Protein

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22
Q

What can 3 bases encode?

A

1 amino acid or a stop

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23
Q

What two things allow the genome to vary in individuals?

A

Polymorphisms and mutations

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24
Q

What 2 sequence variations are there within a gene?

A

Changes in the promotor sequence

Changes in the exon sequence (one that change an amino acid, sequence changes that do not)

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25
Q

What two sequence changes in the DNA between genes are there?

A

Single nucleotide polymorphisms (SNPs)

Larger deletions or duplications

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26
Q

Give the definition of polymorphisms

A

Any variation in the human genome that does not cause a disease in its own right. It may however, predispose to a common disease

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27
Q

What is a mutation?

A

A gene change that causes a genetic disorder

Any heritable change in the human genome

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28
Q

Classical genetic diseases occur because?

A

One mutation is sufficient to cause disease e.g. achondroplasia, muscular dystrophy)

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29
Q

What does multifactorial diseases mean?

A

Multiple polymorphisms cause a risk of disease

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30
Q

What is the key equation for clinical genetics?

A

Disease = gene + environment

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31
Q

Before DNA is transcribed what has to happen?

A

It has to be unpacked

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32
Q

What three things allow a chromosome to be recognised?

A
  1. Banding pattern with specific stains
  2. Length
  3. Position of the chromosome
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33
Q

What rearrangement has occured if all the chromosomal material is still present?

A

Balanced

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34
Q

What chromosome rearrangement would have occured if there is extra or missing chromosomal material?

A

Unbalanced

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35
Q

Define aneuploidy

A

Whole extra or missing chromosome

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36
Q

Define translocation

A

Rearrangement of chromosomes

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37
Q

What disease occurs: trisomy 21?

A

Down syndrome - extra chromosome 21 (47 XY +21)

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38
Q

What is Robertsonian translocation?

A

Two acrocentric chromosomes stuck end to end

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39
Q

What can occur with a trisomy 14?

A

Miscarriage

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40
Q

What will increase the recurrence of down syndrome?

A

If the primary trisomy 21 is caused by robertsonian translocation

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41
Q

What disease is caused by trisomy 18?

A

Edward syndrome

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42
Q

What disease is associated with 45 X?

A

Turners syndrome

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43
Q

What disease is associated with 47 XXY?

A

Klinefelters syndrome

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44
Q

What is FISH?

A

Fluoresence in Situ Hybridisation

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45
Q

What do chromosomes carry?

A

Genes

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46
Q

What is the male chromosome complement?

A

46 XY

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47
Q

What is the female chromosome complement?

A

46 XX

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48
Q

What 2 things can unbalanced rearrangements cause?

A

Mutliple malformations

Miscarriage

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49
Q

What is the first line chromosome test?

A

Array CGH

50
Q

What 2 diseases is Gonadal Mosaicism most common in?

A
  1. Duchenne Muscular Dystrophy

2. Osteogenesis Imperfecta

51
Q

What causes a recurrence risk for autosomal dominant conditions even if the parent is unaffected?

A

Gonadal Mosaicism

52
Q

Chromosome changes indicate treatment: Her2 amplification?

A

Monoclonal antibody: Trastuzamab

53
Q

Chromosome changes indicate treatment: Philadelphia chromosome?

A

Tyrosine Kinase Inhibitor: Imatinib

54
Q

What genetic change can contribute towards cancer?

A

Somatic mosaicism for a chromosomal abnormaility

55
Q

What is penetrance?

A

The liklihood of having a disease if you have a gene mutation. 100% prevelance means you will always get the disease if you have the mutation.

56
Q

What name is given to diseases that segregate in families in the manner predicted by Mendel’s Law?

A

Mendelian disorders: essentailly a disease that is predominantly caused by a change in a single gene (high penetrance)

57
Q

What are chromosome aneuplodies?

A

Extra or missing chromosomes

58
Q

What two methods are in place to find genetic faults?

A
  1. PCR and conventional (Sanger) sequencing

2. Next Generation Sequencing (NGS)

59
Q

Give an example of focused genetic testing?

A

PCR

60
Q

What is reduced or abolished in a DNA promotor mutation?

A

Reduced or no transcription

Reduced or no protein

61
Q

What occurs if splice consensus is altered?

A

An mRNA decay in translation

Abnormal or absent protein

62
Q

What occurs if a base change makes a new stop?

A

mRNA decay at translation

Short or absent protein

63
Q

What occurs if a base change alters amino acid sequence?

A

Different or non-functioning protein

64
Q

What are the 7 types of mutations in DNA sequences?

A
  1. Wild type
  2. Stop
  3. Missense
  4. Insertion
  5. Deletion (out of frame)
  6. Deletion (in frame)
  7. Triplet expansion
65
Q

What do promotor and splice site sequence changes do?

A

Stop transcription or cause abnormal splicing

66
Q

What can a trinucleotide repeat expansion cause?

A

Replication of a trinucleotide

67
Q

What is genetic heterogeneity?

A

The same disease might be caused by mutations in one of several genes

68
Q

What are the 4 types of Mendelian Inheritance?

A

Autosomal dominant
Autosomal recessive
X-linked
(Mitochondrial)

69
Q

With an autosomal dominant mutation what is the risk of an affected child if the parents are affected?

A

50%

70
Q

What are the 4 types of autosomal dominant mutations?

A 
Wild type
Missense
Deletion (in frame)
Premature stop
Deletion (frameshift)
71
Q

In an autosomal recessive mutation, what do you need to cause disease?

A

2 faulty copes of the gene

72
Q

In an autosomal recessive mutation what is the risk of an affected child if the parents are carriers?

A

25%

73
Q

Give an example of an autosomal recessive disease?

A

Phenylketonuria

74
Q

In an X linked recessive disease where does the gene fault lie?

A

On the X chromosome

75
Q

In an X-linked recessive inheritance: for a female carrier what percentage of male children will be affected and what percentage of female children will be carriers?

A

50%

50%

76
Q

In an X-linked recessive inheritance: if an infected male has children what percentage of them will be normal and what will all the female chilren be?

A

All male children will be normal

All female children will be carriers

77
Q

In female cells how many x chromosomes are active?

A

one

78
Q

What gene is essential for X inactivation?

A

the XIST gene at Xq13

79
Q

Give one mechanism of X inactivation

A

Methylation

80
Q

Give two types of variation?

A

Single Nucleotide Polymorphisms

Copy Number Variation

81
Q

What variation is an alteration in the DNA sequence?

A

A single nucleotide polymorphism

82
Q

What are copy number variations?

A

Extra or missing stretches of DNA

83
Q

Define expression

A

Variation in disease severity if you have the mutation

84
Q

What are the 4 M’s of Non-Mendelian Inheritance?

A

Multifactorial
iMprinting
Mitochonddrial
Mosaicism

85
Q

What disorder has high penetrance and small environmental contribution?

A

Mendelian disorders

86
Q

What disease is a genetic change as a risk factors and penetrance for any one mutation is low?

A

Multifactorial disease

87
Q

What to methods are there for working out if a disease phenotype has a genetic contribution to its causation?

A

Recurrence risk in siblings

Twin studies

88
Q

What is Filaggrin deficiency?

A

A null allele polymorphism

Strongly associated with eczema

89
Q

What type of disorder does epigenetic modification of DNA come under?

A

Non-Mendelian inheritance patterns

90
Q

What bases just methylation usually occur on?

A

Cytosine bases

91
Q

What leads to the modification of histones (including de-acetylation) and represses transcription?

A

DNA methylation

92
Q

What mutation causes RETT syndrome?

A

Mutation in the MECP2 gene on Xq28.13

93
Q

Give 2 features of Angelman syndrome

A 
Developmental delay
Intellectual disability
Ataxia
Epilepsy
Happy demeanor
Frequent laughing and smiling
94
Q

What working copy of gene do you need to avoid Angelman’s syndrome?

A

UBE3A

95
Q

What chromosome is UBE3A on?

A

15

96
Q

What is special about the copy of UBE3A from your father?

A

It is methylated

97
Q

What is imprinting?

A

Variation in gene expression depending on which parent you inherit the gene from

98
Q

What is imprinting controlled by?

A

Methylation

99
Q

What does methyl cytosine mutate easily into?

A

Thymine

100
Q

Where else is DNA kept?

A

Mitochondrial DNA

101
Q

What mutations occur in mitochondrial DNA?

A

Point mutations and deletions occur

102
Q

What is heteroplasmy?

A

Different daughter cells contain different proportions of mutant mitochondria

103
Q

Give 2 symptoms of mitochondrial disease?

A 
Myopathy
Diabetes
Deafness
Optic atrophy
Stroke like episodes
Encephalitis
104
Q

How is mitochondrial inheritance transmitted?

A

Maternal transmission only

105
Q

What 4 genes are involved in cancer?

A

Oncogenes - switch these on for cell division
Tumour supressors - switch these on to stop cell division
DNA repair genes - repair DNA damage
Drug metabolism - genes that metabolise carcinogens

106
Q

What type of inheritance does retinoblastoma have?

A

Autosomal dominant

107
Q

What 3 methods are there for activating oncogenes?

A

Duplication of the gene
Activation of the gene promotor
Change in amino acid sequence

108
Q

What is Imatinib (Glivec) a specific inhibitor of?

A

ABL oncogene

109
Q

What occurs in interphase of the cell cycle?

A

The cell grows, accumulating nutrients needed for mitosis and duplicating its DNA

110
Q

What happens during the mitotic phase of the cell cycle?

A

The cell splits intself into two distinct cells, often called daughter cells

111
Q

In G1 of the cell cycle what happens?

A

The cell makes new proteins

112
Q

If the cell is not ready to move onto S phase what happens?

A

It enters G0 and carries out its normal acitivity

113
Q

What occurs in synthesis of the cell cycle?

A

DNA replication

114
Q

What occurs in G2 phase?

A

The cell prepares to divide

115
Q

Depending on the location of the centromere, what can chromosomes be classified as?

A

Submetacentric
Metacentric
Acrocentric

116
Q

What does splicing consist of?

A

The removal of introns

117
Q

What does transcription involve?

A

The synthesis of a single strand of mRNA by RNA polymerase

118
Q

Where does splicing take place?

A

In the nucleus

119
Q

What is translation?

A

The synthesis of a protein from a mRNA template

120
Q

Where does protein synthesis occur?

A

In ribosomes

121
Q

What are ribosomes made up of?

A

Ribosomal RNA and proteins

122
Q

When is translation terminated?

A

When the ribosome comes across one of the three base combinations known as termination codons (or stop codons) at hte end of the gene: UAA, UAG, UGA

JL Principles (12 decks)

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