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IMS > Strand 1 - genes > Flashcards

Strand 1 - genes Flashcards

1
Q

Which nitrogenous bases are purine and pyrimidine?

A

Adenine and guanine are purine
Thymine and cytosine are pyrimidine

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2
Q

Which pair of nitrogenous bases bind via 2 hydrogen bonds and which via 3?

A

Adenine and thymine bond with 2 hydrogen bonds
Cytosine and guanine bond with 3 hydrogen bonds

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3
Q

What charge are DNA and histones?

A

DNA is negatively charged and histones are positively charged

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4
Q

What is DNA wrapped round a histone called?

A

Nucleosome

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5
Q

What do nucleosomes form when coiled?

A

Chromatin fibres

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6
Q

What do chromatin fibres form?

A

Arranged on a protein scaffolding to form a chromosome

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7
Q

Name 7 examples for non coding DNA

A

Introns
Viral DNA
pseudogenes
Genes for RNA
Tandem repeats
Telomeres
Promotor regions

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8
Q

Why do tandem repeats occur?

A

DNA polymerase III slips during DNA replication

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9
Q

What are telomeres?

A

Caps at the end of each chromosome for protection which get worn down over time

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10
Q

What are Pseudogenes?

A

They are mutated genes which have evolved to become inactive

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11
Q

Give 2 examples of coding RNA

A

MRNA
Viral genomes

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12
Q

Give two examples of structural RNA

A

RRNA
TRNA

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13
Q

Give two examples of regulatory RNA

A

MicroRNA
Xist

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14
Q

What is xist

A

Xist switches off one copy of X chromosome

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15
Q

What is another name for the template strand?

A

The antisense strand

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16
Q

What do single stranded DNA binding proteins do?

A

Keep strands unzipped

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17
Q

What does topoisomerase do?

A

Stops the strands from over coiling

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18
Q

What direction does DNA polymerase III add the bases?

A

5’-3’

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19
Q

How does DNA polymerase III remove incorrect bases?

A

Using 3’-5’ exonuclease activity

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20
Q

How is DNA replicated on the lagging strand?

A

Primer binds close to helicase forming Okazaki fragments which are joined by DNA ligase

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21
Q

What ingredients do you add to the test tube for PCR

A

DNA sample
Primers
DNA taq polymerase
Nucleotides
Buffer

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22
Q

What are the steps to carrying out PCR?

A

Denaturing (94-95)
Annealing (50-56)
Extension (72)
Repeat approx 30 times

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23
Q

What is a gene mutation?

A

An alteration in the nucleic acid sequence of the genome of an organism

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24
Q

How do mutations arise?

A

Errors during replication (point mutations/replication slippage)
Mutagens (radiation/chemicals)

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25
Q

What is the difference between purine and pyrimidine

A

Purine has two rings, pyramidine has one

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26
Q

What are the three types of RNA function?

A

Coding structural regulatory

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27
Q

What are three ways to prevent mutations?

A

Melanin (to protect DNA in the skin)
Peroxisomes (organelle that makes antioxidant enzymes)
Making good life choices

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28
Q

How do we repair mutations due to nicks (breaks of phosphodiester bonds)?

A

DNA ligase

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29
Q

How do we repair mutations due to single stranded damage to bases?

A

Base excision repair for small damage
Nucleotide excision for larger damage

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30
Q

How do we repair damage due to double stranded DNA breaks?

A

Non-homologous end joining

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31
Q

What does DNA polymerase III do to fix mutations in DNA replication?

A

Proofreading activity

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32
Q

For the mutations which DNA polymerase III can’t repair what happens?

A

Mismatch repair (4 proteins detect lack of H bonds between mismatched base pairs)

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33
Q

If there are too many mutations for the cell to repair what happens?

A

Apoptosis is initiated

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34
Q

What is a frame shift mutation?

A

Shifts the reading frame. Caused by deletions that are not in multiples of 3

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35
Q

What are the 4 types of mutation?

A

Frame shift
Silence
Missence
Nonsense

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36
Q

What happens with a silence mutation?

A

A base is substituted but it still codes for the same amino acid so no effect

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37
Q

What happens with a missense mutation?

A

Codes for a different amino acid. Only effects one so usually has small effect especially if similar shape/charge

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38
Q

What happens with a nonsense mutation?

A

Changes to a stop codon. Has big effect if at start of protein

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39
Q

What type of inheritance does cystic fibrosis follow?

A

Autosomal recessive

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40
Q

Why does cystic fibrosis occur and what does the mutation do?

A

Caused by mutation in gene encoding the CFTR protein. The CFTR protein is a membrane protein that transports chloride ions

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41
Q

How does the mutation in the gene encoding for the CFTR protein cause thick mucus?

A

Cl ions can’t exit the cells. Sodium then follows the Cl and exits the mucus into the the cell so there is less water in the mucus making it thick

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42
Q

What effects does having thick mucus cause?

A

In the lungs there are recurrent infections
In the pancreatic ducts there is malabsorption

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43
Q

What kind of condition is neurofibromatosis?

A

Autosomal dominant
(Half of the cases aren’t from parents and just occur due to mutation)

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44
Q

What are the two types of neurofibromatosis and what protein is damaged?

A

NF1 - Neurofibrin
NF2 - Merlin
Both proteins are normally tumour suppressor genes

45
Q

What tumours are most common in NF1and NF2?

A

NF1 - neurofibromas
NF2 - schwannomas

46
Q

What kind of condition is phenylketonuria?

A

Autosomal recessive

47
Q

What protein is affected by phenylketonuria?

A

Phenylalanine hydroxylase

48
Q

What does phenylalanine hydroxylase do?

A

Metabolises the amino acid phenylalanine

49
Q

What kind of diet do you need to follow if you have phenylketonuria?

A

A strict phenylalanine free diet

50
Q

What happens if phenylketonuria patients don’t follow a phenylalanine free diet?

A

Phenylalanine builds up in the body and damages the brain
Effects such as microcephaly (small head), intellectual disability, seizures

51
Q

What type of condition is Huntington’s disease?

A

Autosomal dominant

52
Q

What causes Huntington’s disease?

A

Caused by CAG repeats in the gene that codes for the huntingtin protein

53
Q

What affects the severity of your symptoms in Huntington’s?

A

The amount of repeats on the gene that codes for the huntingtin protein
Gets progressively worse through generations as slipping of polymerase increases

54
Q

What is genetic anticipation?

A

When a disease gets progressively worse through generations

55
Q

Describe the anatomy of a normal metaphase chromosome

A

P arm = short arm
Q arm = long arm
Centromere in middle
Telomeres on the ends

56
Q

Why is the photo of all the chromosomes lined up in order called

A

Karyotype

57
Q

How do scientists identify chromosomes?

A

Size
Banding pattern
Centromere position

58
Q

Which chromosomes are acrocentric?

A

13, 14, 15, 21, 22, Y

59
Q

What abnormalities can be picked up on a karyotype?

A

Number of chromosomes
Material location
Amount of material

60
Q

What is the word for having an abnormal number of copies of an individual chromosome?

A

Aneuploidy

61
Q

What are the two types of aneuploidy called?

A

Monosomy - missing one
Trisomy - one extra

62
Q

What is the word for having an abnormal number of sets of chromosomes?

A

Polyploidy (e.g monopolid, diploid, triploid)

63
Q

What is the difference in chromosomes for people with Down syndrome?

A

They have trisomy 21

64
Q

What are the clinical features of Down’s syndrome?

A

Characteristic facial features
Mild-moderate intellectual disability
Short stature
Congenital heart disease
Endocrine problems
Increased risk of leukaemia and Alzheimer’s

65
Q

What change in the chromosomes causes Edward’s syndrome?

A

Trisomy 18

66
Q

What are the clinical features of Edward’s syndrome?

A

Intra-uterine growth restriction
Most die during pregnancy
Overlapping fingers
Rocker-bottom feet
Congenital heart/kidney disease
Microcephaly (small head)

67
Q

What change in chromosomes causes patau syndrome?

A

Trisomy 13

68
Q

What are the clinical features of patau syndrome?

A

Intra uterine growth restriction
Most die during pregnancy
Cleft lip/palate
Extra fingers/toes
Brain abnormalities
Congenital heart disease

69
Q

What syndromes does the 12 week pregnancy screening look for?

A

Edward’s, Down’s, Patau’s

70
Q

What changes in chromosomes causes Klinefelter syndrome?

A

47 XXY

71
Q

What are the clinical features of klinefelters syndrome?

A

Tall stature
Normal intellect,
Infertile
Little facial/ body hair

72
Q

What changes in chromosomes causes turner syndrome?

A

Monosomy X

73
Q

What are the clinicial features of turner syndrome?

A

Infertility
Short stature
Lymphoedema (puffy hands and feet)
Webbed neck
Endocrine abnormalities
Congenital heart disease
Normal intellect

74
Q

What is a deletion in genetics?

A

Loss of a segment of genetic material from a chromosome

75
Q

What is duplication in genetics?

A

Gain of a segment of genetic material from a chromosome

76
Q

What genetic change causes di George syndrome?

A

22q11.2 microdeletion

77
Q

What are the clinical features of di george syndrome?

A

Congenital heart and kidney disease
Nasal speech
Characteristic facial features
Hypocalcaemia
Intellectual disability
Increased risk of psychiatric disorders

78
Q

What genetic change causes Prader Willi syndrome?

A

15q11 -q13 deletion

79
Q

What are the clinical features of Prader willi syndrome?

A

Low tone at birth
Short stature
Characteristic facial features
Challenging behaviours and hyperphagia (excessive eating)
Intellectual disability
Incomplete pubertal development

80
Q

What is translocation?

A

The relocation of chromosome material to the wrong place

81
Q

What are the two types of translocation?

A

Reciprocal
Robertsonian

82
Q

What is reciprocal translocation?

A

When 2 different chromosomes have exchanged segments with each other

83
Q

What is robertsonian translocation?

A

An entire acrocentric chromosome attaches at another centromere

84
Q

What pregnancy complications are associated with balanced reciprocal translocations?

A

Recurrent miscarriage
Multiple congenital abnormalities

85
Q

What condition is reciprocal translocation the leading cause for?

A

Chronic myeloid leukaemia

86
Q

What is the chromosomal abnormality that is the leading cause of chronic myeloid leukaemia?

A

Reciprocal translocation between chromosomes 9 and 22

87
Q

Define locus?

A

Specific location on a chromosome

88
Q

Define allele

A

Alternate forms of as gene at the same locus

89
Q

Define homozygous

A

Both alleles at a gene locus are the same

90
Q

Define homozygous

A

Both alleles at a gene locus are the same

91
Q

Define heterozygous

A

The two alleles at a gene locus are different from one another

92
Q

Define genotype

A

A persons DNA sequence at a particular locus

93
Q

Define genotype

A

A persons DNA sequence at a particular locus

94
Q

Define phenotype

A

A persons clinical features

95
Q

Define phenotype

A

A persons clinical features

96
Q

Define syndrome

A

A group of traits or conditions that tend to occur together and characterise a recognisable disease

97
Q

Name 5 common autosomal dominant conditions

A

Huntingtons
BRCA 1 and 2
Neurofibromatosis
Autosomal dominant polycystic kidney disease
Marfan syndrome

98
Q

What does it mean if a condition arises de novo?

A

Occurs for the first time in an affected individual without a family history

99
Q

Name 4 common autosomal recessive conditions

A

Cystic fibrosis
Sickle cell anaemia
Spinal muscular atrophy
Phenylketonuria

100
Q

Name 3 common x linked conditions

A

Duchenne muscular dystrophy
Fragile X syndrome
Haemophilia A

101
Q

Name 2 common X linked dominant conditions

A

Rett syndrome
Craniofrontonasal syndrome

102
Q

Describe the mitochondrial genome

A

Circular chromosome containing 37 genes

103
Q

Why is there increased risk of aneuploidy with advanced maternal age?

A

Increase in nondisjunction and aneuploidy is often incompatible with life

104
Q

What are some examples of conditions that become more likely with increased paternal age?

A

Achondroplasia
Noonan syndrome
Thanatophoric dysplasia
Osteogenesis imperfecta
Apert syndrome

105
Q

Define penetrance

A

The likelihood that a clinical condition will occur when a particular genotype is present
E.g Huntingtons is penetrant

106
Q

What is variable expressivity?

A

The range in signs and symptoms that can occur in different people with the same genetic condition

107
Q

What is allelic heterogeneity?

A

Different pathogenic variants in a single gene associated with multiple different phenotypes

108
Q

What is locus heterogeneity?

A

When one phenotype can be caused by pathogenic variants in multiple different genes

109
Q

What is mosaicism?

A

When only some of an individuals cells have a specific variant

IMS (12 decks)

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