inheritance and genetic diseases Flashcards

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1
Q

How is genetic variation generated?

A
  • mutation
  • diploid cells (random fertilisation)
  • homologous recombination between chromosomes during meiosis
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2
Q

Describe homologous recombination

A
  • occurs during long prophase of meiosis 1
  • 2-3 crossover events per chromosome per meiosis
  • highly similar DNA sequence binds to complementary sequence on homologous chromosome
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3
Q

How does genetic variation happen during gamete formation?

A
  • independent assortment of chromosomes
  • homologous recombination
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4
Q

What is non-disjunction?

A

When a pair of homologous chromosomes fail to seperate during meiosis

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5
Q

What are the 3 types of survivable trisomy?

A
  • 21 (down’s syndrome)
  • 13 (patau’s syndrome)
  • 18 (edwards syndrome)
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6
Q

What are autosomal chromosomes?

A

not sex chromosomes

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7
Q

How are genetic diseases passed down through the generatons?

A
  • autosomal dominant
  • autosomal recessive
  • x-linked
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8
Q

Define genotype?

A

set of genes carried by an individual

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9
Q

Define phenotype?

A

observable characteristic of an organism

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10
Q

Define allele?

A

an alternative form/different version of a gene

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11
Q

What percentage of miscarriages are due to chromosomal abnormalities?

A

around 50%

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12
Q

What is Turner’s syndrome?

A

monosomy of C chromosome

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13
Q

What are some other sex chromosome disorders (XXY, XXX, XYY)?

A
  • XXY: Klinefelter
    syndrome (male,
    reduced fertility, lower IQ)
    May go undiagnosed
  • XXX: undiagnosed
  • XYY: undiagnosed
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14
Q

What is CFTR and where is the gene for it located?

A
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • chromosome 7
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15
Q

What is an example of an autosomal ‘incomplete’ recessive disease?

A

sickle cell disease

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16
Q

Which gene is mutated in sickle cell disease and where is it found?

A
  • HBB gene
  • chromosome 11
17
Q

What is an example of an autosomal dominant disease?

A

Huntington’s disease

18
Q

What gene is mutated in Huntington’s disease and where is it located?

A
  • HTT gene
  • chromosome 4
19
Q

Give an example of a X-linked recessive disease?

A

haemophilia A

20
Q

What is haemophilia A caused by?

A
  • x-linked recessive trait
  • deletion/inversion in F8 gene
21
Q

Describe haemophilia A

A
  • blood clots slower
  • loss of function, lack of blood clotting factor VIII
22
Q

How common are monogenic disorders?

A

1 in 200 births