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Cels191 > L-15 > Flashcards

L-15 Flashcards

1
Q

What is Down syndrome represented by in a karyotype

A

3rd copy of 21st chromosome

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2
Q

What is Aneuploidy? Give an example

A

To possess an abnormal amount of a particular chromosome

Down syndrome

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3
Q

How common is Down syndrome?

A

Occurs in 1/750 live births

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4
Q

What is the risk factor for down syndrome? What are the stats to back this up?

A
  • maternal age

- 40% of cases occur when mothers are older than 45

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5
Q

What causes Down syndrome? Which version of this is more common

A
  • nondisjunction during meiosis

- 95% of cases have 2 maternal chromosomes (2nd division)

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6
Q

What is nondisjuction?

A

Failure of chromosomes to separate properly during meiosis

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7
Q

What is Klinefelter syndrome?

A

Genetic condition where male has an extra X chromosome (XXY)

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8
Q

What are the symptoms of Klinefelter syndrome?

A
  • infertility
  • small poorly functioning testicles

In worse cases:

  • weaker muscles
  • greater height
  • less body hair
  • breast growth
  • lower libido
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9
Q

How common in Klinefelter syndrome?

A

Occurs in 1-2/1000 live male births

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10
Q

Is Klinefelter syndrome more likely to be a result of maternal or paternal nondisjuction?

A

Neither is more likely

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11
Q

What is Turner syndrome?

A

Genetic condition where females may be partially of fully missing a sex chromosome (XO)

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12
Q

What are the symptoms of Turner syndrome?

A
  • skin folds around neck
  • intellectual impairment
  • infertility
  • individuals do not naturally develop breasts of a menstrual cycle
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13
Q

How common is Turner syndrome?

A

1/2000-5000 live female births

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14
Q

What is polyploidy?

A

Possession of multiple sets of chromosomes

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15
Q

What is polyploidy caused by?

A

Meitotic error resulting in unreduced gametes with the 2n number of chromosomes

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16
Q

What can self-fertilisation of polyploids lead to?

A

An auto plaid zygote with the 4n number of chromosomes

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17
Q

Can offspring with polyploid karyotypes be variable?

A

Yes in plants

18
Q

What is an example of polyploidy in animals ?

A

Triploid pathogenic lizard- New Mexico Whiptail

19
Q

How are offspring of the New Mexico Whiptail produced?

A
  • Asexually

- New indivuals produced by mating of parent species in a process that prevents the formation of healthy males

20
Q

What can other chromosomal abnormalities be caused by?

A
  • deletions
  • inversions
  • duplications
  • translocations
21
Q

What is a deletion mutation?

A

Removal of a chromosomal segment

22
Q

What is an inversion mutation?

A

Reversal of a segment within a chromosome

23
Q

What is a duplication mutation?

A

A repeat of a segment within a chromosome

24
Q

What is a translocation mutation?

A

Moving a segment from one chromosome to another nonhomologous chromosome

25
Q

What is cri du chat syndrome?

A

Genetic condition caused by the deletion of the tip of the short arm of chromosome 5

26
Q

What are the symptoms of cri du chat syndrome?

A
  • severe intellectual imparement
  • most offspring wont reach adulthood
  • problems with larynx + nervous system give affected infants a meow like cry
27
Q

What is the Philadelphia translocation?

A

A segment of chromosome 9 is translocated onto chromosome 22 and a segment of chromosome 22 is translocated onto chromosome 9

28
Q

What does the Philadelphia translocation cause?/ what condition is the Philadelphia translocation highly correlated with?

A

95% of patients with chronic myeloid leukaemia have the Philadelphia translocation

29
Q

What is familial Down syndrome also known as?

A

Translocation down syndrome

30
Q

What percentage of recorded Down syndrome cases do familial Down syndrome patients make up?

A

4.5%

31
Q

What is the cause of familial Down syndrome?

A
  • robertsonian translocation

- long arm of chromosome 21 is attached to chromosome 14

32
Q

What is the phenotype of an individual with the robertsonian translocation?

A

Normal but act as carrier

33
Q

How many possible zygotes are formed from mating of an individual with the robertsonian translocation with a normal individual? Name their associated phenotypes

A
  • 6
  • 3 lethal
  • 1 Down syndrome
  • 1 normal
  • 1 carrier
34
Q

What is the change of an offspring having familial Down syndrome when the mother has the robertsonian translocation? Father?

A
  • 15%

- >5%

35
Q

What is a Barr body?

A

Visible dense region in the nucleus which is a condensed and inactivation X chromosome

36
Q

What is the name for the process of X inactivation?

A

Lyonisation

37
Q

What genotypes will have a Barr body?

A
  • XX
  • XXY
  • XXX
38
Q

What genotypes will not have a Barr body?

A
  • XY
  • XO
  • XYY
39
Q

Why can women with the genotype XXX live near normal lives and have limited symptoms

A

They will have 2 Barr bodies so the genetic material is not interfering with each other

40
Q

What is a visible example of mosaic lyonisation?

A

Fur colour in cats

41
Q

What is a condition in women effected by lyonisation? How?

A
  • anhidrotic ectodermal dysplasia ( no sweat glands)
  • If only present in one X chromosome then random inactivation in early cells will lead to mosaic patterning of skin with and without sweat glands
42
Q

Why does lyonisation not affect all X linked genetic conditions?

A

gene products can travel around the body and have effects everywhere

Cels191 (35 decks)

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