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Genes Evo & Dev Y1 > GED L15 Notes > Flashcards

GED L15 Notes Flashcards

1
Q

What is aneuploidy?

A 
•	Aneuploidy:
	Chromosome abnormality -> abnormal number of chromosomes -> no loss / gain of complete chromosome set. 
	Types:
-	Monosomy (Monosomic):
 Loss of single chromosome (2n – 1)
-	Trisomy (Trisomic):
 One extra chromosome (2n + 1)
-	Tetrasomy (Tetrasomic):
 Extra pair of chromosomes (2n + 2)
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2
Q

Name the types of aneuploidy?

A
  • Monosomy (Monosomic):
  • Trisomy (Trisomic):
  • Tetrasomy (Tetrasomic):
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3
Q

Name the process in which there is abnormal chromosome segregation in meiosis?

A

 Non-disjunction

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4
Q

What is Non-disjunction?

A

 Non-disjunction:
 Mistake -> chromosome segregation during meiosis
&raquo_space; Produce aneuploid gametes

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5
Q

Describe Aneuploidy in Autosomes

A

• Aneuploidy -> Autosomes:
 20-50% human conceptions -> aneuploid
- < 0.5% live births
All autosomal monosomies (2n -1) -> Inviable
 Trisomy 13 (Patau Syndrome) & Trisomy 18 (Edwards Syndrome)
Death -> children within few months.

	Down’s Syndrome:
 Charcteristics:
-	Characteristic facial features
-	Short stature
-	Learning disabilities
-	Higher risk -> Heart defects
-	Alzheimers &amp; some cancers -> 1/1000 
 Causes:
	 Trisomy (2n +1):
-	Trisomy 21
	Robertsian Translocation:
-	Chromosome 21 &amp; 14
	Genetic mosaicism:
-	Mix of normal &amp; trisomy 21 cells 
>>Non-disjunction -> early embryonic mitotic divisions
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6
Q

What is a characteristic of autosomal monosomies in autosomes?

A

All autosomal monosomies (2n -1) -> Inviable

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7
Q

Give examples of aneuploidy in autosomes

A

 Trisomy 13 (Patau Syndrome) & Trisomy 18 (Edwards Syndrome)
 Down’s Syndrome:

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8
Q

Name the type of aneuploidy in autosomes which causes death of children within months.

A

 Trisomy 13 (Patau Syndrome) & Trisomy 18 (Edwards Syndrome)
Death -> children within few months.

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9
Q

Describe Down’s Syndrome

A 
	Down’s Syndrome:
 Charcteristics:
-	Characteristic facial features
-	Short stature
-	Learning disabilities
-	Higher risk -> Heart defects
-	Alzheimers &amp; some cancers -> 1/1000 
 Causes:
	 Trisomy (2n +1):
-	Trisomy 21
	Robertsian Translocation:
-	Chromosome 21 &amp; 14
	Genetic mosaicism:
-	Mix of normal &amp; trisomy 21 cells 
>>Non-disjunction -> early embryonic mitotic divisions
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10
Q

What are the characteristics of Down’s Syndrome?

A

Charcteristics:

  • Characteristic facial features
  • Short stature
  • Learning disabilities
  • Higher risk -> Heart defects
  • Alzheimers & some cancers -> 1/1000
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11
Q

What are the causes of Downs Syndrome?

A 
 Causes:
	 Trisomy (2n +1):
-	Trisomy 21
	Robertsian Translocation:
-	Chromosome 21 &amp; 14
	Genetic mosaicism:
-	Mix of normal &amp; trisomy 21 cells 
>>Non-disjunction -> early embryonic mitotic divisions
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12
Q

Describe genetic mosaicism

A

 Genetic mosaicism:
- Mix of normal & trisomy 21 cells
»Non-disjunction -> early embryonic mitotic divisions

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13
Q

What chromosomes does Robertsian Translocation occur on & what disease is this present in?

A

 Robertsian Translocation:

- Chromosome 21 & 14 –> Down’s Syndrome

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14
Q

Describe Trisomy & the chromosome on which it is located

A

 Trisomy (2n +1):

- Trisomy 21

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15
Q

Describe Aneuploidy in sex chromosomes

A 
•	Aneuploidy -> Sex Chromosomes:
	Normal human karyotype
-	46 XY -> Males ; 46 XX -> Females
	Monosomy (2n -1)
 Turner Syndrome (XO) -> (45, X)
-	Sterile females
-	Short stature
-	Some -> learning difficulties
-	1/2500 female births
-	At least 1 X required -> embryonic development
	Trisomy (2n + 1)
Klinefelter Syndrome (47, XXY)
                   Triplo-X (47, XXX)
                   XYY Syndrome (47, XYY)
                   Some individuals -> more than 47 chromosomes -> (48, XXXY / 48, XXYY)
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16
Q

What are the characteristics of the normal human karyotype?

A

 Normal human karyotype

- 46 XY -> Males ; 46 XX -> Females

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17
Q

Name the types of aneuploidy in sex chromosomes

A

 Monosomy (2n -1) Trisomy (2n + 1)

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18
Q

What disease is monosomy found in (Aneuploidy -> sex chromosomes) ?

A

 Turner Syndrome (XO) -> (45, X)

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19
Q

What is the chromosomal no. in monosomy?

A

 Monosomy (2n -1)

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20
Q

Describe the characteristics of Turner Syndrome

A

 Turner Syndrome (XO) -> (45, X)

  • Sterile females
  • Short stature
  • Some -> learning difficulties
  • 1/2500 female births
  • At least 1 X required -> embryonic development
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21
Q

Name the diseases in which Trisomy is found (Aneuploidy -> sex chromosomes)?

A

Klinefelter Syndrome (47, XXY)
 Triplo-X (47, XXX)
 XYY Syndrome (47, XYY)
 Some individuals -> more than 47 chromosomes -> (48, XXXY / 48, XXYY)

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22
Q

What is the chromosome number & conformation in normal human karyotype?

A

 Normal human karyotype

- 46 XY -> Males ; 46 XX -> Females

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23
Q

What is the chromosome number & conformation in Turner Syndrome?

A

 Turner Syndrome (XO) -> (45, X)

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24
Q

What is the chromosome number & conformation in Klinefelter Syndrome?

A

Klinefelter Syndrome (47, XXY)

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25
Q

What is the chromosome number & conformation in Triplo-X?

A

 Triplo-X (47, XXX)

26
Q

What is the chromosome number & conformation in XYY Syndrome?

A

 XYY Syndrome (47, XYY)

27
Q

What is the chromosome number & conformation in individuals with more than 47 chromosomes?

A

 Some individuals -> more than 47 chromosomes -> (48, XXXY / 48, XXYY)

28
Q

What does X chromosome inactivation cause?

A

• X chromosome inactivation switches off all but one X chromosome

29
Q

Describe maternal age & trisomy

A

• Maternal Age & Trisomy
 Incr. trisomy
 Responsible for incr. miscarriage -> older women.
 95% -> trisomy 21
 Maternal non-disjunction -> meiosis 1
 Human oocytes
 Paused -> late meiotic prophase I (diplotene)
&raquo_space; Alongside paired, replicated chromosomes
 Begins before birth
&raquo_space; Maintained -> decades
-> Until egg matures -> menstrual cycle
 Loss of cohesion -> Prophase I
 Aneuploidy -> older women
» Premature loss -> cohesion
-» 2 univalents -> segregate independently
> Aneuploid (n +1) gametes

30
Q

What is a result of incr. trisomy?

A

 Incr. trisomy

 Responsible for incr. miscarriage -> older women

31
Q

What process is trisomy 21 responsible for & what percentage does it occur?

A

 95% -> trisomy 21

 Maternal non-disjunction -> meiosis 1

32
Q

Describe maternal age & trisomy in terms of human oocytes

A

 Human oocytes
 Paused -> late meiotic prophase I (diplotene)
&raquo_space; Alongside paired, replicated chromosomes
 Begins before birth
&raquo_space; Maintained -> decades
-> Until egg matures -> menstrual cycle

33
Q

Describe the pause of human oocytes in meiosis

A

 Human oocytes
 Paused -> late meiotic prophase I (diplotene)
&raquo_space; Alongside paired, replicated chromosomes
 Begins before birth
&raquo_space; Maintained -> decades
-> Until egg matures -> menstrual cycle

34
Q

Describe loss of cohesion in prophase I

A 
	Loss of cohesion -> Prophase I 
 Aneuploidy -> older women 
>> Premature loss -> cohesion 
->> 2 univalents -> segregate independently 
      >  Aneuploid (n +1) gametes
35
Q

Describe extranuclear genomes of mitochondria & chloroplasts

A

• Extranuclear genomes -> mitochondria & chloroplasts:
- Circular dsDNA genomes
- Ribosomes -> mitochondria & chloroplasts
» Different -> cytoplasmic ribosomes
» Sensitive -> Bacterial antibiotics
 Mitochondrial Genomes / DNA:
- Components -> Translation
Eg. tRNAs & rRNAs
- Structural genes -> proteins involved -> oxidative phosphorylation
Eg. Cytochrome oxidase, NADH-dehydrogenase, ATPase
 Chloroplast Genomes / DNA:
- Genes encoding tRNAs & rRNAs involved -> translation
- Structural genes -> proteins involved -> photosynthesis
Eg. Biphosphate decarboxylase

• Transmission -> Extranuclear Genomes:

36
Q

Describe ribosomes of mitochondria & chloroplasts & the type of genomes they contain

A

• Extranuclear genomes -> mitochondria & chloroplasts:
- Circular dsDNA genomes
- Ribosomes -> mitochondria & chloroplasts
» Different -> cytoplasmic ribosomes
» Sensitive -> Bacterial antibiotics

37
Q

Describe mitochondrial Genomes / DNA

A

 Mitochondrial Genomes / DNA:
- Components -> Translation
Eg. tRNAs & rRNAs
- Structural genes -> proteins involved -> oxidative phosphorylation
Eg. Cytochrome oxidase, NADH-dehydrogenase, ATPase

38
Q

Describe chloroplast genomes / DNA

A

 Chloroplast Genomes / DNA:
- Genes encoding tRNAs & rRNAs involved -> translation
- Structural genes -> proteins involved -> photosynthesis
Eg. Biphosphate decarboxylase

39
Q

Describe transmission of extranuclear genomes

A 
•	Transmission -> Extranuclear Genomes:
	 Egg 
 Diameter -> ~100um 
 > 100,000 copies mitochondrial DNA
	Sperm
 Diameter -> ~5um
 < 1000 copies mitochondrial DNA
	Transmission -> mitochondrial &amp; chloroplast genomes 
	Uniparental pattern 
>> Usually maternal inheritance
   ->> Females transmit -> All children
   ->> Males never transmit
	Paternal mammalian mitochondria &amp; sperm components (excl. nucleus) destroyed after fertilisation. 
	Plants:
 Maternal inheritance common 
 Paternal &amp; Biparental inheritance also found
40
Q

Describe characteristics of the egg in terms of mitochondrial DNA

A

 Egg
 Diameter -> ~100um
 > 100,000 copies mitochondrial DNA

41
Q

Describe the characteristics of the sperm in terms of mitochondrial DNA

A

 Sperm
 Diameter -> ~5um
 < 1000 copies mitochondrial DNA

42
Q

Describe transmission of mitochondrial & chloroplast genomes

A 
	Transmission -> mitochondrial &amp; chloroplast genomes 
	Uniparental pattern 
>> Usually maternal inheritance
   ->> Females transmit -> All children
   ->> Males never transmit
43
Q

Describe what happens to paternal mammalian mitochondria & sperm components after fertilisation

A

 Paternal mammalian mitochondria & sperm components (excl. nucleus) destroyed after fertilisation.

44
Q

What is destroyed after fertilisation?

A

 Paternal mammalian mitochondria & sperm components (excl. nucleus) destroyed after fertilisation.

45
Q

Name the types of inheritance found in plants -> Extranuclear genome transmission

A

 Plants:
 Maternal inheritance common
 Paternal & Biparental inheritance also found

46
Q

Describe mitochondrial DNA disease

A

• Mitochondrial DNA Disease:
- ~1/200 healthy individuals -> pathological mtDNA mutation
- ~ 1/10,000 adults -> mtDNA disease
- > 1000 mitochondrial proteins encoded -> nuclear genome
 Mutations here can cause mitochondrial disease
- Signs & symptoms
Highly variable -> Even within family
- Same mtDNA mutation
 Different signs & symptoms -> diff individuals

47
Q

Describe characteristics of mitochondrial DNA disease

A

• Mitochondrial DNA Disease:
- ~1/200 healthy individuals -> pathological mtDNA mutation
- ~ 1/10,000 adults -> mtDNA disease
- > 1000 mitochondrial proteins encoded -> nuclear genome
 Mutations here can cause mitochondrial disease

48
Q

What are the signs & symptoms of mitochondrial DNA disease

A

Highly variable -> Even within family
- Same mtDNA mutation
 Different signs & symptoms -> diff individuals

49
Q

Describe heteroplasmy

A

• Heteroplasmy:
 Mutation -> mitochondrial genome
Mixture -> normal & mutant mitochondria
&raquo_space; Passive segregation -> mitochondria -> cell division
 Proportion -> mutant mitochondria -> affects severity
» Varies between
-» Individuals
-» Tissues -> single individual

50
Q

What affects the severity of heteroplasmy?

A

 Proportion -> mutant mitochondria -> affects severity

51
Q

What does the severity of heteroplasmy vary in?

A

 Proportion -> mutant mitochondria -> affects severity
» Varies between
-» Individuals
-» Tissues -> single individual

52
Q

What is heteroplasmy and how is it caused?

A

• Heteroplasmy:
 Mutation -> mitochondrial genome
Mixture -> normal & mutant mitochondria
&raquo_space; Passive segregation -> mitochondria -> cell division

53
Q

Describe mitochondrial Replacement therapy

A

• Mitochondrial Replacement Therapy:
 Maternal Spindle Transfer:
 Repair -> egg -> before fertilisation
 Metaphase II spindle & associated chromosomes -> mother’s egg
&raquo_space; Transplanted -> donor egg
-» Nucleus removed
Some unhealthy mitochondria possibly transferred alongside mother’s nucleus.

54
Q

Name the process in which mitochondrial replacement therapy occurs

A

 Maternal Spindle Transfer:

55
Q

Describe the process of mitotic spindle transfer

A

 Maternal Spindle Transfer:
 Repair -> egg -> before fertilisation
 Metaphase II spindle & associated chromosomes -> mother’s egg
&raquo_space; Transplanted -> donor egg
-» Nucleus removed
Some unhealthy mitochondria possibly transferred alongside mother’s nucleus.

56
Q

Describe monosomy

A
  • Monosomy (Monosomic):

 Loss of single chromosome (2n – 1)

57
Q

What is monosomy?

A
  • Monosomy (Monosomic):

 Loss of single chromosome (2n – 1)

58
Q

Describe Trisonomy?

A
  • Trisomy (Trisomic):

 One extra chromosome (2n + 1)

59
Q

What is Trisonomy?

A
  • Trisomy (Trisomic):

 One extra chromosome (2n + 1)

60
Q

Describe Tetrasomy?

A
  • Tetrasomy (Tetrasomic):

 Extra pair of chromosomes (2n + 2)

61
Q

What is Tetrasomy?

A
  • Tetrasomy (Tetrasomic):

 Extra pair of chromosomes (2n + 2)

Genes Evo & Dev Y1 (23 decks)

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