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LF104: Molecules, Cells And Organisms > Lecture 52. Chromosomal (Segmental) Variation > Flashcards

Lecture 52. Chromosomal (Segmental) Variation Flashcards

1
Q

What are chromosomal mutations?

A

Change in the chromosome number per cell
Large-scale (segmental) change in chromosome structure
Visible by microscopy

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2
Q

Why investigate chromosomal mutations?

A

Cytological insight into meiosis
Medical insight in causes of genetic disease
Molecular insight of how genes interact throughout a genome
Evolutionary insight (e.g., origin of new species)

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3
Q

What does n mean in terms of chromosomes?

A

Number of chromosome sets

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4
Q

What does 1n represent?

A

Monoploid

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5
Q

What does 2n represent?

A

Diploid

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6
Q

What does 3n represent?

A

Triploid

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7
Q

What does 4n represent?

A

Tetraploid

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8
Q

What does aneuploid mean?

A

Change in number of some but not all chromosomes

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9
Q

Is monoploidy useful in most animal species?

A

No, it is non-viable in most animal species

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10
Q

In what animals is monoploidy useful?

A

Social insects (ants, bees and wasps)
Males are monoploid & develop by parthenogenesis (gametes from mitosis)

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11
Q

Why is monoploidy useful in plant breeding?

A

Pollen grains subjected to cold shock begin to divide

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12
Q

What is an example of a triploid plant?

A

Banana

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13
Q

What are examples of tetraploid plants?

A

Coffee, cotton, peanut, potato, oilseed rape

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14
Q

What are examples of hexaploid plants?

A

Oat and wheat

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15
Q

What is an example of an octaploid plant?

A

Strawberry

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16
Q

What does paleotetraploid mean?

A

Looks like and is functionally a diploid, but used to be a tetraploid

17
Q

What are examples of paleotetraploid plants?

A

Cabbage and soybean

18
Q

What are examples of tetraploid animals?

A

African clawed frog, viscacha rat, rainbow trout

19
Q

What is a common cause for the origin of new plant species?

A

Polyploidy

20
Q

What increases with higher ploidy?

A

Size of organism

21
Q

What are the two origins of polyploidy?

A

Autopolyploidy and allopolyploidy

22
Q

What does autopolyploidy mean?

A

Derived from the same diploid species

23
Q

What does allopolyploidy mean?

A

Derived from different progenitor species

24
Q

How was hexaploid wheat derived?

A

Derived from three ancestral diploid species (each n=7)

25
Q

What are the genomes in hexaploid wheat referred to as?

A

A, B & D

26
Q

What can be used to disrupt spindle assembly and thereby block chromosomal segregation?

A

Colchicine

27
Q

What are the consequences of meiosis in a triploid?

A

Highly sterile gametes

28
Q

What can meiosis in an autotetraploid result in?

A

Two bivalents (normal)
One quadrivalent (normal)
Univalent + Trivalent (abnormal)

29
Q

What occurs after meiosis malfunctions?

A

Non-disjunction

30
Q

What are the consequences of non-disjunction in meiosis I?

A

Trisomic and monosomic daughter cells (both lethal)

31
Q

What are the consequences of non-disjunction in meiosis II?

A

Disomic daughter cells (normal)

32
Q

What are the consequences of miss-aligned repeat sequences?

A

Unequal crossing-over & gain or loss of repeats

33
Q

What is a pericentric inversion?

A

A large segmental inversion that encompasses the centromere

34
Q

What is a paracentric inversion?

A

A large segmental inversion that does not encompass the centromere

35
Q

What happens if there is no recombination within an inversion loop?

A

No deletion or duplication is possible

36
Q

What happens if a crossover within an inversion loop takes place?

A

Dicentric and acentric chromosomes will be created

37
Q

What occurs in heterozygous translocation?

A

One pair of chromosomes is interchanged whilst the other pair remains normal

38
Q

What occurs in homozygous translocation?

A

Both pairs of chromosomes are interchanged

39
Q

How can cancer be caused by somatic translocation?

A

ABL encodes a protein kinase that transduces a signal for cell proliferation, which is initiated by growth factor
Chimeric protein is always active (cancerous)

LF104: Molecules, Cells And Organisms (33 decks)

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