Lecture 52. Chromosomal (Segmental) Variation

Question 1

What are chromosomal mutations?

Answer 1

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

Question 2

Why investigate chromosomal mutations?

Answer 2

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)

Question 3

What does n mean in terms of chromosomes?

Answer 3

Number of chromosome sets

Question 4

What does 1n represent?

Answer 4

Monoploid

Question 5

What does 2n represent?

Answer 5

Diploid

Question 6

What does 3n represent?

Answer 6

Triploid

Question 7

What does 4n represent?

Answer 7

Tetraploid

Question 8

What does aneuploid mean?

Answer 8

Change in number of some but not all chromosomes

Question 9

Is monoploidy useful in most animal species?

Answer 9

No, it is non-viable in most animal species

Question 10

In what animals is monoploidy useful?

Answer 10

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

Question 11

Why is monoploidy useful in plant breeding?

Answer 11

Pollen grains subjected to cold shock begin to divide

Question 12

What is an example of a triploid plant?

Answer 12

Banana

Question 13

What are examples of tetraploid plants?

Answer 13

Coffee, cotton, peanut, potato, oilseed rape

Question 14

What are examples of hexaploid plants?

Answer 14

Oat and wheat

Question 15

What is an example of an octaploid plant?

Answer 15

Strawberry

Question 16

What does paleotetraploid mean?

Answer 16

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

Question 17

What are examples of paleotetraploid plants?

Answer 17

Cabbage and soybean

Question 18

What are examples of tetraploid animals?

Answer 18

African clawed frog, viscacha rat, rainbow trout

Question 19

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

Answer 19

Polyploidy

Question 20

What increases with higher ploidy?

Answer 20

Size of organism

Question 21

What are the two origins of polyploidy?

Answer 21

Autopolyploidy and allopolyploidy

Question 22

What does autopolyploidy mean?

Answer 22

Derived from the same diploid species

Question 23

What does allopolyploidy mean?

Answer 23

Derived from different progenitor species

Question 24

How was hexaploid wheat derived?

Answer 24

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

Question 25

What are the genomes in hexaploid wheat referred to as?

Answer 25

A, B & D

Question 26

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

Answer 26

Colchicine

Question 27

What are the consequences of meiosis in a triploid?

Answer 27

Highly sterile gametes

Question 28

What can meiosis in an autotetraploid result in?

Answer 28

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

Question 29

What occurs after meiosis malfunctions?

Answer 29

Non-disjunction

Question 30

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

Answer 30

Trisomic and monosomic daughter cells (both lethal)

Question 31

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

Answer 31

Disomic daughter cells (normal)

Question 32

What are the consequences of miss-aligned repeat sequences?

Answer 32

Unequal crossing-over & gain or loss of repeats

Question 33

What is a pericentric inversion?

Answer 33

A large segmental inversion that encompasses the centromere

Question 34

What is a paracentric inversion?

Answer 34

A large segmental inversion that does not encompass the centromere

Question 35

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

Answer 35

No deletion or duplication is possible

Question 36

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

Answer 36

Dicentric and acentric chromosomes will be created

Question 37

What occurs in heterozygous translocation?

Answer 37

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

Question 38

What occurs in homozygous translocation?

Answer 38

Both pairs of chromosomes are interchanged

Question 39

How can cancer be caused by somatic translocation?

Answer 39

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