rearrangement of chromosome structure

Question 1

chromosome arms

Answer 1

sort arm = P arm
long arm = Q arm
- arms are on either side of the centromere

Question 2

what can induce rearrangement of chromosome structure

Answer 2

exposure to uv or chemicals

Question 3

pericentric inversion

Answer 3

• heterozygote has one normal chromosome and one with an inverted segment
• the inverted segment will do everything to align so that meiosis I can act upon it

Question 4

in paracentric inversion how do homologous sequences line up

Answer 4

in prophase I the chromosome forms an inversion loop for the sequence to align
- no gain or loss in genetic material

Question 5

translocation

Answer 5

when a segment from one chromosome is detached and reattached to a different (nonhomologous) chromosome
- ADDED

Question 6

reciprocal translocation

Answer 6

pieces of two nonhomologous chromosomes are exchanged without the loss of any genetic material
- TRADED

Question 7

pairing of reciprocal translocation chromosomes in a tetravalent (4N)

Answer 7

• a crosslike configuration forms in prophase I of meiosis to like up homologous sections
• in anaphase I the chromosome will separate one of three different ways
  1) alternate segregation - all genes present in each copy
  2 and 3) adjacent-1 and -2(rare) segregation - some genes are present in 2 copies and some missing
• only alternate creates viable gametes

Question 8

compound chromosomes

Answer 8

formed by the fusion of homologous chromosomes, sister chromatids or homologous chromosome segments
- possible way to get down syndrome other than nondisjunction

Question 9

Robertsonian translocations

Answer 9

• formed by the fusion of 2 non-homologous chromosomes at their centromere
• only works if the short arm is so short it contains no or non-essential genes

Question 10

how do robertsonian translocations form

Answer 10

1) the short arm of one chromosome is exchanged with the long arm of another
2) this creates a large metacentric chromosome and a fragment that often fails to segregate in other gametes and is lost

Question 11

down syndrome from translocations

Answer 11

5% or less of cases are due to Robertsonian translocation of chromosome 21 long arm onto chromosome 14 long arm