Inversion

1
Inversion

• Segment of a chromosome breaks, turn through 180
  and attach again.
• A B . C D E F G H
• A D C . B E F G H
• pericentric inversion
• A B . C F E D G H
• paracentric inversion

2
Potential pairing

• Incomplete terminal pairing
• Incomplete interstitial pairing
• Complete pairing

3
(No Transcript)
4
Length of inverted area

• RL B C 2D E 2F (C E) / B / 2

5
Problem

• You study Tribolium brachystachyum and find 2n
  4x 24. Your meiotic analyses reveal a fragment
  in 12 anaphase I cells and two fragments in 7
  anaphase I cells. A chromosome bridge with two
  fragments were present in 6 anaphase I cells a
  chromatid bridge with a fragment in 58 a
  chromatid bridge in 17 and 65 anaphase I cells
  appeared normal. Three dyads contained a bridge
  in each cell of the dyad nine dyads contained a
  bridge in only one of the cells and four dyads
  contained a fragment. Name the abnormality
  present. Use the data supplied to calculate the
  relative length of the abnormality. What
  percentage of pollen grains should be fertile in
  T. brachystachyum?

6
Inclusive inversion

• A B . C D E F G H
• A B . C G F E D H
• A B . C G E F D H

7
Overlapping inversion

• A B . C D E F G H
• A B . C F E D G H
• A B . C F G D E H

8
Problem

• You are studying an organism with 2n 2x 4.
  Chromosome pair 1 consists of segments A-G with
  the centromere between A and B. The chromosome
  pair is heterozygous for a paracentric inversion
  of C-E. Incomplete interstitial pairing with a
  three stranded double cross-over occurs with
  chiasmata between C D and D E. Chromosome
  pair 2 consists of segments 1-8 with the
  centromere between 1 and 2. The chromosome pair
  is heterozygous for a terminal reverse
  duplication of 2 segments. A four stranded
  double cross-over occurs with chiasmata between 5
  6 and 7 8. Sketch the different meiotic
  stages in this organism.

9
Problem

• You are studying a taxon and determine that a
  series of different types of structural
  chromosomal evolution occurred. Indicate which
  type of chromosomal evolution occurred in each
  case and give the phylogenetic relationships
  between the following groups
• a) A B F E D D E F C G H b) A B C D E F G H
• c) A X Y Z B F E D D E F C G H
• d) A X Y Z D E F C G H e) A B F E D C G H

10
Problem

• You discover a new cytotype with a chromosome
  segment sequence of A F G C B E D H. The only
  cytotype known for this taxon is A B C D E F G H.
  What is the most parsimonious way in which this
  cytotype could have originated? What is the name
  of this type of chromosomal evolution?

11
Problem

• The taxon you are studying is evolving by means
  of a series of inversions. What are the
  phylogenetic relationships among these groups?
• a) A E G F B C D H b) A B C D E F G H
• c) A E D C B F G H d) A E B F G C D H
• e) A B C F E D G H f) A B D E F C G H