Question 2 (11 points) In the plant genus Triticum there are many different poly
ID: 65261 • Letter: Q
Question
Question 2 (11 points)
In the plant genus Triticum there are many different polyploid species, as well as diploid species. Crosses were made between three different species, and hybrids were obtained. The meiotic pairing was observed in each hybrid, and this is recorded in the following table. (Hint#1: A bivalent is two homologous chromosomes paired at meiosis, and a univalent is an unpaired homolog at meiosis. HINT #2 : For this question, review your knowledge of chromosome inheritance and pairing in meiosis along with what you learned about auto- and allopolyploids in this module. For review, see pages 591-599 in the textbook.)
a) Using the information gathered from the crosses above, deduce the F1 chromosome number (ploidy) from each cross.
b) Using the information gathered from the crosses above, deduce the somatic chromosome number of each parent species used.
c) State which species are polyploid and whether they are autopolyploids or allopolyploids.
d) Describe how the observed chromosome pairing pattern arose in the the F1 of Cross 1.0.
Explanation / Answer
(a)
Cross
Number of chromosomes
T. turdigum x T. monococcum cross
(7 bivalents + 7 univalents) = 21
T. aestivum x T. monococcum cross
(7 bivalents + 14 univalents) = 28
T. aestivum x T. turdigum cross
(14 bivalents + 7 univalents) = 35
Use the above information to calculate number of somatic chromosome in each species
Number of somatic chromosomes in T. turdigum
14
Number of somatic chromosome in T. monococcum
7
Number of somatic chromosome in T. aestivum
21
(b) Based on the above information we can say
(C)T. turdigum – autopolyploids
T. aestivum -- allopolyploid.
(d) Observed chromosome pairing pattern arose in the the F1 of Cross 1.0.
Cross 1
Bivalent is formed by the T. turdigum and univalent is formed by the T. monococcum
Cross 2
Due to allopolyploid nature of the T. aestivum, between two species bivalent is formed and we can also see the formation of univalent from the chromosomes of the two species
Cross 3
Autopolyploid nature of T. turdigum will form the bivalents between the two species, chromosomes of T. aestivum are seen forming the univalent.
Cross
Number of chromosomes
T. turdigum x T. monococcum cross
(7 bivalents + 7 univalents) = 21
T. aestivum x T. monococcum cross
(7 bivalents + 14 univalents) = 28
T. aestivum x T. turdigum cross
(14 bivalents + 7 univalents) = 35
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