polyploidy

Question 1

monoploidy

Answer 1

only one set of chromosomes (N)

Question 2

polyploidy

Answer 2

more than the normal number of sets of chromosomes
tetraploid = 4N
triploid = 3N

Question 3

true or false triploids are not fertile?

Answer 3

true

Question 4

Autopolyploids

Answer 4

• usually have double chromosomes
• chromosome sets are all identical (identical homologous groups)
• all chromosomes are derived from the same species
• have more vegetative growth and less seed production (especially 3N)

Question 5

autopolyploidy through mitosis

Answer 5

• goes through steps correctly except during cytokinesis there is no cell division
• same species doubled its own genetic material
• if happened in animal, cell dies

Question 6

autopolyploidy in meiosis

Answer 6

• in meiosis I cell doesn’t separate due to non-disjunction
• produces a 2n gamete to enter meiosis II
• meiosis II happens normally and in fertilization 2n gamete fuses with n gamete to produce an autotriploid (3n)

Question 7

why is polyploidy more common in plants

Answer 7

it is easier for them to reproduce asexually

Question 8

sterile

Answer 8

not able to reproduce

Question 9

why are many polyploids sterile

Answer 9

due to problems with pairing and separation of homologous chromosomes in meiosis

Question 10

Polyploidy example: 3N = 33 bananas

Answer 10

meiosis I creates 11 bivalents and 11 univalents
- in anaphase I, one chromosomes is excluded and ends up on one side which causes uneven gametes
OTHER POSSIBILITY
meiosis I creates 11 trivalents
- all homologous chromosomes stick together and end up on same side

Question 11

triploid cell in meiosis: pairing of 2 or 3 homologs

Answer 11

1) in meiosis I, two homologous chromosomes pair whereas the other segregates randomly OR all three pair and segregate randomly
2) in meiosis II, some of the resulting gametes have 2 chromosomes and some have 1

Question 12

triploid cell in meiosis: no pairing of homologs

Answer 12

1) in meiosis I, none of the chromosomes pair and all three move to the same cell after anaphase I
2) in meiosis II, some gametes have 3 chromosomes and some have none

Question 13

True or false - if the homologous chromosomes aren’t separated in meiosis I they will be separated in meiosis II

Answer 13

False - meiosis II will always separate sister chromatids even if homologous chromosomes were not separated in meiosis I

Question 14

viable gametes

Answer 14

segregation decisions go the same way by all cells

Question 15

allopolyploids

Answer 15

result from crosses between 2 or more species
- gametes have to be able to fertilize each other meaning reproductive system of species must be similar enough

Question 16

breeding allopolyploids example: plants

Answer 16

1) gametes from two diploid plants unite to form a hybrid
2) the hybrid is sterile because meiosis is highly irregular
3) the chromosomes are doubled creating a tetraploid (allotertaploid)
4) meiosis in the tetraploid is regular because there are homologous pairs
5) the euploid gametes produced by the tetraploid can combine to propagate the organism sexually

Question 17

why can’t sterile hybrids produce gametes

Answer 17

• meiosis doesn’t work
• chromosomes A and B aren’t homologous
• however mitosis can still work

Question 18

chromosome doubling in sterile hybrids

Answer 18

• makes a sterile hybrid able to reproduce
• meiosis I can now happen on the A’s and B’s seperatly

Question 19

true or false - plants that can reproduce asexually are still viable if A and B are no compatible

Answer 19

ture

Question 20

when is 2N not a true diploid

Answer 20

when chromosomes are doubled in hybrids and the now 4N species makes 2N gametes
- not true diploid because you don’t have pairs

Question 21

allohexaploidy example: bread

Answer 21

species 1: 2N =14
species 2: 2N = 14
both have N7 gametes and produce a 2N = 14 sterile offspring
- gametes are not homologous so no meiosis can happen

Question 22

true or false : when a species is labeled 2N means they have 2 homologous sets

Answer 22

false - implies 2 sets of chromosomes but not that they are necessarily homologous

Question 23

what happens when a 2N species is crossed with a 4N species

Answer 23

produces a 3N sterile species
- the gametes it produces will not be viable
- if the offsprings chromosomes double it will be a 6N species
- 6N = 6 sets of chromosomes, but 3 sets of diploids

Question 24

interspecies cross in animals: the mule

Answer 24

donkey 2N = 62 produces N = 31 gametes
horse 2N = 64 produces N = 32 gametes
mule is 2N = 63 sterile
- since it is sterile, not a diploid

Question 25

bivalent

Answer 25

pair of physically associated chromosomes that have undergone duplication to form a group of 4 chromatids present in metaphase I