Lecture 15

Question 1

4 characteristics of chromosome

Answer 1

1. found in matched pairs
2. pairs segregate 1:1 in meiosis
3. pairs segregate independently
4. correct # chromosomes required for development

Question 2

what is ploidy?

Answer 2

of sets of chromosomes

Question 3

what does it mean if something is euploid?

Answer 3

all chromosomes are found in the same number

Question 4

which type of euploids are sterile?

Answer 4

all odd number euploids

Question 5

2 types of polyploidy and what they mean

Answer 5

AUTOPOLYPLOIDY: extra chromosomes from same species/source

ALLOAUTOPLOIDY: extra chromosomes from diff species/source

Question 6

what does it mean for chromosomes to be aneuploids?

Answer 6

not a full set of chromosomes –> missing a chromosome or has an extra chromosome

Question 7

2 types of aneuploids and formula for number of chromosomes

Answer 7

MONOSOMIC: 2n-1

TRISOMIC: 2n+1

Question 8

polyploidy in animals vs plants

Answer 8

uncommon in animals
common in plants

Question 9

why is polyploidy uncommon in animals?

Answer 9

because it means it’s lethal

Question 10

what type of ploidy are seedless bananas and watermelons?

Answer 10

triploid

Question 11

2 somatic consequences of autopolyploidy?

Answer 11

1. increased size
2. lethality

Question 12

1 germline consequence of autopolyploidy

Answer 12

no germ cells because aneuploid

Question 13

describe chromosome segregation in meiosis 1 and 2

Answer 13

MEIOSIS 1
- Homologous chromosomes pair up and line up at the metaphase plate
- homologous chromosomes randomly segregate to 2 different daughter cells

MEIOSIS 2
- Each chromosome lines up at the metaphase plate
- Sister chromatids segregate to 4 different daughter cells

Question 14

describe the issue with meiosis in triploids

Answer 14

for each homologous chromosome pair, there is an extra chromosome that does not have a partner

Question 15

describe meiosis in triploids producing aneuploid gametes

Answer 15

some of the unpaired chromosomes go to one cell and some go to the other cell in meiosis 1

meiosis 2 produces 4 aneuploid cells

Question 16

describe meiosis in triploids producing euploid gametes

Answer 16

all of the unpaired chromosomes go to the same daughter cell in meiosis 1

meiosis 2 produces 4 euploid cells (2 are normal haploid gametes, the other 2 are diploid)

Question 17

describe the viability of diploid cells produced from meiosis of triploids

Answer 17

the cells are viable –> doesn’t necessarily make organism viable but the cell itself is viable

Question 18

probability of euploid gamete (i.e. probability that all unpaired chromosomes go to 1 cell)

Answer 18

(1/2)^(n-1)

Question 19

describe meiosis of tetraploids and what this allows in plants

Answer 19

makes all diploid –> plants are viable bc they fertilize each other to re-make the tetraploids

Question 20

2 spontaneous causes of autopolyploidy

Answer 20

1. fertilization by multiple sperm
2. errors in mitosis making diploid gametes

Question 21

3 induced/intentional causes of autopolyploidy

Answer 21

1. disruption of chromosome segregation in plants
2. fertilization by diploid germ cell from tetraploid plant
3. selection

Question 22

describe how polyploidy can be generated thru selective breeding using example of making triploid

Answer 22

Question 23

describe how polyploidy can be generated with colchinone

Answer 23

disrupt mitosis with colchicine –> chromosomes separate but no division –> makes tetraploid cell