Bentzen 11 - Chromosome Variations II

Question 1

What is aneuploidy?

Answer 1

An increase or decrease in the number of individual chromosomes (eg. trisomy)

Question 2

What is polyploidy?

Answer 2

The increase in the number of sets of chromosomes (ef. every copy of every chromosome being triploid)

Question 3

What are the four most common types of aneuploidy in diploid (2n) individuals?

Answer 3

Nullisomy (loss of both members of a pair of homologous chromosomes)

Monosomy (Loss of a single chromosome)

Trisomy (Gain of a single chromosome)

Tetrasomy (gain of two homologous chromosome)

Question 4

What is double monosomic aneuploidy?

Answer 4

Loss of 2 non-homologous chromosomes (rare)

Question 5

What is double trisomic aneuplody?

Answer 5

Gain of two non-homologous chromosomes (rare)

Question 6

What are two origins of aneuploidy?

Answer 6

1. Nondisjunction in meiosis or mitosis

2. Deletion of a centromere leads to chromosome loss

Question 7

What is the gamete outcome in trisomy?

Answer 7

May be viable

Question 8

What is the gamete outcome in monosomy?

Answer 8

Usually not viable, except for sex chromosomes

Question 9

What is the most common cause for human spontaneous abortion?

Answer 9

Aneuploidy

Question 10

What causes trisomy 21 (Downs Syndrom)?

Answer 10

Nondisjunction in the first meiotic division. 75% of the time the nondisjunction occurs in the mom

Question 11

Why is it that trisomy occurences increase with increasing maternal age?

Answer 11

Possibly due to fact that oocytes are fomed by birth, in arrested stage of meiosis

Question 12

What is familial down syndrome?

Answer 12

When an extra copy of chromosome 21 is attached to another chromosome (form parent who underwhent Robertsonian translocation and subsequently has 45 chromosomes- but normal phenotype)

Question 13

Where is polyploidy common?

Answer 13

In plants

Question 14

What is autopolyploid?

Answer 14

Multiples of the same genome (eg. autotetraploid - 4n)

Question 15

What is allopolyploid?

Answer 15

Multiples of closely related genome (eg. allotetraploid - 4n; 2n from species I and 2n from species II)

Question 16

What can produce autotetraploid?

Answer 16

Nondisjunction of all chromosomes during MITOSIS

Question 17

What can cause autopolyploidy?

Answer 17

Nondisjunction of all chromosomes during meiosis. (eg. diploid gamete plus normal gamete equals autotriploid (3n))

Question 18

Why are people with autopolyploidy normally sterile?

Answer 18

Most gametes produced are genetically ubalanced

Question 19

How can sterile hybrid organisms be converted into fertile ‘new’ species?

Answer 19

Chromosome doubling by mitotic nondisjunction

Question 20

How can you generate allopolyploids?

Answer 20

By adding two 2n amphidiploids together you can make a allotetraploid cross between the two organisms. If the allotetraploid organisms is viable than this is a cross which makes a new species (like a cabbish)

Question 21

What is cell volume correlated with? Which is in turn correlated with?

Answer 21

Cell volume correlated with nucleus volume and nucelus volume correlated with genome size. This is why polyplois often have bigger leaves, fruits and seeds