WK 4

Question 1

Changes in Chromosome Number are of two basic types:

Answer 1

aberrant euploidy and aneuploidy

Question 2

Ploidy

Answer 2

refers to the number of sets of chromosomes in the nucleus

Question 3

Euploidy

Answer 3

general term used to refer to organisms with multiples of the basic chromosome set. The cells contain only complete chromosome sets.

Question 4

Aberrant Euploidy

Answer 4

when a cell has more or less than the normal number of chromosome sets, entire set is affected; changes in whole chromosome sets

Question 5

Polyploid

Answer 5

three or more sets of chromosomes (triploid or higher ploidy)

Question 6

Aneuploid

Answer 6

organism gains or loses one or more chromosomes, but not a complete set (“not euploid”). The chromosome number of aneuploids is not an exact multiple of the haploid number, n., single chromosome or few chromosomes affected; changes in parts of chromosome sets

Question 7

How to get a tetraploid

Answer 7

Mitosis in zygote fails
Other mitotic divisions are normal and have a tetraploid every time
Most triploids are mosaics (some triploid and some normal)
Longest living was 1 year

Question 8

How to get a triploid

Answer 8

triploid infants can be liveborn, but do not survive long. Most result from fertilization of an egg by two sperm (dispermy) (one egg fertilized by two sperm = 3 haploid cells instead of 2). Other cases result from failure of one of the meiotic divisions in either sex, resulting in a diploid egg or sperm.

Question 9

Types of aneuploidy

Answer 9

in autosomes:
Nullisomy: 2n – 2
Monosomy: 2n–1
Trisomy: 2n+1
Tetrasomy: 2n+2
In haploids: n + 1 = disomy
For sexchromosomes, we list the copies of each chromosome: XXY, XXX, XYY, XO (“O” stands for absence of a chromosome)

Question 10

Nullisomy

Answer 10

2n – 2