Chapter 3 part 1

Question 1

Aneuploidy

Answer 1

a variation in the number of particular chromosome within a set
most commonly causes abnormal phenotype
monosomy, trisomy, and tetrasomy

Question 2

Euploidy

Answer 2

a variation in the number of complete sets of chromosome

a complete set of somatic cells is 46 chromosomes (44 autosomes and 2 sex chromosomes)

Question 3

Trisomy

Answer 3

The presence of a chromosome additional to the normal complement (2N+1)
small chromosomes; 21, 18, 13, and 16

Question 4

Monosomy

Answer 4

Loss of one member of a homologous pair of chromosomes (2N-1)
45,X Turner syndrome

Question 5

Tetrasomy

Answer 5

The presence of four chromosomes instead of the normal 2

Question 6

Non-disjunction

Answer 6

The failure of two members of a homologous chromosome pair to separate during cell division so that both pass to the same daughter cell

Question 7

Polyploidy

Answer 7

Any multiple of the haploid number of chromosomes
Triploidy (3N) 69,XXY
Tetraploidy (4N) 92, XXYY

Question 8

Triploidy

Answer 8

A cell with 3 times the number of chromosomes

69,XXY

Question 9

Tetraploidy

Answer 9

Twice the normal diploid number of chromosomes

92,XXYY

Question 10

Dispermy

Answer 10

when one egg is fertilized by 2 sperms

Question 11

Disomy

Answer 11

The normal state of an individual having 2 homologous chromosomes, or when a gamete receives 2 chromosomes

Question 12

Nullisomy

Answer 12

When a gamete receives no chromosomes during non-disjunction

This can lead to monosomy

Question 13

Paternal/Maternal chromosme

Answer 13

the Chromosome coming from the father/mother

Question 14

Mechanisms of Chromosome Non-disjunction

Answer 14

Possibly the aging of the primary oocyte since meiosis I last many years in females
Also the reduction of meiosis recombination between homologous chromosomes can lead to non-disjunction

Question 15

Explain why it is important to know if non-disjunction has occured

Answer 15

Non-disjunction can lead to phenotypic changes in the fetus caused by monosomy or trisomy

Question 16

Explain the causes of trisomy

Answer 16

failure of chromosome separation during meiosis

Trisomy 21 is caused by a non-disjunction of maternal chromosomes of anaphase I

Question 17

Explain the differences between paternal and maternal origin of the extra chromosomes 21 in down Syndrome

Answer 17

most cases of the extra chromosome come from the mother. 95% are from the mother and of those, 77% are from meiosis I non-disjunction

Question 18

Most commonly seen chromosome disorders caused by numerical abnormalities

Answer 18

Down Syndrome(Trisomy 21)
Edward’s Syndrome (Trisomy 18)
Pataul Syndrome(Trisomy 13)
Monosomy of X chromosome

Question 19

Paternal origin of numerical abnormality

Answer 19

Down's Syndrome 95% maternal
Edward's Syndrome 90% maternal
Pataul Syndrome 85% maternal
Turner Syndrome 80% paternal
Klinefelter syndrome 56% maternal (47,XXY)

Question 20

Explain gene dosage effect in trisomy 21, trisomy 18, and trisomy 18

Answer 20

The extra chromosome is present in every cell of the person’s body, this causes physical changes to the person