Chapter 8 Part 2

Question 1

Aneuploidy

Answer 1

Change in the number of individual chromosomes; most often an increase or a decrease of one or two chromosomes

Ex. Trisomy 21… instead of having two pairs of homologous pair…we have three chromosomes that make a homologous pair…attributes to down syndrome disorder

Question 2

Polyploid

Answer 2

Possession of more than two sets of chromosomes

Ex… 3n or 4n or 5n…sets of chromosomes than maybe 2n

Question 3

What can Aneuploidy?

Answer 3

1. A chromosome may be lost in the course of mitosis or meiosis…for example, if its centromere is deleted….Loss of the centromere prevents the spindle microtubules from attaching, so the chromosome fails to move to the spindle pole and does not become incorporates into a nucleus
2. The small chromosome generated in Robertsonian Translocation may be lost in mitosis or meiosis
3. Aneuploidy may arise through nondisjunction, the failure of homologous chromosomes or sister chromatic to separate in meiosis or mitosis

Question 4

Non-disfunction

Answer 4

This process leads to some gametes or cells that contain an extra chromosome and other gametes or cells that are missing a chromosome

Question 5

Monosomy

Answer 5

Is the loss of a single chromosome, represented as 2n -1

A human monosomic zygote has 45 chromosomes

Question 6

Nullisomy

Answer 6

Is the loss of both members of a homologous pair of chromosomes

It is represented as 2n-2, where n refers to the haploid number of chromosomes

Thus, among humans who normally possess 2n=46 chromosome, a nullisomic zygote has 44 chromosomes

Question 7

Trisomic

Answer 7

Is the gain of a single chromosome, represented as 2n + 1

The gain of a chromosome means that there are three homologous chromosome

Most cases of Down syndrome results from trisomy of chromosome 21

Question 8

Tetrasomy

Answer 8

Is the gain of two homologous chromosomes, represented as 2n+2

A human tetratomic zygote has 48 chromosomes

Tetrasomy is not the gain of any two extra chromosomes but rather the gain of two homologous chromosomes, so there are four homologous copies of a particular chromosome

Question 9

What happens when more than one aneuploid mutation may occur in the same individual?

Answer 9

An individual that has an extra copy of each two different – non homologous – chromosomes is referred to as being double trisomic; this condition is represented as 2n + 1 + 1

Similarly, a double monosomic individual has two fewer non homologous chromosomes than normal 2n - 1 -1

A double tetratomic individual has two extra pairs of homologous chromosomes

2n + 2 + 2

Question 10

What effects does Aneuploidy cause in animals and plants?

Answer 10

It affects the number of gene copies but not their nucleotide sequences, the effects are mostly likely due to abnormal gene dosage

Question 11

Extra Stuff –> Just for fun/flip the card!

Answer 11

Aneuploidy in humans usually produces such serious development problems that spontaneous abortion results

Only about 2% of all fetuses with a chromosome mutation survive to birth

Causes have been arise to a genetic variant known as PLK4 that increases this outcome by interfering with centrioles

Question 12

Down syndrome

Answer 12

Trisomy 21 –> see definition in one of the other cards

Question 12

Down syndrome

Answer 12

Trisomy 21 –> see definition in one of the other cards

Question 13

Familial Down syndrome

Answer 13

Arises in offspring whose parents are carriers of chromosomes that have undergone a Robertsonian translocation, most commonly between chromosome 21 an chromosome 14: the long arm of 21 and the short arm of 14 exchange places

The long arms of 21 and 14 remain homologous to normal 14

The short arm of 21 and 14 leaves the cytoplasm resulting in monosomy 21

Question 14

Translocation carriers

Answer 14

Individual organisms heterozygous for a chromosome translocation…they possess only 45 chromosomes…but are more likely to produce children with Down Syndrome

Question 15

Explain why human and other mammals, sex chromosomes have more mutations commonly than autosomal chromosomes

Answer 15

Dosage compensation prevents the expression of additional copies of X-linked genes in mammals, and there is little information in the Y-chromosome, so extra copies of the X and Y chromosomes do not have major effects on development

Question 16

Uniparental Disomy

Answer 16

Normally, the two chromosomes of a homologous pair are inherited from two different parents – one from the father and one from the mother

“Both homologous chromosomes inherited from the same parents”

Example…PW syndrome

Question 17

Genetic Mosaic

Answer 17

Condition in which regions of tissue within a single individual have different chromosome constitutions

Question 18

Gynandromorphs

Answer 18

Individual organism that is a genetic mosaic for the sex chromosomes, possessing tissues with different sex-chromosome constitutions

Example:

XX - fruit fly female
XO - fruit fly Male

Question 19

Autopolyploidy

Answer 19

In which all chromosome sets are from a single species

Question 20

Allopolyploidy

Answer 20

In which chromosome sets are from two or more species

Question 21

Colchicine

Answer 21

A chemical that induces artificial nondisjunction by disrupting the formation of the spindle apparatus

–> used in agriculturally and ornamentally important plants

Question 22

Unbalanced Gametes

Answer 22

A gamete produced by meiosis in such an autotriploid might receive, say, two copies of chromosome 1, one copy of chromosome 2, and three copies of chromosome 3, and no copies of chromosome 4