8.18-8.23: Alterations of Chromosome Number and Structure

Question 1

What is nondisjunction?

Answer 1

The failure of a tetrad or a sister chromatid to split at meiosis I or meiosis II, respectively.

Question 2

If a tetrad fails to split at meiosis I, how many chromosomes will the resulting gametes have.

Answer 2

Half will have n+1 chromosomes, other half will have n-1 chromosomes.

Question 3

If a sister chromatid fails to split at meiosis II, how many chromosomes will the resulting gametes have.

Answer 3

1 gamete will have n+1 chromosomes, one will have n-l, and the other half will have normal gametes.

Question 4

What causes more irregularities in cells, the nondisjunction of a homologous pair or that of a sister chromatid?

Answer 4

A homologous pair.

Question 5

pg 144 shows diagrams of

Answer 5

…nondisjunction

Question 6

End of 8.18 question: explain how nondisjunction could result in a diploid gamete.

Answer 6

A diploid gamete would result if the nondisjunction affected all the chromosomes during one of the cell divisions (ie. they all went to one side of the cell). If meiosis I all nondisjunction, and meiosis 2 normal, or if meiosis 1 normal and both meiosis 2 total nondisjunction

Question 7

What is a karyotype?

Answer 7

an ordered display of magnified images of an individual’s chromosomes arranged in pairs. It shows the chromosomes condensed and doubled, as they appear in the metaphase of mitosis.

Question 8

How are karyotypes discovered using the white blood cells lymphocytes?

Answer 8

1) mitosis is stimulated in blood sample
2) mitosis is stopped at metaphase
3)blood culture is put in centrifuge
4)hypotonic solution is added, making red blood cells burst and white blood cells spread out.
4)centrifuge again, separates swollen white blood cells.
5) red blood cells are discarded, and a preservative is added to white blood cells, which go under the microscope for a karyotype.

Question 9

End of 8.19 Question: How would the karyotype of a human female differ from the male karyotype?

Answer 9

Instead of an XY combination for thee sex chromosomes, there would be a homologous pair of X chromosomes (XX).

Question 10

What causes Down Syndrome?

Answer 10

In chromosome pair 21 on a karyotype, there is one extra chromosome, giving a the body a total of 47 chromosomes.

Question 11

What is the officially name for Down Syndrome?

Answer 11

Trisomy 21.

Question 12

What usually happens when a genetic malfunction occurs? Why does this not occur in Down Syndrome?

Answer 12

The body spontaneously aborts the baby. It does not seem to upset the genetic balance all that much.

Question 13

What does being born with trisomy 21 do?

Answer 13

Physical characteristics: round face, flattened nose bridge, small teeth, short stature
Conditions- heart defects, susceptibility to respiratory infections, leukemia, and Alzheimer’s disease, shorter lifespan. Sterility in all men, and a 50% down syndrome will be passed down from women.

Question 14

When is it more likely for a women to give birth to a child with Down Syndrome?

Answer 14

Older age, nearing menopause.

Question 15

End of 8.20 Question: For mothers of age 47, the risk of having a baby with Down Syndrome is about _____ per thousand births, or ____ %

Answer 15

40, 4.

Question 16

How many children born have Down Syndrome?

Answer 16

1/700.

Question 17

Why does nondisjunction in sex chromosomes not usually affect survival?

Answer 17

Y chromosomes is very small with very few genes, only having one X chromosome would not be that different.

Question 18

What is Klinefelter syndrome and what does it do? Where does it come from?

Answer 18

When a male (XY) is born with an extra X chromosome (XXY). Has male reproductive anatomy, but is sterile. Has female body characteristics. Comes from nondisjunction in meiosis of egg or sperm formation.

Question 19

Do females or males with an extra X or Y chromosome appear any different? Where does this genetic malfunction come from?

Answer 19

Females, no. Men tend to be taller (XYY). XXX comes from nondisjunction in egg or sperm formation, XYY from nondisjunction in sperm formation.

Question 20

What are other variations of Klinefelter syndrome and what do they do?

Answer 20

XXYY, XXXY, XXXXY. All male, usually have developmental disabilities more than XY or XXY.

Question 21

What is Turner syndrome and what does it do? Where does it come from?

Answer 21

Females with only one X chromosome, designated XO. Have a short stature, skin between neck and shoulders, poor development of breasts (artificial introduction of estrogen can help). They are sterile. No effect on intelligence. Only case where lacking a chromosome is not fatal

Question 22

How common is Klinefelter syndrome?

Answer 22

1/1000 live male births

Question 23

How common is XYY birth?

Answer 23

1/1000 live male births

Question 24

How common is XXX birth?

Answer 24

1/1000 live female births

Question 25

how common is Turner Syndrome?

Answer 25

1/2500 live female births

Question 26

Can errors in mitosis and meiosis create new species? If so, what are they called?

Answer 26

Yes, polyploids.

Question 27

Define polyploid.

Answer 27

A species which has more than two sets of homologous chromosomes in each somatic cell.

Question 28

What are some examples of polyploid plants?

Answer 28

1/2 of flowering plants, wheat, potatoes, cotton.

Question 29

What is a tetraploid

Answer 29

a organism that results from the fertilization of a diploid (2n) egg with a diploid (2n) sperm, making a 4n.

Question 30

How can polyploids constitute a new species in just one generation?

Answer 30

If meiosis II fails and only meiosis I occurs, the gametes created are diploid, but still gametes. When they self-fertilize, they will create polyploid offspring.

Question 31

Where is polyploid offspring most commonly found?

Answer 31

In plants which can self-fertilize, as well as amphibians.

Question 32

End of 8.22 Question: What is a polyploid organism?

Answer 32

A organism with more than two sets of homologous chromosomes in its body cells.

Question 33

What causes a chromosome to break?

Answer 33

Errors in meiosis and radiation.

Question 34

What are the types of damaging changes in a chromosome?

Answer 34

Deletion, duplication, inversion and translocation.

Question 35

What is deletion?

Answer 35

When a chromosomal fragment disappears from the cell, leaving an empty space in the genetic makeup.

Question 36

What is duplication?

Answer 36

The chromosomal fragment copies itself than attaches its dual self as an extra segment to its sister chromatid or homologous pair.

Question 37

What is inversion?

Answer 37

When a chromosomal fragment reattaches to the original chromosome, but in reverse orientation.

Question 38

What is translocation?

Answer 38

The chromosomal segment joining an non-homologous chromosome. They many even trade sections, called reciprocal translocation. (see page 148)

Question 39

Which is the least harmful of the changes in chromosomal structure?

Answer 39

Inversion: genetic material is there, just not in correct order.

Question 40

What is cri du chat "cat-cry" syndrome?

Answer 40

A case of deletion in chromosome 5 that leads to physical abnormalities and early death.

Question 41

How can translocations be present in people with Down Syndrome?

Answer 41

They may have only a part of a third chromosome for chromosome 21, the other part of the chromosome is attached to a different pair.

Question 42

What is CML? What is it caused by?

Answer 42

CML is chronic myelogenous leukemia. It is caused by reciprocal translocation during the mitosis of cell that will become white blood cells. A large portion of Chromosome 22 is exchanged for a small piece of Chromosome 9. These changes get rid of cell cycle regulation.

Question 43

Why is cancer not usually not inherited?

Answer 43

Because the chromosomal changes in cancer are usually confined to somatic ells.

Question 44

End of 8.23 Question: How is reciprocal translocation different from crossing over?

Answer 44

Reciprocal translocation swaps chromosome segments between nonhomologous chromosomes. Crossing over exchanges corresponding segments between homologous chromosomes.