Cytogenetics

Question 1

What is a karyotype?

Answer 1

• the exact diploid chromosome set of the organism.
• the karyotype is particular to an individual or to related groups (eg. species).

Question 2

What is a karyogram?

Answer 2

the physical measurement of the chromosomes fro a photoicrograph where the chroosomes are arranged in the descending order (longest to shortest).
different groupings are also possible.

Question 3

What is a karyogram used for?

Answer 3

the detection of:
- sex
- genetic disorders

Question 4

Explain the structure of chromosoes.

Answer 4

DNA—> nucleosomes—> nucleosome array (solenoid or zigzag)—> interphase chromosome (thread like) —> metaphase chromosome (X shape)

Question 5

What are the classifications of chromosomes?

Answer 5

1) metacentric
2) subetacentric
3) acrocentric
4) telocentric

Question 6

How do scientists identify chromosomes?

Answer 6

1) size
2) binding patterns
3) centromere postion (metacentric (V), subetacentric (L), acrocentric (J), telocentric (rod))

Question 7

Which chromosomes do humans have?
How many groups are human chromosoes divided into?
What classification is used in huans?
How is classification done?

Answer 7

• metacentic
• submetacentric
• acrocentric
  (HUMANS DO NOT HAVE TELOCENTRIC CHROMOSOMES!)
• divided into 7 groups (A-G)
• using DENVER classification
• classification is done considering the size of the chromosome (large —> small) and the position of the centromere)

Question 8

What is a karyogram?

Answer 8

The organized view of a karyotype.

Question 9

How to write normal male and normal female karyotype?

Answer 9

accurate way of writing a karyotype: number of chromosomes (including autosomes), gender

male karyotype: 46, XY

feale karyotype: 46, XX

Question 10

What is FISH?

Answer 10

FISH stands for Fluorescent Hybridization in Situ
It is used to detect the location of DNA sequences on chromosomes.

1) scientists create fluorescent probes (allowing for fluorescent stains)
2) probes are labelled with fluorescent dies, and are mixedwith chroosome DNA
3) the dye allows scientists to see the location of the DNA sequence on the chromosome.

Question 11

How to prepare a karyotype?

Answer 11

1) metaphase cells are required
eg. blood, cultured cells, bone marrw cells, chorionic villi

2) chemically induce cell dvision

3) stop mitotic cells from dividing (arresting cells at metaphase, when the chromosomes are condensed)

4) cells are stained

5) chromosomes are arranged into homologous pairs according to size

Question 12

What is the syndrome named if they have 3 X chromosomes?

Answer 12

triple XXX syndrome

Question 13

Which chroosoes can humans have?

Answer 13

triple XXX, XXY syndrome, XYY syndrome

Question 14

What is cytogenetics?

Answer 14

a branch pf genetics, that is concerned with the study of the structure and function of the cell, especially the chromosomes.

Question 15

What is a karyotype?

Answer 15

The chromosomes of a cell, usually displayed as a systemized arrangement of chromosome pairs in descending order of size.

Question 16

What is the trend in chromosome numbers?

Answer 16

Chromosome numbers within species is usually constant, but it varies among different species.

Question 17

Cells from which tissues are used for cytogenetics?

Answer 17

intensely dividing tissue cells such as:
- bone marrow,
- lymph nodes,
- embryonic chorionic cells.

Question 18

What is the human chromosome number?

Answer 18

2n = 46

Question 19

What are the different parts of chromosomes?

Answer 19

chromatid - one whole side
telomere - ending of chromosome arms
short arm (p)
long arm (q)
centromere

Question 20

What is the letter of the “short arm” of the chromosomes?

Answer 20

p

Question 21

What is the letter of the “long arm” of the chromosomes?

Answer 21

q

Question 22

How is the number of chromosomes connected to cell development?

Answer 22

No connection between the number of the chromosomes and the indensivity of development.

Question 23

What are the four chromosome types?

Answer 23

• metacentric
• submetacentric
• acrocentric
• telocentric

Question 24

How are chromosomes classified? Based on what?

Answer 24

Chromosomes are classified based on the relative position of the centromere.

Question 25

Explain the karyotype of pigs.

Answer 25

• 38 chromosomes
• 4 homologous pairs of metacentric chromosomes
• 9 homological pairs of submetacentric chromosomes
• 6 homologous pairs of telocentric chromosomes.

Question 26

What is an idiogram?

Answer 26

a diagrammatic sketch or interpretative drawing of chromosomes based on physical characteristics visible in the karyogram.

Question 27

The ratio of what allows for the classification of chromosomes into several basic morphologic types?

Answer 27

the ratio of the lengths of the two arms

Question 28

How are the chromosomes in a karyogram ordered?

Answer 28

from largest to smallest

Question 29

What does organising the chromosomes into homologous groups allow for?

Answer 29

the detection of non-disjunction

Question 30

What does comparing the banding patterns of homologous chromosomes allow for?

Answer 30

aids in the detection of chromosomal aberrations eg. deletions, inversions or translocations.

Question 31

What does a karyogram allow for?

Answer 31

1) discovery of the sex of the organism
2) checking for diseases by:
a) non-disjunction (visual chromosome shape)
b) chromosomal aberrations (binding pattern)