Cytogenetics Flashcards
What is a karyotype?
- the exact diploid chromosome set of the organism.
- the karyotype is particular to an individual or to related groups (eg. species).
What is a karyogram?
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.
What is a karyogram used for?
the detection of:
- sex
- genetic disorders
Explain the structure of chromosoes.
DNA—> nucleosomes—> nucleosome array (solenoid or zigzag)—> interphase chromosome (thread like) —> metaphase chromosome (X shape)
What are the classifications of chromosomes?
1) metacentric
2) subetacentric
3) acrocentric
4) telocentric
How do scientists identify chromosomes?
1) size
2) binding patterns
3) centromere postion (metacentric (V), subetacentric (L), acrocentric (J), telocentric (rod))
Which chromosomes do humans have?
How many groups are human chromosoes divided into?
What classification is used in huans?
How is classification done?
- 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)
What is a karyogram?
The organized view of a karyotype.
How to write normal male and normal female karyotype?
accurate way of writing a karyotype: number of chromosomes (including autosomes), gender
male karyotype: 46, XY
feale karyotype: 46, XX
What is FISH?
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.
How to prepare a karyotype?
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
What is the syndrome named if they have 3 X chromosomes?
triple XXX syndrome
Which chroosoes can humans have?
triple XXX, XXY syndrome, XYY syndrome
What is cytogenetics?
a branch pf genetics, that is concerned with the study of the structure and function of the cell, especially the chromosomes.
What is a karyotype?
The chromosomes of a cell, usually displayed as a systemized arrangement of chromosome pairs in descending order of size.
What is the trend in chromosome numbers?
Chromosome numbers within species is usually constant, but it varies among different species.
Cells from which tissues are used for cytogenetics?
intensely dividing tissue cells such as:
- bone marrow,
- lymph nodes,
- embryonic chorionic cells.
What is the human chromosome number?
2n = 46
What are the different parts of chromosomes?
chromatid - one whole side
telomere - ending of chromosome arms
short arm (p)
long arm (q)
centromere
What is the letter of the “short arm” of the chromosomes?
p
What is the letter of the “long arm” of the chromosomes?
q
How is the number of chromosomes connected to cell development?
No connection between the number of the chromosomes and the indensivity of development.
What are the four chromosome types?
- metacentric
- submetacentric
- acrocentric
- telocentric
How are chromosomes classified? Based on what?
Chromosomes are classified based on the relative position of the centromere.
Explain the karyotype of pigs.
- 38 chromosomes
- 4 homologous pairs of metacentric chromosomes
- 9 homological pairs of submetacentric chromosomes
- 6 homologous pairs of telocentric chromosomes.
What is an idiogram?
a diagrammatic sketch or interpretative drawing of chromosomes based on physical characteristics visible in the karyogram.
The ratio of what allows for the classification of chromosomes into several basic morphologic types?
the ratio of the lengths of the two arms
How are the chromosomes in a karyogram ordered?
from largest to smallest
What does organising the chromosomes into homologous groups allow for?
the detection of non-disjunction
What does comparing the banding patterns of homologous chromosomes allow for?
aids in the detection of chromosomal aberrations eg. deletions, inversions or translocations.
What does a karyogram allow for?
1) discovery of the sex of the organism
2) checking for diseases by:
a) non-disjunction (visual chromosome shape)
b) chromosomal aberrations (binding pattern)
