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MD1S2: Cell Biology and Genetics > Morphology of Chromosomes and Karyotyping > Flashcards

Morphology of Chromosomes and Karyotyping Flashcards

1
Q

What are chromosomes?

A

Rod-shaped, filamentous bodies present in the nucleus which are the carriers of genes

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2
Q

When are chromosomes visible?

A

Visible during cell division

Not visible in active nuclei because of their high-water content

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3
Q

How do chromosome size and shape change during the cell cycle?

A

Interphase: Longest & thinnest
Prophase: Progressive decrease in length and increase in thickness
Anaphase: Chromosomes are smallest
Metaphase: Chromosomes easily observed, very thick, quite short and well spread in the cell

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4
Q

When are chromosome measurements taken?

A

Mitotic metaphase

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5
Q

How can chromosomes be identified?

A

Size
Shape (position of centromere)
Banding patterns from specific stains (Giemsa)

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6
Q

How can chromosomes be classified according to centromeric position?

A

Metacentric
Subcentric
Acrocentric

Telocentric exists only in rodents

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7
Q

What are the arms of a chromosome called?

A

p (petit): short arm
q (quinine): long arm

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8
Q

Describe the metacentric chromosome

A

Centromere at or near the middle of the chromosome
Both arms of the chromosome are of about equal length
The centromere is sometimes called the “primary constriction”

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9
Q

Describe the submetacentric chromosome

A

Submetacentric chromosomes have their centromere located closer to one end of the chromosome than the other

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10
Q

Describe the acrocentric chromosome

A

Acrocentric chromosomes have their centromere close to one end
There is a secondary constriction - thin strands of chromatin of variable length tipped with non coding DNA often referred to as chromosomal satellites
The secondary constriction contains the loci for the ribosomal RNA (rRNA) genes, (the Nucleolar Organizing Region)

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11
Q

What are the seven chromosome groups?

A

Group A, B, C, D, E, F and G

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12
Q

What are the characteristics of Group A chromosomes?

A

Largest metacentric and submetacentric chromosomes
Chromosome 1-3

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13
Q

What are the characteristics of Group B chromosomes?

A

Large submetacentric
Chromosomes 4 and 5

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14
Q

What are the characteristics of Group C chromosomes?

A

Similar, medium size chromosomes
Arranged in order of decreasing size submetacentric
Chromosomes 6-12 and X

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15
Q

What are the characteristics of Group D chromosomes?

A

Medium-sized acrocentric plus satellites
Chromosomes 13-15

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16
Q

What are the characteristics of Group E chromosomes?

A

Smaller metacentric and submetacentric chromosomes
Chromsomes 16-18

17
Q

What are the characteristics of Group F chromsomes?

A

Even smaller metacentric and submetacentric chromosomes
Chromosomes 19-20

18
Q

What are the characteristics of Group G chromosomes?

A

Smallest acrocentric with satellites
Y chromosome with no satellites
Group 21, 22 and Y

19
Q

Darkly staining regions of chromosomes are called …

A

heterochromatic regions or heterochromatin

Rich in cytosine and guanine bases with active genes
Replicates early in S phase

20
Q

Lightly staining regions of chromosomes are called …

A

euchromatic region or euchromatin

Rich in adenine and thymine bases
Contain few active genes

21
Q

What ae the two groups of heterochromatin?

A

Constitutive heterochromatin remains permanently in the heterochromatic stage
Facultative heterochromatin consists of euchromatin that takes on the staining and compactness characteristics of heterochromatin during some phase of development

22
Q

What are the functions of centromeres?

A

Required for the segregation of the chromatids during meiosis and mitosis

23
Q

What are the functions of telomeres?

A

Provide terminal stability to the chromosome and ensure its survival

24
Q

What is a karyotype?

A

Standard arrangement of chromosome pairs in order of decreasing length

25
Q

What is an idiotype?

A

A diagrammatic representation of a species’ karyotype showing all of its morphological features

26
Q

What is G (Giemsa) banding?

A

Helps to identify each chromosome by the pattern of alternating light and dark bands
It is the standard analytical method in cytogenetics

27
Q

What are the characteristics of Edwards Syndrome?

A
28
Q

What are the characteristics of Down Syndrome?

A
29
Q

What are the characteristics of Patau’s Syndrome?

A
30
Q

What are the characteristics of Turner Syndrome?

A
31
Q

What are the characteristics of Kleinfelter’s Syndrome?

A

47 chromosomes (XXY) & a sex chromatin Barr body or 48 (XXXY) (more X chromosomes = >chance of mental impairment)
Cause: Nondisjunction of XX homologue
Found only in males and detected at puberty
Incidence: 1 in 500 males
Characteristics: Sterility, testicular atrophy, hyalinization of seminiferous tubules, gynecomastia.

MD1S2: Cell Biology and Genetics (5 decks)

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