L1: Cytogenetics

Chromosome

Composed of chromatin fibers, undergoes folding, coiling, and supercoiling during prophase, with distinct parts like telomeres and centromeres.

Karyotype

General morphology of somatic chromosomes arranged by size, keeping centromeres in a straight line.

Ideogram

Diagrammatic representation of a species' karyotype showing all chromosomal morphological features.

Numerical abnormalities

Chromosomal abnormalities like Down syndrome (trisomy 21), Patau syndrome (trisomy 13), Edwards syndrome (trisomy 18), Turner syndrome (45, X), and Kleinfelter’s Syndrome (47, XXY).

Non-disjunction

Unequal distribution of chromosomes during mitosis, meiosis, or embryogenesis, leading to abnormal chromosome numbers.

Structural abnormalities

Include deletions, insertions, duplications, translocations, and inversions, altering chromosome structure.

Cytogenetic technology

Techniques like Peripheral blood lymphocyte culture, Giemsa banding, and Fluorescence In Situ Hybridization (FISH) used to analyze chromosomes.

1. What are chromosomes composed of?

Chromatin fibres

2. What happens to chromosomes during prophase?

They undergo folding, coiling, and supercoiling

3. What are the ends of chromosomes called?

Telomeres

4. Where is the site of spindle attachment on a chromosome?

Centromere

5. What is a nucleosome?

DNA double helix wrapped around histone proteins

6. What are the regions of a chromosome called?

Arms (p and q)

7. What are the bands on a chromosome?

p: 3, 2, 1 and q: 1, 2, 3, 4

8. What are the subbands on a chromosome?

p23, q11, q12, q24: 1-3, p22: 1-2, p11: 1-5, q13: 1-4

9. What is the term for a chromosome with a centrally located centromere and two arms of equal length?

Metacentric chromosome

10. What is the term for a chromosome with a slightly off-center centromere and a short arm (p) and a long arm (q)?

Submetacentric chromosome

11. What is the term for a chromosome with a centromere located near one end and a long arm and a short arm?

Acrocentric chromosome

12. What is a karyotype?

The general morphology of the somatic chromosomes arranged in descending order of size

13. What is an ideogram?

A diagrammatic representation of the karyotype of a species showing all morphological features of the chromosomes

14. What is the cause of Down syndrome?

Trisomy 21 (extra copy of chromosome 21)

15. What are the symptoms of Down syndrome?

Facial dysmorphology, IQ less than 50, moderate to severe mental handicap

16. What is the cause of Patau syndrome?

Trisomy 13 (extra copy of chromosome 13)

17. What are the symptoms of Patau syndrome?

Small head, small or missing eyes, heart defects, extra fingers, abnormal genitalia, mentally retarded, cleft palate

18. What is the cause of Edwards syndrome?

Trisomy 18 (extra copy of chromosome 18)

20. What is the cause of Turner syndrome?

Monosomy X (45, X)

21. What are the symptoms of Turner syndrome?

Very short stature, infertility, broad chest, widely spaced nipples, webbed neck, unaffected IQ and lifespan

22. What is the cause of Kleinfelter's syndrome?

Trisomy XXY (47, XXY)

23. What are the symptoms of Kleinfelter's syndrome?

Scarce beard, longer fingers and arms, testes are small and fail to produce normal levels of testosterone, delicate skin, low mental ability, slight IQ reduction, normal lifespan

24. What is non-disjunction?

Unequal distribution of chromosomes due to failure of separation during mitosis, meiosis, or embryogenesis

25. What are the types of structural abnormalities in chromosomes?

Deletion, insertion, duplication and deletion, translocation, inversion