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MGD > Session 10 > Flashcards

Session 10 Flashcards

0
Q

What is chromatin made up of?

A
  • DNA
  • Non-histone proteins
  • RNA
  • Histones (H1, H2A, H2B, H3, H4)
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1
Q

What are chromosomes made up of?

A
  • Chromatin
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2
Q

Which histones interact directly with DNA?

A
  • H2A, H2B, H3 and H4
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3
Q

Do all histones between species?

A
  • H1 varies

- H3 and H4 are highly conserved

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4
Q

What structure do histones help DNA form?

A
  • Beads on a string

- Nucleosomes

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5
Q

What is the difference between Euchromatin and Heterochromatin?

A
  • E: lightly packed chromatin often under active transcription
  • H: tightly packed chromatin so no transcription
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6
Q

How many pairs of chromosomes do humans have?

A
  • 23 pairs
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7
Q

When do chromosomes replicate?

A
  • S phase of the cell cycle
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8
Q

What is the chromosomal basis of sex determination?

A
  • Normal male: 46XY

- Normal female: 46XX

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9
Q

What types of abnormalities can occur in chromosomes?

A
  • Numerical abnormalities
  • Structural abnormalities
  • Chromosome mutations within one chromosome
  • Chromosome mutations with two chromosomes
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10
Q

What types of numerical chromosomal abnormalities are there?

A
  • Polyploidy (eg triploidy, tetraploidy)
  • Aneuploidy (an abnormal number that is not a multiple of the haploid number):
    ~ Monosomy (loss of one chromosome ie one ‘chromosome pair’ exists as a single chromosome)
    ~ Trisomy (gain of one chromosome ie one ‘chromosome pair’ exists as a triplet)
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11
Q

What types of structural abnormalities are there?

A
  • Are physical changes to one or more of the chromosomes
  • Balanced (change does not cause any missing or extra genetic info)
  • Unbalanced (change caused missing or extra genetic info)
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12
Q

What you of chromosome mutations within one chromosome are there?

A
  • Deletion (loss of genetic info)
  • Duplication (some genetic material is doubled)
  • Inversion (no loss of genetic material but is rearranged instead)
  • Ring chromosome (loss of telomeres of ends of both arms and formation of a ring)
  • Isochromosome (creation of two non-identical chromosomes - one is a combination of the two short arms, the other is a combination of the two long arms)
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13
Q

What types of chromosome mutations of two chromosomes are there?

A
  • Inversion (no loss of genetic material, but rearrangement of genetic material to a non-homologous chromosome)
  • Reciprocal translocation (no loss of genetic material, but an exchange of genetic material between non-homologous chromosomes)
  • Robertsonian translocation (rearrangement of genetic material between two chromosomes - q-arms (long) of two acrocentric chromosomes combine to form one ‘super-chromosome’ with the loss of both p-arms (short))
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14
Q

How are karyotypes produced?

A
  • ‘cut and paste’ of chromosome pictures into a systematically organised set of metaphase chromosomes organised into pairs
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15
Q

How are chromosomes organised in Karyotyping?

A
  • Chromosome 1 is the largest and chromosome 22 is the smallest
  • Chromosomes are numbered and grouped according to their size and the position of their centromere
  • The 23rd pair of chromosomes are the sex chromosomes (XX/XY)
16
Q

What type of reasons may patients be referred for karyotyping?

A
  • Constitutional (congenital) abnormalities

- Acquired abnormalities

17
Q

What types of congenital chromosomal abnormalities are there that can be tested for by karyotyping?

A
  • Prenatal screening (eg Down’s syndrome, especially in raised maternal age (>35 years); family history of chromosomal abnormality; abnormal ultrasound of foetus)
  • Birth defects (malformations; mental retardation)
  • Abnormal sexual development (eg Kleinfelter’s syndrome)
  • Infertility
  • Recurrent foetal loss
18
Q

Give examples of acquired chromosomal abnormalities that can be tested for by karyotyping

A
  • Leukaemia and related disorders
19
Q

What is FISH?

A
  • Fluorescent in situ hybridisation
  • Technique where single-stranded nucleic acids (usually DNA, less often RNA) are allowed to interact so that complexes, or hybrids, are formed by molecules with sufficiently similar complementary sequences
  • Through nucleic acid hybridisation, the degree of sequence identity can be determined, and specific sequences or genes can be detected and located on a give chromosome

MGD (9 decks)

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