18 - Chromosome structure Flashcards

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1
Q

At what phase of mitosis can chromosomes be easily distinguished?

A

During Metaphase

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2
Q

What is the organised representation of all the chromosomes in metaphase known as?

A

The Karyotype.

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3
Q

What is a chromosome?

A

A highly coiled fibre of chromatin, with nucleotides along the surface.

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4
Q

What does the biochemical analysis of nucleosomes reveal?

A

A protein core in which the DNA is wrapped around, the protein subunits of the nucleotide are known as core histones.

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5
Q

What do the N-terminal tails of the 8 core histones do?

A

They project out of the nucleosome and are free to interact with other proteins, they facilitate the regulation of chromatin structure and function.

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6
Q

What is the function of Linker Histones?

A
  • They strap the DNA onto histones octamers and limit movement of DNA relative to the histone octamer.
  • They also stabilise the formation of the 30nm fibre and facilitates the establishment of transcriptionally silent heterochromatin.
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7
Q

How is the DNA packaged?

A

By histone octamers into compact 30nm chromatin scaffolds.

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8
Q

What is chromatin engineered to do?

A

To permit flexible responses to altered transcription factor activity caused by changes in cell differentiation status and signalling pathway activities.

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9
Q

What does interphase chromatin do?

A

It comprises a set of dynamic fractal globules (globules within globules) that can reversibly condensed and decondense without becoming knotted.

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10
Q

What is the nuclear periphery in interphase cells composed of?

A

Transcriptionally inactive DNA, The RNA transcripts are usually in the centre and excluded from the periphery.

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11
Q

What do chromosomes contain?

A

Specialised DNA sequences that facilitate reliable and complete DNA replication and segregation of duplicated chromosomes during cell division.

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12
Q

What are centromeres?

A

They are structures connected to the mitotic spindle in mitosis, they are the areas in which the 2 sister chromatids join. They are also connected to the kinetochore.

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13
Q

What are telomeres?

A
  • They are specialised repetitive DNA sequences at the end of the chromosome.
  • They exist as single stranded TTAGGG repeats synthesised by the telomerase enzyme
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14
Q

What is the importance of telomeres?

A

They define chromosome ends and maintain chromosome integrity.

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15
Q

What does chromosome segregation during cell division require?

A

The attachment of chromosomes to the mitotic or meiotic spindle

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16
Q

What does the alpha-satellite DNA in centromeres do?

A

They readily form condensed chromatin with histone octamers containing unusual subunits

17
Q

What is the purpose of the kinetochore inner plate?

A

It binds to chromatin containing the alpha satellite DNA.

18
Q

What is the purpose of the kinetochore outer plate?

A

It binds to the protein components of the mitotic spindle, eg microtubules.

19
Q

What is the kinetochore in yeast?

A

A basket that links a single nucleosome of centromeric chromatin to a single microtubule.

20
Q

What is increased biological complexity of organisms accompanied by?

A

More genes including an increasing amount of non-protein coding DNA for regulating transcription and organising access to protein coding genes.

21
Q

What are the 3 different types of repeated DNA that makes up almost half of the human genome?

A

DNA transposons, Retroviral transposons, Non-retroviral polyA transposons.

22
Q

What are transposons?

A

Mobile genetic elements that jump around the genome also called transposable elements.

23
Q

What do transposons do?

A

They encode transposase which allow them to move around by a cut and paste mechanism

24
Q

How do retroviral transposons function?

A
  • They act like retroviruses and use reverse transcriptase to integrate at new genomic locations.
  • they use self encoded reverse transcriptase
25
Q

How

A