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FLC > Cell Nucleus > Flashcards

Cell Nucleus Flashcards

1
Q

List the main functions of the cell nucleus?

A
  • stores and maintains DNA
  • DNA replication
  • Transcription
  • Ribosomal biogenesis
  • Nucleoplasm and cytoplasm communication control
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2
Q

How is DNA stored in the nucleus?

A

As chromosomes

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3
Q

How many chromosomes are present in humans?

A

23 pairs / 46 chromosomes

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4
Q

How many base pairs do diploid cells contain?

A

6x10⁹ base pairs of DNA

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5
Q

How is DNA in chromosomes so compact?

A

DNA has a negative charge
Histone proteins are positively charged
- DNA wraps around histones

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6
Q

What is a nucleosome?

A

A length of DNA coiled around a core of histones

- the building blocks of chromatin

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7
Q

How are nucleosomes even more compact?

A

Wrap themselves into 30nm fibres

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8
Q

Describe the structural features of a chromosome

A
  • single DNA molecule
  • Linear in eukaryotes
  • contains genes
  • contains, Telomeres, Centromeres, and replication
    origins
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9
Q

What is the significance of Centromeres?

A

Required during cell division

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10
Q

What is the role of the telomeres?

A

Protect the chromosome ends

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11
Q

Is number of chromosomes an organsim has significant?

A

Different organisms have different chromosome no.’s

Chromosome no. doesn’t affect the complexity of organisms

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12
Q

How can chromosomes be identified?

A

Using idiography and idiograms

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13
Q

How do idiograms work?

A

Chromosomes are patially digested and stained wit Giesma

- show chromosome banding patterns

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14
Q

What factors do we measure to identify which chromosome it is?

A

We can use the

  • length
  • centromere position
  • banding pattern
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15
Q

How do we differentiate between the two chromosome arms?

A

p - short arm

q - long arm

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16
Q

What is Heterochromatin?

A

Heterochromatin is a tightly packed form of DNA

17
Q

List the distinguishing features of heterochromatin

A
  • Gene poor
  • Dark
  • In periphery of nucleus: found near centromeres &
    telomeres
  • Highly condensed (resistant to gene expression)
  • 10% of genome
18
Q

What is Euchromatin?

A

Euchromatin is a lightly packed form of chromatin that is enriched in genes

19
Q

List some features of euchromatin

A
  • Gene rich
  • Light
  • Located centrally in nucleus
  • Less condensed (expressed genes)
  • Majority of genome
20
Q

How can chromosomal abnormalitites be observed?

A

Spectralkaryotyping

21
Q

What are chromosome territories?

A

Regions of the nucleus preferentially occupied by particular chromosomes

22
Q

What is the role of Chromomosome territories?

A

Store and control access to DNA

23
Q

What occurs at the replication Factories in the nucleus?

A

Nascent DNA production

24
Q

Explain what is meant by Nascent DNA?

A

DNA of the lagging strand

25
Q

What is produced at Transcription factories?

A

Nascent RNA

26
Q

What are spliceosomes?

A

Irregular domains containing splicing factors

27
Q

Which process occurs at the nucleoli?

A

Ribosome biogenesis

28
Q

What is the significance of DNA replication factories?

A

Contain all the enzymes and factors required for semi conservative replication

29
Q

What factors do RNA transcription factories contain?

A
  • RNA Polymerase II
  • Template DNA Strand
  • Newly synthesised mRNA
30
Q

How does ribosome biogenesis occur at the nucleolus?

A
  1. transcription of rRNA genes
  2. producing large 45S rRNA precursor
  3. Cleavage of RNA into 18s, 5.8s and 28s
  4. assembly of rRNA subunits
31
Q

What are the final ribosomal subunit sizes?

A

Small ribosomal subunit: 18s

Large ribosomal subunit: 5.8s, 28s (5s)

32
Q

How are chromosomes arranged in the interphase nucleus?

A

They form non overlapping domains

Homologous pairs dont’ lie adjacent to one another

33
Q

How many rRNA genes are copied per haploid genome?

A

~ 200

34
Q

Where are rRNA genes located?

A

In tandem copies on the accrocentric chromosomes

35
Q

Why are rRNA genes needed in such abundances?

A
  • single mRNA can be translated many times
  • amplifies final product
  • rRNA molecules are the final products
36
Q

Describe the structure of the nucleur envelope?

A

2 lipid bilayers

37
Q

How many nuclear pores in a mammalian cell nucleus?

A

Approx. 3000-4000 nucleur pores

38
Q

What is the function of the nucleur pores?

A

Nuclear export - rRNA, mRNA, proteins
(require nucleur export signal)

Nucleur Import - Histones, DNA, RNA
(require nucleur localisation sequence)

FLC (34 decks)

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