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Cell Biology > The Nucleus, Nuclear Organisation and Karyotype > Flashcards

The Nucleus, Nuclear Organisation and Karyotype Flashcards

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1
Q

Eukaryotic cells include…

A

…all plants and animals as well as many single celled organisms: algae, amoebae, fungi and moulds

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2
Q

Eukaryotes are cells with …

A

…a true nucleus

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3
Q

Unlike prokaryotes, eukaryotic cells contain …

A

…extensive internal membranes that define a collection of subcellular structures – organelles

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4
Q

The cytoplasm also contains a network of fibres called the …

A

…cytoskeleton

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5
Q

The cytoskeleton gives the cell…

A

…strength and rigidity and also control movement within the cell.

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6
Q

Plant cells are surrounded by…

A

…a rigid cell wall and contain a large membrane bound vacuole and chloroplasts.

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7
Q

Size of prokaryotes?

A

2mm (2 x 10-6 m)

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8
Q

Size of eukaryotes?

A

10 – 100 mm
(1x10-5 – 1x10-4 m)

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9
Q

Amount of DNA in prokaryotes?

A

1.36 mm

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10
Q

Amount of DNA eukaryotes?

A

990 mm

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11
Q

Number of genes in prokaryotes?

A

4377

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12
Q

Number of genes in eukaryotes?

A

30-38000

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13
Q

DNA organisation of prokaryotes?

A

1 circular chromosome in nucleoid

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14
Q

DNA organisation of eukaryotes?

A

2 or more chromosomes in membrane bound nucleus

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15
Q

Despite their differences, prokaryotic and eukaryotic cells have many …

A

…biochemical pathways in common – thus believed to have descended from the same ancestral cell.

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16
Q

What is the nucleus surrounded by?

A

a double membrane

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17
Q

What does the inner membrane of the nucleus do?

A

Defines the nucleus

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18
Q

Describe the outer membrane of the nucleus.

A

continuous with rough endoplasmic reticulum (ER)

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19
Q

Function of the nucleolus?

A

nuclear organizer, RNA / Ribosome synthesis occurs here.

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20
Q

WHats chromatin?

A

combination of DNA and protein

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21
Q

Whats nucleoplasm?

A

equivalent to the cytoplasm but in the nucleus – nucleotides and enzymes are dissolved in here.

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22
Q

Function of nuclear pores?

A

serve as channels regulating the movement of material between the nucleus and the cytoplasm

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23
Q

Give an example of something which leaves the nucleus via nuclear pores.

A

mRNA leaves the nucleus via a nuclear pore to be transcribed in the cytoplasm.

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24
Q

What actually are nuclear pores?

A

protein complexes (~100 proteins) >1250 kDa, tightly regulate what goes in and out of nucleus.

25
Q

How many nuclear pores are there per nucleus?

A

There are around 3000 – 4000 pores per nucleus.

26
Q

In addition to mRNA, what else can move through nuclear pores?

A

proteins can also move through the nuclear pores. (Why would we need proteins to move into the nucleus?)

27
Q

Why would we need proteins to move into the nucleus?

A
  • Gene expression
  • DNA replication and repair
  • RNA processing and transport
28
Q

How does RNA and Ribosome synthesis occur?

A

This occurs via transcription of the ribosomal RNA genes.

29
Q

In the nucleolus, a number of different sized…

A

…rRNA molecules are formed which, with proteins, make up the ribosome.

30
Q

How many strands of rRNA do eukaryotic ribosomes contain?

A

Eukaryotic ribosomes contain four strands of rRNA

31
Q

What are the four strands of rRNA in eukaryotic ribosomes?

A

28S, 18S, 5.8S, and the 5S rRNAs

32
Q

What does the S value indicate?

A

the “S” values indicate the size of the Strand “s” is the Svedberg coefficient

33
Q

What is the S value a measure of?

A

a measure of the rate of sedimentation
under the influence of density gradient sedimentation.

34
Q

The genes for most of the rRNAs (28S, 18S, and 5.8S rRNAs), used to construct the ribosome are found…

A

…in the nucleolus

35
Q

Function of RNA polymerase I?

A

transcribes the 28S, 18S, and 5.8S rRNAs as a single unit within the nucleolus, which results in a 45S ribosomal precursor RNA.

36
Q

This 45S pre-rRNA synthesised by RNA polymerase I is processed to become…

A

…the 18S rRNA of the 40S (small) ribosomal subunit and to the 28S and 5.8S rRNAs of the 60S (large) ribosomal subunit.

37
Q

Function of RNA Polymerase III ?

A

transcribes the 5S rRNA, which is also found in the 60S ribosomal subunit;
this process takes place outside of the nucleolus.

38
Q

The ribosomal subunits created are the …

A

…60S and 40S subunits; these subunits join during protein synthesis to form the whole 80S ribosome.

39
Q

Human nuclear DNA is around …

A

…2m in length

40
Q

To fit within a living cell …

A

…DNA must be extensively compacted

41
Q

Compacting of DNA is aided by…

A

…DNA-binding proteins (such as histones)

42
Q

Length of DNA in a human cell =

A

2m

43
Q

Total length of DNA in human body =

A

74,400,000,000 km

44
Q

DNA is not ‘naked’ in the nucleus: exists as a…

A

nucleoprotein complex known as
Chromatin (histone / DNA complex =nucleosome)

45
Q

What are the 5 different histone classes?

A

H1, H2a, H2b, H3 and H4 (in a nucleosome there is: 1H1, 2H2a, 2H2b, 2H3 and 2H4 = 9)

46
Q

What is Phosphorylation with kinase enzymes ?

A

kinase enzymes add phosphate groups

47
Q

Phosphorylation with kinase enzymes can promote…

A

…nucleosome loosening to allow DNA replication and transcription.

48
Q

Removal of phosphate groups from histones with phosphatase enzymes …

A

…promotes DNA condensation (i.e. chromosome formation).

49
Q

What enzyme is used to remove phosphate groups from histones?

A

phosphatase enzymes

50
Q

Describe Chromosome territories

A

the different chromosomes will occupy different regions of the Nucleus.

51
Q

DNA exists in a complex with …

A

…histone proteins inside the nucleus (chromatin)

52
Q

DNA wraps around a…

A

…histone protein core, forming structures known as nucleosomes

53
Q

Each nucleosome consists of …

A

…8 histone proteins, with 146 base pairs of DNA wrapped around 1.67 times in a left-handed supercoil, giving a beads on a string appearance.

54
Q

Biochemical modification of the DNA and histone proteins allows for …

A

…the opening (euchromatin) or condensing (heterochromatin) of the DNA.

55
Q

Heterochromatin and Euchromatin are important for…

A

…gene expression control as well as mitosis.

56
Q

Chromosomes can be stained and examined using…

A

…light microscope.

57
Q

Whats a karyotype?

A

Organising the chromosomes by size and shape.

58
Q

The chromosomes can be organised by size and shape into a …

A

…karyotype

59
Q

In humans there are usually […] of each chromosome (diploid 2C) in our […] cells.

A

In humans there are usually two of each chromosome (diploid 2C) in our somatic cells.

Cell Biology (19 decks)

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