the nucleus

Question 1

what is the nucleus surrounded by?

Answer 1

Surrounded by double membrane nuclear envelope, except for links to cytosol via nuclear pores.

Question 2

what does the nucleus involve?

Answer 2

Involved in synthesis of mRNA, rRNA, tRNA

Question 3

what does it house?

Answer 3

Houses the genetic material
membranous sac containing densely packed proteins & DNA.

Question 4

what is the structure of DNA

Answer 4

double helix and a chemically inert structure. and also contains 2 antiparallel strands

Question 5

what does antiparallel strands run

Answer 5

1 strand runs 5′ to 3′ while the other runs 3′ to 5′).

Question 6

what does purine and pyrimidine bases project

Answer 6

toward the axis of the helix

Question 7

what are the base pairs

Answer 7

A and T
C and G

Question 8

what does adeine pair up with

Answer 8

purine adenine always pairs with pyramidine thymine

Question 9

what does prymidinae cystonie pair up with?

Answer 9

pyramdiine cytosine always pairs with purine guanine

Question 10

what is the nucleoplasm?

Answer 10

proteins & DNA suspended in aqueous medium

Question 11

what is the nucleous?

Answer 11

region involved in ribosome synthesis

Question 12

how is the nuclear envelope formed

Answer 12

formed by 2 concentric membranes

Question 13

what are nuclear pores?

Answer 13

transport into and out of the nucleus

Question 14

what is the nuclear localisation signal

Answer 14

short amino acid sequence that acts as a signal for the transport of proteins from the cytoplasm into the cell nucleus

Question 15

how is the the inner nuclear membrane formed?

Answer 15

formed by using Cytoskeletal nuclear lamina

Question 16

is the nucelous membrane bound?

Answer 16

NO

Question 17

what is the function of nucelous?

Answer 17

ribosome assembly

Question 18

what is the fibrillar centre?

Answer 18

(pale): contains inactive (not being transcribed) DNA

Question 19

what is the Dense fibrillar component

Answer 19

contains pre-rRNA molecules in the process of being transcribed from DNA templates

Question 20

what is the Granular component

Answer 20

contains mature ribosomes, ready for export into cytoplasm

Question 21

how does the ribsosmes get assemebled in the nucelous?

Answer 21

from rRNA molecules (transcribed from DNA template; pre-rRNA transcript processed by snRNA) & ribosomal proteins

Question 22

what does the greater size or complexity of an eukaryotic cell mean?

Answer 22

genomes means that elaborate mechanisms are needed for Packaging of DNA

Question 23

what is the role of chromatin?

Answer 23

DNA Packaging
DNA Replication and Repair
Regulation of Gene Expression

Question 24

what is heterochromatin? (dense)

Answer 24

found where there are few or no genes, or in gene-containing regions where the genes are inactive

Question 25

what is Euchromatin (less dense)

Answer 25

found where there are many active genes

Question 26

what is chromatin arranged as?

Answer 26

repeated units ‘Nucleosomes

Question 27

what is dna bound to?

Answer 27

bound to proteins called ‘Histones’ to form chromatin.

Question 28

why do we call it supercoiled DNA

Answer 28

if the axis of a double helix is coiled around itself we call it supercoiled

Question 29

why are supercoiled DNA called topoisomers?

Answer 29

genetically identical, but topologically different

Question 30

how is the DNA packaged?

Answer 30

1) naked DNA arranged into nucleosomes
2)nucleosomes are supercoiled in compact solenoid fibres
3)these fibres are arranged into loops attached to “chromosome scaffolding proteins)

Question 31

what is the exception we get to see chromosomes under a microscope?

Answer 31

as cell gets ready to divide chromosomes condense into short, ‘homologous pair’ dyad structures

Question 32

breifly explain what happens during mitosis and meiosis?

Answer 32

dissolution of the Nuclear Envelope
Chromosome dyads migrate (along cytoskeletal fibres) to opposite poles of a spindle within the nucleus.
nuclear envelope re-forms x2 around the 2 sets of separated chromosomes

Question 33

what does the nucelous envelope seperate?

Answer 33

separates the contents of the nucleus from the cytoplasm.

Question 34

nuclear pore and routes?

Answer 34

Nuclear pores are the only routes between the nucleus and cytoplasm.

Question 35

what is the nucelous involved in?

Answer 35

Transcription and processing of RNA
Ribosome assembly