Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Cell Bio Semester 1 > Nucleus > Flashcards

Nucleus Flashcards

1
Q

what is found in the nucleus?

A

DNA, RNA, proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what kind of membrane does the nucleus have?

A

double memb- 2x phospholipid membs
inside- contact w/ nuclear lamina
outside- contact w/ ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

function of nucleus?

A
  • separate fragile chromosomes from cytoskeletal cytoplasmic filaments
  • separate RNA transcription from TRANSLATION machinery
  • regulate RNA export
  • regulate import/export of other proteins

ENABLES ADDITIONAL COMPLEXITY OF EUKARYOTIC CELLS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how could the nucleus have evolved to exist?

A
  • DNA and ribosomes were attached to cell memb at many points
  • memb INVAGINATES forming MESOSOMES
  • repeated invagination forms NUCLEUS
  • ER formed from invaginations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is DNA?

A

double helix of a SUGAR PHOSPHATE BACKBONE with PAIRS OF BASES protruding into the middle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does T bond with? how many h bonds?

A

with A, 2 H bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does C bond with? how many h bonds?

A

G, 3 H bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

in the double helix, one turn is how many base pairs?

A

roughly 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what does the helix structure cause?

A

MAJOR (big) and MINOR (small) groove

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

function of DNA

A
  • store genetic info

- for replication and expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what decides where transcription starts?

A

REGULATORY (promotor) sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

when does RNA processing take place?
what does RNA processing do?
where does it occur?

A

1- takes place after transcription by RNA polymerase II
2- it:
- tops and tails the message (CAPPING and POLYADENYLATION)
- removes introns (SPLICING)
3- in NUCLEUS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are non sex chromosomes called?

A

AUTOSOMES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

where is the telomere on a chromosome?

A

at the ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the function of telomeres?

A

PROTECTION- as ends are most vulnerable to nucleases (degrade DNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what happens to telomeres with age?

A

SHORTEN w/ age

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

function of centromere?

A
  • hold metaphase chromosomes together

- attaches to mitotic spindle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

structure of centromere?

A
  • repetitive sequences
  • highly packaged
  • don’t contain genes (like telomeres)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the name of the short and long arms of chromosomes?

A 
p = short arm 
q = long arm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

in terms of classifying autosomes, what are the three names that you can give autosomes?

A

1- METACENTRIC (centromere in middle)
2- SUBMETACENTRIC (centromere is intermediate)
3- ACROCENTRIC ( centromere is TERMINAL)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are the levels of packaging of DNA from double helix to chromosome?

A 
1 DNA in double helix
2 beads-on-a-string form of chromatin
3 30nm chromatin fiber of packed nucleosomes
4 chromosome section in extended form
5 condensed  section of chromosome 
6 entire chromosome condensed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the structure of NUCLEOSOMES (beads-on-a-string) (packaging factor 3x)?
how is an octamer made?
what kind of bonding is present?

A
  • core nucleosomes made of histone proteins
  • OCTAMER from: 2 of each H2A, H2B, H3 and H4
  • DNA winds 1.65 times around the histone core to form the nucleosome
  • H bonds form between DNA and histone octamer
  • each nucleosome separated from next by up to 80nt of LINKER DNA
23
Q

can DNA in nucleosome structure be used for transcription?

A

yes, as the packaging is loose enough for RNA polymerase etc

24
Q

what is the first structure formed in the packaging of DNA? what is the packaging factor?

A

NUCLEOSOME- (beads on a string)

3x packaging factor

25
what is the second structure formed in the packaging of DNA? | what is the packaging factor?
chromatin thread-----> 30nm FIBRE 10x packaging factor
26
what is the structure of the 30nm fibre?
- H1 in centre pulls nucleosome into spiral - interactions between the tails of 4 core histones help nucleosomes attach to each other - O forms 30nm fibre
27
can DNA in 30nm fibre structure be used for transcription?
no, it is too tightly packaged
28
what else is found in the 30nm fibre structure?
- REGULATORY PROTEINS like transcription factors that can control how DNA is accessed - removal of reg. proteins makes DNA more accessible for transcription and vice versa
29
what is the third structure formed from the packaging of DNA? what is its structure?
- LOOPED DOMAINS | - held in place, "scaffolded" by proteins
30
how can DNA in a tightly packed looped domain be accessed for gene expression?
- histone modifying enzymes and chromatin remodelling complexes
31
what are the visible differences in HETEROCHROMATIN and EUCHROMATIN? what are the other differences?
HETEROCHROMATIN: DARK, highly packaged DNA O silenced genes EUCHROMATIN: LIGHT, active genes
32
what is the fourth structure formed in the packaging of DNA? how is this structure formed? what is the packaging factor?
LOOPED DOMAINS----->COILED MITOTIC CHROMOSOME - formed using ENZYMES called CONDENSINS - use ATP to wind+ package chromatin - packaging factor= 10,000x
33
do nuclear proteins (eg histones, transcription factors) move in or out of the nucleus via nuclear envelope?
IN
34
do RNA molecules (eg mRNA, rRNA, tRNA) move in or out of the nucleus via nuclear envelope?
OUT
35
do ribosome subunits (assembled in nucleus) move in or out of the nucleus via nuclear envelope?
IN AND OUT
36
what can pass through the nuclear pore and HOW? | how do large molecules pass through?
- small molecules can DIFFUSE through - med size diffuse slowly - large molecules are regulated by ACTIVE TRANSPORT
37
what can pass through the nuclear pore and HOW? | how do large molecules pass through?
- small molecules can DIFFUSE through - med size diffuse slowly - large molecules are regulated by ACTIVE TRANSPORT
38
what is a nuclear localisation signal?
a.a sequence that | tags a protein for import into nucleus by nuclear transport
39
what are nuclear localisation signals made of?
- rich in POSITIVELY CHARGED (basic) amino acids eg ARg, Lys, Pro
40
what happens if one a.a in a nuclear localisation signal is changed?
- mutant will not go into the nucleus (stay in cytoplasm)
41
how is nuclear import of proteins different to the translocation of proteins across ER membranes?
in nuclear import, the proteins transported are FOLDED, whereas in translocation across memb (like mitochondria and ER), proteins are UNFOLDED
42
what are the properties of NLS?
- position in protein seq is VARIABLE - sequence can be SPLIT WITHIN THE PRIMARY SEQUENCE making it bipartite - after they import a protein into nucleus, they are NOT REMOVED
43
what recognises NLS?
nuclear import receptors called IMPORTINS
44
how is protein cargo transported across the nuclear membrane?
- IMPORTINS (receptors) bind to NLS on cargo and to FG repeats of nuclear pore complex - protein cargo passes from one subunit to the next and it eventually reaches the nucleus
45
once the cargo protein is in the nucleus, what happens?
- importin-cargo complex DISSOCIATES | - importin can be recycled
46
how is nuclear import regulated? ie how can you control what stays in, goes back out etc?
- nuclear receptors binding to a hormone (eg glucocorticoid) ALLOWS the protein to go into the nucleus
47
where is the nuclear envelope?
- enmeshed between two networks of intermediate filaments
48
what does the nuclear envelope consist of?
inner and outer memb
49
where is the nuclear lamina found?
in between the inner and outer membs
50
what is the structure of nuclear lamina? what is it made of? | what is its function?
- 2D lattice of fibres called INTERMEDIATE FIBRES - made of LAMINS proteins - function: provides support and important in organisation
51
what is the structure of a lamin?
- globular head ends - rod like central domain in a HELIX O forming a DIMER - pairs of dimers (tetramers)twist into long filaments
52
what is the structure of a lamin?
- globular head ends - has COOH and NH2 terminals on each end - rod like central domain in a HELIX O forming a DIMER - pairs of dimers (tetramers)twist into long filaments
53
how does the lamina attach to the membrane?
- LIPID like anchor on COOH terminus of each lamin attaches to inner nuclear phospholipid membrane

Cell Bio Semester 1 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions