Exam #4: Structure & Organization of Nucleic Acids Flashcards Preview

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Flashcards in Exam #4: Structure & Organization of Nucleic Acids Deck (44):
1

What is non-coding DNA?

Non-protein coding sequences

2

List four types of non-coding DNA

1) Spacer Sequences
2) Introns
3) Genes encoding nonprotein-coding RNA
4) Repetitious DNA (most abundant)

3

Exon

Sequence of DNA translated into protein

4

Intron

Sequences of DNA that are spliced out

5

Gene Family

Genes that have a similar nucleotide sequence & encode similar proteins

6

Pseudogenes

Mutation of a gene gives rise to an inactive duplicate

7

How do gene families arise?

Spontaneous mutation and meiotic accidents

8

What is chromatin?

Complex of DNA and protein

9

How many chromosomes are found in a diploid human cell?

46: 2 sex chromosomes & 44 autosomes

10

How is the mitochondrial genome different from the nuclear genome?

- Circular molecule
- Present in multiple copies per organelle
- encodes 13 proteins & 24 RNA molecules
- Not extensively associated with proteins

11

Heterochromatin

- Stained
- Complex with proteins
- Transcriptionally inactive
- Periphery

12

Euchromatin

- Translucent
- Transcriptionally active
- Decondensed

13

What processes occur in the nucleolus?

Assembly of ribosomal subunits

14

Key features of the nuclear pore complex

- Nuclear basket on the nuclear side
- Protein ring anchored to the double membrane
- Central transporter inside protein ring
- Filaments on cytoplasmic side

15

Ran-dependent import into the nucleus

Ran & Importin = Protein & Ribosomal subunits into the nucleus
1) Importin + Cargo enters nucleus
2) Importin/Cargo + Ran-GTP= Cargo released
3) Ran-GTP/Importin= Exported to Cytoplasm
4) GTP hydrolyzed= Ran-GDP + Importin dissociate
5) Ran-GDP re-enters nucleus

16

Ran-dependent export from the nucleus

Ran & Exportin = protein out of the nucleus
1) Cargo + Exportin
2) Cargo/Exportin + Ran-GTP= Exported
3) GTP hydrolyzed= Dissociation in cytoplasm
4) Ran-GDP & Exportin re-enter nucleus

17

Semi-conservative Replication

- Each strand of parental DNA serves as a template for synthesis of a new complimentary DNA strand
- Each daughter DNA contains 1 parental strand and 1 newly synthesized strand

18

Replication Origin

Where replication begins; multiple origins on each chromosome

19

Bidirectional Replication

Replication is bidirectional from each origin

20

What are the nucleotide donors for DNA synthesis?

dATP, dGTP, dCTP, and dTTP

21

What is the significance of the pyrophosphate formed during chain elongation?

- Pyrophosphate is released as each nucleotide is incorporated into DNA
- Hydrolysis of pyrophosphate drives the reaction to the right

22

Key features shared by DNA polymerase

Note, y-DNA polymerase synthesizes mitochondrial DNA
1) Template-directed
2) Primer is required
3) Synthesize 5'-->3'
4) Newly synthesized DNA is anti-parallel to template

23

DNA Helicase

Use ATP-energy to unwind DNA double helix for replication

24

Single stranded DNA binding proteins

bind unwound DNA to prevent re-association

25

Topoisomerase

Relieve the supercoiling created by undwinding by nicking and religating DNA

26

RNA primer

Required for DNA synthesis; synthesized by DNA polymerase alpha

27

Leading Strand

Primer points toward the replication fork and synthesizes continuously

28

Lagging Strand

Primer points away from the replication fork and is synthesized in fragments

29

Okazaki Fragment

Fragments of DNA synthesized on lagging strand

30

Telomeres

End of chromosome with special TTAGGG sequence repeats

31

How are telomeres replicated?

Enzyme Telomerase that contains RNA molecule complimentary to telomere that acts as a template for extension of the 3' end of DNA

32

Satellite DNA

Simple-sequence DNA i.e. identical repeats of short DNA sequences confined to the centromere & telomere

33

Example of a gene family

B-globin has 5 genes clustered together on chromosome 11: 2x adult globins, 2x fetal globins, and 1x embryonic globin

34

3 Levels of DNA Condensation

1) DNA wrapped around histones to form nucleosome
2) Nucleosomes associated to form 30nm solenoid fiber
3) 30nm solenoid fibers form 300nm loop domains

35

What organelle separates transcription and translation?

Nucleus

36

What does the separation of transcription from translation allow?

Post-transcriptional modification of RNA

37

mRNA Export from Nucleus

Ran-Independent

38

ORC

Origin of Replication Complex: protein that marks origin of replication

39

Primase

DNA Polymerase alpha

40

DNA Ligase

joins Okazaki fragments

41

DNA polymerase gamma

Elongates DNA

42

Topoisomerase Inhibitors

- Topoisomerase: Relieves supercoiling during replcation
- Drugs can inhibit this process and work as anti-cancer drugs or antibiotics

43

Doxorubicin

Human Topoisomerase inhibitor used in cancer chemotherapy

44

Nalidixic Acid & Ciprofloxacin

Bacterial topoisomerase inhibitors that work as anti-biotics