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Flashcards in Chapter 1 Deck (35)
1

What are the steps of gene expression?

2

When and where does gene expression occur?

Transcription occurs in the nucleus throughout interphase

Translation of RNA (protein synthesis) occurs in the cytoplasm throughout the cell cycle.

3

When and where does DNA replication occur?

Occurs during S phase in the nucleus

4

What are the steps of interphase?

G1 phase: cellular growth (ex. skin epithelial cells, Gi tract, follicle cells, nucleated red cells)

G0 phase: resting, non-dividing cells (most cells including muscle, nerve, liver cells)

S phase: DNA synthesis; two sister chromatids linked at centromere

G2 phase: replicated DNA is checked for errors before cell division

5

6

What allows cells to go from G1 to S phase?

A GF (hormonal signal; ex. EGF, PDGF) that binds to tyrosine protein kinase receptor

7

What chemotherapeutic agents target the S, G2, and M phases of the cell cycle? 

S phase: methotrexat, 5-flurouracil

C2 phase: belomycin

M pahse: paclitaxel, vincristine, vinblastine

8

What chemotherapeutic agent targets non cell-cycle speciifc phases?

cyclophosphamide, cisplatin

9

What comprises a nucleotide?

nitrogenous base, five carbon sugar (pentose) and phosphate

(Base covalently link to 1' carbon of sugar

and phosphate groups attached to 5' carbon of sugar)

10

What are the types of bases?

Purines: adenine, guanine (2 rings)

Pyrimidines: cytosine, uracil, thymine (1 ring)

 

11

What comprises a nucleoside?

Nitrogenous base + sugar

(Base covalently link to 1' carbon of sugar)

12

Where are the purines found?

DNA & RNA

13

Where are the pyrimidines found?

Cytosine: DNA & RNA

Uracil: RNA

Thymine: DNA

14

What is a nucleic acid?

polymers of nucleotides joined by 3',5' phosphodiester bonds

phosphate group found at 5' end and hydroxyl group found at 3' end

15

How can you tell the difference between DNA and RNA?

1. type of pyrimidine base

(Uracil=RNA; Thymine=DNA)

2. Type of pentose

(Ribose with 2' OH=RNA; Deoxyribose=DNA)

16

How is the base sequence of a nucleic acid written by convention?

5' --> 3'

17

What are the features of double stranded DNA?

1. Two strands are antiparallel

2. The two strands are complementary

[A pairs with T (2 hydrogen bonds) and G pairs with C (3 hydrogen bonds)

3. Chargaff's rules

Total purines = Total pyrimidines

% A = % T (%U)

% G = % C

 

18

What is Watson-Crick DNA?

Right-handed double helical DNA 

B-DNA

Hydrophilic sugar-phosphate backbone=outside of double helix

hydrogen-bonded base pairs = center of molecular

19

What is Z-DNA?

Left-handed double helical form of DNA

occurs in G-C rich sequences

20

What is the action of daunorubicin and doxorubicin?

Anti-tumor drugs for leukemia

Intercalate between bases of DNA and interfere with topoisomerase II activity, which prevents proper DNA replication

21

What is the action of Cisplatin?

Binds tightly to DNA, which causes structural distortion and malfunction

Treats bladder and lung cancers

22

How is DNA denatured?

heat, alkaline pH, chemicals (formamide, urea)

23

In what experiments is renaturing (annealing) important?

Southern blot, PCR

24

What is hybridization?

probe DNA binds to target complementary DNA sequences

25

What is negatively supercoiled DNA?

DNA that is wound more loosely than Watson-Crick DNA

required for most biologic reactions

26

What is positively supercoiled DNA?

DNA that is wound more tightly than Watson-Crick DNA

27

What is the function of topiosomerases?

change the amount of supercoiling

Make transient breaks in DNA strands by breaking and resealing the sugar-phosphate backbone 

28

What is chromatin?

nuclear eukaryotic DNA that is associated with histones and non-histone proteins

29

What histones are present in nucleosomes and what is the their function?

Two copies of H2A, H2B, H3 and H4

Condenses DNA

Histones = Positively charged because rich in arginine and lysine 

DNA = negatively charged because PDE bonds

 

30

What is a 10 nm chromatin?

DNA with (H2A, H2B, H3, H4) x 2

AKA nucleosome

Octomer of 8 proteins 

Sensitive to nuclease

31

What is 30 nm chromatin?

nucleosome with H1 protein 

More compact than 10 nm chromatin

32

What are the two types of chromatin in interphase?

Euchromatin and heterochromatin

33

Describe euchromatin.

More opened and available for gene expression 

Active gene expression (transcription)

Apoptosis

Corresponds to nucleosomes (10 nm fibers) [also 30 nm fibers]

34

Describe heterochromatin.

 

More highly condensed and assocaited with areas of chromosomes that are not expressed

Inactivate gene expression

Barr body=inactive X chromsome in female somatic cell  

mitotic chromosomes

35

Describe the DNA during mitosis.

highly condensed to allow separation of sister chromatids

only time in the cell cycle when the chromosome structure is visible 

no gene expression