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biochem > Chapter 1 > Flashcards

Chapter 1 Flashcards

1
Q

What are the steps of gene expression?

A
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2
Q

When and where does gene expression occur?

A

Transcription occurs in the nucleus throughout interphase

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

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3
Q

When and where does DNA replication occur?

A

Occurs during S phase in the nucleus

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4
Q

What are the steps of interphase?

A

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

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5
Q
A
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6
Q

What allows cells to go from G1 to S phase?

A

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

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7
Q

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

A

S phase: methotrexat, 5-flurouracil

C2 phase: belomycin

M pahse: paclitaxel, vincristine, vinblastine

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8
Q

What chemotherapeutic agent targets non cell-cycle speciifc phases?

A

cyclophosphamide, cisplatin

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9
Q

What comprises a nucleotide?

A

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)

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10
Q

What are the types of bases?

A

Purines: adenine, guanine (2 rings)

Pyrimidines: cytosine, uracil, thymine (1 ring)

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11
Q

What comprises a nucleoside?

A

Nitrogenous base + sugar

(Base covalently link to 1’ carbon of sugar)

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12
Q

Where are the purines found?

A

DNA & RNA

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13
Q

Where are the pyrimidines found?

A

Cytosine: DNA & RNA

Uracil: RNA

Thymine: DNA

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14
Q

What is a nucleic acid?

A

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

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

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15
Q

How can you tell the difference between DNA and RNA?

A
  1. type of pyrimidine base

(Uracil=RNA; Thymine=DNA)

  1. Type of pentose

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

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16
Q

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

A

5’ –> 3’

17
Q

What are the features of double stranded DNA?

A

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
Q

What is Watson-Crick DNA?

A

Right-handed double helical DNA

B-DNA

Hydrophilic sugar-phosphate backbone=outside of double helix

hydrogen-bonded base pairs = center of molecular

19
Q

What is Z-DNA?

A

Left-handed double helical form of DNA

occurs in G-C rich sequences

20
Q

What is the action of daunorubicin and doxorubicin?

A

Anti-tumor drugs for leukemia

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

21
Q

What is the action of Cisplatin?

A

Binds tightly to DNA, which causes structural distortion and malfunction

Treats bladder and lung cancers

22
Q

How is DNA denatured?

A

heat, alkaline pH, chemicals (formamide, urea)

23
Q

In what experiments is renaturing (annealing) important?

A

Southern blot, PCR

24
Q

What is hybridization?

A

probe DNA binds to target complementary DNA sequences

25
Q

What is negatively supercoiled DNA?

A

DNA that is wound more loosely than Watson-Crick DNA

required for most biologic reactions

26
Q

What is positively supercoiled DNA?

A

DNA that is wound more tightly than Watson-Crick DNA

27
Q

What is the function of topiosomerases?

A

change the amount of supercoiling

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

28
Q

What is chromatin?

A

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

29
Q

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

A

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
Q

What is a 10 nm chromatin?

A

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

AKA nucleosome

Octomer of 8 proteins

Sensitive to nuclease

31
Q

What is 30 nm chromatin?

A

nucleosome with H1 protein

More compact than 10 nm chromatin

32
Q

What are the two types of chromatin in interphase?

A

Euchromatin and heterochromatin

33
Q

Describe euchromatin.

A

More opened and available for gene expression

Active gene expression (transcription)

Apoptosis

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

34
Q

Describe heterochromatin.

A

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
Q

Describe the DNA during mitosis.

A

highly condensed to allow separation of sister chromatids

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

no gene expression

biochem (18 decks)

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