L.4 DNA

Question 1

DNA

Answer 1

Deoxyribonucleic Acid

Is a macro molecule that stored genetic

information in all living organisms.

Question 2

DNA vs RNA

Answer 2

Ribonucleid Acid

The sugar on the ribose has a Hydrogen atom on carbon 3

Question 3

Nulceosides vs Nucleotides

Answer 3

A nucleoside is a 5 carbon sugar with its nitrogenous bases

A nucleotide is a 5 carbon sugar with its nitrogenous bases and 3 phosphate groups

Question 4

Describe nucleotides in DNA

+

Abreviations

Answer 4

Nucleotides in DNA contain deoxyribose, in RNA they contain ribose

Nucleoties are abreviated by letters

A Adeninde, C Cytosine, G Guanine, T Thymine, U Uracil

Question 5

How is DNA organized?

Answer 5

Dna is organized accoring to the Watson-Crick model

• Backbone is composed of alternating sugar and phosphate groups and always reads 5’ to 3’
• The two strands have polarity and are anti-parallel, they wind in a double helix
• A pairs with T, and U in RNA, G pairs with C always

Question 6

Purined vs Pyridimines

Answer 6

Pure as Gold

Purines A and G have 2 Rings

Cut the Pie

Pyrimidines C, U & T 1 Ring

A + T via 2 hydrogen bonds

G + C via 3 Hydrogen bonds

Question 7

What constitutes an aromatic molecule

Answer 7

Purines and pyrimides are biologial aromatic heterocyles.

Aromatic Compounds are

Cyclic

planar

Conjugated

and contain

4n + 2pie electrons (where n is any integer HUCKELS RULE)

Question 8

What is Chargaff’s Rule?

Answer 8

Chargaff’s Rule states that the purines and pyrimidines are equal in number in a DNA molecule,

and that becuase of base-pairing, the qty of adenine is equal to the qty of Thymine, ect.

Question 9

B-DNA vs Z-DNA

Answer 9

Most DNA is B DNA, forming a right-handed helix.

Low concentrations of Z DNA, with zig-zag shape may be see with high GC contentor salt concentration

Question 10

Chemicals that denature and reanneal DNA?

Answer 10

Denature; Healt, Alkaline pH, formaldehyde and Urea.

Removal of these condition may reanneal DNA

Question 11

How many chromosomes in Eukaryotic/Human Cells?

Answer 11

DNA is organized in 46 chromosomes

Question 12

What are histones and name the 5 histones

Answer 12

Histones are nucleoproteins

H1

H2A

H2B

H3

H4

Question 13

What are histones used for?

Answer 13

DNA is wound around histone proteins,

to form nucleosomes, wich may be stabalized by another histone proteins H1.

As a whole DNA and its associated histones make up chromatin in the nucleus.

Question 14

Heterochromatin vs Euchromatin

Answer 14

Heterochromatin is dense, transcriptionally silent DNA that appears Dark under light microscopy.

Euchromatin is less dense, transcriptionally active DNA and appears light.

Question 15

What are telomeres?

Answer 15

Telomeres are the ends of chromosomes.

The contain high GC (TTAGGG) content to prevent unraveling.

Durring DNA replication, telomeres are sligly shortened, although this can be (partially) reverswd by the enzyme telomerase.

Question 16

What are centromeres?

Answer 16

Centromeres are at the middle of chromosomes, and hold sister chromatid together, untila they are separated at anaphase in mitosis.

Also have high GC content.

Question 17

Steps and Proteins Involved in DNA Replication

Answer 17

Question 18

Leading vs Lagging strand

Answer 18

Leading strand requiresonly one primer and can be synthesized continuously.

Lagging strand requires many primers and is synthesized in descrete sections called Okazaki Fragments.