BIOCHEM Chp.6 NDA

Question 1

What is the diff b/w RNA and DNA composition?

Answer 1

RNA is made of ribose and single-stranded, whereas DNA is made of deoxyribose and double-stranded

Question 2

What is the composition of purines?

Answer 2

2 ring structures found in adenine and guanine nucleic acids

Question 3

What is the diff b/w purines and pyrimidines?

Answer 3

purines have 2 rings, whereas pyrimidine has 1 ring

Question 4

Which pyrimidine is ONLY found in DNA?

Answer 4

Thymine

Question 5

Which pyrimidine is ONLY found in RNA?

Answer 5

uracil

Question 6

What is the structure of DNA?

Answer 6

2 strands that run antiparallel with the sugar-phosphate backbone on the outside of the helix and the nitrogenous base on the inside

Question 7

What is the complementary base pairing of DNA?

Answer 7

Adenine always pairs with thymine via 2 hydrogen bonds, and guanine always pairs with cytosine with 3 hydrogen bonds

Question 8

What does the chargeoffs rule state?

Answer 8

the amount of A equals the amount of T, and the amount of G equals the almond of C in DNA

Question 9

What is the diff b/w B and Z-DNA?

Answer 9

B-DNA is a right-handed helix, and it turns every 3.4/10 bases, the Z-DNA is a zigzag appearance left-handed helix that turns every 4.6/12 base

Question 10

What are common forms used to denature/anneal DNA?

Answer 10

Heat, alkaline pH, chemicals like formaldehyde and urean

Question 11

What is recombinant endonuclease?

Answer 11

enzymes that recrognize palindromic sequences - the 5’ to 3’ sequence of one strand is identical to the 5’ to 3’ sequence of the other strand

Question 12

How are nucleosomes formed?

Answer 12

DNA wound around histone proteins (H2A, H2B, H3, H1, and H4)

Question 13

What is the diff b/w heterochromatin and euchromatin?

Answer 13

heterochromatin is dense, transcriptionally silent DNA that appears dark under light microscopy. euchromatins are less dense DNA, transcriptionally active, and appear light under light microscopy

Question 14

What is the purpose of telomeres and centromeres?

Answer 14

Telomeres are at the end of chromosomes and contain high GC content to prevent the unraveling of the DNA. Centromeres are in the middle of chromosomes and contain high GC content to maintain a strong bond between the sister chromatids until they are separated during anaphase in mitosis

Question 15

What is the role of single-stranded DNA-binding proteins?

Answer 15

they keep unwounded strands from reannealing or being degraded

Question 16

What is the role of DNA topoisomerases?

Answer 16

releases torsional strain caused by supercoiling

Question 17

What does it mean when DNA is semiconservative?

Answer 17

1 old parent strand and 1 new daughter strand is incorporated into each of the 2 new DNA molecules

Question 18

What is the diff b/w prokaryotic and eukaryotic chromosomes?

Answer 18

prokaryotes have circular chromosomes that contain only 1 origin of replication. eukaryotes have linear chromosomes that contain many origins of replication

Question 19

What is the diff b/w the leading and lagging strand?

Answer 19

the leading strand requires only 1 primer and can be continuously synthesized. the lagging strand requires many primers and is synthesized in discrete sections called Okazaki fragments

Question 20

Which enzyme removes RNA primers?

Answer 20

DNA Polymerase I (in prokaryotes) or RNase H (in eukaryotes)

Question 21

What is the role of DNA ligase?

Answer 21

fuses the DNA strands to create one complete molecule

Question 22

How are oncogenes formed?

Answer 22

they are developed from mutations of proto-oncogenes and promote cell cycling

Question 23

What is the role of tumor suppressor genes?

Answer 23

they code for proteins that reduce cell cycling or promote DNA repair; mutation of these genes can lead to cancer because mutated cells pass through the cell cycle unchecked

Question 24

What is the role of MSH2 and MLH1?

Answer 24

they complete mismatch repair during G2 of the cell cycle

Question 25

What is the role of nucleotide excision endonuclease?

Answer 25

nucleotide excision repair fixes helix-deforming lesions of DNA (such as thymine dimers) via a cut-and-patch process that requires an excision endonuclease during G1 and G2

Question 26

What is the role of AP Endonuclease?

Answer 26

base excision repair fixed nondeforming lesions of the DNA helix (such as cytosine deamination) by removing the base, leaving an apurinic/apyrimidinic (AP) Site. An AP Endonuclease then removes the damaged sequence, which can be filled with the correct bases

Question 27

What is recombinant DNA?

Answer 27

DNA is composed of nucleotides from two different sources

Question 28

What are genomic Libraries?

Answer 28

genome libraries contain large fragments of DNA, including both coding and noncoding regions of the genome, and can not be used to make recombinant proteins or for gene therapy

Question 29

What are cDNA Libraries?

Answer 29

expression libraries contain smaller fragments of DNA and only include the exons of genes expressed by the sample tissue, and they cannot make recombinant proteins or for gene therapy

Question 30

What is the role of di-deoxyribonucleotides?

Answer 30

it terminates the DNA chain because they lack a 3’-OH group

Question 31

What is hybridization?

Answer 31

the joining of complementary base pair sequences

Question 32

What is gene therapy?

Answer 32

a method of curing genetic deficiencies by introducing a functional gene with a viral vector

Question 33

How are transgenic mice created?

Answer 33

they are created by integrating a gene of interest to the germline or embryonic stem cells of a developing mouse

Question 34

How are knock-out mice created?

Answer 34

by deleting a gene of interest

Question 35

How is DNA cloning completed?

Answer 35

DNA cloning introduces a fragment of DNA into a vector plasmid

Question 36

What is the role of primase?

Answer 36

RNA primer that begins DNA replication

Question 37

What is the diff b/w DNA polymerase in prokaryotes and eukaryotes?

Answer 37

DNA Polymerase III adds nucleotide to the growing daughter strand, and DNA Polymerase I fills in the gaps left after RNA primer excision in prokaryotes.
DNA Polymerase alpha adds nucleotide to the growing daughter strand in eukaryotes

Question 38

How can DNA polymerase distinguish b/w the daughter and parent strands?

Answer 38

the parent strand is more heavily methylated than the daughter strand, allowing DNA Polymerase to distinguish b/w the two strands