dna structure/replication

Question 1

what are the subunits of nucleic acids

Answer 1

nucleotides

Question 2

what are the components of nucleotides

Answer 2

nitrogenous base
pentose sugar
phosphate group

Question 3

nucleotides of DNA

Answer 3

purines (adenine and guanine)
pyrimidines (thymine and cytosine)

Question 4

what are chargaffs rules

Answer 4

base composition of DNA varies in different species; bases present in particular ratios: A%=T%, G%=C%

human DNA: A=T=30.3%, G=C=19.9%

Question 5

how did Franklin’s X-ray crystallography results contribute to the understanding
of the structure of DNA?

Answer 5

the image she captured was the first X-ray image of DNA and this image led to the discovery of DNA’s molecular structure by Watson and Crick; it revealed the helical shape of the DNA molecule

Question 6

dna structure

Answer 6

-right-handed double helix
-two anti-parallel sugar-phosphate backbones
-nitrogenous bases paired in specific combos. in interior (A-T & C-W)

Question 7

what do the subunits of dna look like

Answer 7

nucleotides consisting of a nitrogenous base, pentose sugar and phosphate group; purines and pyridimines

Question 8

what bonds hold the subints of dna together

Answer 8

phosphodiester bonds

Question 9

what is a phosphodiester bond

Answer 9

bond between hydroxyl (attached to the #3 carbon) of one nucleotide & phosphate (attached to the #5 carbon) of the next nucleotide

Question 10

how do you distinguish the 5’ and 3’ ends of nucleic acids

Answer 10

dna is anti parallel so the 5’ end will have a free hydroxyl on the 5’ carbon while the 3’ end will has a free phosphate on the #3 carbon

Question 11

what bonds hold together the two strands of DNA

Answer 11

hydrogen bonds (weak bond but multiple can make a stable bond)

Question 12

what is the process of DNA replication

Answer 12

synthesis of DNA for growth, repair, and hereditary purposes

Question 13

what is the central dogma of biology

Answer 13

theory stating that genetic information flows only in one direction from DNA –> RNA –> proteins, or RNA –>protein; nuceleotides are the language of DNA and RNA, while amino acids are the language of proteins

Question 14

describe the chemical reaction of DNA replication

Answer 14

replication is semiconservative meaning that each strand in DNA double helix acts as a template for the synthesis of a new complementary strand; always one original strand

Question 15

what is the origin of replication

Answer 15

sequence in a genome at which replication is initiated; eukaryotic chromosome may have hundreds or thousands of replication origins

Question 16

what is the replication bubble

Answer 16

the structure formed by the seperation of two DNA strandsby the helicase enzyme

Question 17

what is the replication fork

Answer 17

the point at which the two strands of DNA are seperated to allow replication of each strand; one replication bubble has two

Question 18

helicase

Answer 18

unwinds double helix at replication forks; seperates into two strands

Question 19

single stranded binding proteins

Answer 19

binds to and stabilizes single stranded DNA until it is used as a template; binds seperated strands and keep them single stranded

Question 20

topoisomerase

Answer 20

relieves overwinding strain ahead of replication fork by breaking, swiveling, and rejoining DNA strands; relieves tension of over-twisted strands

Question 21

primase

Answer 21

synthesizes an RNA primer at 5’ end of leading strand and at 5’ end of each okazaki fragment of the lagging strand; makes primer (short complementary strands of nucleotides) required to start DNA replication

Question 22

DNA polymerase III

Answer 22

uses parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or pre-existing DNA strand; catalyzes formation of phosphodiester bonds between nucleotides; makes new dna 5’->3’; moves along template strand 3’->5’

Question 23

DNA polymerase I

Answer 23

removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides added to the 3’ end of adjacent fragment; attaches, hydrolyses, primes, synthesizes DNA strand to full gap, falls off

Question 24

DNA ligase

Answer 24

joins okazaki fragments of lagging strand; on leading strand join 3’ end of the DNA that replaces primer to rest of leading strand DNA; makes phophodiester bond between okazaki fragments

Question 25

direction of leading strand

Answer 25

replicated in 3’ to 5’ direction (same direction as replication fork)

Question 26

direction of lagging strand

Answer 26

replicated in 5’ to 3’ direction

Question 27

why is DNA replication so accurate

Answer 27

if a newly added nucleotide is not complementary to one on the template strand, enzymes remove it and replace it with the correct one; relies heavily on dna polymerases to do this

Question 28

adenine is complemetary to

Answer 28

thymine

Question 29

guanine is complemetary to

Answer 29

cytosine