Theme 1b

Question 1

What are the components of DNA

Answer 1

Pentose sugar, nitrogenous base and phosphate

Question 2

What does the pentose sugar structure look like

Answer 2

Look at photos for reference lol

Question 3

What is the difference between RNA and DNA sugars

Answer 3

Type of chemical group bound to the 2’ carbon

Question 4

What are the nitrogenous bases for DNA and RNA

Answer 4

DNA: adenine (purine), guanine (purine), cytosine (pyrimidine) and thymine (pyrimidine)
RNA: adenine (purine), guanine (purine), cytosine (pyrimidine) and uracil (pyrimidine)

Question 5

What is a nucleoside

Answer 5

Molecules of a sugar and base

Question 6

What is a deoxyribosenucleoside

Answer 6

2-deoxyribose sugar and purine/pyrimidine base
Binds to Cl’ end of deoxyribose/ribose

Question 7

What is the difference between a deoxyribonucleoside and a ribonucleoside

Answer 7

There would be an OH on the 2’ carbon

Question 8

What is a nucleotide

Answer 8

A nucleoside and a phosphate with the phosphate group attached to the 5’ carbon of the ribose and deoxyribose sugars

Question 9

What are some properties of DNA

Answer 9

A polymer of deoxyribonucleotides
-nucleotide monomers polymerize via phosphodiester bonds
-covalent bonds form between phosphate and the C3’ and C5’ of two pentose sugars (pentose phosphate backbone)
-has polarity with a 5’ PO4 end and a C3’ OH end
-charge is negative because of phosphate group

Question 10

What is Chargaff’s rule

Answer 10

% purines (A + G) = % pyrimidine (C + T)
% A = % T and % C = % G

Question 11

What did Watson and Crick do

Answer 11

Pieced together the clues to determine the structure of DNA
-antiparallel
-double helix
-purines are paired with pyrimidines
-exterior is hydrophilic (phosphate heads) and interior is hydrophobic (phosphate tails)

Question 12

How does hydrogen bonding keep DNA intact

Answer 12

H-bonding between bases keeps the strands intact
3 h-bonds between G and C
2 h-bonds between A and T

Question 13

What is nucleic acid hybridization

Answer 13

Annealing of single strands of DNA or RNA
Strands must be complementary in sequence and are highly specific

Question 14

What is Watson and Cricks model of DNA replication

Answer 14

-complementary base pairing
-parental strands act as templates and can unwind by breaking the h-bonds between bases
-semi conservative replication

Question 15

What are the differences between prokaryotic and eukaryotic chromosomes

Answer 15

Prokaryotic: have one circular chromosome sand other small independent circular DNA called plasmids in the cytoplasm
Eukaryotic: linear chromosomes and enclosed in the nucleus

Question 16

What is a centromere

Answer 16

DNA sequences that are required for correct segregation of chromosomes by directing formation of the kinetochore

Question 17

What are the origins of replication

Answer 17

DNA sequences that initiate DNA replication

Question 18

What are telomeres

Answer 18

Sequences of DNA located at the ends of the chromosome that prevent degradation and allow proper replication of the chromosome ends
Because ends of DNA are very unstable

Question 19

What are histones

Answer 19

Basic positively charged proteins that DNA wind around
Only in eukaryotic cells since bacterial cells are much smaller and need DNA to be more compacted

Question 20

How can you tell the difference between a circular DNA and linear DNA

Answer 20

Cut the DNA in half, one fragment means circular DNA, two fragments means linear DNA

Question 21

What is euchromatin

Answer 21

Regions have lower DNA compaction and genes are actively expressed

Question 22

What is heterochromatin

Answer 22

Chromosomal regions of high DNA compaction where gene expression is silenced (no space for for enzymes to activate genes)

Question 23

Constitutive vs facultative heterochromatin

Answer 23

Constitutive: DNA is always highly compacted (centromeres and sub-telomeric regions)
Facultative: can switch to euchromatin depending on cells type and environment