1.4 DNA + Protein Synthesis

Question 1

what are the 3 types of nucleic acids

Answer 1

deoxyribonucleic acid
ribonucleic acid
atp

Question 2

what are nucleic acids made of

Answer 2

nomers called nucleotides

Question 3

describe the structure of a nucleotide

Answer 3

a phosphate group, pentose sugar and nitrogenous base
the phosphate and pentose sugar are linked by an ester bond
pentose sugar and base are linked by glycosidic bond

Question 4

what are the four nitrogenous bases

Answer 4

adenine
thymine
cytosine
guanine

Question 5

what is the difference between a purine and pyrimidine

Answer 5

purine
double ringed structure - A + G
pyrimidine
single ringed structure - C + T

Question 6

what bond links the pentose sugar and phosphate group on separate nucleotides together

Answer 6

phosphodiester bond

Question 7

how many hydrogen bonds between complementary base pairs

Answer 7

A-T has 2 hydrogen bonds

G-C has 3 hydrogen bonds

Question 8

describe the structure of ATP

Answer 8

an adenine base
ribose sugar
three inorganic phosphate groups

Question 9

how does ATP release energy

Answer 9

when energy is needed in the cell, the third phosphate bond is broken during hydrolysis
this is catalysed by ATPase and products are ADP

Question 10

why is ATP used as a source of energy

Answer 10

it is a universal energy source

it is an immediate energy source

Question 11

how does DNA replicate

Answer 11

using semi-conservative DNA replication

Question 12

describe the process of semi-conservative DNA replication

Answer 12

the parental strand is unzipped
- hydrogen bonds broken
-complementary bases are unpaired
-catalysed by DNA helicase
DNA polymerase lines up free nucleotides to their complementary bases
DNA ligase catalyses the formation of hydrogen bonds and phosphodiester bonds
two new daughter strands are formed

Question 13

describe Meselsohn and Stahl’s experiment

Answer 13

• They transferred their heavy DNA to a medium with a lighter isotope.
• They took samples after the DNA replicated for the first time and the second time.
• They extracted the DNA and centrifuged it.
• First replication made hybrid DNA=Destroyed conservative model.
• Second replication made light & hybrid DNA=Destroyed dispersive model.
• Concluded that DNA replication is semiconservative

Question 14

give three features of the DNA code

Answer 14

triplet code
degenerate (64 permutations)
non-overlapping

Question 15

describe the structure of RNA

Answer 15

phosphate group
ribose sugar
nitrogenous bases (adenine, guanine, cytosine, uracil)

Question 16

what are the three types of RNA

Answer 16

mRNA-messenger
tRNA-transfer
rRNA-ribosomal

Question 17

describe differences between ribonucleic acid and deoxyribonucleic acid

Answer 17

RIBONUCLEIC ACID
-pentose sugar is ribose
-3 types
-A,U,C,G
-single stranded
DEOXYRIBONUCLEIC ACID
-pentose sugar is deoxyribose
-only one type
-A,T,C,G
-double-stranded

Question 18

describe the process of transcription

Answer 18

1. DNA dependent RNA polymerase binds onto DNA strand
   complementary base pairs break
   H-bonds break
   helix unwinds
2. enzyme moves along the DNA strand inserting complementary mRNA nucleotides to produce a single strand of mRNA
3. at the end of the gene, the enzyme moves away from the DNA and DNA helix reforms

Question 19

describe the process of translation

Answer 19

1. ribosome binds onto the start codon
2. tRNA molecule with an anti-codon that is complementary to the codon of mRNA fits onto the binding site, carrying a specific amino acid
3. another tRNA binds at the second binding site
4. the amino acids are joined in a condensation reaction to form a dipeptide
5. ribosome moves along the mRNA until a stop codon is reached and a polypeptide is formed

Question 20

define a mutation

Answer 20

change in the arrangement of bases in an individual gene or structure of chromosome

Question 21

name the three types of mutation

Answer 21

point mutation
chromosomal mutation
whole-chromosomal mutation

Question 22

name the three types of point mutations

Answer 22

deletion
insertion
substitution

Question 23

name the four types of chromosomal mutations

Answer 23

gene deletion
gene duplication
inversion
translocation

Question 24

describe the different effects of mutations

Answer 24

• production of a new superior protein - leads to reproductive advantage
• neutral mutations-no change
• production of inferior or no protein- can be fatal or disease-causing

Question 25

what are the causes of mutations

Answer 25

x-rays
ionising radiation
chemicals