Nucleic acids

Question 1

what is the structure of a nucleotide

Answer 1

a pentose sugar with a phosphate group and a base attached

Question 2

what are nucleotides

Answer 2

monomers that make up DNA and RNA

Question 3

what is the structure of a DNA nucleotide and what possible bases are there

Answer 3

a phosphate group attached to a deoxyribose sugar with either an A,G,C or T base attached

Question 4

What are the full names of all the possible bases

Answer 4

adenine, guanine, cytosine, thymine and uracil

Question 5

what is the structure of RNA and what are the possible bases that can be attached

Answer 5

a phosphate group attached to a ribose sugar with either an A,C,G or U base attached

Question 6

what bases are purines

Answer 6

adenine and guanine

Question 7

what bases are pyrimidines

Answer 7

cytosine, uracil and thymine

Question 8

what is the difference between and purine and a pyrimidine

Answer 8

purine contains two carbon-nitrogen rings joined together whereas pyrimidines only have one carbon-nitrogen ring therefore is smaller

Question 9

what are ADP and ATP

Answer 9

phosphorylated nucleotides

Question 10

What is the structure of ADP

Answer 10

adenine, ribose sugar and two phosphate groups

Question 11

What is the structure of ATP

Answer 11

adenine, ribose sugar and three phosphate groups

Question 12

how is ATP synthesised

Answer 12

from ADP and an inorganic phosphate , the ADP is phosphorylated and a new phosphate bond is formed

Question 13

Describe the structure of DNA

Answer 13

composed of two polynucleotide strands joined together to form a double helix shape, hydrogen bonding between bases in a process called complementary base pairing, antiparallel so run in opposite directions, twist to form a double helix

Question 14

what does the base adenine pair with in complementary base pairing

Answer 14

thymine

Question 15

what does the base cytosine pair with in complemenatry base pairing

Answer 15

guanine

Question 16

Describe the process of purifying DNA

Answer 16

break up cells in the sample
make up a detergent solution (washing up liquid, slat and distilled water)
add broken cells to detergent
incubate beaker in a water bath at 60oc
the salt then binds to the DNA and causes it to clump together
the temperature should be high enough to prevent enzymes from breaking down the DNA
allow to cool
filter
add protease enzymes to filtered mixture
dribble cold ethanol down the side of the test tube so it forms a layer on top of DNA- detergent mixture
a white precipitate will form which can then be removed with a glass rod

Question 17

describe the process of DNA replication

Answer 17

DNA helicase breaks down hydrogen bonds between complementary base pairs
helix unzips to form two single polynucleotide chains
each original strand acts as a template
free-floating DNA nucleotides join to the exposed bases using complementary base pairing
the nucleotides on the new strand are joined together by DNA polymerase
this forms the sugar-phosphate backbone
hydrogen bonds form between the bases on the original and new strand
strand retwists to form double helix
each new DNA molecule contains one strand from original molecule and one strand

Question 18

define the term semi-conservative

Answer 18

refers to DNA replication when half of the strands in each new DNA molecule are from the original piece of DNA and the other half are from the new strand

Question 19

Why does DNA replication have to be accurate

Answer 19

to make sure genetic information is conserved

Question 20

what is a mutation

Answer 20

a change in the DNA base sequence

Question 21

what bond joins two nucleotides

Answer 21

phosphodiester

Question 22

what is a gene

Answer 22

a sequence of DNA nucleotides that codes for a polypeptide

Question 23

what codes for an amino acid

Answer 23

base triplet

Question 24

what is the role of messenger RNA (mRNA)

Answer 24

single polynucleotide strand, made in nucleus during transcription, carries genetic code from nucleus to cytoplasm, in mRNA three adjacent bases are called a codon

Question 25

What is transfer RNA

Answer 25

single polynucleotide strand, hydrogen bonds hold its shape, has a specific sequence of three bases and one end called an anti-codon
found in the cytoplasm where it carries the amino acids that are used to make proteins to the ribosomes

Question 26

what is rRNA

Answer 26

forms ribosomes along with proteins, catalyses the formation of peptide bonds between amino acids

Question 27

why is genetic code described as non-overlapping

Answer 27

each base triplet is read in sequence and base triplets don’t share their bases

Question 28

why is genetic code described as degenerate

Answer 28

amino acids can be coded for by more than one base triplet

Question 29

why is genetic code described as universal

Answer 29

the same specific base triplets code for the same amino acids in all living organisms

Question 30

describe the process of transcription

Answer 30

RNA polymerase attaches to DNA and the hydrogen bonds between two DNA strands in the gene break, DNA uncoils,
one the strands is the used as a template
the RNA polymerase lines up free nucleotides alongside the template strand, complementary base pairing means the mRNA strand becomes a complementary copy of the DNA template, except the base T is replaced with U
the RNA nucleotides are then joined to the DNA bases by NA polymerase
RNA polymerase the moves along the DNA assembling the mRNA strand and they hydrogen bonds reform once RNA polymerase has passed by and strands coil back into double helix
when RNA polymerase meets a stop codon, it stops making mRNA and detaches
mRNA then movs out of the nucleus through the nuclear pores and attaches to a ribosome