Nucleic acids

Question 1

what is a nucleotide made from

Answer 1

a pentose sugar, a nitrogenous base, a phosphate group

Question 2

what are the differences between RNA and DNA nucleotides

Answer 2

the pentose sugar in DNA is deoxyribose whereas in RNA it is ribose, also in RNA instead of thymine there is uracil, and RNA is made of a single polynucleotide chain and DNA is made of two

Question 3

what does a purine contain

Answer 3

two carbon-nitrogen rings joined together, A and G

Question 4

what does a pyrimidine base contain

Answer 4

one carbon nitrogen ring, the base is smaller than a purine base, C, T and U

Question 5

how do you join nucleotides and what does this form

Answer 5

join the phosphate of one to the sugar of another via a condensation reaction which forms a phosphodiester bond, forms a polynucleotide which can be broken by hydrolysis

Question 6

what bonds the bases together

Answer 6

hydrogen bonds

Question 7

what does ATP do

Answer 7

provides energy for chemical reactions in the cell,

Question 8

where does ATP come from

Answer 8

synthesised from ADP

Question 9

how to do you purify DNA

Answer 9

using a precipitation reaction

Question 10

what does DNA helicase do in self replication

Answer 10

breaks the hydrogen bonds between the polynucleotide DNA strands

Question 11

what does DNA polymerase do in self replication

Answer 11

joins the nucleotides of new strands

Question 12

why is the copying referred to as semi conservative

Answer 12

because half of the strands in each new DNA molecule are from the original piece of DNA

Question 13

what is a mutation

Answer 13

any change to the DNA base sequence

Question 14

what are the three main types of RNA

Answer 14

mRNA, tRNA and rRNA

Question 15

what is mRNA

Answer 15

made in the nucleus, carries the genetic code from the DNA in the nucleus to the cytoplasm, where its used to make a protein during translation

Question 16

what is tRNA

Answer 16

found in the cytoplasm, has a amino acid binding site, and a sequence of three bases called an anticodon, carries the amino acids that are used to make proteins to the ribosomes during translation

Question 17

what is rRNA

Answer 17

forms the two subunits in a ribosome which moves along the mRNA strand during protein synthesis, rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids

Question 18

describe the kiwi experiment

Answer 18

mix sample (kiwi) with detergent, which breaks down the cell membrane and releases the contents, add salt to break down the hydrogen bonds between DNA and water molecule, add protease enzyme which breaks down the proteins associated with the DNA in the nuclei, add alcohol to make the DNA precipitate out of the solution

Question 19

what are the first steps of transcription

Answer 19

RNA polymerase attaches to the DNA double helix, the hydrogen bonds between the two DNA strands in the gene break and the molecule uncoils. on of the strands is used as a template to make an mRNA copy

Question 20

what is are the second steps transcription

Answer 20

RNA polymerase lines up free RNA nucleotides alongside the template strand, complementary pairing makes it a complementary copy apart from thymine which is uracil, then the bases join together and form an mRNA molecule

Question 21

what are the fourth steps of transcription

Answer 21

RNA polymerase moves along separating the strands and assembling the mRNA strand, once it passes by them the strands coil back into a double helix

Question 22

what are the last steps of transcription

Answer 22

once the RNA polymerase reaches a stop codon it detaches from the DNA, mRNA moves out the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm

Question 23

what are the first steps of transcription

Answer 23

tRNA carry amino acids to the ribosome, the starting tRNA has a anticodon thats complementary to the start codon, then the next and so on

Question 24

what are the second steps of transcription

Answer 24

rRNA in the ribosome catalyses the formation of a peptide bond between the two amino acids attached to the tRNA molecule and the tRNA molecule moves away and this forms a polypeptide chain