2.1.3- Nucleotides + Nucleic Acids

Question 1

what is a nucleotide?

Answer 1

a monomer from which nucleic acids are made?

Question 2

what are the 5 elements are nucleic acids made from?

Answer 2

• carbon
• oxygen
• hydrogen
• nitrogen
• phosphorus

Question 3

what are nucleotides made up of?

Answer 3

• phosphate group
• sugar
• base

Question 4

what are the two different types of nucleic acids?

Answer 4

• DNA

- RNA

Question 5

what are the 4 differences between DNA + mRNA?

Answer 5

• DNA=double-stranded, while mRNA= single-stranded
• dna contains deoxyribose, while mrna contains ribose
• dna contains thymine, whereas mrna contains uracil
• mrna is less stable than dna due to having exposed bases + the fact that uracil is easier to degrade.

Question 6

what type of pentose sugar is found in DNA + mRNA?

Answer 6

• DNA= deoxyribose

- mRNA= ribose

Question 7

what is a purine?

Answer 7

a class of nitrogenous bases that are made up of 2 rings that Adenine + Guanine are members of.

Question 8

what is a pyramidine?

Answer 8

a class of nitrogenous bases made up of a single ring, cytosine, thymine and uracil are members.

Question 9

what bond is formed between 2 nucleotides (polynucleotides)?

Answer 9

• PHOSPHODIESTER BOND
• between the phosphate group (5th carbon) +the hydroxyl group (3rd carbon)
• condensation reaction builds, while hydrolysis reaction breaks them down.

Question 10

how do you write the numbers of a phosphodiester bond?

Answer 10

5”,3”

Question 11

what is a phosphorylated nucleotide?

Answer 11

The process of introducing one or more phosphate groups into a nucleotide to produce a phosphorylated nucleoside.

Question 12

what are the 2 examples of phosphorylated nucleotides?

Answer 12

• ADP

- ATP

Question 13

what is the structure of ATP?

Answer 13

• adenine base
• ribose sugar
• 3 phosphate groups

Question 14

what does ATP do?

Answer 14

• provides energy, so that cells can synthesise, transport + move
• it is released through hydrolysis

Question 15

what does ATP break down into?

Answer 15

• inorganic phosphate ion
• ADP
• energy

Question 16

what is the structure of ADP?

Answer 16

• base
• sugar
• two phosphate groups

Question 17

what is the structure of DNA like?

Answer 17

• very long, so can store increased amounts of info
• base-pairing rules, easy to replicate info
• double helix, stable molecule, where info is stored safely.

Question 18

how is DNA formed?

Answer 18

-hydrogen bonding between complementary base pairs on 2 anti-parallel DNA polynucleotides

Question 19

what are the two complementary base pairs in DNA, and how many hydrogen bonds do they form?

Answer 19

• Adenine + Thymine = forms 2 hydrogen bonds

- Cytosine + Guanine = forms 3 hydrogen bonds

Question 20

what bases are purines?

Answer 20

• adenine

- guanine

Question 21

what bases are pyramidines?

Answer 21

• cytosine

- thymine

Question 22

what is a double-stranded/double helix DNA?

Answer 22

• 2 single strands of DNA twist around each other forming a double-helix
• this helix is held by hydrogen bonds between nitrogenous bases on different strands
• it is anti-parallel

Question 23

how many bases are in DNA and how many codons does this then make?

Answer 23

• 4 bases = A-T, C-G

- makes 64 different codons

Question 24

what is the function of DNA?

Answer 24

• holds genetic info
• codes for the primary structure of proteins
• store these codes, called genes

Question 25

what is the definition of GENES?

Answer 25

a sequence of nucleotides that code for a polypeptide.

Question 26

what is single-stranded DNA?

Answer 26

a long chain of nucleotides

Question 27

what is SEMI-CONSERVATIVE DNA REPLICATION?

Answer 27

when half of the parent strand is conserved

Question 28

what is the first stage of semi-conservative replication?

Answer 28

- DNA helicase unzips DNA by breaking hydrogen bonds between complementary bases. - helicase = enzyme

Question 29

what is the second stage of semi-conservative replication?

Answer 29

- the free DNA nucleotides become attracted to the exposed bases by complementary base pairing - the free strands act as templates

Question 30

what is the third stage of semi-conservative replication?

Answer 30

-free nucleotides join by phosphodiester bonds by DNA polymerase (enzyme) to form a phosphate sugar backbone.

Question 31

what is the fourth stage of semi-conservative replication?

Answer 31

-each DNA molecule is then made up of one OLD strand, and one NEW strand of DNA.

Question 32

what is the importance of semi-conservative replication?

Answer 32

- it conserves genetic information with accuracy. | - prepares cells for mitosis

Question 33

what are the 3 types of mutations in the base sequence?

Answer 33

- base deletion (the loss of genetic material) - insertion (the addition of genetic material) - substitution (where one base pair is replaced with another base pair)

Question 34

what does generate coding mean?

Answer 34

when amino acids have more than one corresponding codon

Question 35

what does degenerate coding mean?

Answer 35

when amino acids have more than one corresponding codon

Question 36

what are INTRONS?

Answer 36

the non-coding sections of DNA

Question 37

what are EXONS?

Answer 37

the coding regions of DNA.

Question 38

what are the 3 features of the genetic code?

Answer 38

-it is non-overlapping (each triplet is read only once, with triplets not sharing bases) -it is degenerate (more than one triplet codes for the same amino acids, reducing phenotypic effect of mutations). -contains start and stop codons (which start/stop protein synthesis).

Question 39

what can mutations cause?

Answer 39

phenotypic effects

Question 40

what can mutations cause?

Answer 40

phenotypic effects - production of sticky mucus and causes cystic fibrosis - sickle cell anaemia

Question 41

what do mutations of the base sequence of DNA cause?

Answer 41

- alters the amino acid sequence | - alters the proteins, so has many effects.

Question 42

what is nucleic acid transcription?

Answer 42

the process of copying + transporting genes out of the nucleus and into the ribosomes, to produce RNA

Question 43

what is the first stage of transcription?

Answer 43

-part of the DNA that contains the genes unzips when hydrogen bonds between two strands break

Question 44

what are the 2nd and 3rd stages of transcription

Answer 44

- complementary free RNA nucleotides line up opposite the anti-sense strand, acting as a template. - these then join by phosphodiester bonds to create a single-stranded mRNA

Question 45

what is the last stage of transcription?

Answer 45

- it stops at the end of the gene, with mRNA then moving out of the nucleus through a pore and attaching to a ribosome in the cytoplasm - double helix reforms

Question 46

what is an anti-sense strand?

Answer 46

a complementary copy of the sense strand that doesn't code for a protein but acts as a template.

Question 47

what happens during translation?

Answer 47

amino acids join together to form polypeptide chains

Question 48

what is the first stage of translation?

Answer 48

-mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and carries them to the ribosome.

Question 49

what is the second stage of translation?

Answer 49

- tRNA attaches itself to mRNA by complementary base pairing - two molecules attach to mRNA at a time

Question 50

what is the third stage of translation?

Answer 50

-the amino acids attached to two tRNA molecules join by a peptide bond and then tRNA molecules detach themselves from the amino acids, leaving them behind

Question 51

what is the last stage of translation?

Answer 51

-this process is repeated, leading to the formation of a polypeptide chain until a stop codon is reached on mRNA and ends the process of protein synthesis

Question 52

what is a sense strand?

Answer 52

a strand that contains a code for protein to be synthesised.

Question 53

what does the condensation of nucleotides form?

Answer 53

- a long/strong phosphate-sugar backbone | - base that is attached to sugars