DNA

Question 1

What is a monomer of DNA called?

Answer 1

A nucleotide

Question 2

What is DNA made up of?

Answer 2

• deoxyribose sugar
• nitrogenous base
• phosphate group

Question 3

How do dinucleotides and polynucleotides of DNA form?

Answer 3

• condensation reaction
• between hydroxyl group of deoxyribose and hydroxyl group of phosphate group
• forms phoshophideser bonds

Question 4

Describe the structure of DNA

Answer 4

• deoxyribose sugar
• double helix (bigger, long)
• unable to leave the nucleus
• contains thymine

Question 5

Describe the DNA double helix

Answer 5

• strands are antiparallel
• hydrogen bonds between bases
• sugar-phosphate backbone between bases (makes mutations relatively uncommon)

Question 6

What is the benefit of the sugar-phosphate backbone?

Answer 6

makes mutations relatively uncommon

Question 7

What is 5’?

Answer 7

The carbon 5 of the deoxyribose is closest to the end

Question 8

What is 3’?

Answer 8

The carbon 3 of the deoxyribose is closest to the end

Question 9

Describe the hydrogen bonding between base pairs

Answer 9

• C-G = 3 bonds
• A-T = 2 bonds

Hence, if there are more C-G base pairs, the molecule of DNA is more stable

Question 10

Describe the structure of DNA in relation to its function

Answer 10

• very stable -> passes from generation to generation without changing
• two strands -> weak hydrogen bonds allow the strand to be separated so the core can be read and copied for DNA replication and protein synthesis. Complementary base pairing ensures accuracy
• large -> carries a lot of information
• sugar-phosphate backbone -> code (more chemically reactive nitrogenous base pairs) protected from chemical and physical dangers and damage
• sequence of base pairs -> contain genetic info to code for proteins, achieved through infinite variability of polynucleotide chains
• forms genetic code -> base sequence along polynucleotide chains determines the characteristics of an organism that are inherited from its parents
• strong -> many hydrogen bonds
• double-helix -> compact
• two complementary strands -> two copies of information, useful for repair, copying and error checking

Question 11

How many possible codons are there?

Answer 11

64

Question 12

Describe the severity of different types of mutation

Answer 12

• substitution -> can have no effect
• insertion -> can have no effect/a big effect
• délétion -> has a big effect

Question 13

What is a purine?

Answer 13

• a heterocyclic aromatic organic compound
• consists of a pyrimidine ring fused to an imidazole ring (double it ring structure)
• guanine and adenine

Question 14

What is a pyrimidine?

Answer 14

• a heterocyclic aromatic organic compound
• contains 2 nitrogen atoms at positions 1 and 3 of a six member ring (single ring structure)
• cytosine and thymine
• similar time benzène and pyridine

Question 15

What is a gene

Answer 15

A short section of DNA that codes for a polypeptide chain

Question 16

What is a cistron?

Answer 16

A posh, scientific word for gene! It

Question 17

What is a locus?

Answer 17

The location of a gene in the DNA strand

Question 18

What relevance does DNA have to proteins?

Answer 18

• the sequences of DNA causes the sequence of amino acids
• if there is a mutation, the shape of the protein changes because the bonds form in different places, causing it to hold differently, so the protein may not be able to complete its function

Question 19

What are introns?

Answer 19

Non-coding DNA

Question 20

What are exons?

Answer 20

Coding DNA

Question 21

What is degenerate code? Hence, how is DNA a degenerate code?

Answer 21

• more than one DNA triplet codes for the same amino acid
• some amino acids are only coded for by a single DNA triplet
• some amino acids can be coded for by up to 6 DNA triplets

Question 22

What is the start DNA triplet?

Answer 22

The triplet which codes for MET (an amino acid)

Question 23

How many stop triplets are there?

Answer 23

3

Question 24

What are chromosomes?

Answer 24

• only visible when a cell is dividing
• how we can tell if a cell is undergoing mitosis and calculate mitotic index
• appear as two chromatids attaches at the centromere (when DNA replication has occurred)

Question 25

Describe the centromere

Answer 25

* non-coding DNA | * contains kinetochore

Question 26

What are histones?

Answer 26

Proteins that are associated with DNA strands that make us have chromosomes

Question 27

What is chromatin?

Answer 27

DNA associated with histones

Question 28

How is DNA wound?

Answer 28

Around histones, coiled and looped

Question 29

What are homologous chromosomes?

Answer 29

A cell with a full set of chromosomes, 23 maternal and 23 parental, whic carry the same genes

Question 30

What are alleles?

Answer 30

Alternative versions of a gene

Question 31

How do alleles differ from one another?

Answer 31

Different base sequence and therefore....: • différent primary structure • différent tertiary structure

Question 32

Define universal

Answer 32

Triplets code for the same amino acid across all organisms

Question 33

Define non-overlapping

Answer 33

DNA triplets are only read once

Question 34

Which level of protein structure is encoded in DNA?

Answer 34

Primary

Question 35

What is DNA?

Answer 35

Deoxyribonucleic acid (CHONP)

Question 36

What is a nucleotide?

Answer 36

* nitrogen-containing organic substances which play a vital role in every aspect of an organism’s life * can occur singly (mononucleotide) or combined (polynucleotide) * composed of 1 nitrogen-containing organic base, à pentose sugar and 1 or more phosphate group

Question 37

What is a nucleic acid?

Answer 37

* chain of nucleotides formed by condensation reactions * joined by phosphodiester bonds between the hydroxyl groups of the phosphate group and the pentose sugar * AKA: polynucleotides

Question 38

Describe the shape of DNA

Answer 38

* two helical polynucleotide chains forming a double helix * sugar-phosphate backbone protects the pairs of bases which hold the polynucleotide chains together through complementary base pairing

Question 39

Describe nitrogenous bases

Answer 39

* held together by complementary base pairing: hydrogen bonds between the hydrogen atom of a base in one chain and the oxygen and nitrogen atoms of the complementary base in the other chain * bases can only form in their pairs because of their sizes and shapes; they are specific * guanine and adenine are both purines * cytosine and thymine are both pyrimidines