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Biology A Level > DNA > Flashcards

DNA Flashcards

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1
Q

What is a monomer of DNA called?

A

A nucleotide

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2
Q

What is DNA made up of?

A
  • deoxyribose sugar
  • nitrogenous base
  • phosphate group
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3
Q

How do dinucleotides and polynucleotides of DNA form?

A
  • condensation reaction
  • between hydroxyl group of deoxyribose and hydroxyl group of phosphate group
  • forms phoshophideser bonds
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4
Q

Describe the structure of DNA

A
  • deoxyribose sugar
  • double helix (bigger, long)
  • unable to leave the nucleus
  • contains thymine
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5
Q

Describe the DNA double helix

A
  • strands are antiparallel
  • hydrogen bonds between bases
  • sugar-phosphate backbone between bases (makes mutations relatively uncommon)
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6
Q

What is the benefit of the sugar-phosphate backbone?

A

makes mutations relatively uncommon

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7
Q

What is 5’?

A

The carbon 5 of the deoxyribose is closest to the end

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8
Q

What is 3’?

A

The carbon 3 of the deoxyribose is closest to the end

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9
Q

Describe the hydrogen bonding between base pairs

A
  • C-G = 3 bonds
  • A-T = 2 bonds

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

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10
Q

Describe the structure of DNA in relation to its function

A
  • 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
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11
Q

How many possible codons are there?

A

64

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12
Q

Describe the severity of different types of mutation

A
  • substitution -> can have no effect
  • insertion -> can have no effect/a big effect
  • délétion -> has a big effect
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13
Q

What is a purine?

A
  • a heterocyclic aromatic organic compound
  • consists of a pyrimidine ring fused to an imidazole ring (double it ring structure)
  • guanine and adenine
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14
Q

What is a pyrimidine?

A
  • 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
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15
Q

What is a gene

A

A short section of DNA that codes for a polypeptide chain

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16
Q

What is a cistron?

A

A posh, scientific word for gene! It

17
Q

What is a locus?

A

The location of a gene in the DNA strand

18
Q

What relevance does DNA have to proteins?

A
  • 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
19
Q

What are introns?

A

Non-coding DNA

20
Q

What are exons?

A

Coding DNA

21
Q

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

A
  • 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
22
Q

What is the start DNA triplet?

A

The triplet which codes for MET (an amino acid)

23
Q

How many stop triplets are there?

A

3

24
Q

What are chromosomes?

A
  • 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)
25
Q

Describe the centromere

A
  • non-coding DNA

* contains kinetochore

26
Q

What are histones?

A

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

27
Q

What is chromatin?

A

DNA associated with histones

28
Q

How is DNA wound?

A

Around histones, coiled and looped

29
Q

What are homologous chromosomes?

A

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

30
Q

What are alleles?

A

Alternative versions of a gene

31
Q

How do alleles differ from one another?

A

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

32
Q

Define universal

A

Triplets code for the same amino acid across all organisms

33
Q

Define non-overlapping

A

DNA triplets are only read once

34
Q

Which level of protein structure is encoded in DNA?

A

Primary

35
Q

What is DNA?

A

Deoxyribonucleic acid (CHONP)

36
Q

What is a nucleotide?

A
  • 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
37
Q

What is a nucleic acid?

A
  • 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
38
Q

Describe the shape of DNA

A
  • 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
39
Q

Describe nitrogenous bases

A
  • 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

Biology A Level (45 decks)

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