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Biology yr 12 > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

1
Q

What are Nucleic Acids?

A

Polymers made from Nucleotides (2 types = DNA and RNA)

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2
Q

What is DNA?

A
  • DeoxyriboNucleic Acid
  • found in all organisms (animals, plants, microorganisms)
  • carries genes
  • genes = section of DNA that codes for a protein
  • all organisms are built of proteins
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3
Q

Building block of DNA?

A

 DNA nucleotide (made of phosphate, deoxyribose sugar, nitrogenous base)
 4 types of nucleotides (each has a different base, either Adenine/Thymine/Cytosine/Guanine)

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4
Q

DNA structure?

A

 DNA Double Helix
 join nucleotides by condensation reaction between sugar and phosphate to form a polynucleotide
 join 2 polynucleotides by hydrogen bond between the bases
 A joins with T, C joins with G (complementary base pairing)
 produces double strand
 then coil double strand into Double Helix

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5
Q

Properties of DNA Structure?

A

 Double Stranded = makes DNA more stable & 2 strands act as templates in semi-conservative replication
 Coil into Helix = more compact
 Sugar-phosphate backbone = protects bases (bases code for protein)
 Hydrogen bonds between bases = weak, so double strand separates more easily for semi-conservative replication
 Complementary Base Pairing = ensures identical copies of DNA made by semi-conservative replication

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6
Q

DNA Replication?

A

occurs in interphase before mitosis & meiosis
occurs by semi-conservative replication

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7
Q

Describe Semi-Conservative Replication?

A

DNA double strand separate and act as templates, producing 2 identical copies of the DNA, each has half the original strand and half the new strand

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8
Q

Evidence for semi-conservative replication?

A

 Replicating Bacterial DNA in 2 types of Nitrogen Isotopes, 15N and 14N
 15N = heavy isotope
 14N = light isotope
 Nitrogen found in nitrogenous bases of DNA
 Bacterial DNA made from 15N will have a Heavy Density
 Bacterial DNA made from 14N will have a Light Density
 Experiment = Bacterial DNA made of 15N is replicated in an environment of 14N – produces DNA molecules with half 15/half 14 (semi-conservative replication, original strand = 15N & new strand = 14N), therefore, DNA molecule has medium density

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9
Q

What is RNA?

A

 RiboNucleic Acid
 2 types (mRNA and tRNA)
 mRNA = messenger RNA
 tRNA = transfer RNA
 both single stranded
 both made of RNA Nucleotides (phosphate, ribose sugar, nitrogenous bases - AUCG)

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10
Q

Structure of ATP?

A

 Adenosine Triphosphate
 made from 1 adenosine and 3 phosphates
 formation: ADP + Pi (+ energy used) = ATP
 condensation reaction using ATP Synthase
 carries energy in its bonds
 breakdown: ATP = ADP + Pi (+ energy released)
 hydrolysis reaction using ATP Hydrolase
 releases energy from its bonds

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11
Q

What makes ATP a good deliverer of energy?

A

 immediate source = need to only break one bond (plus bond is weak)
 manageable source = releases small amount of energy

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12
Q

Uses of ATP (releases energy) in organisms?

A

 protein synthesis
 organelle synthesis
 DNA replication
 cell division (mitosis)
 active transport
 metabolic reactions
 movement
 maintaining body temperature

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13
Q

Role of Water in Biology?

A

 found in living organisms = cytoplasm (all organisms), xylem/phloem (in plants), tissue fluid and blood (in animals)
 also acts as habitats for living organisms

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14
Q

Functions of water?

A
  • high heat capacity - buffers and controls internal body temperature (thermoregulation)
  • large latent heat of vapourisation - provides a cooling effect to maintain internal temperature
  • forms strong cohesion between water molecules - allows columns of water to form and move through organisms. Causes surface tension where water meets air.
  • an important solvent - metabolic reactions can occur - enables waste and essential molecules to be transported
  • it is a metabolite in many metabolic reactions - important in essential processes, such as: ATP synthesis, digestion and protein synthesis
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15
Q

Main role of hydrogen ions?

A
  • buffering the blood
  • controlling and altering the PH
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16
Q

Main role of iron ions?

A
  • a component of haemoglobin (transports oxygen)
  • Involved in the electron transport chain in respiration
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17
Q

Main role of sodium ions?

A
  • sodium potassium pump
    - glucose moving into and out of the cell (ileum)
    - Amino acids moving into or out of the cell
    - Establishing a nerve impulse
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18
Q

Main role of phosphate ions?

A
  • nucleic acids (DNA+RNA)- strong sugar-phosphate backbone
  • ATP - respiration - energy
  • phospholipids - important in the membranes of cells
  • NAD and NADP in photosynthesis
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19
Q

What is a Gene?

A

 a section of DNA that codes for a protein
 made out of intron and exon
 intron = non-coding DNA (function e.g. turns gene on or off)
 exon = coding DNA (codes for protein)

20
Q

How does a Gene/Exon code for a Protein?

A

 made out of a sequence of bases
 each 3 bases code for 1 amino acid (called triplet code)
 therefore,
 sequence of bases
 determines sequence of triplet codes
 which determine the sequence of AAs
 = polypeptide chain/primary structure (folds to secondary, then to tertiary/quaternary

21
Q

Properties of triplet code?

A

 degenerate = each AA has more than one triplet code
 non-overlapping = each base is read only once
 stop codes = occur at end of sequence – do not code for an AA

22
Q

How does a mutation lead to a non-functional enzyme?

A

 change in base sequence
 change in sequence of triplet codes
 change in sequence of AAs
 change in primary structure
 change in hydrogen/ionic/disulfide bonds
 change in tertiary structure (3D shape)
 change in active site shape
 substrate no longer complementary
 can no longer form enzyme-substrate complex

23
Q

How is a protein assembled?

A

 by transcription and translation
 transcription = production of a single stranded complementary copy of a gene (called mRNA)
 translation = use sequence of codons on mRNA to assemble protein (tRNA brings in AAs)

24
Q

DNA vs RNA?

A

 deoxyribose sugar vs ribose sugar
 thymine vs uracil
 double stranded vs single stranded
 one type vs two types (mRNA and tRNA)

25
Q

What is mRNA?

A

 messenger RNA
 single stranded complementary copy of a gene
 carries the code for assembling protein (on DNA called triplet code, on mRNA called codon)

26
Q

What is tRNA?

A

 transfer RNA
 single stranded RNA folded over into a ‘clover leaf’ shape (held by hydrogen bonds between the bases)
 has an AA attachment site on the top
 has 3 specific bases on the bottom (anticodon)
 anticodon binds to complementary codons on mRNA

27
Q

What is Transciption?

A

 occurs in nucleolus of nucleus
 producing a single stranded complementary copy of a gene (called mRNA)
 DNA is double stranded, 1 strand called coding strand & 1 strand called template strand, the template strand will be used to build mRNA

28
Q

Transcription process?

A

 DNA Helicase breaks the hydrogen bonds between complementary bases in the gene
 the double strand of the gene unwinds
 leaves 2 separate strands (1 coding strand and 1 template strand)
 complementary RNA nucleotides bind to exposed bases on the template strand
 RNA Polymerase joins the sugar-phosphate backbone of the RNA strand
 leaves pre-mRNA (contains introns and exons)
 the copies of the introns are removed by splicing
 leaves mRNA

29
Q

What is Translation?

A

 takes place on ribosomes of Rough Endoplasmic Reticulum
 uses the sequence of codons on the mRNA to assemble the protein (tRNA brings in AAs)

30
Q

Translation process?

A

 mRNA leaves nucleus via nuclear pore
 mRNA attaches to a ribosome
 complementary tRNA carrying specific AAs bind to the codons on mRNA via their anticodon
 the AAs on the tRNA are joined by peptide bonds

31
Q

What does Meiosis produce?

A

4 genetically different cells, haploid (half the amount of chromosome/DNA)

32
Q

Benefits of Meiosis?

A

produces gametes which will be used in sexual reproduction in animals & plants (2 gametes fuse to form a zygote, zygote develops into organisms)

33
Q

Stages of Meiosis?

A

Interphase/Meiosis I/Meiosis II/Cytokinesis

34
Q

Interphase?

A

G1: protein synthesis
S: DNA replication (doubles set of DNA)
G2: organelle synthesis

35
Q

Meiosis I?

A

Prophase I: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form, crossing over occurs
Metaphase I: homologous pair of chromosomes line up in middle of cell and attach to spindle fibre via centromere
Anaphase I: spindle fibres pull, homologous pair of chromosomes separate to opposite sides by independent assortment
Telophase I: chromosomes uncoil, nucleus reforms (left with 2 nuclei)

36
Q

Meiosis II?

A

Prophase II: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form
Metaphase II: chromosomes line up in middle of cell and attach to spindle fibre via centromere
Anaphase II: spindle fibres pull, centromere splits, sister chromatids move to opposite sides by independent assortment
Telophase II: chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei)

37
Q

Cytokinesis?

A

separating cell into 4 (each receives a nucleus and organelles/cytoplasm)

38
Q

How does Meiosis produce Variation?

A

Crossing Over and Independent segregation

39
Q

What is crossing over?

A

occurs in Prophase I of Meiosis I
homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids – produces new combination of alleles

40
Q

What is independent segregation?

A

-in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate
- in Anaphase II of Meiosis II – the chromatids separate
- independent assortment produces a mix of alleles from paternal and maternal chromosomes in gamete

41
Q

What happens to DNA mass in meiosis?

A

quarters

42
Q

What happens to Chromosome number in meiosis?

A

halves (haploid)

43
Q

What is Mutation?

A

 Change in DNA
 2 types: Chromosome Mutation and Gene Mutation

44
Q

What causes chromosome mutation?

A

 In plants, inherit more than one diploid set of chromosomes – called polyploidy
 In animals, homologous pair of chromosome do not separate in meiosis, so either inherit one extra or one less chromosome – called non-disjunction

45
Q

What is a Gene Mutation?

A

 a change in the base sequence of DNA
 2 types = substitution and insertion/deletion
 substitution = replace one base for another, changes one triplet code can be silent (new triplet code codes for same AA), mis-sense (codes for a different AA, so protein shape changes slightly), non-sense (codes for a stop codon, so polypeptide chain not produced)
 insertion = adding a base, deletion = removing a base
both insertion/deletion causes frameshift, all the triplet codes after the mutation changes, so normal polypeptide chain/protein not produced

46
Q

Semi-conservative replication process?

A

 DNA Helicase breaks hydrogen bonds between the complementary bases
 double strand separates, leaves 2 template stands
 free complementary nucleotides bind to exposed bases on template strands (A to T, C to G)
 DNA Polymerase joins the sugar-phosphate backbone of the new strand

Biology yr 12 (8 decks)

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