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A-Level Bio > Topic 4 > Flashcards

Topic 4 Flashcards

1
Q

Eukaryotic and prokaryotic DNA similarities

A

made of DNA nucleotides containing deoxyribose, phosphate group and a nitrogenous base
nucleotides are joined together by phosphodiester bonds to make a polymer chain

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2
Q

eukaryotic vs prokaryotic DNA

A

p
shorter
circular (not linear)
not associated w histones

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3
Q

mitochondrial/chloroplast DNA and prokaryotic DNA similarities

A

short sequences
circular
not associated with proteins eg histones

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4
Q

a gene

A

a sequence of DNA coding for the amino acid sequence of a polypeptide
or a functional RNA

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5
Q

locus

A

the location on the chromosome a gene occupies

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6
Q

triplet

A

sequence of 3 DNA bases

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7
Q

generic code 3 features

A

degenerate
universal
non overlapping

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8
Q

degenerate meaning

A

each amino acid is coded for by more than one triplet of bases

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9
Q

advantage of degenerate genetic code

A

if a point mutation occurs, even though the triplet of bases may be different, they may still code for the same amino acid and have no effect

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10
Q

universal meaning

A

the same triplet of bases codes for the same amino acid in all organisms

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11
Q

non overlapping meaning

A

each base in a gene is part of 1 triplet of bases that codes for 1 amino acid, so each triplet or codon is read as a discrete unit

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12
Q

advantage of non overlapping DNA

A

if a point mutation occurs it will only affect one codon and therefore one amino acids

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13
Q

introns and where they are find

A

sections of DNA that do not code for polypeptides
found in eukaryotic DNA not prokaryotic DNA

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14
Q

exons

A

sequences of DNA not coding for amino acids

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15
Q

codon

A

3 bases on mRNA that code for a specific AA

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16
Q

start codon

A

three bases at the start of every gene that initiates transcription

17
Q

stop codon

A

three bases at the end of every gene that causes ribosomes to detach and therefore stop translation

18
Q

genome

A

an organism’s full set of genes in a cell

19
Q

proteome

A

the full ramge of proteins a cell is able to produce

20
Q

does the genome change

A

no it shouldn’t

21
Q

does the proteome change

A

yes as it depends on which proteins are currently needed

22
Q

mRNA is found in the

A

cytoplasm
nucleus

23
Q

when is mRNA made during

A

transcription

24
Q

tRNA structure

A

anticodon
amino acid binding site

25
Q

keyword for tRNA

A

SPECIFIC to one amino acid

26
Q

anticodon

A

sequence of three bases complementary to codons on the mRNA

27
Q

tRNA shape and why it’s shaped like that

A

single polynucleotide strand folded into a clover shape
H bonds between base pairs hold the shape

28
Q

tRNA uses

A

involved in translation; brings amino acids that are used to make proteins to the ribosomes

29
Q

2 stages of protein synthesis

A

transcription
translation

30
Q

why is transcription needed

A

mRNA much shorter than DNA
carries genetic code to the ribosome in the cytoplasm to enable the production of the protein

31
Q

transcription

A
  1. DNA helix unwinds, catalysed by DNA helicase, and hydrogen bonds between bases break
  2. One chain of DNA acts as a base
  3. Free mRNA nucleotides in the nucleus align with exposed complementary DNA bases
  4. the enzyme RNA polymerase joins together RNA nucleotides to create a new RNA polymer chain
  5. one gene is copied
  6. mRNA is spliced and leaves the nucleus through nuclear envelope pores
32
Q

Why is splicing needed

A

pre-mRNA freshly transcripted contains introns

33
Q

splicing process in eukaryotes

A

splicesome splices introns out leaving only exons

34
Q

splicing process in prokaryotes

A

none, as prokaryotic teanscription directly creates mRNA

35
Q

Translation steps

A
  1. once the modified mRNA has left the nucleus it attaches to a ribosome at the start codon in the cytoplasm
  2. the tRNA molecule with the complementary anticodon to the start codon aligns opposite to the mRNA, held in place by the ribosome
  3. the ribosome will move along one codon on the mRNA to enable another complementary tRNA to attach to the next codon on the mRNA
  4. the 2 AAs that have been delivered by tRNA are joined by a peptide bond catalysed by an enzyme and requiring ATP
  5. this continues until the ribosome reached the stop codon at the end of the mRNA molecule - the stop codon does not code for an amino acid and therefore the ribosome detached and translation ends
  6. the ppt chain is created and will enter the golgi body for folding and modification

A-Level Bio (9 decks)

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