A-Level Biology > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

(41 cards)

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1
Q

what type(s) of synthesis is nucleic acids involved in

A

hereditary and protein synthesis

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2
Q

what are the 4 main types of nucleic acids

A

DNA mRNA tRNA rRNA

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3
Q

what are the three components of nucleic acid

A

phosphate
sugar
base

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4
Q

DNA nucleotides:

A

phosphate
deoxyribose sugar
base - adenine, guanine, cytosine, thymine

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5
Q

RNA nucleotides:

A

phosphate
ribose sugar
base - adenine, guanine, cytosine, uracil

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6
Q

what type of bonds to condensation reactions make between nucleotides

A

phosphodiester bonds

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7
Q

what does a DNA molecule consist of

A

two stands
double helix
anti - parallel
complementary base pairs

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8
Q

AGpu
CUTpy

A
  • adenine, guanine are 2 ring purines
  • cytosine, thymine (uracil in RNA) are 1 ring pyrimidines - purine always pairs with pyrimidines so DNA is always the same width
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9
Q

what is ATP made of?

A

1 ribose sugar
2 ring nitrogenous base
adenine
3 phosphate groups

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10
Q

why can’t DNA leave the nucleus

A

too long to the nucleus

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11
Q

what is mRNA and can it leave the nucleus?

A

complementary copy of a short length of DNA and can leave the nucleus

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12
Q

what does tRNA do?

A

carries a specific amino acid in protein synthesis

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13
Q

where is rRNA found?

A

in the nucleolus with ribosomes

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14
Q

what is RNA?

A

polymer of RNA nucleotides held together by phosphodiester bonds

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15
Q

what is the DNA double helix held together by?

A

hydrogen bonds

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16
Q

how many base pairs for 1 complementary rotation of the double helix

A

10

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17
Q

why is the width constant on the DNA double helix?

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A

A-T and C-G are both pairings of a single ring with a double ring

18
Q

what is DNA wound round?

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A

histones - so 6m of DNA can fit in nucleus

19
Q

what two steps are involved with cell division

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A
  • nuclear division (mitosis)
  • cytoplasm division (cytokinesis)
20
Q

what happens in mitosis DNA

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A

DNA is replicated before every cell division, and 1 identical copy of each chromosome goes into each daughter cell

21
Q

simplified version of the sequence of replication

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A

DNA replication follows a semi-conservative model, involving DNA helicase unwinding the double helix by breaking hydrogen bonds, then DNA polymerase adding free complementary nucleotides (A-T, G-C) to each template strand in condensation reactions, forming phosphodiester bonds, resulting in two identical DNA molecules, each with one old and one new strand.

22
Q

what do replication errors produce in DNA replication

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A

produce different DNA sequences - mutations
- around 1 million a day in a body and DNA is checked to look for them. If found they can be replaced

23
Q

what are replication errors in DNA replication cause by?

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A

chemicals (smoking)
radiation
chance - time (older, more time, more change of a mutation that may be a problem

24
Q

why is DNA replication called semi - conservative replication

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A

because each new double helix is one original stand and one newly synthesised strand

25
revise Meselson and Stahl experiment
26
extracting DNA (pea practical)
-soap helps to dissolve membranes - salt is added to release the DNA strands by breaking up protein chains that hold nucleic acids together - DNA is not soluble in ethanol, especially when the ethanol is ice cold
27
what is genetic base read in
triplets - each triplet of 3 bases codes for 1 amino acid - always same amino acid - coding in amino acids called the genetic code - universal
28
what is the genetic code?
degenerante (or redundant) some amino acids code for more that 1 triplet - means some changes in base sequences dont put different amino acids in a protein
29
start and stop codons
start codons are always ATG stop codons dont code for amin acids
30
is the genetic code non-overlapping?
yes - if it overlapped each amin acid could only be followed by one of four amin acids, and this does not happen, We know that any amino acids can be followed by any of the 22 amino acids
31
what is mRNA made up of
introns and extrons
32
What are introns?
non coding parts of DNA and they are cut out of the molecule
33
What are extrons and what do they do?
they join together to produce the finished mRNA molecule which then goes onto translation
34
What is the process of protein synthesis?
DNA - mRNA - amino acid sequence - polypeptide - protein
35
What does the DNA describe?
describes how DNA nucleotides or triplets or codons are converted into amino acids
36
what do a number of codons produce?
a gene - length of DNA that codes for a particular characteristic
37
What are the 4 nucleic acids involved in protein synthesis
- DNA = in the nucleus carries genetic code as chromosomes - mRNA = made in the nucleus moves out to cytoplasm - rRNA = found attached to ribosomes - tRNA = reusable molecule in the cytoplasm which transports a specific amino acid and attaches to the mRNA
38
what does DNA determine?
individuals functional or physical trait
39
what two steps does protein synthesis involve?
1. transcription in the nucleus 2. translation in the cytoplasm
40
describe the process of transcription:
1) DNA double helix in the nucleus unwinds exposing bases of gene to be expressed 2) free mRNA nucleotides from the cytoplasm complementarily pair up with the bases of the 3-5 antisense strand 3) mRNA polymerase enzyme joins mRNA nucleotide with phosphodiester bonds to make an mRNA molecule 4) completed mRNA molecule released from DNA and leaves the nucleus through nuclear pore 5) DNA zips up and twists back into double helix
41
describe the process of translation:
1) a ribosome binds the the first two mRNA codons i.e. 6 nucleotides 2) 2 tRNA amin acid complexes complimentarily pair with 2 mRNA codons covered by the ribosomes since they have complementary base sequences 3) peptidyl transferase catalyses formation of peptide bonds between the 2 amino acids in a condensation reaction that eliminates a molecule of water 4) the first tRNA releases its amino acid and leaves ribosome. the tRNA is reused carrying another copy of the same amino acid 5) the ribosome moves along the mRNA by one codon 6) a new complementary tRNA amino acid complex enters the free codon the amino acid just covered 7) the new amino acid will form a peptide bond with the dipeptide to form a tripeptide 8) the second tRNA releases its amino acid resulting in the tripeptide being attached to the third tRNA 9) the second tRNA goes back into the cytoplasm where it will combine with another copy of the same amino acid. This requires ATP and involves a condensation reaction 10) sequence continues until stop codon is reached and the finished polypeptide is released from the ribosome
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