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A Level Bio Edexcel > Unit 1- DNA And Protein Synthesis > Flashcards

Unit 1- DNA And Protein Synthesis Flashcards

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1
Q

Is DNA and RNA a weak acid?

A

Yes

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2
Q

What elements are in nucleotides?

A

CHNOP

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3
Q

What components make up DNA?

A
  • pentose sugar
  • phosphate group
  • nitrogenous base
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4
Q

What is a pyrimidine?

A

Single ring carbon/nitrogen structure

Thymine and cytosine and uracil

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5
Q

What is a purine?

A

A double ring carbon/nitrogen structure

Adenine and guanine

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6
Q

How is the sugar phosphate backbone of DNA made?

A

Nucleotide polymerisation

  • covalent phosphodiester bonds form between phosphate and deoxyribose
  • condensation reaction
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7
Q

Shape of DNA

A
  • 2 polynucleotide strands run anti parallel forming a double helix
  • hydrogen bonds form between the complementary base pairs
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8
Q

What is a gene?

A

A section of DNA that codes for a specific protein
Or
A sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain

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9
Q

What is gene expression?

A

The process by which the instructions in our DNA are converted into functional proteins (expressed)

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10
Q

What are the 2 stages of gene expression in order?

A

Transcription

Translation

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11
Q

What kind of cells have non-coding DNA?

A

Eukaryotes

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12
Q

What are the non-coding sections of DNA known as?

A
  • introns (interruption sequences), they are found inbetween exons in a gene
  • satellite DNA, which are regions of non-coding DNA found between genes
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13
Q

What is the purpose of non-coding DNA?

A
  • structural (to help coil the DNA)
  • some code for RNA but don’t code for a protein (not expressed)
  • control functions (to regulate which genes are expressed)
  • involved in DNA replication
  • contains unused copies of genes
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14
Q

What is the purpose of DNA polymerase in DNA replication?

A

Catalyses the formation of phosphodiester bonds between adjacent nucleotides

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15
Q

What bonds are involved in DNA replication?

A

Covalent phosphodiester bonds

Hydrogen bonds

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16
Q

Describe the process of DNA replication

A
  • DNA helical unwinds and separates the 2 strands of DNA, breaking the hydrogen bonds between base pairs
  • the nucleotides present in the nucleoplasm attach themselves to the bases on the old strands by complementary base pairing
  • DNA polymerase joins the new nucleotides together by strong covalent P bonds forming sugar back bone
  • the 2 strands wind up into a double helix
  • the DNA molecules are identical to each other and the old DNA, each new one containing an old and new strand
17
Q

Where do the nucleotides that bind together to from the new polynucleotide strand come from?

A

Nucleoplasm

18
Q

What are replication forks?

A

A replication fork is simply the site of DNA replication, and as DNA is so large it will have many forks at the same time

19
Q

What are nicks in DNA strands?

A

Where a phosphodiester bond hasn’t formed between 2 adjacent nucleotides due to 2 forks meeting (2 DNA polymerase enzymes colliding and not finishing the job)

20
Q

How are nicks in DNA strands joined?

A

DNA ligase

21
Q

What is the purpose of DNA ligase in DNA replication?

A
  • repairs nicks in DNA

- finds mismatched base pairs and replaces them with the correct base

22
Q

Why is the known method of dna replication known as semi conservative replication?

A

Each new DNA molecule contains one new and one old strand

23
Q

Differences between RNA and DNA? 4

A

RNA

  • contains ribose sugar, instead of deoxyribose
  • has base uracil instead of thymine
  • single stranded
  • shorter
24
Q

What is mRNA?

A
  • messenger RNA
  • Carries the code for a particular protein into the cytoplasm
  • just long enough to contain 1 gene (1000 nucleotides)
  • degrades straight after use
25
Q

Structure of tRNA:

A

Transfer RNA

  • looped clover shape
  • ends in the bases ACC, which bind to the amino acid
  • contains a triplet nucleotide sequence (anticodon) which is complementary to a codon on the mRNA
26
Q

What is rRNA?

A

Binds to proteins to form ribosomes, the site of translation

- 2 subunits and found in cytoplasm

27
Q

What does degenerate mean?

A

There is often more than 1 codon for an amino acid

28
Q

AUG is the codon for methionine, what is the significance of this amino acid?

A

This tends to be the start codon, so all proteins start with this amino acid

29
Q

What amino acids to the stop codons code for?

A

None, when the rRNA reads the stop codon the whole process stops, no more amino acids are bonded

30
Q

What does the term non-overlapping mean?

A

A sequence of six bases can only be read as 2 codons, eg AUGUAG only contains the codons AUG and UAG, not AUG,UGA…

31
Q

Where are proteins synthesised? And why?

A

In the cytoplasm, as this is where the ribosomes are

32
Q

What is another word for post transcriptional modification of mRNA?

A

Splicing

33
Q

What is splicing?

A

When non coding introns are removed from pre-mRNA

34
Q

Where does splicing occur?

A

In the nucleus

A Level Bio Edexcel (51 decks)

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