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Biology A level > 4.2 DNA and protein synthesis > Flashcards

4.2 DNA and protein synthesis Flashcards

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1
Q

where does protein synthesis occur?

A

on ribosomes of the RER

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2
Q

What are the 2 stages of protein synthesis?

A

transcription
translation

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3
Q

where does transcription occur?

A

in the nucleus

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4
Q

What is transcription?

A

where one gene on the DNA is copied into mRNA

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5
Q

What is translation?

A

where the mRNA joins with a ribosome and corresponding tRNA molecules bring the specific amnio acid the codon codes for

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6
Q

Why is a copy of DNA made (mRNA) in protein synthesis?

A

DNA is too large to leave the nucleus and mRNA is much shorter and can fit through the nuclear pores

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7
Q

Why dont we want the DNA to leave the nucleus?

A

in the cytoplasms there may be enzymes that could damage the DNA

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8
Q

What is the process of Transcription?

A
  1. DNA helix unwinds and unzipps which is catalysed by DNA helicase to expose bases as a template
  2. DNA helicase breaks the H bonds between bases - unzipps
  3. one DNA chain acts as a template
  4. free mRNA nucleotides in the nucleus align with complementary DNA base
  5. RNA polymerase moved along the strand of nucleotides forming single standed pre-mRNA
  6. mRNA carries complementary codons
  7. at the end of the sequence mRNA is detached and DNA rewinds
  8. mRNA leaves nucleus where it attaches to ribosomes
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9
Q

What does DNA helicase do?

A

unwinds and unzipps the DNA helix by breaking the H bonds between bases

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10
Q

What does RNA polymerase do?

A

bonds together the RNA nucleotides by phosphodiester bonds to create a new RNA polymer of the genes thats been copied

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11
Q

Why is the mRNA in transcription called pre-mRNA?

A

it has to be modified before it can leave the nucleus

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12
Q

What is splicing?

A

removing introns

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13
Q

What protein is responsible for Splicing?

A

a splicesome

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14
Q

how does a splicesome work?

A

attaches to DNA
it splices and breaks the phosphodiester bonds so therefore splices out the introns

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15
Q

What happens during translation?

A

the polypeptide chain is created using the mRNA base sequence and the tRNA

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16
Q

Where does translation occur?

A

in the cytoplasm

17
Q

What is thr role of the ribosome in translation?

A

it holds the mRNA and tRNA in place

18
Q

How many tRNA molecules can the ribosome hold at one time?

A

2

19
Q

Why is ATP required in translation?

A

to make the peptide bond between amino acids

20
Q

where does splicing occur?

A

in the nucleus

21
Q

What is made after splicing?

A

mature-mRNA

22
Q

In what type of cell does splicing occur in?

A

eukaryotes

23
Q

What are the differences of DNA replication and transcription?

A

DNA polymerase in DNA rep, RNA polymerase in transcript
1 template strand in transcript, 2 template strands in DNA rep
free DNA nucleotides in rep, free RNA nucleotides in transcript

24
Q

What is the process of translation?

A
  1. mRNA attaches to the ribosome
  2. tRNA brings its specific amino acid
  3. tRNA anticodon are complementary to mRNA codon
  4. another tRNA molecule brings its amino acid to the mRNA codon at the ribosome site
  5. amino acids join together by peptide bonds with the use of ATP
  6. ribosome moves along to the next codon and the process repeats until a stop codon is reached, forming a polypeptide chain,
25
Q

Where is the amino acid attachmtn site on the tRNA?

A

at the opposite end to its anticodon

26
Q

What indicates what direction the mRNA should be read?

A

a start codon

27
Q

what is a proteome?

A

The number of different proteins the genome can code for

28
Q

What occurs during post transcriptional modification?

A
  1. removal of methionine from the start of the primary structure
  2. RER buds off as transport vesibles containing the polypeptide to be transferred to the golgi body
29
Q

What happens to the polypeptide in the golgi body?

A
  1. chemical modification - adding a functional group
  2. packages it into lysosomes or secretory vesicles
30
Q

What do lysosomes do?

A

contain hydrollytic enzymes, lysosymes, that digest the bacterial cell wall made of murein

31
Q

What is the chemical group on the end of the polypeptide chain?

A

the amine group

32
Q

How are tRNA and mRNA similar?

A

single stranded
adenine and uracil base pair
made of ribose
unpaired bases

33
Q

How are tRNA and mRNA different?

A

H bonds in tRNA, phosphodiester bonds in mRNA
clover structure in tRNA
amino acid attachment point in tRNA

34
Q

What is meiosis also known as?

A

reduction divison

35
Q

Why is meiosis referred to as reduction division?

A

the number of chromosomes halves

36
Q

How are amino acids added to a polypeptide chain during translation?

A

TRNA brings specific amino acid to ribosome

Anticodon on tRNA binds to codon

Amino acids join by condensation reaction

37
Q

What are 2 molecules ribosomes are made of?

A

nucleic cids and proteins

38
Q

What is the role of a ribosome during in the formation of a poylypeptide?

A
  1. mRNA binds to ribosome
  2. codons at the binding site
  3. allows tRNA with anticodons to bind
  4. catalyses formation of peptide bond between amino acids
  5. moves along mRNA to next codon

Biology A level (27 decks)

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