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Biology sem 1 > 1.5: DNA and Protein Synthesis > Flashcards

1.5: DNA and Protein Synthesis Flashcards

1
Q

What is nucleic acid?

A

A polymer of nucleotide molecules

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2
Q

What is the definition of DNA?

A

a polymer of nucleotide molecules that form the instructions for the synthesis of proteins found within organisms. These nucleotides contain the 5-carbon sugar deoxyribose.

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3
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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4
Q

What does RNA stand for?

A

Ribonucleic acid

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5
Q

What is the definition of RNA

A

a single stranded polynucleotide molecule that exists in 3 forms. Each plays the part in the synthesis of proteins

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6
Q

What is a nucleotide?

A

The monomer of nucleic acids consisting of a phosphate, a sugar and a nitrogenous base.

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7
Q

What is ribose?

A

The 5-carbon (pentose) sugar found in RNA nucleotides

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8
Q

What is the structure of deoxyribose?

A

The 5-carbon sugar found in DNA nucleotides.

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9
Q

What Is the structure and definition of purine?

A

Adenine and Guanine – nitrogenous bases consisting of a double ring structure

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10
Q

What is the definition and structure of pyrimadine?

A

Thymine, Cytosine and Uracil – nitrogenous bases consisting of a single ring structure.

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11
Q

What is a polynucleotide?

A

A polymer consisting of many nucleotide monomers covalently bonded together, e.g. DNA or RNA.

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12
Q

What are the base-pairing rules?

A

Between nitrogenous bases in nucleic acids. A pairs with T (or U) and G pairs with C.

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13
Q

What is messenger RNA (mRNA)

A

a type of RNA polynucleotide involved in protein synthesis. Carries the information coding for a polypeptide from the nucleus to the ribosomes in the cytoplasm

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14
Q

What is transfer RNA (tRNA)

A

a type of RNA polynucleotide involved in protein synthesis. It transports amino acids to the ribosomes to be added to the growing polypeptide chain
Found in the cytoplasm

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15
Q

What is a gene?

A

A length of DNA that carries the code for the synthesis of one (or more) specific polypeptides.

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16
Q

How do the two polynucleotide strands in a DNA molecule run?

A

In opposite directions, Anti-parallel

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17
Q

What is semi-conservative replication?

A

The replication of a DNA strand where the 2 strands unzip, and a new strand is assembled onto each ‘conserved’ strand according to the complementary base-pairing rules. The replicated double helix consists of one old strand and one new strand.

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18
Q

What is the double helix?

A

Describes the structure of DNA, a twisted helix of 2 strands with bases joining the strands.

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19
Q

What are the 2 types of nucleic acid?

A

DNA –Deoxyribonucleic Acid
RNA – Ribonucleic Acid

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20
Q

What are the two types of nucleic acid also known as?

A
  • macromolecules
  • polymers
  • polynucleotides (because they are made up of smaller subunits called nucleotides)
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21
Q

What are the monomers of nucleic acids?

A

nucleotides

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22
Q

What are nucleotides made up of?

A
  • Phosphate group
  • Pentose sugar - deoxyribose or ribose
  • Nitrogen-containing base (organic base)
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23
Q

how many different nitrogen containing bases are there?

A

five

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24
Q

What groups are the nitrogen containing bases?

A

purine bases
pyrimidine bases

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25
Q

What are the purine bases?

A

Adenine
Guanine

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26
Q

What are the pyrimidine bases?

A
  • Thymine
  • Cytosine
  • Uracil
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27
Q

What are the 4 bases in DNA?

A

Adenine and Thymine
Cytosine and Guanine

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28
Q

What are the 4 bases in RNA?

A

Cytosine and Guanine
Adenine and Uracil

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29
Q

What is the structure of DNA?

A
  • Double stranded polynucleotide
  • Nucleotides together joined by condensation reactions between the deoxyribose sugar of one nucleotide and the phosphate group of another. (sugar-phosphate backbone)
  • The nitrogen-containing bases point sideways
30
Q

Where is most DNA found in eukaryotic cells?

A

in the nucleus

31
Q

How are the bases held together?

A

by hydrogen bonds

32
Q

What are the rules between purine and pyrimidine bases?

A

A purine base must always be opposite a pyrimidine base

33
Q

What is the complementary base pairing between Adenine…
and
Cytosine…

A

Adenine always pairs with Thymine

and

Cytosine always pairs with Guanine

34
Q

How many bonds link cytosine and guanine?

A

three

35
Q

How many hydrogen ions link adenine and thymine?

A

Two

36
Q

What are the three types of RNA?

A
  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)
  • Transfer RNA (tRNA)
37
Q

What is the difference in nitrogenous base between DNA and RNA

A

RNA contains the nitrogenous base Uracil instead of Thymine

38
Q

Is RNA double or single stranded?

A

single stranded

39
Q

How does mRNA structure and movement occur?

A
  • long single strand formed into
    a helix
  • Made in the nucleus
  • Passes into cytoplasm
  • Moves to the ribosomes
40
Q

Where is rRNA made, found and roles?

A
  • Made in the nucleolus
  • Found in the cytoplasm
  • Forms ribosomes
  • Ribosomes are made of rRNA & protein
41
Q

What is the role, structures of tRNA?

A
  • Forms clover-leaf shape.
  • One end attaches to a specific amino acid
  • The other end has a triplet of bases used in protein synthesis,
    called the ANTICODON
42
Q

How does DNA replication work?

A
  • When cells divide, each new cell must receive an IDENTICAL copy of the genetic material.
  • DNA must be able to copy itself exactly to form 2 new DNA molecules.
  • This is called DNA replication and it takes place during INTERPHASE in the cell cycle
43
Q

What is the DNA replication process?

A
  • Two strands of DNA must unwind and split apart, hydrogen bonds break.
  • Next, free complementary nucleotides line up against the DNA strands. The nucleotides are first activated by extra phosphate groups
  • The enzyme DNA Polymerase joins them together forming 2 new DNA molecules
44
Q

What were the three theories in the 1950s on semi-conservative replication?

A
  • Conservative replication
  • Dispersive replication
  • Semi-conservative replication
45
Q

What evidence did the meselsohn and stahl produce?

A
  • that each DNA strand serves as a template for the synthesis of the new strands.
  • And each of the 2 DNA molecules produced consist of a) an original strand and
    b) a new strand.
45
Q

What scientists caused the semi-conservative theory of replication to be accepted?

A
  • meselsohn
  • stahl
46
Q

How did meselsohn and stahl use to demonstrate the DNA strands?

A

used the bacteria Escherichia coli (E.coli) and two Nitrogen isotopes – N14 (light) & N15 (heavy)

47
Q

What did the experiment carried out by meselsohn and stahl involve?

A
  • First the E.coli were grown on a media containing N15 (heavy isotope) for many generations.
    So all the nitrogenous bases contained N15.
  • They then separated the DNA using centrifugation and only 1 heavy band was obtained
  • E.coli was then transferred to media containing N14 (light isotope) and allowed to replicate for 1, 2 and 3 generations.
  • Some of the DNA from each generation was extracted and centrifuged.
48
Q

What were the results of the experiment conducted by meselsohn and stahl

A
49
Q

How does DNA control all the cell’s activities

A
  • Chemical reactions control the cells activities
  • All chemical reactions in the cell are controlled by enzymes
  • Enzymes are proteins
  • The sequences of bases on the DNA make up codes for particular protein molecules
50
Q

What does the shape and florin of the protein depend on

A

The exact sequence of Amino acids - primary structure

51
Q

What does the sequence of bases in the DNA molecule control?

A

the exact sequence in which the amino acids join together when a protein is made on the ribosomes

52
Q

What is the triplet code?

A
  • 20 different amino acids, which each are coded by a sequence of 3 bases on the DNA molecule
  • each set of three bases is called a codon
  • sequence of DNA is read in a particular direction and only one of the two strands are used.
53
Q

Why do you use three bases in the triplet code?

A

because each base can not code for 1 amino acids.
There’s 20 different AA, if there were only 2 base pairs 16 different codes are possible

if a comb of 3 bases pairs or triplet codes are used there are 64 different codes. More than enough for 20 AA

After a series of experiments using RNA, the triplet code for each AA was determined

54
Q

What is the degenerate code?

A

discovered that there is more than one triplet code for most amino acids

55
Q

What is a stop codon?

A

3 particular codons that did not code for amino acids at all

56
Q

What is the codon AUG usually called?

A

the start codon

57
Q

What is CUGAGCUAG read as?

A

CUG-AGC-UAG
(non-overlapping)

58
Q

How many genes do humans have as an estimate?

A

14000

59
Q

Where are Amino acids found?

A

found in the cytoplasm

60
Q

What is the shape and structure of tRNA?

A

chain of nucleotides, in the shape of a clover leaf. Each molecule has a different triplet of bases called an anticodon (different for each AA)

61
Q

What is at the other end of every tRNA molecule?

A

a triplet CCA, this is where the amino acid attaches. The tRNA molecule picks up its AA and moves towards the ribosomes.

62
Q

What is translation process?

A
  • The mRNA has already passed from the nucleus to the endoplasmic reticulum by moving through the nuclear pores and entering the cytoplasm
  • the mRNA molecule attaches to a ribosome, the genetic code of mRNA is translated into a AA sequence
63
Q

What is the second stage of the translation process (from AA sequence)

A
  • tRNA molecules bind with the exposed bases of the mRNA.
  • The ribosome holds two amino acids together as a peptide bond forms.
  • This is catalysed by an enzyme.
  • The ribosome moves along the mRNA, and “reads” the next codon.
  • The tRNA is released and passes back to the cytoplasm to pick up another amino acid.
  • The polypeptide chain continues to grow until a “stop” codon is reached.
  • A new protein molecule has been formed!
64
Q

What is an overall summary of protein synthesis?

A
  • A mRNA strand is made of the gene, using ONE strand of the DNA as a template
  • mRNA passes out to cytoplasm and binds to a ribosome
  • The ribosome moves along the mRNA and reads the mRNA codons
  • tRNA molecules bring the correct amino acids to the ribosome, through complementary binding between anticodon and mRNA codon
  • The polypeptide strand is built up
65
Q

Protein synthesis, how does it work?

A
  • proteins are formed using ribosomes in the cytoplasm of a cell
  • the info codes for proteins in the nucleus
  • DNA is too large to move out of the nucleus to the ribosomes
  • info is sent from the DNA to the cytoplasm for transcription
66
Q

What is transcription?

A

where Information in DNA is used to build a molecule of RNA (Ribonucleic acid)

This messenger RNA (mRNA) takes a “message” from the DNA to ribosomes in the cytoplasm.


67
Q

What is the difference between DNA and RNA?

A
  • The pentose sugar in RNA is Ribose not Deoxyribose

  • The nitrogen containing base Thymine is replaced with Uracil.
68
Q

What is the process of Transcription?

A
  • The DNA double helix unwinds and unzips at the start of the gene.

  • Hydrogen bonds between base pairs break and the bases are exposed.
  • Free activated RNA nucleotides align with the exposed DNA nucleotides. On one strand of the DNA molecule only. (template)
  • RNA Polymerase links the RNA
69
Q

What is the second process of transcription (after enzyme links)?

A
  • As the single strand of mRNA forms, the DNA helix reforms behind it.

  • The mRNA molecule contains triplets of bases called codons based on the DNA sequence
  • The mRNA molecule is 
small enough to leave 
the nucleus through a nuclear pore in the 
nuclear envelope.

  • Finally the mRNA 
attaches to a Ribosome 
– (often on the RER).

Biology sem 1 (9 decks)

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