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biology > 2.1 - 2.13 DNA & protein synthesis, genetic code > Flashcards

2.1 - 2.13 DNA & protein synthesis, genetic code Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

mononucleotides

A

the building blocks of DNA & RNA, made up of nitrogenous base, phosphate group and pentose sugar

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2
Q

nucleic acids

A

mononucleotides joined together by condensation reaction that produce phosphodiester bond (sugar-phosphate backbone)

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3
Q

purines

A

nitrogenous bases with two nitrogen-containing rings, adenine and guanine

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4
Q

pyrimindines

A

nitrogenous bases with one nitrogen-containing ring, cytosine, uracil, thymine

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5
Q

conservative replication

A

it is the falsified model of DNA replication. the original double helix remains intact and in some way instructs the formation of new identical double helix made uip of entrely new material

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6
Q

semiconservative replication

A

the accepted model of DNA replication. the DNA unzips and new nucleotides align along each strand; each new double helix contains one strand of the orginal DNA and one made up of new material

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7
Q

DNA helicase

A

it is an enzyme that unzips the two strands of DNA by

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8
Q

DNA ligase

A

it is an enzyme that catalyses the formation of phosphodiester bonds between the nucleotides

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9
Q

DNA polymerase

A

it is an enzyme that lines up the new nucleotides along the DNA template strand

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10
Q

gene

A

a sequence of bases on a DNA molecule which codes for a sequence of amino acids in a polypeptide chain that affects a characteristic in a phenotype of the organism

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11
Q

codon

A

a sequence of 3 bases on DNA and RNA

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12
Q

anticodon

A

a sequence of three bases on tRNA that are complementary to the bases in the mRNA codon

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13
Q

start codon

A

a codon that indicates the start of the amino acid chain (AUG), it codes for methionine amino acid

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14
Q

stop codon

A

a codon that indicates the end of the amino acid chain

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15
Q

transcription

A

it is the process by which the DNA sequence is used to make a strand of mRNA in the nucleus

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16
Q

where does transcription take place?

A

it takes place in the nucleus

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17
Q

translation

A

the process by which the DNA code is converted into a protein from the mRNA strand made in the nucleus

18
Q

what makes up ribosomes?

A

they are made up of RNA molecules and proteins, and consists of one large and one small subunit

19
Q

what does the large subunit of ribosomes do?

A

it is the binding site for tRNA

20
Q

what does the small subunit of ribosomes do?

A

it binds to mRNA

21
Q

tRNA

A

they are small units of RNA that pick up specific amino acids frin the cytoplasm and transport them to the surface of the ribosome to align with mRNA

22
Q

mRNA

A

they are the RNA formed in the nucleus that carries the genetic code out into the cytoplasm

23
Q

complementary strands

A

the strands of RNA formed that complements the DNA acting as the coding strand

24
Q

sense strand

A

carries the genetic code for protein to be produced, it is the same as mRNA except thymine is changed to uracil

25
Q

antisense strand/ template strand

A

the place where mRNA forms, acts as the the template for an mRNA molecule

26
Q

RNA polymerase

A

the enzyme that polymerises the nucleotides to form RNA in a sequence determined by the antisense strand of DNA

27
Q

what is the nature of the genetic code?

A

it is a triplet code that is non-overlapping and degenerate

28
Q

what does non-overlapping code mean?

A

it means each codon only codes for 1 amino acid with no overlap between codons

29
Q

what does degenerate code mean?

A

it means different codons can translate for the same amino acid

30
Q

what are the benefits of having a degenrate code?

A

even if the final base in the triplet is changed, the mutation could still produce the same amino acid and have no effect on the organism

31
Q

what are the benefits of having a non-overlapping code?

A

a change in a single nucleotide mutation would affect only one amino acid instead of three, if it were overlapping

32
Q

what is point mutation?

A

it is a change in a single base of the DNA code

33
Q

what is non-coding DNA?

A

they are DNA that do not code for amino acids

34
Q

why triplet code?

A

because a triplet code of three bases gives 4x4x4=64 possible combinations which are more than enough for 20 amino acids that are coded for

35
Q

how is DNA replicated?

A

when DNA replicates, the two strands of the DNA molecule ‘unzip’ along the line of hydrogen bonds and unravel bythe enzyme DNA helicase. the strands act as templates for the new DNA strands.
the exposed bases attract free DNA nucleotides and new hydrogen bonds are formed between matching base pairs. DNA polymerase lines up and catalyses the linking up of the nucleotides along the template strand. DNA ligase catalyses the fomrmation of phosphodiester bonds between the two strands of DNA.
the result is two new strands of DNA identical with the original piece. the new molecules automatically coil up into the double helix as weak hydrogen bonds form within the structure.

36
Q

what is the process of Meselson and Stahl’s experiment?

A

DNA from bacteria was grown in a medium containing only 15N, after a few generations, the entire bacterial DNA was made using 15N.
the bacteria was then moved to a medium containing only 14N, after 1 round of replication, the bacterial DNA contained 50% 15N & 14N.
after a second round of replication, the DNA appeared as 2 bands, one in the hybrid (half 14N half 15N) band position & one in the position of DNA with only 14N.

37
Q

what are the functions of RNA in protein synthesis?

A
  1. it carries the instructions for a polypeptide from the DNA in the nucleus to the ribosomes where proteins are made
  2. it picks up specific amino acids form the protoplasm and carries them to the surface of the ribosomes
  3. it makes up the bulk of the ribosomes themselves
38
Q

what are the differences between RNA and DNA?

A
  1. it contains a different sugar (ribose vs deoxyribose)
  2. it contains a different base (uracil vs thymine)
  3. it has a single helix instead of a double helix
38
Q

what are the differences between RNA and DNA?

A
  1. it contains a different sugar (ribose vs deoxyribose)
  2. it contains a different base (uracil vs thymine)
  3. it has a single helix instead of a double helix
39
Q

what are polysomes?

A

they are groups of ribosomes, joined by a thread of mRNA that can produce large quantities of a particular protein

40
Q

how is protein synthesised?

A

the genetic code of the DNA of the nucleus is transcribed onto mRNA. this mRNA moves out of the nucleus into the cytoplasm and becomes attached to a ribosome. molecules of tRNA carry individual amino acids to the surface of the ribosome. the tRNA anticodon lines up beside a complementary codon in the mRNA, held in place by hydrogen bonds, while enzymes link the amino acids together. the tRNA then breaks away and returns to the cytoplasm to pick up another amino acid. the ribosome moves along the molecule of mRNA until it reaches the stop codon at the end, leaving a completed polypeptide chain. the message may be read again and again.

41
Q

how is mRNA made in the nucleus during transcription?

A

The sense strand of the DNA strand carries the code for the protein to be formed, but the mRNA forms on the antisense strand of the DNA, also called the template strand. it allows the code of the mRNA to reflect the sense code of the DNA. The mRNA which is formed codes for a polypeptide. Part of the DNA unravels and unzips, exposing the bases which act as a template. Beginning at a start codon, which is also the code for methionine. RNA nucleotides align along the exposed sequence of DNA bases in the normal complementary fashion. Then RNA polymerase joins the chain of RNA nucleotides together. The process ends when the chain reaches a stop codon and the mRNA chain separates from the DNA template, allowing the DNA chains of the double helix to re-join.

biology (9 decks)

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