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nucleotides Flashcards

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Biology 101 flashcards
1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

What does RNA stand for?

A

ribonucleic acid

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3
Q

What is the monomeric unit for nucleic acids?

A

Nucleotides

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4
Q

What are the 3 components of a nucleotide?

A
  • phosphate group
  • pentose (5 carbon sugar) either deoxyribose or ribose
  • nitrogenous base
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5
Q

Name the 5 nitrogenous bases

A
  • thymine
  • guanine
  • adenine
  • cytosine
  • uracil
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6
Q

Name the 4 bases present in DNA

A
  • thymine
  • adenine
  • guanine
  • cytosine
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7
Q

Name the 4 bases present in RNA

A
  • uracil
  • adenine
  • guanine
  • cytosine
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8
Q

Which base is never found in DNA?

A

Uracil

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9
Q

Which base is never found in RNA?

A

Thymine

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10
Q

How are polynucleotides formed?

A
  • condensation reactions occur
  • between the phosphate on carbon 5 of one nucleotide and the hydroxyl group on carbon 3 of another nucleotide
  • water is released
  • phosphodiester bond formed
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11
Q

What sort of bond is formed between nucleotides?

A

Phosphodiester

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12
Q

How are sequences of RNA/DNA given?

A

From the 5’ end to 3’ end

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13
Q

What are the two types of bases?

A

Purines and pyrimidines

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14
Q

What is the structure of purines?

A

two carbon-nitrogen rings

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15
Q

What is the structure of pyrimidines?

A

one carbon-nitrogen ring

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16
Q

Which bases are purines?

A

Adenine and guanine

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17
Q

Which bases are pyrimidines?

A

Cytosine, thymine, and uracil

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18
Q

What does complementary base pairing allow?

A

-DNA to be copied and transcribed

19
Q

What type of bonds hold bases together?

A

Hydrogen bonds

20
Q

How many hydrogen bonds form between Adenine and Uracil/Thymine?

A

2

21
Q

How many hydrogen bonds form between Guanine and Cytosine?

A

3

22
Q

In order to allow for the bases to form hydrogen bonds what must happen to one of the polynucleotide chains?

A

It must be rotated through 180 degrees

23
Q

How does the sugar phosphate backbone run on one of the polynucleotide chains? How does the other polynucleotide chain run? What is this called?

A

From 5’ to 3’ and the other from 3’ to 5’

The antiparallel nature of DNA

24
Q

describe the double helix nature of DNA

A

two DNA polynucleotide strands join together by hydrogen bonding
eacg base can inly join with one particular base- complementary base pairing
two anti parallel polynucleotide strands twist to form DNA molecule

25
Q

Describe the steps involved in extracting DNA

A
  • sample ground up using pestle and mortar
  • sample mixed with detergent
  • salt is added
  • protease is added
  • ice cold ethanol is added down the side of the test tube
26
Q

Why is the sample ground in the extraction of DNA?

A

it breaks down the cell walls

27
Q

Why is detergent added to the sample in the extraction of DNA?

A

breaks down the cell membrane, releasing the cell contents into solution

28
Q

Why is salt added to the sample in the extraction of DNA?

A

neutralises charges on phosphates in sugar phosphate backbone
breaks the hydrogen bonds between DNA and water
makes DNA less soluble

29
Q

Why is protease added to the sample in the extraction of DNA?

A

breaks down the proteins associated with DNA

30
Q

Why is ethanol added to the sample in the extraction of DNA?

A

Causes the DNA to form a white precipitate between the layer of the sample and the ethanol

31
Q

Why is a low temperature maintained throughout the process of DNA extraction?

A

Reduces rate of enzyme controlled reactions that break down DNA

32
Q

steps for DNA replication

A
  1. DNA helicase breaks the hydrogen bonds between the two polynucleotide DNA strands. The helix unzips to form two single strands
  2. each orginal strand acts as a template for a new strand. free roaming DNA nucleotides join to the exposed bases on each original strand by complementary base pairing
  3. the nucleotides of the new strands are joined together by DNA polymerase forming phosphodiester bonds which forms the sugar-phosphate back bone. hydrogen bonds form between the bases on the original and new strand. the strand twists to form a double helix
  4. each bew DNA molecule contains one strand from the original DNA molecule and one new strand. semi conservative
33
Q

what is a gene

A

a sequence of DNA nucleotides that codes for a protein

34
Q

why does transcription need to occur

A

DNA molecules are found in the nuclues but the ribosomes are found in the cytoplasm
DNA is too large to move out of the nucleus so a section is copied into mRNA which is small enough to leave through the nuclear pores

35
Q

features mRNA

A

made in nucleus
bases are called codon
it carries the genetic code from the DNA in the nucleus to the cytoplasm where it is used to make a protein

36
Q

features of tRNA

A

found in cytoplasm
it has amino acid binding site at one end and a sequence of three bases at the other end called anticodons
it carries the amino acid that are used to make proteins to the ribosomes during translation

37
Q

features of rRNA

A

forms the two subunit in a ribosome
the ribosome moves along the mRNA strand during protein synthesis
the rRNA in the ribosomes helps to catalyse the formation of peptide bonds between the amino acids

38
Q

the genetic code properties

A

non overlapping- base triplets dont share their bases
triplets-the code in the base sequence is a triplet code which is a sequence of three bases called a codon
degenerate- some amino acids are coded for for more then one base triplet
universal- the same specific base triplet codes for the same amino acids in all living things

39
Q

transription

A
  1. RNA polymerase attaches to the DNA double helix at the beginning of a gene
  2. DNA helicase breaks the hydrogen bonds between the two DNA strands in the gene and the DNA molecule uncoils
  3. the antisense strand is used as a template strand to make an mRNA copy
  4. free roaming RNA nucleotides will base pair with their complementary bases expose on the template strand
  5. RNA polymerase joins the RNA nucleotides together and forms phosphodiester bonds which forms an mRNA molecule
  6. hydrogen bonds reform when RNA polymerase has passed and the strands coil back into a double helix
  7. the mRNA moves out of the nucleus through the nuclear pores and attaches to a ribosome in the cytoplasm
40
Q

translation

A
  1. mRNA attaches itself to a ribose and tRNA molecules carry amino acids to tge ribosomes
  2. a tRNA molecule with an anticodon that’s complementary to the start codon on the mRNA attaches itself to the mRNA by complementary base pairing
  3. a second tRNA molecule attaches to the next anticodon by complementary base pairing
  4. rRNA in the ribosomes catalyses the formation of the peptide bond between the two amino acids attached to the tRNA molecules. This joins the amino acids together. the first tRNA molecule moves away leaving the amino acid behind
  5. Then another tRNA molecule binds to the next codon on mRNA and its amino acid binds to the second amino acid and the second tRNA molecule moves away
  6. this process continues producing a chain of amino acids until there is a stop codon on the mRNA molecule
  7. the polypeptide chain moves away from the ribosome and translation is complete
41
Q

what does ADP (adenosine diphosphate) contain

A

base adenine
sugar ribose
two phosphate groups

42
Q

what does ATP (adenosine triphosphate) contain

A

base adenine
sugar ribose
three phosphate

43
Q

how to form ATP

A

reaction of ADP and inorganic phosphate using energy from energy releasing reactions
the ADP is phosphorylated to form ATP and a phosphate bond is formed

44
Q

how is energy released from ATP

A

energy is stored in the phosphate bond
when energy is needed by a cell ATP is broken down into ADP and inorganic phosphate
energy is released from the phosphate bond and used by cells

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