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biology lec 01 - molecular biology and DNA > DNA > Flashcards

DNA Flashcards

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1
Q

What is A Genome?

A

the totality of genetic information that is encoded in the DNA or RNA for some viruses.

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2
Q

why do we have different characteristics?

A

Each one of us has his own genetic information (DNA)

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3
Q

All living things are grouped into three domains:

A

Eukaryotes,Prokaryotes and Archea

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4
Q

what does (eu)(karyotes) mean?

A

eu means true, and karyotes stands for nucleus so true nucleus (in eukaryotes Dna is contained in a nucleus)

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5
Q

what does (Pro)(Karyotes) mean?

A

Pro means before, and karyotes stands for nucleus so before nucleus (in prokaryotes Dna is not contained in a nucleus)

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6
Q

what is generally more advanced, a Eukaryotic cell or a Prokaryotic cell?

A

Eukaryotic cell

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7
Q

what separates the nucleus from the rest of the cell (cytoplasm)?

A

a membrane called nuclear envelope

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8
Q

define chromosomes

A

structures that are considered carriers of genetic material

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9
Q

the genetic material is distributed along one chromosome or multiple chromosomes?

A

multiple chromosomes, with the number of chromosomes varying from species to another.

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10
Q

is eukaryotic DNA linear ?

A

Yes

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11
Q

what is the name of the proteins that are complexed within eukaryotic DNA?

A

histones

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12
Q

what does DNA stand for

A

Deoxyribonucleic acid

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13
Q

what is the term used to describe the structure of DNA

A

Double-helix

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14
Q

what is the main role of DNA

A

the long term storage of genetic instructions used in the development and functioning of all known living organisms and some
viruses

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15
Q

what is the double helix derived from

A

two polynucleotide chains that coil around each other

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16
Q

what is DNA often compared to?

A

DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules.

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17
Q

how many chromosomes do humans have in each cell

A

46

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18
Q

what are genes

A

DNA segments that carry genetic information.

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19
Q

what is a nucleotide

A

A nucleotide is the basic building block of nucleic acids (RNA and DNA)

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20
Q

what are the 3 things that make up a nucleotide

A

pentose sugar (Ribose in RNA and Deoxyribose in DNA), nitrogenous base and phosphate group.

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21
Q

what is a nucleoside

A

a nucleotide that has had all its phosphate groups removed

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22
Q

what are the 4 bases in DNA

A

adenine, guanine, cytosine, thymine

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23
Q

what are the 4 bases in RNA

A

adenine,guanine,cytosine, Uracil

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24
Q

how does uracil differ from thymine

A

it is lacking a methyl group on its ring

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25
Q

what type of bases are adenine and guanine

A

purines (fused five and six membered heterocyclic compounds)

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26
Q

what type of bases are cytosine and thymine

A

pyrimidines( six membered rings)

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27
Q

In living organisms, does DNA typically exist as a single molecule or as a pair of tightly held molecules?

A

DNA does not usually exist as a single
molecule, but instead as a pair of molecules that are held tightly
together.

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28
Q

What shape do the two long strands of DNA form when held together?

A

double helix

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29
Q

In a double helix, how is the direction of the nucleotides in one strand oriented compared to the other strand?

A

In a double helix the direction of the nucleotides in one strand
is opposite to their direction in the other strand: the strands are
antiparallels with asymmetric ends.

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30
Q

What is the term used to describe the opposing orientation of DNA strands in a double helix?

A

the strands are said to be antiparallel

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31
Q

What are the asymmetric ends of DNA strands called?

A

they are called the 5’ and 3’ ends

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32
Q

What group is found at the 5’ end of a DNA strand, and what group is found at the 3’ end?

A

the 5’ end having a terminal phosphate group and
the 3’ end a terminal hydroxyl group.

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33
Q

What is the term for the specific bonding between one type of base on one DNA strand and its corresponding base on the other strand?

A

complimentary base pairing

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34
Q

Which type of base forms hydrogen bonds with pyrimidines in complementary base pairing?

A

purines

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35
Q

In complementary base pairing, which base does adenine (A) bond with, and which base does cytosine (C) bond with?

A

with A bonding only
to T, and C bonding only to G.

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36
Q

What is the arrangement of two nucleotides binding together across the double helix called?

A

base pair

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37
Q

Why can hydrogen bonds between base pairs be broken and rejoined relatively easily?

A

they are not covalent bonds

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38
Q

Why are DNA’s two strands considered complementary to each other?

A

because the nucleotide sequence
of one strand determines the sequence of another strand

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39
Q

How does the nucleotide sequence of one DNA strand determine the sequence of the other strand?

A

due to complimentary base pairing

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40
Q

If one DNA strand has the sequence 5’-ACT-3’, what is the sequence of the complementary strand?

A

3’ -TGA- 5’

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41
Q

What base pairing rule do DNA strands follow, specifically with A
and C
pairings?

A

Note that they obey the (A:T) and (C:G) pairing rule.

42
Q

Why does a DNA database only need to store the sequence of one strand?

A

because If we
know the sequence of one strand, we can deduce the sequence
of another strand.

43
Q

By convention, which strand’s sequence is referred to in a DNA database, and in which direction is it written?

A

5’ to 3’ strand (left to right).

44
Q

When is a DNA sequence referred to as the “sense” strand?

A

A DNA sequence is called “sense” if its sequence is the
same as that of a messenger RNA copy that is translated
into protein

45
Q

What is the sequence on the opposite strand of the “sense” strand called?

A

The sequence on the opposite strand is called
the “antisense” sequence.

46
Q

what is transcription

A

it is the process in which DNA is copied or is converted to mRNA

47
Q

what is translation

A

the process by which a cell makes proteins using the genetic information carried in messenger RNA (mRNA)

48
Q

What is the process called when DNA is twisted like a rope?

A

This process is called DNA supercoiling.

49
Q

In its “relaxed” state, how often does a DNA strand circle the axis of the double helix?

A

In its relaxed state, a DNA strand circles the axis once every 10.4 base pairs.

50
Q

What is positive supercoiling, and how does it affect the DNA?

A

Positive supercoiling occurs when the DNA is twisted in the same direction as the helix (counterclockwise), causing the bases to be held more tightly together.

51
Q

What is negative supercoiling, and how does it affect the DNA?

A

Negative supercoiling happens when the DNA is twisted in the opposite direction of the helix, which makes the bases come apart more easily.

52
Q

What type of supercoiling is most common in nature, and which enzymes introduce it?

A

Most DNA in nature has slight negative supercoiling, which is introduced by enzymes called topoisomerases.

53
Q

What is the biological function of negative supercoiling in DNA?

A

Negative supercoiling helps facilitate the separation of DNA strands, which is important during processes like transcription and replication.

54
Q

Why is negative supercoiling advantageous for DNA replication?

A

Negative supercoiling is advantageous because it makes DNA easier to unwind, which helps in replication. Positive supercoiling, being more condensed, would make separation more difficult.

55
Q

What role do topoisomerases play in DNA transcription and replication?

A

Topoisomerases help by unwinding the DNA helix, making it easier for the DNA to undergo transcription and replication.

56
Q

What do all the functions of DNA depend on?

A

All the functions of DNA depend on interactions with proteins.

57
Q

How can protein interactions with DNA occur?

A

Protein interactions with DNA can be non-specific, or the protein can bind specifically to a single DNA sequence.

58
Q

What type of proteins can bind specifically to a single DNA sequence?

A

Certain proteins can bind specifically to a single DNA sequence.

59
Q

What is an example of an enzyme that binds to DNA?

A

An example of an enzyme that binds to DNA is polymerase.

60
Q

What do polymerases do when they bind to DNA?

A

Polymerases copy the DNA sequence during transcription and DNA replication.

61
Q

What holds DNA within chromosomes?

A

DNA is held in complexes with structural proteins within chromosomes.

62
Q

What do structural proteins do to DNA

A

Structural proteins organize DNA into a compact structure called chromatin.

63
Q

How is DNA organized in eukaryotes?

A

In eukaryotes, DNA binds to small basic proteins called histones, forming chromatin.

64
Q

How does DNA organization differ between eukaryotes and prokaryotes?

A

In eukaryotes, DNA binds to histones, while in prokaryotes, multiple types of proteins are involved in organizing DNA.

65
Q

What is the structure formed by histones and DNA?

A

Histones form a disk-shaped complex with DNA called a nucleosome.

66
Q

How do histones bind to DNA?

A

Histones bind to DNA through non-specific interactions, where the basic residues of histones form ionic bonds with the acidic sugar-phosphate backbone of DNA.

67
Q

What type of interaction occurs between histones and DNA?

A

The interaction is non-specific and involves ionic bonds between the basic residues in histones and the acidic sugar-phosphate backbone of DNA. This allows histones to organize and compact the DNA.

68
Q

What is the basic structural unit of DNA packaging in eukaryotes?

A

The basic structural unit of DNA packaging in eukaryotes is the nucleosome.

69
Q

What is the structure of a nucleosome?

A

A nucleosome consists of a segment of DNA wound around eight histone proteins.

70
Q

What is chromatin?

A

Chromatin is the complex combination of DNA and proteins that makes up chromosomes.a

71
Q

Where is chromatin found?

A

Chromatin is found inside the nuclei of eukaryotic cells.

72
Q

What are the major components of chromatin?

A

The major components of chromatin are DNA and histone proteins.

73
Q

What is the function of chromatin?

A

The function of chromatin is to package DNA into a smaller volume so it can fit inside the cell.

74
Q

What is chromatin during cell division?

A

Chromatin is the substance that becomes visible as chromosomes during cell division.

75
Q

What is the basic unit of chromatin?

A

The basic unit of chromatin is the nucleosome, which is composed of 146 base pairs (bp) of DNA and eight histone proteins.

76
Q

How does the structure of chromatin change?

A

The structure of chromatin changes dynamically, at least in part, depending on the need for transcription.

77
Q

What happens to chromatin during the metaphase of cell division?

A

During metaphase, chromatin condenses into visible chromosomes.

78
Q

What is the state of chromatin when the cell is not dividing?

A

When the cell is not dividing, chromatin is less condensed.

79
Q

What is heterochromatin?

A

Heterochromatin is a tightly packed form of chromatin that is generally transcriptionally inactive, meaning it is not usually involved in gene expression.

80
Q

What is euchromatin?

A

Euchromatin is a loosely packed form of chromatin that is transcriptionally active, allowing for gene expression.

81
Q

How do heterochromatin and euchromatin differ in their structure?

A

Heterochromatin is more condensed, making it tightly packed, while euchromatin is less condensed and more open.

82
Q

What are histones?

A

Histones are proteins closely associated with DNA molecules.

83
Q

What is the function of histones?

A

Histones have two main functions: they play a role in the structure of chromatin and are important in the regulation of gene expression.

84
Q

How many types of histones have been identified?

A

Five types of histones have been identified: H1 (or H5), H2A, H2B, H3, and H4.

85
Q

What role do H1 and H5 histones play?

A

H1 and its homologous protein H5 are involved in the formation of higher-order chromatin structures.

86
Q

What role do the other four types of histones play?

A

The other four types of histones (H2A, H2B, H3, and H4) associate with DNA to form nucleosomes.

87
Q

How are histones organized into superclasses?

A

Histones are organized into two superclasses: core histones (H2A, H2B, H3, and H4) and linker histones (H1 and H5).

88
Q

What types of amino acids are abundant in histones?

A

Histones contain a high proportion of basic amino acids, specifically arginine and lysine, which help facilitate binding to the negatively charged DNA molecule.

89
Q

What is the role of linker histones?

A

Linker histones (H1 and H5) bind to the DNA that enters and exits the nucleosome and help shift the equilibrium of chromatin toward a more condensed, higher-order structure.

90
Q

Which histones are considered core histones, and what is their function?

A

Core histones include H2A, H2B, H3, and H4. They associate with DNA to form nucleosomes, the basic units of chromatin.

91
Q

How do linker histones affect chromatin structure?

A

Linker histones promote the formation of more condensed, higher-order chromatin structures, which play a role in chromatin organization and gene regulation.

92
Q

How is a nucleosome core particle formed?

A

Two of each core histone (H2A, H2B, H3, and H4) assemble to form a nucleosome core particle by wrapping 146 base pairs of DNA around the histone proteins in a 1.65 left-handed super-helical turn.

93
Q

What is the role of the linker histone H1?

A

The linker histone H1 binds the nucleosome and the entry and exit sites of the DNA, locking the DNA in place and allowing the formation of higher-order chromatin structures.

94
Q

how many base pairs of DNA are wrapped around the nucleosome core particle?

A

146 base pairs of DNA are wrapped around the nucleosome core particle.

95
Q

What structural change does the linker histone H1 facilitate?

A

The linker histone H1 facilitates the formation of higher-order chromatin structures by locking the DNA into place around the nucleosome.

96
Q

What is a chromosome?

A

A chromosome is an organized structure of DNA and protein found in cells.

97
Q

What does a chromosome contain?

A

A chromosome contains a single piece of coiled DNA that includes many genes, regulatory elements, and other nucleotide sequences.

98
Q

What role do DNA-bound proteins play in chromosomes?

A

DNA-bound proteins in chromosomes serve to package the DNA and control its functions.

99
Q

What type of chromosome do prokaryotes typically have?

A

Prokaryotes, including bacteria and archaea, typically have a single circular chromosome.

100
Q

Are there variations in prokaryotic chromosomes?

A

Yes, there are many variations of prokaryotic chromosomes.

101
Q

How does the size of prokaryotic chromosomes vary?

A

The size of prokaryotic chromosomes differs from species to species, measured in base pairs.

biology lec 01 - molecular biology and DNA (3 decks)

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