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Biology H > Unit 1 > Flashcards

Unit 1 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the two strands of DNA held together by?

A

Weak hydrogen bonds between the bases

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2
Q

How do bases pair?

A

complementary base pairing
adenine-thymine
cytosine-guanine

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3
Q

What are the subunits of DNA called?

A

nucleotides

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4
Q

Draw the structure of DNA

A

-phosphate
-deoxyribose sugar
-base
-nucleotide
-3’ end
-5’ end
-weak H2 bond

-sugar forms strong bond with phosphate below: sugar-phosphate backbone
-carbons are numbered 1-5
-double stranded
-anti-parallel: the 2 strands run in opposite directions to each other (5’—>3’ / 3’—>5’)

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5
Q

Prokaryotes

A

organisms which lack a true membrane-bound nucleus e.g. bacteria

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6
Q

Eukaryotes

A

organisms which have a membrane-bound nucleus that stores their genetic material e.g. animal cells

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7
Q

ribosome
nucleus
cell membrane
chloroplast
mitochondria

A

ribosome-site of protein synthesis
nucleus-controls cell division and cell chemistry
cell membrane-controls the movement of materials in and out of cells
chloroplast-site of photosynthesis
mitochondria-site of aerobic respiration

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8
Q

Prokaryote DNA

A

circular chromosome and structures called plasmids

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9
Q

Eukaryote DNA

A

linear chromosomes held inside the nucleus

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10
Q

Where can circular chromosomal be found in eukaryotic cells?

A

mitochondria and chloroplasts

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11
Q

What is special about yeast cells?

A

-Eukaryotic
-Can have plasmids

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12
Q

structure of a linear chromosome (eukaryotes)

A

-DNA
-Histone Protein
-Nucleosome
(beads ion a string-Dna wound on nucleosomes)
-double helix

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13
Q

Why is DNA unique?

A

It can copy itself exactly. This is essential for replication of chromosomes before any cell division

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14
Q

Semi conservative?

A

DNA replication is semi conservative-each new molecule contains one new and one original strand

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15
Q

What are the two enzymes involved in DNA replication?

A

DNA pyolymerase
DNA ligase

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16
Q

DNA replication steps

A

1-DNA unwinds
2-H2 bonds break
3-DNA strands separate to form 2 template strands (lagging and leading)
5-Primer binds to 3’end
4-DNA polymerase adds DNA nucleotides, using complementary base pairing, to the 3’end of the template DNA strand
5-H2 bonds form between bases
6-sugar-phosphate bond forms between nucleotides
7-DNA molecule recoils in double helix

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17
Q

What does DNA polymerase require to start replication and what isn’t it?

A

A primer-a short strand of nucleotides which binds to the 3’end of the template DNA strand allowing polymerase to add DNA nucleotides
-Primers are complementary to specific target sequences at the two ends of the region of DNA to be amplified

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18
Q

Describe the formation of the leading strand

A

Replication of the parental DNA strand which has the 3’end at the bottom is continuous and forms the leading strand

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19
Q

Describe the formation of the lagging strand

A

The lagging strand has to be replicated in fragments and its formation is described as discontinuous.

5’end at bottom

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20
Q

What does ligase do? (and what is it?)

A

Enzyme that joins the fragments in the lagging strand

bonds fragments of replicated DNA into lagging strand

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21
Q

Direction of replication

A

5’ to 3’
‘nucleotides added to the 3’ end of template strand)

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22
Q

What does DNA polymerase do? (and what is it?)

A

Bonds nucleotides into backbone

Enzyme which adds nucleotides to the 3’end of the template strand to form a new strand

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23
Q

What is required for DNA replication?

A

DNA-Acts as a template
Primer-start point for replication
Free nucleotides l-used to make the new complementary strand
DNA polymerase
Ligase
ATP(energy)

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24
Q

What is PCR?

A

The Polymerase Chain Reaction

(It is a useful tool in DNA technology.)

It is a way of amplifying (making copies of) target regions of DNA.

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25
Q

Steps of PCR

A

1-DNA is heated between 92-98 to separate the 2 strands (DNA is denatured)

2-It is then cooled to between 50-65 to allow the primers to bind (anneal) to target sequences

3-It is then heated to between 70-80 for the heat-tolerant polymerase to replicate the region of DNA (heat-tolerant so that it does not denature)

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26
Q

Uses of PCR

A

PCR can amplify DNA to:
-help solve crimes
-settle paternity suites
-diagnose genetic disorders

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27
Q

What can DNA samples be analysed with?

A

Gel electrophoresis

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28
Q

How is a cell’s genotype determined?

A

By the sequence of DNA bases in its genes

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29
Q

How is a cell’s phenotype determined?

A

By the proteins that are synthesised when two genes are expressed

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30
Q

How much of an organism’s genome is expressed?

A

A fraction of the gene

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31
Q

What is the structure of a protein (coded for by a gene) determined by?

A

By the sequence of amino acids

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32
Q

What are amino acids linked by?

A

peptide bonds to form polypeptides

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33
Q

What do polypeptide chains do?

A

Fold to form the three-dimensional shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids

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34
Q

Two types of polypeptide chains

A

fibious-long parallel strands
globular-folded together in a spherical shape (or incorporates another chemical)

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35
Q

What does gene expression involve?

A

The creation of a protein from a gene through 2 stages:
-transcription
-translation

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36
Q

Chromatography

A

A technique that can be used to separate amino acids

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37
Q

3 types of RNA involved in transcription and translation

A

mRNA (messenger), tRNA (transfer), rRNA (ribosomal)

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38
Q

What is RNA?

A

-single-stranded
-composed of nucleotides containing ribose sugar, phosphate and one of the four bases: cytosine, guanine, adenine, uracil

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39
Q

What is Transcription?

A

The process in which a copy of DNA is made, mRNA, in the nucleus

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40
Q

Steps of transcription

A

1-RNA polymerase moves along the DNA, unwinding the helix
2-The weak H2 bonds, between the bases, break
3-RNA polymerase adds free RNA nucleotides pair up with their complementary bases on the DNA
4-RNA polymerase enzyme controls the formation of the backbone between adjacent RNA nucleotides forming an RNA chain
5-Weak H2 bonds between DNA and RNA break. This leaves a single strand of mRNA. This is called the primary transcript
6-The 2 strands of DNA come together again and wind up.

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41
Q

What is the mRNA primary transcript made up of?

A

coding (exons) and non-coding regions (introns)

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42
Q

What is RNA splicing?

A

The introns of the primary transcript are removed. The exons are joined together to form the mature transcript. The order of exons is unchanged during the splicing.

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43
Q

Alternative RNA splicing

A

Different proteins can be expressed from one gene (as a result of alternative splicing)

Different mature transcripts are produced from the same primary transcript depending on which exons are retained.

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44
Q

What happens during translation?

A

mRNA is translated into proteins by ribosomes in the cytoplasm

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45
Q

What is used to determine the sequence of amino acids in the protein?

A

codons on the mRNA

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46
Q

What are codons?

A

A triplet of bases on mRNA that code for one amino acid

47
Q

tRNA

A

-transfer RNA
-found in the cytoplasm
-folds due to complementary base pairing
-a tRNA molecule had an anticodon (triplet of bases) at one end and an attachment site for a specific amino acid on the other end
-transfers amino acid from cytoplasm to ribosome

48
Q

Where is the site of translation?

A

ribosome

49
Q

What are ribosomes made up of?

A

-rRNA (ribosomal RNA)
-protein

50
Q

Steps of translation

A

-Begins at a start codon in mRNA and ends at a stop codon on mRNA
-The ribosome reads three bases (codon) at a time
-tRNA carries a specific amino acid to the ribosome and anticodons on tRNA bond to codons by complementary base pairing
-Peptide bonds join the amino acids together (polypeptide chain) (to form proteins)
-Each tRNA then leaves the ribosome (discharged) as the polypeptide is formed

51
Q

What is cellular differentiation?

A

The process by which a cell expresses certain genes to produce proteins characteristic for that type of cells
This allows a cell to carry out specialised functions

52
Q

What directs a cell’s development?

A

The selective switching on and off of genes

53
Q

What are stem cells?

A

Unspecialised cells in animals that can divide (self-renew) and/or differentiate

54
Q

What are meristems?

A

regions of unspecialised cells in plants that can divide (self-renew) and/or differentiate

55
Q

Embryonic stem cells

A

-cells in the very early embryo can differentiate into all the cell types that make up an organism
—>PLURIPOTENT

-All the genes in embryonic stem cells can be switched on so these cells can differentiate into any cell type

56
Q

Where do we find tissue stem cells?

A

-bone marrow
-brain
-testes
-ovary
-skin
-intestines
-muscles

57
Q

What are tissue stem cells involved in?

A

growth, repair, and renewal of the cells found in that tissue

58
Q

What is a property of tissue stem cells?

A

They are multi potent as they can differentiate into all of the types of cell found in a particular tissue type.

For example, blood stem cells located in bone marrow can give rise to all types of blood cell.

59
Q

Therapeutic uses of stem cells

A

-bone marrow transplant to tread leukaemia
-cornea repair
-regeneration of damaged skin
-repair of damaged or diseased organs or tissue

60
Q

research value of stem cells

A

-embryonic stem cells can self renew, under the right conditions, in the lab
-stem cells research provides information on how cell processes such as cell growth, differentiation and gene regulation work
-research uses stem cells being used as model cells to study how diseases develop or being used for drug testing

61
Q

controversy surrounding stem cell use

A

-Use of embryonic stem cells invokes destruction of embryos
-Some people believe that life begins at fertilisation and using embryonic stem cells is destroying a potential life

62
Q

What is an organism’s genome?

A

Its entire hereditary information encoded in DNA

63
Q

What is a gene?

A

A sequence of DNA that codes for a protein

64
Q

What parts make up the genome?

A

coding (code for proteins)
non-coding (do not code for proteins)

Most of the eukaryotic genome consists of non-coding sequences

65
Q

What do non-coding regions of DNA do?

A

-regulate transcription
-transcribed but never translated
Non-translated forms of RNA are not translated into protein (e.g. tRNA and rRNA)
-no known function

66
Q

What are mutations?

A

Changes in the structure or mass of an organism’s DNA.

/changes in the genome

They are rare.

67
Q

What do mutations result in?

A

no protein or an altered protein.

68
Q

What do you call an organism possessing a mutation?

A

Mutant

69
Q

What is a mutagenic agent? + examples

A

Something that increases the frequency of mutations

-chemicals e.g. mustard gas
-radiation e.g. gamma rays

70
Q

What does a single gene mutation involve?

A

A change in one of the base pairs in DNA sequence of a single gene

71
Q

What can single gene mutations be the result of?

A

-substitution (one base/nucleotide replaced with another in DNA)
-insertion (nucleotide/base added to DNA)
-deletion (nucleotide/base removed from DNA)

of nucleotides within a gene

72
Q

Frameshift mutations

A

insertions or deletion

cause all of the codons and all of the amino acids after the point of mutation to be changed

major effect in the structure of the protein produced

73
Q

substitution

A

point mutatjon
major or minor effect

base replaced with anorher

examples-missense or nonsense, splice site

74
Q

Missense mutations

A

result in one amino acid being changed for another

may result in a non-functional protein or have little effect on the protein

75
Q

Nonsense mutations

A

result in a premature stop codon being produced which results in a short protein

76
Q

Splice site mutations

A

inclusion of introns in the mature mRNA transcript

exclusion of exons in the mature mRNA transcript

may in turn be translated into an altered protein (longer or shorter) which does not function properly

77
Q

Chromosome structure mutations

A

Deletion
duplication
inversion
translocation

78
Q

deletion (chromosome structure mutations)

A

where a section of a chromosome is removed

protein not produced

79
Q

duplication

A

where a section of a chromosome is added from its homologous partner

set of genes being repeated

can be detrimental

one copy of gene functions normally
one copy can mutate

80
Q

inversion

A

where a section of a chromosome is reversed (flipped 180)

often results in formation of non-viable gametes

81
Q

Translocation

A

where a section of a chromosome is added to another chromosome (not its homologous partner)

82
Q

evolutionary importance of gene duplication

A

allows potential beneficial mutations to occur in the second/ duplicated copy of gene which is free from selection pressures (it can become altered without affecting the original genes function)

The original gene will still be expressed (function will not be lost)

83
Q

What is evolution?

A

The changes in organisms over generations as a result of genomic variations

These variations take the form of changes in the frequencies of certain genetic sequences (or alleles of genes)

84
Q

What does evolution result in?

A

the formation of new species over time

85
Q

vertical transfer of genetic material

A

genetic sequences are inherited vertically from parent to offspring (down the generations) as a result of sexual or asexual reproduction

86
Q

horizontal transfer

A

Prokaryotes (bacteria and viruses) can exchange genetic material horizontally (between members of the same generation). This can then result in rapid evolutionary change

e.g. the spread of antibiotic resistance in bacteria

87
Q

spread of antibiotic resistance

A

A significant amount of horizontal gene transfer still occurs in modern day promaryotes

Resistance to antibiotics has occurred through the transfer of plasmids carrying antibiotic resistance genes from bacteria to bacteria

88
Q

What is natural selection?

A

The non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deterioration sequences

Traits that are advantageous are selected for and traits which are disadvantageous are selected against

89
Q

Types of selection

A

stabilising
directional
disruptive

90
Q

stabilising selection

A

an average phenotype is selected for and extremes of the phenotype range are selected against

mean remains unchanged

91
Q

directional selection

A

one extreme of the phenotype range is selected for

a new mean is created in the population

92
Q

disruptive selection

A

two or more phenotypes are selected for

two or more new means are created in the population

93
Q

2 types of speciation

A

allopatric speciation
sympatric speciation

94
Q

Allopatric speciation

A

occurs when gene flow between two (or more) populations is prevented by a geographical barrier

95
Q

examples of geographical barriers

A

rivers
mountain ranges
sea

96
Q

sympatric speciation

A

two (or more) population live in close proximity in the same environment but still become genetically isolated
This happens due to a behavioural or ecological barrier

97
Q

examples of ecological barriers

A

temperature
pH
salinity
humidity
altitude

98
Q

examples of behavioural (reproductive) barriers

A

if individulas in a population become fertile at different times of the year

their organs change

or their courtship is different or unattractive

Then individuals cannot mate

99
Q

What is the genomics?

A

The study of genomes

100
Q

What does genomic sequencing involve?

A

Determining the sequence of bases individual genes or entire genomes

101
Q

What happened in 2003?

A

The DNA sequence of the human genome was completed

Since the Human Genome Project, the genome of several organisms has been sequenced e.g. pathogenic bacteria/virus which helps to create vaccines

102
Q

What can computer programs be used to do in genomic sequencing?

A

To identify base sequences by looking for sequences similar to known genes

103
Q

Bioinformatics

A

The fusion of molecular biology, statistical analysis and computer technology to compare genomes of organisms

104
Q

After sequenced, the genome of organisms can be compared for a variety of purposes. Name one of these purposes.

A

Members of disease causing micro-organisms - do they have important genetic sequences in common?

105
Q

What has comparison of many genomes revealed?

A

That DNA sequences of important genes are highly similar (conserved) from one organism to the next

e.g genes coding for proteins involved in aerobic respiration, or for key enzymes

106
Q

What is phyologenetics

A

The study of evolutionary history and relationships

107
Q

Phylogenetically-what can genetic sequence data be used for?

A

To study the evolutionary relatedness among groups of organisms

108
Q

Over time, what happens to a group of closely related living organisms?

A

They accumulate mutations e.g. nucleotide substitutions which gradually alter the genome

109
Q

What is evolutionary distance?

A

A measure of how related two genomes are.

The number of differences per unit length of DNA between two genomes.

This can be used to produce phylogenetic trees

110
Q

What can be used as a molecular clock?

A

The number of substitutions which differ between 2 groups. This indicated the length of time since the group diverged and can be used as a molecular clock

If genetic sequences differ by only a few bases, it suggests the groups share a common ancestor and diverged recently

111
Q

What is the main sequence of events in evolution?

A

Evolution of life on earth

Evolution of cells similar to prokaryotes

Evolution of last universal ancestor

Evolution of prokaryotes able to photosynthesise

Evolution of eukaryotes

Evolution of multicellular organisms

Evolution of animals

Evolution of vertebrates

Evolution of land plants

112
Q

What is pharmacogenetics?

A

The use of genome information in the choice of drugs

113
Q

What can an individual’s personal genome sequence be used to do?

A

Select the most effective drugs and dosage to treat their disease (personalised medicine)

114
Q

Why is mRNA so much shorter than DNA?

A

because they are copied from only a limited region of the DNA

(only transcribes one gene)

Biology H (11 decks)

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