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Biology Year 1 > Chapter 2 - Nucleic Acids > Flashcards

Chapter 2 - Nucleic Acids Flashcards

1
Q

What is a diploid

A

A cell/organism that has a pair of homologous chromosomes (it has 2 alleles of each gene)

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2
Q

What is a gene

A

A sequence of DNA that codes for a protein and therefore a phenotype
Eg blood type

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3
Q

What is an allele

A

A different form of a gene

Eg A, B or O

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4
Q

What is a genotype

A

The combination of alleles that an organism has

Eg AA, BB etc

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5
Q

What is a phenotype

A

The physical expression of the genotype and it’s interaction with the environment
Eg skin colour

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6
Q

What is meant by a dominant allele

A

An allele that is always expressed in the phenotype

Eg functional proteins

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7
Q

What is meant by a recessive allele

A

Alleles that are only expressed when homozygous

Eg non-functional proteins

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8
Q

What is meant by a co-dominant allele

A

Where both alleles are expressed in the phenotype (so phenotype is intermediate)

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9
Q

What is meant by homozygous

A

When both alleles are the same

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10
Q

What is meant by heterozygous

A

When alleles are not the same

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11
Q

What is meant by the locus

A

The position of a gene on a chromosome

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12
Q

Where are alleles of a gene placed on a chromosome

A

On the same locus

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13
Q

What is meant by monohybrid inherited

A

Inheritance of a characteristic is controlled by only one gene

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14
Q

What is meiosis

A

Cell division to form gametes

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15
Q

What are gametes

A

Haploid sex cells (sperm and eggs)

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16
Q

What is meant by haploid

A

A cell with a single set of unpaired chromosomes
Or
A cell with one of each homologous pair

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17
Q

What is meant by diploid

A

A cell with 2 complete sets of chromosomes

Both homologous pairs, one from each parent

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18
Q

What is mitosis

A

Cell division for growth and repair

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19
Q

How are the number of divisions different in meiosis and mitosis

A

There are 2 in meiosis and 1 in mitosis

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20
Q

What are the 2 divisions in meiosis called

A

Meiosis I

Meiosis II

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21
Q

How many daughter cells are produced in meiosis

A

4

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22
Q

How many daughter cells are produced in mitosis

A

2

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23
Q

How can the daughter cells from meiosis be explained

A

They are genetically different to each other

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24
Q

Why are daughter cells in meiosis genetically different to each other

A
  • Crossing over

- Independent segregation

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25
Q

What is meant by crossing over

A

The exchange of alleles between homologous chromosomes, resulting in a different combination of alleles

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26
Q

What is meant by independent segregation

A

Formation of random combinations of chromosomes in metaphase, instead of homologous pairs

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27
Q

How can daughter cells from mitosis be explained

A

Genetically identical

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28
Q

What happens before meiosis takes place

A

Interphase

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29
Q

What happens in interphase

A

DNA replicates, so rather than just single chromosomes there are now x shaped chromosomes

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30
Q

What are sister chromatids

A

Two parts to a chromosome, that are chromosomes if they are on their one
Identical to each other

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31
Q

What is the centromere

A

The point that joins the sister chromatids in a chromosome

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32
Q

What are the stages of meiosis

A

Prophase
Metaphase
Anaphase
Telophase

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33
Q

How many times does each stage of meiosis occur

A

Twice

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34
Q

What happens in prophase I in meiosis

A
  • Chromosomes condense so become visible

- Nuclear membrane breaks down

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35
Q

What happens in metaphase I in meiosis

A
  • Homologous pairs line up next to each other
  • Spindle fibres form
  • spindle fibres attach centromeres to centrioles
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36
Q

What happens in anaphase I

A
  • Homologous pairs are seperated

- They ate pulled apart to opposite poles as spindle fibres contract

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37
Q

What happens in telophase I

A
  • Nuclear membranes form (around each side of chromosomes)

- Cell divides

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38
Q

What happens in prophase II

A

Nuclear membrane break down

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39
Q

What happens in metaphase II

A
  • Chromosomes line up on equator

- Spindle fibres form, attaching to centromeres and centrioles

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40
Q

What happens in anaphase II

A
  • Chromatids separate

- Pulled towards opposite poles

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41
Q

What happens in telophase II

A
  • Nuclear membrane reform

- 2 Cells divides into 4 daughter cells all together

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42
Q

What is a characteristic of daughter cells at the end of meiosis

A

The are not genetically identical to each other

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43
Q

What are nucleotides

A

The monomers that make up polynucleotides

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44
Q

What are examples of polynucleotides

A

DNA and RNA

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45
Q

What does a nucleotide of DNA consist of

A

Phosphate group
Deoxyribose
Nitrogen containing base

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46
Q

Draw a nucleotide of DNA

A

Circle
Line down to pentagon
Line across to rectangle

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47
Q

What are the bases of DNA

A

Adenine
Thymine
Cytosine
Guanine

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48
Q

What are the characteristics of DNA

A
  • It is double stranded (double helix)
  • A long polynucleotide
  • Carries genetic information which codes for proteins
  • Relatively simple structure
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49
Q

Draw a nucleotide of RNA

A

Phosphate group as circle
Ribose sugar (Pentagon)
Rectangular base

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50
Q

What does DNA stand for

A

Deoxyribonucleic acid

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51
Q

What does RNA stand for

A

Ribonucleic acid

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52
Q

What are the characteristics of RNA

A
  • Single stranded
  • Short polynucleotides
  • Transfer genetic codes from DNA in nucleus to ribosomes in cytoplasm
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53
Q

What are the bonds between DNA nucleotides

A

Phosphodiester bonds

54
Q

What are the phosphate group and pentode sugar parts of DNA nucleotides known as in a strand of DNA

A

Sugar-phosphate backbone

55
Q

How can the structure of DNA be described

A

Antiparallel

56
Q

What does antiparallel mean

A

The strands of DNA run in opposite directions

57
Q

What are the bonds between bases called in DNA

A

Hydrogen bonds

58
Q

What does adenine bond to and how many bonds are there

A

Thymine

2

59
Q

What does cytosine bond to and how many bonds are there

A

Guanine

3

60
Q

What does semi-conservative DNA replication mean

A

That DNA contains one new strand and one original strand

61
Q

Explain semi conservative DNA replication

A
  • DNA helicase unzips DNA by breaking hydrogen bonds
  • Both strands act as templates
  • Free DNA nucleotides attach by complementary base pairing
  • DNA polymerase joins nucleotides forming phosphodiester bonds (condensation reaction)
  • Hydrogen bonds reform
62
Q

What enzyme unzips DNA

A

DNA helicase

63
Q

What enzyme joins nucleotides together

A

DNA polymerase

64
Q

What reaction takes place for phosphodiester bonds to form

A

Condensation reaction

65
Q

Why can DNA polymerase work continuously in just one direction

A
  • DNA is antiparallel
  • Nucleotides son each strand are arranged differently
  • Active site of DNA polymerase has a specific tertiary structure
  • Only substrates with complementary shape/orientation can bind to active site to form enzyme-substrate complex
66
Q

What is a leading strand

A

A new strand of DNA formed continuously in semi-conservative replication

67
Q

What is a lagging strand

A

A new strand of DNA formed in segments

68
Q

What is DNA ligase

A

Enzyme that connects segments together in a lagging strand

69
Q

Describe the method used to prove semi-conservative DNA replication

A
  • Place cultured bacteria in heavy nitrogen (15N)
  • Centrifuge this
  • Transfer bacteria into light nitrogen (14N), so that new nitrogenous bases cultured show up different to original
  • Centrifuge
  • Replicate again in light nitrogen
70
Q

How do the method for proving semi-conservative replication actually prove it?

A
  • Starting population is cultured in a growth medium containing heavy nitrogen (nitrogen is in nitrogenous bases)
  • when centrifuged one band can be observed
  • Cells are transferred to a medium with only light nitrogen (14N)
  • After one replication, the DNA was intermediate between 14N and 15N
  • This is twice the thickness due to new DNA
  • After 2 replications in 14N, intermediate and light bands can be observed
    This proves that DNA replication is semi-conservative
71
Q

What is meant by the DNA antisense strand

A
  • The strand of DNA that acts as a template for mRNA
72
Q

What is meant by the DNA sense strand

A

The strand of DNA that is complementary to the antisense strand and is not used as a template

73
Q

What enzyme is used to unwind DNA

A

DNA helicase

74
Q

What is created using the antisense strand as a template

A

Pre-mRNA

75
Q

How will Pre-mRNA be different to the DNA sense strand

A

It will have uracil instead of thymine

76
Q

What is used to catalyse the addition of a nucleotide on Pre-mRNA (create a phosphodiester bond)

A

RNA polymerase

77
Q

What happens to the Pre-mRNA polynucleotide after it has been made

A

Splicing

78
Q

What is splicing

A

The removal of introns

79
Q

Why are introns removed?

A

They are non-coding regions

80
Q

What Pre-mRNA is spliced, what is created

A

mRNA

81
Q

What does ATP stand for

A

Adenosine triphosphate

82
Q

What is ATP used for

A

The main energy source to carry out processes in cells

83
Q

Why is ATP useful

A
  • It releases energy in small amounts
  • It is broken down in a single reaction so also releases energy quickly
  • Can add phosphate to other molecules do they are more reactive
  • Is easily resynthesised (reversible reaction)
84
Q

How is ATP formed

A

ADP + Pi

85
Q

What reaction takes place when ATL is formed

A

A condensation reaction

86
Q

What enzyme is used form ATP

A

ATP synthase

87
Q

What reaction takes place when ATP is broken down

A

Hydrolysis

88
Q

What enzyme is used when ATP is broken down

A

ATP hydrolase

89
Q

What is ATP made up of

A

3 phosphate groups
A ribose sugar
Adenine

90
Q

What is ADP made up of

A

2 phosphate groups
A ribose sugar
Adenine

91
Q

How can hydrolysis of ATP be useful

A

It can be used to release energy for other reactions in a cell

92
Q

How does hydrolysis of ATP help to provide energy for other reactions in cells

A

An inorganic phosphate is released to phosphorylase other compounds
- this makes them more reactive

93
Q

What is meant by an inorganic phosphate

A

It contains no carbon

94
Q

What is meant by phosprylation

A

Adding phosphate to

95
Q

What is a water molecule made up of

A

2 hydrogens atoms and one oxygen

96
Q

Water is a _____ molecule

A

Polar

97
Q

What makes water a polar molecule

A

It has a positive and negative end

98
Q

Why does water have a negative end

A

Impaired electrons on the oxygen have a negative charge

99
Q

Why does water have a positive end

A

Hydrogens‘ electrons is closer to oxygen so has a slightly positive charge

100
Q

Why are water molecules attracted to each other

A

There are intermolecular forces between molecules formed by poles of the molecules (oxygen of one molecule being attracted to hydrogen of another)

101
Q

What are the main properties of water

A
  • Good solvent
  • Metabolite
  • Cohesion
  • Temperature Control
  • High specific heat capacity
  • Ice floats on water
102
Q

What is a solvent

A

A liquid that other substances can dissolve in

103
Q

How is water a good solvent

A
  • Ionic compounds such as sodium chloride are made from positive and negative ions
  • Water is polar
  • Positive charges of water will add up for negative ions, and vice versa
  • Ions will become neutral so leave compound and dissolves
104
Q

What is the importance of water being a solvent

A

It allows substances to be transported in animals and plants

105
Q

What is meant by a metabolite

A

It is involved in reactions either as a reactant or a product

106
Q

How is water a metabolite

A

It is involved in condensation and hydrolysis reactions

107
Q

What is the importance of water being a metabolite to hydrolysis reactions

A

This allows digestion of large molecules

108
Q

What is the importance of water being a metabolite to condensation reactions

A

This allows synthesis of important molecules such as proteins

109
Q

What is meant by cohesion of water

A

The property that makes its molecules attracted to each other

110
Q

How does water have strong cohesion

A

Due to its polarity, strong hydrogen bonds hold water together, so that mass flow occurs

111
Q

What is meant by mass flow (of water due to cohesion)

A

It flows as a continuous stream

112
Q

What is the importance of water having strong cohesion

A
  • Transport of substances eg xylem

- surface tension of water

113
Q

How is water good for temperature control of organisms

A

It’s has a large latent heat of vaporisation

114
Q

How does the large latent heat of vaporisation of water helps temperature control

A
  • It takes a lot of energy to break hydrogen bonds between the molecules
  • Evaporation occurs when water molecules have high kinetic energy
  • They take this energy with them as water vapour
  • Causing body of water to cool as it has less energy (eg sweating)
115
Q

What is meant by the heat capacity of water

A

The amount of heat energy needed to increase the temperature of 1kg of water by 1°C

116
Q

How does water have a high specific heat capacity

A
  • Hydrogen bonds between water molecules take high energy to be broken apart
  • Meaning water can absorb large amounts of heat before temperature rises significantly
117
Q

What is the importance of water having a high specific heat capacity

A
  • Organisms made up of water increase body temperature slowly
  • Aquatic environments remain a stable temperature
118
Q

How does ice float on water

A

It is less dense than water

119
Q

What is the importance of ice floating in water

A
  • Provide habitat

- Reflect heat

120
Q

What is an inorganic ion

A

A compound not containing carbon

121
Q

Where do inorganic ions occur in organisms

A
  • In cytoplasm

- In body fluids

122
Q

What is an ion

A

An atom that has lost or gained electrons (has a charge)

123
Q

What are positive ions called

A

Cations

124
Q

What are negative ions called

A

Anions

125
Q

What is pH a measure of

A

Hydrogen ions in a solution

126
Q

What does hydrogen ions effect

A
  • They are very reactive
  • So react with proteins
  • change tertiary structure
  • Change active site
  • No enzyme-substrate complex’s
127
Q

Where are iron ions important

A

In haemoglobin

128
Q

Why is haemoglobin important

A

Carries oxygen in red blood cells

129
Q

What is haemoglobin

A

A protein with a quaternary structure (4 polypeptide chains)

130
Q

What are sodium ions crucial for

A

Co-transport

131
Q

How are sodium ions useful for co-transport

A

Help other molecules move across membranes eg glucose

132
Q

What are phosphate ions useful for

A
  • Phosphate In ATL, so provide energy

- Condensation reactions between phosphate groups to form polynucleotides

Biology Year 1 (10 decks)

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