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Biomedical Science Year 1 > Genetics > Flashcards

Genetics Flashcards

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Biology 101 flashcards
1
Q

Wild type

A

An unmodified natural isolate of a species

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2
Q

Mutant

A

An organism that differs from the wild type as a result of a specific change to its DNA sequence

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3
Q

Mutation

A

A specific change in the DNA/RNA sequence of an organism that is different from that in the wild type

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4
Q

Allele

A

Different forms of a gene that arise by mutation and that are found at the same place on a chromosome in both the wild type and in a mutant

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5
Q

Phenotype

A

An identifiable or observable trait that can be altered by a mutation

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6
Q

Genotype

A

The nucleotide sequence of a region of DNA

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7
Q

Advantages of using bacteria?

A

– Relatively simple organisms
– Easy to genetically manipulate
– Short generation times
– Haploid organisms

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8
Q

Why is bacteria being a haploid organism an advantage?

A

It is much easier to identify cells with a particular type of mutation as they have an immediate effect on the behaviour/appearance of the organism

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9
Q

What are Darwinian principles?

A

Mutations occur randomly and are passed on by vertical gene transfer

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10
Q

How do bacteria inherit DNA?

A

Via vertical gene transfer and lateral gene transfer

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11
Q

What is vertical gene transfer?

A

Inherit DNA from parents

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12
Q

What is lateral gene transfer?

A

Inherit DNA from other bacteria / viruses in the environment

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13
Q

What is genetic transformation?

A

The ability of a bacterial cell to take up cell-free DNA from the environment. First discovered in 1928 by Fred Griffith

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14
Q

What is bacterial conjugation?

A

Gene transfer from one bacterial cell (the donor) to another (the recipient) by direct cell-to-cell contact

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15
Q

What is transduction?

A

Gene transfer mediated by a bacterial virus

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16
Q

What is the central dogma?

A

DNA makes RNA makes protein

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17
Q

What are the 3 stages of transcription?

A

Initiation, elongation, termination

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18
Q

What is initiation?

A

RNA polymerase binds to a promoter sequence in the DNA and starts transcription

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19
Q

What is elongation?

A

RNA polymerase moves along the strand of DNA using the template strand to decode the DNA to RNA

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20
Q

What is termination?

A

RNA polymerase recognises sequence in the DNA that tells it to stop synthesising RNA

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21
Q

What are the most common types of RNA?

A

Messenger RNA, ribosomal RNA, transfer RNA

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22
Q

What term is used to describe the direction of chromosomal replication?

A

Bidirectional

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23
Q

Name 6 types of mutation

A

Base pair changes, frameshifts, deletions, inversions, duplications, insertions

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24
Q

What are the 3 potential consequences of base change mutations?

A

Silent mutation, missense mutation, nonsense mutation

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25
Q

What is mutation frequency?

A

Frequency at which mutation occurs over time

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26
Q

Equation for mutation frequency

A

MF =m / N
Where m= number of mutants and N= total number of bacteria

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27
Q

How do frameshift mutations occur?

A

By the insertion or deletion of a number of bases not divisible by 3

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28
Q

What are the 2 types of base changes that can occur?

A

Transitions and transversions

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29
Q

What is a transition (base change)?

A

Purine → purine or pyrimidine → pyrimidine

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30
Q

What is transversion (base change)?

A

Purine → pyrimidine or pyrimidine → purine

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31
Q

How many codons are stop codons?

A

3

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32
Q

Name 3 ways in which we can select mutants

A

Negative selection, enrichment, positive selection

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33
Q

What is negative selection?

A

Selects against the mutant growing

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34
Q

What is enrichment?

A

The use of negative selection to inhibit growth of mutants and then killing wild type growing cells using an antibiotic

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35
Q

What is positive selection?

A

Uses selective conditions where only the mutants win grow

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36
Q

Genome

A

The sum total of genetic material in an individual organism

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37
Q

Genomics

A

The acquisition, storage, retrieval and analysis of DNA sequence data

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38
Q

Which direction does E. coli replicate in?

A

Bidirectionally

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39
Q

How many proteins does E. coli encode?

A

4400

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40
Q

What rate does E. coli replicate at?

A

850 bases per sec per replication fork

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41
Q

What is metagenomics?

A

The study of genetic material recovered directly from environmental samples

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42
Q

What is recombinant DNA?

A

When 2 pieces of DNA are ligated under artificial conditions to perform a modified function

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43
Q

Function of DNA ligase?

A

Sticks fragments of DNA together

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44
Q

Function of Taq polymerase?

A

PCR - creates multiple copies of DNA fragment

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45
Q

Function of reverse transcriptase?

A

Copies RNA into DNA

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46
Q

Name 2 types of cleavage patterns

A

Symmetrical cleavage (blunt ends)
Asymmetrical cleavage (sticky ends)

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47
Q

Intron

A

Any nucleotide sequence within a gene that is removed by RNA splicing during maturation of the final RNA product

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48
Q

Exon

A

Any part of a gene that will encode a part of the final mature RNA produced by that gene a introns have been removed by RNA splicing

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49
Q

Advantages of bacteria as a host

A

Simple cells
Short generation time
Large yields of product
Low costs

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50
Q

Disadvantages of bacteria as a host

A

Eukaryotic proteins can fold correctly and lose biological activity
Proteins can be toxic to the bacterial cell
No post- translational modifications

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51
Q

Advantages of yeast as a host

A

Simple unicellular eukaryote
Resembles mammalian cells
Grows quickly and cheaply
Performs post-translational modifications

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52
Q

Disadvantages of yeast as a host

A

Contains proteases → degrade some recombinant proteins
Post - translational modifications may differ from mammalian cells

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53
Q

Advantages of insect cells as a host

A

High-level protein expression
Correct folding of mammalian proteins
Post-translational modifications
Cheaper than mammalian cell culture

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54
Q

Disadvantage of insect cell as a host

A

Post- translational modifications may differ from mammalian cells

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55
Q

Advantages of mammalian cells as a host

A

Best place to produce mammalian proteins
Correct folding of mammalian proteins
Post-translational modifications

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56
Q

Disadvantages of mammalian cells as a host

A

Complex cells
Grow to lower cell densities
Expensive

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57
Q

What is a model organism?

A

A well established experimental biological system

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58
Q

Characteristics of model organisms

A

Rapid rate of development
Easily manipulated
Short lifespan
Readily available
Large numbers of offspring per generation

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59
Q

3 types of model organism

A

Genetic, genomic, experimental

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60
Q

Name some common eukaryotic models for genetic analysis

A

Yeast, fruit fly, worm, zebrafish, mouse

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61
Q

Homologue

A

A gene related to another gene by descent from a common ancestral DNA sequence

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62
Q

Orthologue

A

Genes in different species that evolved from a common ancestral gene

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63
Q

Prologue

A

Prologues are genes generated by a duplication event (e.g. Human alpha and beta haemoglobin genes)

64
Q

Define gene knockout

A

Gene sequences are completely or partially removed and gene expression is completely eliminated

65
Q

Define gene knockdown

A

Techniques that reduce/interfere with the expression of the gene

66
Q

Characteristics of S. Cerevisiae

A

Small size and simple growth and storage conditions
Rapid growth rate
Can exist as diploid or haploid cells
12.8 Mbp genome~ 6000 genes

67
Q

What is a disease model?

A

A mutant mode organism that mimics the phenotypes observed in a human disease

68
Q

Characteristics of S. pombe

A

Fission yeast - splits to divide
13 Mbp with ~5000 genes

69
Q

Characteristics of Drosophila melanogaster

A

Small ~ 3mm
Life cycle approx 2 weeks, females can lay up to 100 eggs per day
Genome 165 Mbp, encoding ~14,000 genes

70
Q

Characteristics of C. elegans

A

Small (~1mm)
Short life cycle, egg to egg takes approx 3 days
Short lifespan 2-3 weeks
Genome 97 Mbp, 5 pairs of autosomal chromosomes and one pair of sex chromosomes
~ 20,000 genes

71
Q

Characteristics of zebrafish

A

Lay ~ 200 eggs per week = ~35,000 eggs ( 2-4 years)
Sexually mature by 3-4 months old, a generation interval of 2-3 months
Transparent embryos
1.7 Gbp genome - 25 chromosomes

72
Q

Characteristics of mouse

A

25,000 genes on 20 chromosomes (2.6 Gbp)
2 month breeding cycle, 6-15 offspring perlitter

73
Q

Name some diseases a mouse can model

A

Down syndrome, cystic fibrosis, cancer, glaucoma, epilepsy, heart disease, muscular dystrophy, ovarian tumours

74
Q

Pros and cons of mouse disease models

A

Pro- A very powerful approach to understanding the role of a particular gene in a mammal and its role in a disease
Con- The production of knockouts is very expensive and time consuming. Also ethical considerations

75
Q

Banding pattern for G - banding

A

Dark bands are AT rich

76
Q

Banding pattern for R- banding

A

Dark bands are GC rich

77
Q

Banding pattern for Q - banding

A

Dark bands are AT rich

78
Q

Banding pattern for C - banding

A

Dark bands are constitutive heterochromatin

79
Q

What is letter for short arms?

A

P

80
Q

What is the letter for long arms?

A

Q

81
Q

What are telomeres?

A

Specialised regions at the end of chromosomes

82
Q

What are the major functions of telomeres?

A
  1. They allow the cell t distinguish a real chromosome end from an unnatural end caused by a chromosome break
  2. They solve the problems that cells have replicating the ends of linear chromosome – the end replication problem
83
Q

What is euchromatin?

A

Relatively uncondensed chromatin associated with active (expressed) genes

84
Q

What is heterochromatin?

A

Condensed chromatin, associated with repetitive gene poor regions that are inactive (silenced)

85
Q

What are minichromosomes?

A

Relatively short chromosomes but rich in genes

86
Q

What are B chromosomes?

A

Additional chromosomes possessed by some but not all individuals in a population

87
Q

What are holocentric chromosomes?

A

Do not have a single centromere but have multiple kinetochores throughout their length

88
Q

What are polytene chromosomes?

A

Giant chromosomes

89
Q

What are kinetochores?

A

Protein structures located at the centromere that serve as an attachment point for the mitotic spindles

90
Q

What is the centrism?

A

A region of the cytoplasm containing a pair of centrioles

91
Q

What is the synaptonemal complex?

A

A nucleoprotein zipper that forms between the paired homologous chromosomes

92
Q

What is a trisomy

A

3 copies of a particular chromosome rather than 2

93
Q

What is aneuploidy?

A

Chromosome number is not an exact multiple of the haploid number

94
Q

Trisomy 8

A

Warkany syndrome 2

95
Q

Trisomy 12

A

Chronic lymphocytic leukaemia

96
Q

Trisomy 13

A

Patau syndrome

97
Q

Trisomy 18

A

Edward’s syndrome

98
Q

Trisomy 21

A

Down syndrome

99
Q

What is the klinefelter karyotype?

A

More than one X chromosome

100
Q

What is the turner karyotype?

A

Single X chromosome

101
Q

Features of the Y chromosome

A

PARs = pseudo autosomal regions – share pomology with X chromosome
MSY = male specific region of the Y – does not synapse with the X chromosome
SRY = sex determining region Y – produces testis determining factor (TDF) which triggers undifferentiated gonadal tissue of the embryo to form testes

102
Q

What is the Lyon hypothesis?

A
  1. Inactivation is random at an early point in development
  2. Once inactivated all progeny cells have the same X chromosome inactivated
103
Q

Which codon does translation start on?

A

Methionine

104
Q

What are Mendel’s laws?

A

1st law - the 2 copies of each gene segregate
2nd law - the copies of each gene segregate independently of those of other genes

105
Q

Name some autosomal recessive conditions

A

Albinism, tay-sachs, cystic fibrosis

106
Q

Name some autosomal dominant conditions

A

Huntington’s disease, polydactyly, achondroplastic dwarfism

107
Q

Name some x-linked recessive disorders

A

Haemophilia, deuteranopia (red-green colour blindness)

108
Q

Name an X - linked dominant disorder

A

Vitamin D - resistant rickets

109
Q

What is epistasis?

A

A situation where one mutation hides the phenotype of another

110
Q

How is recombination frequency expressed?

A

As a percentage

111
Q

What is the equation for recombination frequency?

A

(No. Of recombinants/ total progeny) x 100

112
Q

What are syntenic genes?

A

Those grouped in the same way on the chromosomes of two or more species

113
Q

What is modern genome organisation?

A

The result of mistakes in the replication and segregation of ancestral genomes

114
Q

Result of duplication events

A

Generation of multi-gene families, within which individual genes evolve to have different functions

115
Q

What is a haplotype?

A

A set or linked polymorphic markers

116
Q

How old are prokaryotes?

A

Very old - predate 3.75BYA

117
Q

Are eukaryotes older or prokaryotes?

A

Prokaryotes

118
Q

How did the mitochondrion originate?

A

As an endosymbioticbacterium that colonised the common ancestor of eukaryotic cells approximately 2BYA

119
Q

How do we know mitochondria were bacteria?

A

They have their own small genome and its genes are bacterial genes

120
Q

What is Hsp 70

A

70 kD mitochondrial heat shock protein

121
Q

What are the roles of Hsp 70?

A
  1. Allows proteins made in the cytosol to be imported into the mitochondrion
  2. The assembly of Fe-S clusters (essential cofactors of some mitochondrial proteins that function in the ETC)
122
Q

What are the two main theories for the origin of modern humans?

A

The multinational model and the Out of Africa hypothesis

123
Q

Why is yeast a good model for human genetic disease?

A

These diseases are commonly associated with conserved fundamental processes such as the cell division cycle

124
Q

Examples of cancer linked genes found in Saccharomyces cerevisiae

A

DNA repair gene - MSH2
Coul cycle checkpoint gene - ATM

125
Q

Examples of human disease genes found in Saccharomyces cerevisiae

A

WRN/BLM genes
NF1

126
Q

What is developmental biology?

A

The study of the process by which organisms grow and develop

127
Q

What is developmental genetics?

A
  • Uses developmental biology knowledge and techniques to understand congenital anomalies and genetic disease
  • Involves the use of model organism to study developmental processes
128
Q

How long is human pregnancy usually?

A

38-40 weeks

129
Q

How is human pregnancy broken up?

A

Into embryonic (up to 8 weeks) and foetal ( 8 weeks - term) periods

130
Q

When does organogenesis occur?

A

During embryogenesis

131
Q

When do most congenital anomalies occur

A

In first 8 weeks

132
Q

What is a model organism?

A

A well established experimental biological system

133
Q

What was the last common ancestor of humans and flies?

A

Ikaria wariootia - 550 million years old

134
Q

Why is Drosophila useful?

A
  • Genome sequence
  • Short life cycle
  • Easily accessible larvae
  • Most genes have homologues in mammals
135
Q

Why are zebrafish useful?

A
  • Transparent as embryos
  • Genome sequenced
  • Easy to manipulate genetically and experimentally
  • Capable of regenerating many body parts
136
Q

Why are amphibians useful?

A
  • Large embryos that can be easily manipulated
  • Capable of regenerating many body parts
137
Q

Why are birds useful?

A
  • Large accessible eggs
  • Easy to manipulate and image
  • Genetics very complex
138
Q

Why are mice useful?

A
  • Genome sequenced
  • Large numbers of mutants available
  • Relatively rapid life cycle
  • Possible to manipulate genome
139
Q

Why do we need animal models?

A
  • Can’t experiment on humans
  • Can’t model disease processes in cell culture
  • Can’t test toxicity of new drugs or disease treatments in cell culture
140
Q

What are 3 fundamental processes of developmental biology?

A
  1. Morphogenesis
  2. Differentiation
  3. Growth
141
Q

What is morphogenesis?

A

The emergence of form

142
Q

What is differentiation?

A

Process by which cells become specialised

143
Q

What is body plan?

A

The map of an organism

144
Q

Where does the antero-posterior axis run?

A

Head to tail

145
Q

Where does the dorso-ventral axis run?

A

Back to belly

146
Q

Where does the left-right axis run?

A

Between the two lateral sides of the embryo

147
Q

What are the four components to cell-signalling?

A
  • Release and transmission of signal by source cell
  • Reception of the signal by the target cell
  • Transduction of the signal
  • Cellular response
148
Q

What are morphogens?

A

Growth factors that pattern the embryo

149
Q

What are congenital malformations?

A

Those already present at birth

150
Q

What are possible genetic causes of congenital malformations?

A

Chromosomal defects, syndromes, single genes, multi-gene interactions

151
Q

What are possible environmental causes of congenital malformations?

A

Maternal diabetes, fever, prescription drugs, recreational drugs, pollutants, dietary deficiencies

152
Q

What is cytogenetics?

A

A branch of genetics concerned with how the chromosomes relate to cell behaviour

153
Q

When do we see chromosomes?

A

In mitosis

154
Q

What is metacentric?

A

P arm and q arm approx. same length

155
Q

What is sub-metacentric?

A

P arm shorter than q arm

156
Q

What is acrocentric?

A

Satellite structure present on p arm

157
Q

What does a BLAST search allow you to do?

A

Identity similar protein sequences to one that you search with?

Biomedical Science Year 1 (8 decks)

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