exam Flashcards
(139 cards)
1
Q
what did friedrich miescher do?
A
Isolated “nuclein” from human pus
2
Q
How discovered the double helix structure?
A
rosalind franklin
3
Q
what is a nucleotide?
A
sugar + base + phosphate
4
Q
what is a nucleoside?
A
sugar + base
5
Q
are base pairs
planar or tetrahedral
A
planar
6
Q
what is a karyotype?
A
a way of visualising chromosomes?
7
Q
what is a nucleosome?
A
DNA wraps twice around 8 core histone proteins
8
Q
what is euchromatin?
A
less compact DNA form
contains genes that are frequently expressed
9
Q
what is heterochromatin?
A
more compact
contains DNA that is not transcribed
10
Q
Is RNA or DNA more stable?
A
DNA
11
Q
describe bacterial gene expression
A
No nuclear membrane
One cytoplasmic compartment
No histones
Coupled transcription and translation
12
Q
where does Transcription and translation take place in bacteria?
A
cytoplasm
13
Q
what is required for RNA polymerase to bind and initiate transcription at the appropriate site?
A
a promoter
14
Q
what is an operon?
A
Genes of related function
15
Q
how many promoters in an operon?
A
1
16
Q
why is a promoter needed?
A
required for RNA polymerase to bind and initiate transcription at the appropriate site
17
Q
What so sigma factors do in bacteria?
A
recruit the RNA polymerase complex to promoters
18
Q
control of gene expression in eukaryotes can occur through…
A
Changes in chromatin condensation
Histone modifications that activate or repress transcription
DNA methylation which represses gene expression
19
Q
what is an open reading frame?
A
a continuous stretch of codons that may begin with a start codon (usually AUG) and ends at a stop codon
20
Q
what increases the number of distinct proteins that can be encoded in a genome?
A
Post-transcriptional editing of mRNA
21
Q
What does RNA editing involve?
A
addition or deletion of uridine to mRNA
the deamination of adenine to produce inosine (A-to-I editing)
the deamination of cytosine to produce uracil (C-to-U editing)
22
Q
what is a UTR?
A
un translated region
23
Q
What does stability of mRNA depend on?
A
how much protein is translated in the cell
24
Q
how are siRNAs made?
A
produced from double-stranded, foreign RNAs during the process of RNA interference.
25
How are eukaryotic genomes arranged?
linear chromosomes
26
What are LINEs?
long interspersed nuclear elements
27
what are SINEs?
Short interspersed nuclear elements
28
what are transposons?
can insert copies elsewhere in the genome
29
what are the 2 categories of transposons?
cut and paste
replicative
30
what is an allele?
broadly used term to describe alternative forms of a heritable trait
31
what is polymorphism?
variation within a population of a given trait
32
what are SNPs?
single nucleotide polymorphisms
33
what is an intergenic region?
no phenotypic effect
34
what mechanisms do cells have to prevent and correct mutations?
Proofreading DNA polymerase(s)
Post-replication mismatch repair
DNA repair by homologous recombination
Cell cycle checkpoints
35
can UV lead to point mutations?
Yes
36
what are intercalating agents?
Planar(flat) molecules
intercalate (insert) between base pairs
37
What do base modifying agents do?
Covalently alter a base causing it to mispair
38
what do deaminating agents do?
remove amino (-NH2) groups
39
what do hydroxylating agents do?
add hydroxyl (-OH) groups
40
what do alkylating agents do?
add alkyl (-CH3 or -CH3CH2) groups
41
what do retrotransposons do?
transpose via mRNA
42
What is the heteroduplex structure in homologous recombination called?
D-loop
43
Can Homologous recombination repair double strand breaks?
yes
44
can Homologous recombination generate crossovers?
yes
45
is recombination a universal process?
yes
46
what does recombination require?
homologous sequences
47
what happens in meiosis 1?
reduction division
48
what happens in meiosis 2?
separation of sister chromatids
49
what is it called when homologues PAIR in meiosis?
synaptonemal complex
50
are the products of meiosis haploid or diploid?
haploid
51
what is a gene?
basic unit of biological information, specific segment of DNA that encodes a protein
52
what is an allele?
alternative forms of a gene
53
what is a genotype?
alleles at a locus
54
what is a phenotype?
observable characteristics
55
what is a homozygote?
identical (YY) alleles at a locus
56
what is a Heterozygote?
different (Yy) alleles at a locus
57
what is a monohybrid cross?
cross one gene
58
what is a dihybrid cross?
gene between more than one gene
59
What do dihybrid crosses reveal?
Mendel’s Law of Independent Assortment.
60
what do monohybrid crosses reveal?
Mendel’s Law of Segregation.
61
what is incomplete dominance?
heterozygotes show an intermediate phenotype e.g. red x white = pink!
62
what is co-dominance?
heterozygotes show phenotype of both alleles
63
what does pleiotropy mean?
One gene contributes to more than one trait
64
what can lethal alleles cause?
can cause skewed phenotypic ratios
- not born
65
what can gene combinations give rise to?
novel phenotypes
66
what is epistasis?
a gene interaction in which the effects of an allele at one gene hide the effects of alleles at another gene
67
what do complementation tests determine?
if a phenotype arises from mutations in the same or separate genes
68
what is penetrance?
measures the percent of individuals with a given genotype who exhibit the phenotype associated with the genotype
69
what is expressivity?
measures the extent to which a given genotype is expressed at the phenotypic level
70
how was linkage discovered?
discovered because in certain crosses, a greater number of offspring with ‘parental’ genotypes were generated than expected
71
what indicates linkage?
A greater number of parental offspring than expected
72
what are recombinants?
Non-parental genotypes arise due to crossing over during meiosis I
73
what does frequency of recombination between 2 genes depend on?
on the distance between them.
74
what 2 qualities do genetic maps have?
linear
additive
75
what does linkage indicate?
2 genes on one chromosome
76
what is a karyotype?
an individual's complete set of chromosomes.
77
what does haploid mean?
the presence of a single set of chromosomes in an organism’s cells
78
are sexually reproducing organisms haploid or diploid?
diploid
79
what are euploid organisms?
Organisms with multiples of the basic chromosome set (genome)
80
what are polyploids?
have more than 2 chromosome sets
81
what does aneuploid mean?
Individuals whose chromosome number differs by one or a small number of chromosomes
82
what does autosomal mean?
non-sex determining
83
How do you know if its an X-linked recessive trait?
more males than females express the trait
the characteristic often skips a generation
if the female expresses the characteristic,
all of her male offspring will express the trait
84
How to tell if its a dominant trait?
vertical patterns of affected individuals
85
How to tell if its a recessive trait?
horizontal patterns of affected individuals
86
How to tell if its an autosomal recessive trait?
Consanguinity often present between parents
87
How to tell if its an autosomal trait?
Males and females affected with equal probability
88
How to tell if its an X-linked recessive trait?
Males affected, female carriers
89
How to tell if its an X-linked dominant trait?
All daughters of affected males are affected
90
How to tell if its a mitochondrial trait?
Non-Mendelian
Maternal inheritance
91
what complications affect interpretations of pedigrees?
New mutations
Penetrance
Expressivity
Delayed onset
Anticipation
Imprinting
92
what is the lod score eq?
log 10 (odds linked/ odds unlinked)
93
what are lod scores?
are logarithms, so data from separate families can be pooled from different pedigrees by adding lod scores
94
what are the 3 different types of polygenic trait?
Metric: continuous scale
Meristic: discrete scale
Threshold: present or absent
95
what are threshold traits?
Discrete phenotypes (e.g. affected or unaffected) that are multifactorial
96
what is the equation between environment, genotype and phenotype?
phenotype = genotype + environment
Vp = Vg +Ve + Vge
Vg = Va + Vd + Vi
97
What is the equation for Broad sense heritability?
H^2 = Vg/Vp
98
What is the equation for narrow sense heritability?
H^2 = Va/Vp
99
what values should H^2 be between?
0 and 1
100
what is the infinitesimal model?
A simple model of the inheritance of quantitative traits, which assumes an infinite number of unlinked loci, each with an infinitesimal effect
101
When does hardy-weinberg eqm apply?
Organisms are diploid, sexual and have discrete generations
Allele frequencies are the same in each sex
Mendelian segregation occurs
Mating occurs at random
Population size is large so no genetic drift
No gene flow (immigration/ emigration)
No mutation
No selection
102
what are the hardy-weinberg assumptions?
pop size is large
no genetic drift
no migration/gene flow
no mutation
no selection
103
What are the 4 postulates of evolution by natural selection?
Individuals within species are variable
Some of the variations are passed on to offspring
In most generations, more offspring are produced than can survive.
Survival and reproduction are not random: individuals with the highest reproductive success are those with the most favourable variations
104
why does evolution occur?
because of changes in allele frequencies!
105
what is driift?
the chance difference in transmission of alleles, leading to fluctuations in allele frequency
106
what is the founder effect?
Drift in small populations can produce biased allele frequencies
107
what is fitness W?
the reproductive success of a genotype relative to the optimum genotype.
Fitness W = 1 – s
108
what happens to allele freq when s is high?
they change rapidly
109
what does s determine?
how fast allel freq changes
110
what are the Modes of Selection on Quantitative Traits?
Stabilising selection
Directional selection
Disruptive selection
111
what is stabilising selection?
intermediate variants are selected for, reduces variance of a trait. Arguably the most common mode e.g. birth weight in humans
112
what is directional selection?
individuals at one extreme are selected for, shifts the mean value of a trait. Tends to be associated with changing environments e.g. size of European black bears
113
what is disruptive selection?
individuals at both extremes are selected for, leading to a bimodal distribution. Associated with sympatric speciation (within a population) e.g. African fire birds
114
what is kin selection?
changes in gene frequency across generations driven by interactions between related individuals
115
what is the coefficient of relatedness?
r = (1/2)^n
Where n = connection removed from self
116
what is hamilton's rule?
reformulated the definition of fitness as the number of an individual’s alleles in the next generation
117
what is speciation?
lineage-splitting event that produces two or more separate species
118
what is Biological Species Concept?
A species is defined as a group of organisms capable of interbreeding and producing fertile offspring.
119
what are the 2 types of speciation?
allopatric
sympatric
120
what is speciation reinforced by?
Pre-mating isolation
Post-zygotic isolation
121
what is pre-mating isolation?
Behavioural choices
Spatial constraints
Temporal isolation
Mechanical incompatibility!
122
what is post-zygotic isolation?
Hybrid inviability
Hybrid sterility
123
what is muller ratchet?
accumulation of deleterious mutations (which can be removed by sexual reproduction & recombination)
124
what is grandualism?
evolution generally occurs uniformly and by the steady and gradual transformation
125
what is punctuated-equilibrium?
evolution is marked by isolated episodes of rapid speciation between long periods of little or no change
126
what are homologous structures?
Similarity by common descent,
similar form and function,
similar developmental trajectory
127
what are analogous structures?
Different ancestry,
same function,
different developmental trajectory
128
what is dollos law?
Evolution is not reversible
129
what is co-evolution?
The evolution of reciprocal adaptations of two or more species that have prolonged close interactions
130
where do you expect to find co-evolution?
Mutualism (++)
Parasitism, predation (-+)
Competition (--)
131
where do you not expect to find co-evolution?
Commensalism (o+)
Amensalism (-o)
132
what is an arms race?
Situations where an innovation one species leads to a counter innovation in the other
133
what is adaptive radiation?
the spread of new species of common ancestry into different niches, involving an excess of cladogenesis over extinction.
134
what is convergent evolution?
the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches
135
what is ecological release?
when a species expands its niche within its own habitat or into a new habitat where there is little competition for resources, which remain abundant (also release from predators and disease)
136
what kind of structures are evidence of radiation?
homologous
137
what kind of structures are evidence of convergent evolution?
analogous
138
what are the Limitations of convergent evolution?
Contingency
Functional/physical constraints
Developmental constraints
Genetic constraints
139
