Unit 2 Flashcards
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1
Q
Which type of DNA makes functional RNA molecules
A
Non-coding RNA
2
Q
What DNA codes for proteins
A
Coding-DNA
3
Q
What is the name of the discrete units of hereditary
information consisting of a specific nucleotide sequence in DNA.
A
Genes
4
Q
Does more genes mean for a bigger genome size?
A
No
5
Q
What are the names of the proteins that condense DNA in eukaryotic cells.
A
Histones
6
Q
What is the name of the condensed form of DNA pairs with proteins
A
Chromatin
7
Q
What is the name of DNA wrapped around a histone complex?
A
Nucleosome
8
Q
What is the chromatin that is loose and found in the throughout the nucleus and is hardly visible?
A
Euchromatin
9
Q
What is the name of the dark staining compact chromatin found close to the nuclear membrane.
A
Heterochromatin
10
Q
Which group loosens the interactions of the histone proteins with the DNA.
A
Acetyl group
11
Q
When is euchromatin found in the cell?
A
When it is not dividing and the genes are active
12
Q
Are the genes active when they are condensed in Heterochromatin
A
No
13
Q
Which group helps to condense the Heterochromatin?
A
Methyl group
14
Q
What is the process of gene activation or deactivation called?
A
Epigenetic’s
15
Q
Why does histone condense chromatin?
A
Histones are positively charges and DNA is negatively charged, so adding Histone creates a force that brings DNA together.
16
Q
What is the smallest unit of uniform length that can code for the 20 amino acids?
A
3 nucleotide bases
17
Q
What is the name of the triplets of nucleotide bases?
A
codon
18
Q
Which noncoding element regions can be used to enhance or repress the expression of a gene?
A
Control elements
19
Q
What is the name of the noncoding region where the transcription of DNA will start?
A
Promoter
20
Q
Which sequence is used to stop the DNA transcription?
A
Polyadenylation sequence
21
Q
What is the type of DNA that makes up most of our genome?
A
Non-coding DNA
22
Q
What are telomeres
A
They are non-coding DNA sequences made up of one repeating sequence of DNA that are at the end of chromosomes that prevent genes from being eroded. In humans, this sequence is TTAGGG which is repeated.
23
Q
Are chromosomes fully replicated during cell division?
A
No they are not, the telomeres shrink every time a cell divides
24
Q
What are the three steps of transcription?
A
Initiation, Elongation, Termination?
25
What are the two processes that make up gene expression?
Transcription and translation
26
What is the molecule that splits up the double helix of DNA and reads the template strand to create a mRNA strand?
RNA polymerase II
27
In which way does RNA Polymerase II read DNA strands?
In the 3' to 5' direction
28
What do transcription factors do?
They permit the RNA polymerase to attach itself to the sequence that is to be read
29
Where can transcription factors bind themselves?
Promoter regions of DNA
30
What is a common eukaryotic promoter?
TATA box
31
At which end end of the RNA sequence does RNA polymerase add a nucleotide?
The 3' carbon
32
Why is the human genetic code redundant?
To minimise the impact of mutations on the specimen.
33
What is the molecule used to translate the DNA sequence into a protein?
tRNA
34
What are anticodons?
They are molecules that base pair with a specific codon of mRNA.
35
What are the structures in which the synthesis of polypeptides will occur?
Ribosomes
36
What is the main constituent of the ribosome
rRNA
37
How many tRNA binding sites are there in ribosomes, and what are their names?
3 zones. Aminoacyl (A site), Peptidyl (P site) and Exit (E site).
38
What are the three steps of translation?
Initiation, Elongation and Termination
39
What are the three events that happen in the initiation step of translation?
1. The small ribosomal subunit binds to mRNA in the P site.
2. The initiator tRNA binds to the mRNA at the start codon.
3. The large ribosomal subunit binds to the small ribosomal subunit, which requires energy in the form of GTP.
40
What are the steps of elongation?
A new tRNA molecule binds itself to its complementary codon in the A site of the ribosome. GDP is than used to form a dehydration reaction between the polypeptide chain found on the tRNA in the P site and the amino acid of the tRNA in the A site. An elongation factor than translocates the tRNA in the A site to the P site and of the P site to the E site which requires GDP. In the E site, the tRNA exits the ribosome. This is than repeated.
41
What are mutations?
They are changes in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus.
42
What are point mutations?
They are a change in a single nucleotide pair of a gene
43
What are the different types of point mutations?
Base-pair substitutions, single base insertions, and single base
deletions.
44
What is a base pair substitution?
It is the replacement of one nucleotide and its partner with another pair of nucleotides
45
What are silent mutations?
They are basepair substitutions that have no effect on the coded protein due to the redundancy of the genetic
code.
46
What are missense mutations
They are base pair substitutions that change one amino acid to another
47
What are nonsense mutations?
They are base pair substitutions that change one amino acid into a stop codon.
48
What are insertion and deletion mutations?
They are additions or losses of nucleotide pairs in a gene. (cause a shift in all other nucleotide sequence which has disastrous effects if the insertion is not a multiple of three.)
49
What are mutagens and name some of them.
Mutagens are things that interact with DNA and cause mutations. Some physical mutagens are: UV light and analogue nucleotides that insert themselves in DNA instead of the proper base pair.
50
What is the central dogma?
It states that DNA is transcribed into RNA which is than translated into a protein.
51
What are somatic cells?
They are all the cells in the body that are not the reproductive cells and reproduce via mitosis.
52
What are gametes?
The reproductive cells in your body and the cells that produce them via meiosis.
53
Why do cells divide?
To repair tissue, to enable growth and to reproduce
54
What are daughter cells?
They are the two new cells that come from a single cell that has performed mitosis.
55
What are the two main phases of the cell cycle?
Interphase (95% of the cell's life) and mitotic phase (5% of the cell's life).
56
What are the three events in interphase?
Growth phase 1 (G1), DNA synthesis and Growth phase 2 (G2)
57
What are the two main events of the mitotic phase?
Mitosis and cytokinesis
58
Describe the events that occur during growth phase 1
1. there is extensive synthesis organelles, and the cell eventually reaches mature size for its type; the centrosomes begin duplicating.
2. there are many important regulatory proteins synthesized in this
phase.
59
What happens to DNA when the cell divides?
The DNA is condensed in the from the form of chromatid to the ultra compact form of chromosomes.
60
Describe the events that occur during DNA synthesis
All DNA is replicated so that there is a copy of each chromosome. (All 46 chromosomes in the cell are replicated in an exact copy)
61
How many chromosomes does the average human have?
46 individual chromosomes and 23 pairs of chromosomes.
62
What is the name of the two types of chromosome and what do they indicate?
Autosomes (all 22 pairs of chromosomes that are found in all humans), Sex chromosomes (The chromosome that are unique to each sex)
63
What are homologous chromosomes?
They are are similar chromosomes that include the same genes but may have different versions of these
genes, called alleles.
64
What is the ploidy number and what is the human ploidy number?
It is the number of complete sets of
chromosomes in a cell. The human ploidy number is 2n.
64
What are alleles?
Different version of the same genes
65
How does the process of DNA replication occur?
The two strands in the cell separate and each serve as a template for the two new DNA strands. This original strand is called the parental DNA and the two new DNA strands are called daughter strands.
66
What is the enzyme used in DNA replication?
DNA polymerase
67
In what direction will daughter strands grow?
They will grow from the 5' to the 3' direction.
68
Why is DNA replication said to be semi conservative?
This is said because after replication, each new DNA molecule will consist of
one strand present in the parental duplex and one newly synthesized
“daughter” strand.
69
What is the name of copied chromosomes?
Sister chromatids
70
How are chromatids bound together?
Via the centromere that attaches them in their center.
71
How many chromosomes, sister chromatids and individual chromatids are there after S phase.
46 chromosomes, 46 sister chromatids and 92 individual chromatids.
72
What happens during the second growth phase of the cell?
The cell slightly increases in size and centrosomes finish duplicating.
73
What are the microtubules formed by centrosomes during cell division called?
Spindle fibers.
74
What are the five stages of mitosis?
In order: Prophase, prometaphase, metaphase, anaphase and telophase?
75
What occurs during prophase
1. Chromatin condenses into chromosomes.
2. Nuclear envelope remains intact (but the nucleolus disintegrates).
3. Duplicated centrosomes separate and move around the nucleus.
4. Microtubules extend between the centrosomes forming the mitotic spindle.
76
What occurs during prometaphase?
1. Nuclear envelope breaks down and DNA is now condensed into chromosomes.
2. Centrosomes are now positioned at opposite ends of the cell.
3. Some microtubules attach to the chromosomes at the centromere via the kinetochores.
77
What occurs during metaphase?
1. Chromosomes become aligned along the cell midline (metaphase plate).
2. for each chromosome, the kinetochores of the sister chromatids are attached to microtubules coming from opposite poles.
78
What occurs during anaphase?
1. Centromeres break and chromatids separate, and they are no longer referred to as sister chromatids.
2. Chromosomes are pulled to opposite ends of the cell, using microtubules as tracks.
3. The cell elongates at the end of anaphase, each pole of the cell
has a complete set of chromosomes.
79
What occurs during Telophase?
1. One copy of each chromosome is present at opposite ends of the cell.
2. Chromosomes start to loosen and become less coiled.
3. Microtubules (spindle fibers) disappear.
4. Nuclear envelope forms around the DNA.
5. Telophase is the end of nuclear division, but cell division is not complete.
80
What is the cleavage furrow?
The zone where the cell begins picking off during telophase.
81
What happens during cytokinesis
The cell pinches inward with a contractile ring of microfilaments forming a cleavage furrow. The two cells eventually separate forming two new daughter cells with equal amounts of cytoplasm.
82
What is a major difference between plant cell division and animal cell division?
Plants do not separate using microfilaments to form a cleavage furrow, they use vesicles to transport material to form between the cell to form a cell wall. This eventually creates two new daughter cells separated by a cell wall.
83
What is the other step a cell may take after reproducing?
It can exit the cell reproduction cycle and enter G0 phase where it does not prepare to enter S phase. When doing so it does not reproduce and can stay there as long as it sees fit.
84
What are some cells in that are often in G0 phase and what can a cell do while in G0 phase.
Some examples are liver cells, nerve cells. In this phase the cell can perform remain active by performing highly specialized functions.
85
Why is there regulatory mechanisms to control cell division?
So that cells don't divide in an uncontrolled and chaotic manner. It is also to prevent cells that are defective from reproducing.
86
What regulatory mechanisms control cell division?
1. There are receptors that interact with molecules on neighbouring cells to monitor cell density in a tissue; this leads to density-dependent inhibition of growth.
2. There are also anchoring proteins hold cells in place within their tissues and prevent cells from establishing themselves in other tissues if they dislodge; this is called cell adhesion.
3. DNA and cellular function are checked by regulatory proteins during
the cell cycle; this occurs during cell cycle checkpoints
87
What happens to cell reproduction if cell density increases too much?
They stop reproducing and enter G0 phase.
88
How do cells remain locked in place in healthy tissues?
They are locked in place via anchoring proteins.
89
What happens if a cell's anchoring is lost?
It either is brought back and anchored again, or it performs apoptosis.
90
How many checkpoints are there to regulate the cell cycle and when to they occur?
There are three checkpoints to regulate the cell cycle and they occur in the late phase of G1, at the end of G2 and at the end of the mitotic phase.
91
Which cell reproduction checkpoint is the most important in humans?
The G1 checkpoint or otherwise called the restriction checkpoint is the most important as it is the one that allows cells to reproduce if they pass through.
92
What do cell reproduction checkpoints monitor to check if a cell can pass?
G1: is there DNA damage?
G2: is there any DNA damage?
Has all the DNA been replicated?
Are there any parts of the DNA
that are incompletely replicated?
M: Are all chromosomes properly
aligned? Are the kinetochores
attached to the spindle fiber?
93
Which proteins are responsible of cell checkpoints and what is the most important protein that is responsible for cell checkpoints?
Regulatory proteins, p53
94
How do somatic cells duplicate themselves
mitosis
95
How are gametes produced
meiosis
96
What is cancer?
It is unregulated growth of damaged cells in the body that can proliferate endlessly due to mutation in their regulatory DNA. These cells are dangerous as they can take all nutrients from a section and do not respect the cell checkpoints.
97
How many chromosomes are in somatic cells
46 (23 homologous pairs)
98
How many chromosomes are in gamete cells
23 (no pairs)
99
What is the union between a male and female gamete (a fertilized egg)
zygote
100
101
what are the different versions of a same gene called
alleles
102
How many autosomes are found in the human body
44 (22 pairs)
103
Which phase is present in mitosis but not meiosis
prometaphase
104
What are all the phases of meiosis
Interphase, prophase 1/2, metaphase 1/2, anaphase 1/2, telophase 1/2, cytokinesis
105
What happens in early S phase.
chromosomes are duplicated, resulting in 2 sister chromatids held together at centromeres and centrosomes replicate.
106
What happens in Prophase 1
nuclear envelope disappears and chromatin condenses into chromosomes. Centrosomes continue to separate and move to opposite poles.
107
through which process are tetrads formed
Synapsis
108
What are tetrads
the grouping of homologous pairs of chromosomes
109
What is the difference between dominant genes and recessive genes?
An allele of a gene is said to be dominant when it effectively overrules the other (recessive) allele.
110
What is a phenotype?
Observable physical characteristic coded by a gene.
111
What is the law of segregation?
It states that during the formation of gamete, each gene separates from each other so that each gamete carries only one allele for each gene
112
What is blended inheritance?
It is an early hypothesis regarding how heredity worked: genetic material contributed by both parents mixes in a manner analogous to how paint colours might be mixed.
113
What are true breeding individuals?
They are individuals that possess two alleles of the same type and are therefore homozygous.
114
What is a genotype?
Genotypes describe the combination of alleles in a particular individual
115
What is a phenotype?
phenotype refers to the physical manifestation of an individual’s genotype.
| (is also impacted by the environment)
116
Does the position of a gene in a chromosome affect the chance of its expression in offspring?
Yes
117
What is the law of independent assortment?
It states that states the alleles of two (or more) different genes get sorted into gametes independently of one another
118
When will the law of independent assortment apply?
It will apply if the alleles are on different chromosomes or if they are far apart on the chromosome? (because of the crossing over event)
119
When can we conclude that the law of independent assortment does not apply?
When the observed ratio does not match the expected ratio.
120
How do we calculate the number of different allelic possible combinations of an individual?
2^(Number of heterozygous genes)
121
What is gene penetrance?
It is defined as the proportion of individuals of a genotype that also express an associated trait
122
What is gene expressivity?
Expressivity is the degree to which trait
expression differs among individuals. In other words, individuals with the same genotype can also have a variability of symptoms in a population sharing the same genotype.
123
What is incomplete dominance?
They are genes that do not show complete dominance over another gene, a heterozygous form can be
intermediate between both homozygous forms. When there is incomplete dominance, the phenotype always reflects genotype and genotypic ratio is the same as the phenotypic ratio.
124
What is codominance?
It is when each allele displays a unique phenotype, and heterozygous individuals express both distinct phenotypes.
125
By how many alleles is the human blood group determined?
Five (IA, IB, i) and the rhesus factor (r,R)
126
What is epistasis?
Defined as the presence of certain alleles of one gene that prevent or mask the expression of alleles of a different gene, resulting in a new phenotype.
127
What is pleiotropy?
The production by a single gene of two or more apparently unrelated effects.
128
Why is sex linked inheritance different from autosomal inheritance?
Males only possess one X chromosome and women possess two which has an impact on the gene expression of males that possess a certain genotype in their X chromosome versus women who possess a genotype in their X chromosome. This is not the case in autosomal inheritance where the sex will not impact the genetic information passed down to an offspring.
129
What is a hemizygous individual?
A term that describes a person who has only one copy of a gene rather than the usual two copies.
130
What is dosage compensation?
A mechanism that makes genetic expression equivalent in the two sexes by modifying gene expression. (In mammals this is caused by the inactivation of one X chromosome)
131
What is a Barr body?
It is a dense, metabolically inactive X chromosome
132
Is inactivation of the X chromosome programmed on one of the chromosomes?
No it is random
133
What does aneuploidy mean?
it describes abnormalities caused by the presence of an extra or absence of a chromosome.
134
What does polyploidy mean?
It describes the presence of multiple sets of chromosomes
135
What are nondisjunction events?
It is when chromosomes fail to
separate.
136
Can nondisjunction events happen in autosomal and sex chromosomes?
Yes they can happen in both.
137
Why do aneuploidies arise?
They arise as a result of abnormal meiotic AND mitotic divisions.
138
What is trisomy 21?
It is the result of an aneuplodie in a gamete cell. This causes the embryo to have an extra 21 chromosome.
139
Does the moment when a nondisjunction happen change the produced gamete cells?
Yes it does, in the case of a nondisjunction in prophase 1 there will be two gametes produced with twice the amount of genes and two empty gametes. In the second case there will be two normal cells and a cell with an extra chromosome.
140
Is a phenotype only affected by its matching genotype?
No, the phenotype is a manifestation of a genotype and of the environment. So phenotypes are a continuum of phenotypes rather than a discrete phenotype category.
141
What are some environmental conditions that affect the expression of a certain gene?
Diet, general health, sleep, etc.
142
What is the general rule when thinking of a phenotype expression in relation to genes and nature?
The general rule is the following: genes set the limits for the phenotype, and the environment molds the phenotype within its limits.
143
Is gene expression constant throughout a person's lifetime?
NO it may or may not vary during the lifespan of an individual.
144
Why can variation in gene expression be useful for an individual?
It can help individuals cope with environmental changes?
145
What seasonal plasticity is observed in Nemoria arizonaria?
The summer brood feeds on oak leaves and resembles an oak twig,
while spring brood feeds on and resembles oak catkins
145
What happens to Daphne if there are predators in the environment?
Individuals (normally have round heads with no spines) in the population develop very sharp spines on their heads to protect them from their predators
146
What is the difference between codominance and incomplete dominance.
In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype
147
What permits the chromosomes to move when attached to the spindle fibers?
The motor proteins in the kinetichores and the breakdown of the bond in the centromere.
148
What is taxonomy?
the branch of science concerned with classification, especially of organisms; systematics.
149
What are the taxon groups?
Kingdom, Phylum, Class, Order, Family, Genus, and Species
150
How does the binomial naming system function?
It works by combining the genus and species name to give a full latin name.
151
What did James Hutton discover
He discovered that the earth was much older than it was previously though by looking at geological evidence.
152
What did Thomas Robert Malthus identify?
That human societies and their populations could outgrow their supply
of food, causing reproductive rates to be constrained and population growth
to slow.
153
What was the theory proposed by Jean-Baptiste Lamarck
that organisms could change over time based on two principles: 1) use and disuse and 2) inheritance of
acquired traits. ( the most important is the inheritance of acquired traits model)
154
What was Charles-Darwin's theory?
That natural selection and descent with modification over time would lead organisms to change and to learn as the better suited individuals would leave behind more offspring which would help their genes propagate.
155
What is homology?
It describes a characteristic that is similar between organisms as a result of common ancestry. (may no longer be identical as adaptive radiation, a process where organisms evolve and adapt to new environments, causes modifications to the original
characteristic.
156
What is adaptive radiation
A process where organisms evolve and adapt to new environments, causes modifications to the original
characteristic.
157
Define analogous structures?
Characteristics that are similar between unrelated organisms; these structures
evolved not from common ancestry but from similar selective pressures from
the environment
158
On which group does evolution occur?
On populations
159
What is the definition of a gene pool?
A gene pool refers to all the alleles for all the genes present in a population.
160
Do individuals of a population have the same number of genes and kind of genes?
Yes
161
What is microevolution?
Microevolution is the creation of new
alleles from mutations but also the change in proportions of alleles in a population’s gene pool from one generation to the next.
162
How do we determine if microevolution is happening?
if the proportion of individuals of any genotype changes from one generation to the next, there is microevolution.
163
What is genotype frequency?
genotype frequency is the proportion
of a particular genotype in the
population (requires a large sample
size to be representative of the population)
164
What is allele frequency?
Allele frequency is the proportion of a
specific allele in a population. (requires a large sample size to be representative of the population)
165
Will alleles change with time if there are no outside factors requiring it?
NO
166
What is the Hardy-Weinberg Principle
It says that in a large population where all male-female matings are equally likely and occur randomly, allele frequency in the population will not change over generations.In sum, if allele and genotype frequencies do not change over time, a population is not evolving.
167
Are populations usually at equilibrium for long periods of time?
No
168
What are factors that can prevent microevolution from occurring?
Absence of mutations, Random mating, No natural selection, Extremely large population size and Absence of migration
169
How is allelic frequency calculated?
We define: p as the dominant allele frequency and q as the recessive allele frequency. (applies to diploid organisms)
p+q=1
170
How is EXPECTED genotype frequency calculated.
We define: p as the dominant allele frequency and q as the recessive allele frequency. (applies to diploid organisms)
p^2 + 2 pq + q^2 = 1
Where p is the genotype frequency of a dominant allele homozygous individual, 2pq is the genotype frequency of a heterozygous dominant individual and q is the genotype frequency of a homozygous recessive individual.
171
How do we know a species is departing from a Hardy-Weinberg equilibrium?
If the degree of departure between observed allele frequency and those
expected by the HW there is evolution.
172
What are some causes of microevolution?
Mutations, Choice of mating partners, Natural selection, Genetic drift, Gene flow resulting from migration, etc.
173
What is natural selection?
natural selection occurs as the environment selects for the best suited
individuals. Best suited individuals have a reproductive advantage and will be chosen more often to mate which will cause their genes to perpetuate in greater quantities.
174
What is genetic drift?
genetic drift is an event that randomly samples a small group of organisms from a much larger population
175
What is genetic flow?
Gene flow is the flow of alleles into or out of a population via migration.
176
How are new genes and new alleles created?
By random mutations.
177
Are mutations usually transmitted from one individual to another?
No, most of them occur in somatic cells and therefore are wiped out when the host dies.
178
What is the mutation rate in animals and plants?
About 1 in every 100,000 genes per
generation
179
What is the impact of genetic recombination in sexually reproducing populations?
It causes the combination of new alleles that may produce the creation of new phenotypes that may or may not be advantageous. If the phenotype is advantageous, natural selection may increase its frequency.
180
What is a random shift in population?
It describes a random evolutionary change in a population and how allele frequencies can fluctuate unpredictably from one generation to the next.
181
What are the consequences of a shift in population.
Alleles may be eliminated from population purely by chance regardless they are beneficial or harmful. It also decreases genetic variation within a population and increases genetic
differences among different populations. (If there are less survivors, there will be a greater chance of deviation from the expected result)
182
What is the bottleneck effect and what are its consequences?
Bottleneck effect occurs when the numbers of individuals in a large
population are drastically reduced by a disaster. It can cause some alleles to be overrepresented and others to be
underrepresented or even eliminated among the survivors.
183
What is founder's effect and what are its consequences?
Founder effect occurs when a few
individuals become isolated from a larger population. This causes a population to only have a small portion of genetic variation compared to the original population. This cause the allele frequency to be very different than that of the parent population.
184
What are the causes of gene flow and what are its consequences?
It is the results from the movement of fertile individuals between populations
causing a movement of alleles. The consequences of gene flow include: Loss/gain of genetic variation and it tends to reduce differences
between populations that reproduce over time.
185
What is the only factor that can lead to the adaptation of an individual to its environment?
Natural selection
186
What leads to macroevolution?
The combination of positive mutations and natural selection.
187
Can natural selection create new genotypes that will create variations in a population?
No, natural selection increases the frequencies of certain genotypes,
fitting organisms to their environment over generations, but will not
create entirely new genotypes. Mutation are the ones creating new genotypes.
188
How does an allele become fixed?
It is so advantageous in an environment that it ends up replacing all other alleles.
189
What is the difference between negative selection and positive selection?
Negative selection is natural selection
that decreases the frequency of a
harmful allele while positive selection is natural selection that increases the
frequency of a favorable allele.
190
What is directional selection?
It occurs when conditions favour individuals exhibiting one extreme of a phenotypic range. This shifts a population’s phenotypic character in
one direction or the other of the curve. (towards the favoured phenotype) It is usually seen when a population’s environment changes or when
members of a population migrate to a new habitat.
191
What is disruptive selection?
It occurs when conditions favour individuals at both extremes of a phenotypic range. This causes the population's phenotypic character to form shift towards the two favoured phenotypes forming two spikes at opposing ends on the population curve.
192
What is stabilizing selection?
It occurs when conditions act against both extreme phenotypes and favours intermediate variants. This causes the population curve to have a higher peak near the midline of these opposing phenotypes. This mode of selection reduces variation.
193
What is speciation?
Speciation is the process by which one species splits into two or more
new species
194
What is macroevolution?
Major evolutionary change. The term applies mainly to the evolution of whole taxonomic groups over long periods of time.
195
What is the definition of a species?
It defines a taxon as individuals that can reproduce and produce viable fertile offspring.
196
What is the morphological species concept?
The morphological species concept is a concept that characterizes a species based on its structural features, like body shape.
197
What are the two main barriers causing individuals to be unable to reproduce together?
Prezygotic barriers and postzygotic barriers.
198
What are the 5 prezygotic barriers and how to they impede reproduction?
habitat isolation (individuals that occupy different habitats in the same area), temporal isolation (species breed during different times of the day, seasons, or years), behavioral isolation (different courtship rituals and other unique behaviours), mechanical isolation (mating can be attempted but morphological differences prevent its successful completion) and gametic isolation (sperm of one species may not be able to fertilize the eggs of another species)
199
What are the 3 postzygotic barriers and how to they impede reproduction?
Reduced hybrid viability (genes of different parent species interact
in ways that impair the hybrid’s
development or survival), Reduced hybrid fertility (hybrids are healthy and vigorous but are sterile), Hybrid breakdown (first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring are feeble or sterile)
200
What is the phylogenetic species concept?
traces phylogenetic history of organisms to define in which group they belong (comparing morphology & molecular sequences).
201
What is the ecological species concept?
Views a species in terms of its ecological niche.
202
Why does specification occur?
Speciation occurs due to reduced gene flow
203
What are the ways in which specification can occur? Name them and describe them.
1) allopatric speciation occurs when geographic separation of populations
restricts gene flow.
2) sympatric speciation occurs in
geographically overlapping populations
when biological factors, such as
chromosomal changes and nonrandom
mating, reduce gene flow.
204
What is sexual selection?
The idea of sexual selection arose from the observation that many animals
have evolved features that may be deleterious in some ways. Despite potentially affecting their survivability, these features help maximize their reproductive success.
205
What are the two processes involved in sexual reproduction selection?
1) Mate choice or intersexual selection selects for features that make an
organism more attractive to the opposite sex.
2) intrasexual competition selects for features that help an individual intimidate or fight off same-sex rivals.
206
What is handicap theory?
Handicap Theory (Indicator Traits) suggests deleterious features are condition-dependent and have associated costs. Therefore, if individuals can handle these costs, this might suggest superior genetic quality.
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What does the Hamilton-Zuk Hypothesis propose?
It posits that sexual ornaments are indicators of parasite and disease-resistance.
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Can natural selection predict the environment and select for what will be advantageous in the future?
No it cannot it can only select fro what is the most advantageous at the moment.
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What can evolutionary novelties arise from?
1) gradual refinement of existing structures over long periods of time
2) major changes in body can result from changes in developmental
genes or genes that control spatial organization of body parts.
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What do Hox genes provide?
The positional information in an animal embryo. These gene products prompt cells to develop into structures appropriate for a particular location.
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Why are Hox genes mutations interesting?
Mutations could duplicate Hox genes,
allowing one gene to continue coding for proteins that regulate normal development. The copied Hox gene could be further mutated without too many deleterious effects. Further mutations and duplications could
give rise to new physical features which would allow for evolution.
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What is phylogenetics?
Phylogenetics is the science of classifying organisms according to common ancestry based on their characteristics.
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What are the two related patterns produced by evolution.
1) Nested patterns of similarities
found among species on present day earth,
2) The historical pattern
of evolution recorded by fossils.
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How are phylogenies created?
They can be created by identifying: 1) morphological characteristics
2) molecular characteristics.
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What is a monophyletic group?
A monophyletic group, sometimes called a clade, includes an ancestral taxon and all of its descendants. A monophyletic group can be separated from the root with a single cut, whereas a non-monophyletic group needs two or more cuts.
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What is a paraphyletic group?
A paraphyletic group is a group of any size and systematic rank that originated from a single common ancestor, but does not – as opposed to a monophyletic group – contain all descendants from this ancestor
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What is a polyphonic group
Polyphyletic groups include organisms that are grouped together despite not being closely related. They may include organisms that have similar traits or appearances but do not share an evolutionary history. Polyphyletic groups may be those that were once considered monophyletic.
218
What are homologous and analogous characters?
Homologous: Characteristic present in the common ancestor of the two groups and retained over time.
Analogous: Characteristic that evolved independently in the two groups as an adaptation to similar environments
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What do we need to develop
hypotheses of evolutionary relationships?
Homologies that are shared by
some, but not all, of the members of them group under consideration. These are called shared derived characters or
synapomorphies.
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How can comparing sequences allow us to know how much difference there is between two species.
if the species are closely related, the DNA will differ at only one or a few sites. If they are different they will be related by a further ancestor.
221
How can molecular clocks be used to determine the time it has been since genes have evolved?
The number of point mutations is
proportional to the time elapsed
since the species branched from
the common ancestor so the approximate time where the mutation happened can be found.
222
How old is the oldest confirmed existence of life?
3.5 billion years old
223
What are the four stages that are hypothesized to have created life.
1) Abiotic synthesis of small organic molecules, such as amino acids and
nitrogenous bases.
2) Joining of small molecules into macromolecules, such as proteins and
nucleic acids.
3) Packing of these molecules into protocells, droplets with membranes
that maintained an internal environment.
4) Origin of self-replicating molecules that eventually made inheritance
possible and natural selection could work to make improvements.
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How and when did earth form?
Earth formed about 4.6 billion
years ago, condensing from a vast cloud of dust and rocks that surrounded our young sun.
225
What is the name and the characteristics of the first geological eon of the earth?
The Hadean:
The planet had just formed and was very hot due to high volcanism and frequent collisions with other Solar System bodies..
Early earth may have had an atmosphere with many reducing agents: hydrogen gas, carbon monoxide, methane, ammonia, and hydrogen sulfide.
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What did Haldane and Oparin hypothesize?
1) Earth’s early atmosphere was a reducing environment in which organic
molecules could have formed.
2) Energy for this organic synthesis could have come from lightning and intense UV radiation
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What did the Miller-Urey experiment demonstrate?
They found that biomolecules such as amino acids and nitrogenous bases could be synthesized in an environment that resembled the early Earth environment.
228
What is the hypothesis regarding the creation of polymers?
That polymers may have been created by dripping monomers on hot sand or clay.
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What are the characteristics of life that protocells demonstrate?
Ability to divide (reproduce), maintain simple, metabolic reactions, and ability to maintain an internal environment (homeostasis).
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What are protocells?
They are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure.
231
What is the first replicating molecule that is hypothesized to have appeared? Why is it this molecule?
RNA
Ribozymes (RNA enzymes) can make copies of RNA (provided that they are supplied monomers).
RNA could have catalyzed protein formation (as do ribosomes).
RNA molecules are more “flexible” than DNA because they are:
single stranded and can fold to create different shapes
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Does natural selection apply to self reproducing molecules?
Yes
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Why is earth's fossil record an incomplete picture of the life that was once on earth?
Not all organisms can be calcified and preserved as fossils. Very few individuals die in the right location to be fossilized.
234
How is radiometric dating used to know the age of the fossil?
We mesure the presence of a isotope with a known half life to find the age of the fossil.
235
What are stromatolites?
3.5-billion-year-old, rocklike
structures composed of layers of bacteria and sediment. (oldest fossils)
236
How long did procaryotes dominate? Who were they replaced by?
1.5 billion years. They were replaced by autotrophes that could produce all the compounds necessary to their survival by using energy such as light.
237
How did photosynthesis transform the atmosphere?
It changes the earth's atmosphere composition by creating oxygen in large quantities.
238
When did the oxygen change in the atmosphere occur and what is it named?
2.4 billion years ago. It was the oxygen revolution.
239
What did the oxygen revolution cause? Why?
Atmospheric O2 would have helped
remove atmospheric methane, a
powerful greenhouse gas.
its removal would have caused gigantic
cooling events, resulting in a glaciation
period called Snowball Earth.
240
What are characteristics defining animals?
1. No cell walls
2. Multicellular
3. Internal and external mobility
4. Heterotrophy, obtaining organic food molecules by eating other organisms or substances
5. Three embryonic tissues, including an endoderm, ectoderm, and mesoderm
6. Collagen, a glycoprotein in the extracellular matrix of connective tissue
241
What are the body plan characteristics used to characterize animalia?
Symmetry and presence of segmentation, cephalization, and appendages
242
What are the types of symmetry?
1) Asymmetric organisms have no observable symmetry.
2) radially symmetric organisms are shaped like a pie or barrel and are symmetrical along any plane in a single central axis
3) bilaterally symmetric organisms have a central longitudinal plane that divides the body into two halves
243
What is metamerism? What does it do?
Metamerism is a linear series of
body segments fundamentally
similar in structure. It provides advantages, like compartmentalization of organ systems and specialization of body regions.
244
What did specialization allow?
It influenced the evolution of a centralized nervous system.
245
What is cephalization?
The concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo's development.
246
What is a recombinant chromatid?
It is a chromatid that has formed a chiasma with a homologous chromosome. Therefore they have exchanged genetic information and are a recombination of both genes.
