UNIT 2 Flashcards
1
Q
What is nessesairy for reproduction, growth and repair/regeneration of an organism?
A
Cell division
2
Q
Unicellular organisms use cell division primarily for what?
A
reproduction
3
Q
For multicellular organisms, cell division is important for what ? (2 reasons)
A
reproduction, in growth and repair of tissues.
4
Q
What results in two new cells that are exact copies of one another in prokaryotes?
A
binary fission
5
Q
Prokaryotes have how many chromosomes usually?
A
one chromosome ,(a single molecule of DNA); usually circular.
6
Q
In eukaryotes, the nuclei divide by what? (What methods ,How do it reproduce?)
A
mitosis or meiosis
7
Q
What is mitosis?
A
division of somatic (non sex) cells
8
Q
in mitosis, what can result of it? why is it used by the body?
A
Tissue repair, body growth, replace worn- out cells
9
Q
What is meiosis?
A
division of germ (sex) cells
10
Q
What does meiosis produce?
A
Production of eggs in the ovary or sperm in the testes; used for sexual reproduction
11
Q
How many phase do the mitotic cell cycle has ? And what are they called?
A
has two main phases: interphase and mitosis (m phase).
12
Q
Interphase makes up how many pour-cent of cell cycle?
A
~90%
13
Q
Interphase has how many sub-phase and how are they named?
A
has three sub-phases: G1, S, and G2.
14
Q
What happens in the G1 (gap 1) phase ? And how does chromosomes look?
A
Cellular growth & maintenance; chromosomes are single, unreplicated structures
15
Q
What is the restriction point?
A
its where a commitment is made to replicate DNA and then divide the cell; “surface area : volume imbalance”
16
Q
What happens in the S phase (synthesis) ? And how does chromosomes look?
A
DNA replicates; one chromosome becomes two sister chromatids
17
Q
What happens in the G2 (gap 2) phase ?
A
Cellular growth & preparation for mitosis (i.e., duplication of centrosomes, etc.)
18
Q
What is the M phase( mitosis)?
A
It is a nuclear division.
19
Q
How many sub-phases does the M phases have? And how are they named?
A
It has 5 sub-phases: prophase, prometaphase, metaphase, anaphase, telophase.
20
Q
Mitosis makes up how many pour-cent of the cell cycle?
A
~10%
21
Q
When does cytokinesis occur?
A
It is a cytoplasmic division, and may occur right after mitosis.
22
Q
What stimulates the cell cycle?
A
Cyclin-Cdk complexes, growth factors, and hormones
23
Q
A pedigree analysis of mitochondrial phenotypes shows what?
A
▪An affected mother passes the trait to all her children.
▪An affected father passes it to none of the children.
▪Examples: MELAS syndrome, oncocytoma, mostly traits affecting cellular respiration.
24
Q
In eukaryotic chromosomes DNA molecules are extensively….. in order to fit in the nucleus.
A
“packed”
25
How is the packing of the DNA molecules achieved?
by winding DNA molecules around histone proteins forming nucleosomes. This complex of DNA and histones is called chromatin.
26
What is just strands of chromatin?
Eukaryotic chromosomes
27
What protein around the DNA forms nucleosomes?
histone
28
What happens during the S phase ? And it’s “consequences “?
each chromosome must make a copy of itself./Each chromosome is now composed of two identical sister chromatids held together at the centromere.
29
As soon as mitosis begins what happens in the nucleus?
the chromosomes condense even more forming the characteristic shape of mitotic chromosomes.
30
What is the shape of the chromosomes when they condense?
mitotic chromosomes
31
What happens after the DNA replicates ?
the centrosome doubles.
32
A centrosome consist of what?
of two centrioles at right angles to each other.
33
When does the centrosome move to opposite ends of the nuclear envelope?
At G2 to M transition
34
What leads to the formation of the spidle structure?
These initiate formation of microtubules
35
What happens during prophase?(3 things) in mitosis
– chromosomes condense; just now
become visible as paired chromatids.
–a kinetochore (ring of protein) develops in the centromere region of every chromosome.
–centrosomes serve as poles (or mitotic centers); microtubules form between the poles to make the spindle.
36
What are the two type of micro tubules that the spindle has?
* Polar microtubules: form the spindle structure (i.e., microtubule tracks).
* Kinetochore microtubules: attach to kinetochores on the chromosomes. Sister chromatids attach to opposite halves of the spindle.
37
What happens during prometaphase?( mitosis//2)
– nuclear envelope & nucleolus disappear.
–chromosomes gradually pushed towards the middle of the cell.
38
What happens during metaphase? ( 2///mitosis)
–chromosomes are now in the middle of the
cell: the equatorial plate.
–At the end of metaphase, the centromeres (holding the chromatid pairs together) separate.
39
What happens during anaphase? ( mitosis)
– each member of the pair of chromatids (now called a daughter chromosome) migrates to its pole along the microtubule track.
40
What happens during telophase? ( 4///mitosis)
– spindle structure breaks down
– chromosomes uncoil and become less condensed (i.e., as in interphase)
– nuclear envelopes & nucleoli re-form
– production of two nuclei whose chromosomes are identical to each other and to those of the cell that began the cycle.
41
What is cytokinesis?
its the division of the cytoplasm; usually follows nuclear division.
42
In animals cell cytokinesis happens by ?
cytoplasm divides by plasma membrane furrowing (also called cleavage) caused by contraction of cytoplasmic microfilaments.
43
In plants cell cytokinesis is accomplished by?
cytokinesis is accomplished by vesicle fusion forming the cell plate (i.e., the beginning of the new cell wall).
44
What are centrosomes made up of?
2 centrioles at a perpendicular angle from each other
45
Asexual reproduction is based on what? how does it happen?
mitosis of the nucleus.
46
What are the two ways (asexually) for asexual organisms to reproduce?
* It may be a unicellular organism reproducing itself
| * Cells of multicellular organisms that break off to form a new individual
47
What are the offspring of asexual reproduction called? And why are they called that?
clones — genetically identical to the parent
48
If there is any variations asexually it results from what?
mutations
49
In sexual reproduction, the offsprings are identical or non identical to their parents?
non identical
50
Sexual reproduction results in what genetically?
in shuffling of genetic information in a population. No two individuals have exactly the same genes.
51
What is meiosis?
its the nuclear division that produces gametes that differ genetically from the parents, and also from each other.
52
What are gamete?
sexual cells, such as egg and sperm cells
53
What are the somatic cells? what are they or not specialized in? And what does it contain?
are body cells not specialized for reproduction///homologous (same size & shape; similar information) pairs of chromosomes with corresponding genes.
54
What can be called the pair of chromosomes in somatic cells?
diploid; 2n
55
What is called one of every pair of chromosomes ?
homolog
56
What do gamete contain?
they contain only one set of chromosomes (haploid; n), and are specialized for reproduction.
57
What goes into the haploid (single set of chromosomes)gamete? And what happens to the offspring?
There is a random selection of half of a parent’s chromosomes that goes into the haploid gamete; therefore, offspring are not exactly like their parents. And no two offspring are alike.
58
What is fertilization?
its the event when two haploid gametes (female egg & male sperm) fuse to form a diploid (2n) zygote cell.
59
When the two gametes fuse what is called the thing formed?
zygote
60
What are the différant sexual life cycles?
Haplontic life cycle,Alternation of generations and Diplontic life cycle
61
What kingdoms are part of the haplontic life cycle? How are gametes?
fungi and most protists; zygote is the only diploid stage.
62
What kingdoms are part of the alternation of generations? How are gametes?
plants and photosynthetic protists (i.e., algae); meiosis gives rise to haploid spores.
63
What kingdoms are part of the diplontic life cycles? How are gametes?
animals; gametes are the only haploid stage.
64
The meiosis consist of?( # of divisions)
2
65
The number of chromosomes goes from.... to....?
2 to 1
66
How many times are the DNA replicated in meiosis?
1
67
What are called the parent cells of the gamete? (Before meiosis)
Germ cells
68
The gametes are different or the same from the parent cell and each other?
different from the parent cell and from each other.
69
In meiosis, what happens during prophase 1?
homologous chromosomes pair up (synapsis), and material is exchanged by crossing-over (also called recombination) between non-sister chromatids of two adjacent homologs
70
In meiosis, what happens during prometaphase 1?
nuclear envelope & nucleolus disappear.
71
In meiosis, what happens during metaphase 1?
paired homologs now at the equatorial plate. Each chromosome has one kinetochore and associates with polar microtubules for one pole.
72
In meiosis, what happens during anaphase 1?
homologous chromosomes separate; daughter nuclei contain only one set of chromosomes. Each chromosome still consists of two chromatids.
73
In meiosis, what happens during telophase 1? (see image 3)
the nuclear envelope reaggregates; it’s followed by interphase called interkinesis.
74
DNA does it replicate before meiosis 1 or 2?
meiosis 2
75
In meiosis 2 what sisters separate ?
the sister chromatids separate.
76
What is the results of meiosis? (How much cells does it end up with)
The result of meiosis is four cells, each with a haploid chromosome content.
77
What ensures that the genetic composition of each haploid gamete is different from that of the parent and from that of the other gametes?
Both crossing over during prophase I -AND- the random selection of which homolog of a pair migrates to which pole during anaphase I
78
The more chromosome pairs there are in a diploid cell, the greater the ....?
the diversity of chromosome combinations generated by meiosis.
79
How can you calculate the probabilities of the outcomes of dihybrid crosses?
you have to multiply the outcomes from each of the individual monohybrid components.
80
What does autosomal inheritence mean?
This means that males and females are equally likely to inherit the gene. Since the autosomes are all the chromosomes that are not sex chromosomes.
81
How does human geneticists evaluate the crosses of humans?
using pedigrees
82
What does the pedigrees show?
phenotype segregation in several generations of related individuals.
83
Why does human pedigrees do not show clear proportions ?
Since humans have such small numbers of offspring
84
Since humans have such small numbers of offspring, human pedigrees do not show clear proportions. What does that mean for the results in other words?
In other words, outcomes for small samples fail to follow the expected outcomes closely.
85
A pedigree analysis of the dominant allele for a given phenotype shows what? (3)
▪Every affected person has an affected parent.
▪About half of the offspring of an affected person are also affected (assuming only one parent is affected).
▪The phenotype occurs equally in both sexes.
86
A pedigree analysis of the recessive allele for a given phenotype shows what? (3)
▪If neither parent has a given phenotype, but it shows up in their progeny, the trait is recessive and the parents are heterozygous.
▪Half of the children from such a cross will be carriers (heterozygous for the trait).
▪The chance of any one child’s getting the trait is 1/4.
87
Why does different alleles exist?
because any gene is subject to mutation into a stable, heritable new form.
88
Can alleles mutates?
Yes, randomly
89
How is called the common allele in a population?
wild type
90
How are called the other allele present with a wild type?
mutant alleles
91
Mutant alleles may produce what?
a phenotype different from that of the wild-type allele.
92
How much alleles can a population have for a given gene?
more than two alleles
93
Even if more than two alleles exist in a population, any given individual can have....?
no more than two of them: one from the mother and one from the father.
94
What is the incomplete dominance ?
This mode of inheritance
95
What are the factors that show incomplete dominance?
Heterozygotes may show an intermediate phenotype which might seem to support the blending theory.
96
What “happens” in codominance? With example using the ABO blood 🩸?
In codominance, two different alleles for a gene
are both expressed in the heterozygotes.
In the human ABO blood group system the alleles for blood type are A, B, and O.
▪AA or AO, results in type A. ▪BB or BO, results in type B. ▪OO results in type O.
▪AB results in type AB. The alleles are called codominant.
97
What are pleiotropy alleles?
are single alleles that have more than one distinguishable phenotypic effect.
98
pleiotropy alleles are caused by what ?
by the same protein produced by the same allele.
99
When does epistasis occur?
| With an example?
occurs when the alleles of one gene cover up or alter the expression of alleles of another gene.
• An example is coat color Labrador retrievers.
▪Allele B (black) dominant to b (brown)
▪Another locus determines if any coloration occurs. Allele E (pigment deposition) is dominant to e (no pigment deposition— yellow)
100
What are complementary genes?
In another form of epistasis, two genes are mutually dependent: the expression of each depends on the alleles of the other
101
What are polygenic inheritance ( quantitative trait loci ) ?
Complex inherited characteristics controlled by groups of several genes
102
In polygenic inheritance , each alleles _ or _ the phenotype?
intensifies or diminishes
103
In polygenic inheritance, variations are continuous (quantitative) or qualitative?
continuous (or quantitative)
104
What does locus or loci mean?
Gene
105
In polygenic inheritance, variations are due to what?(2 factors)
multiple genes with multiple alleles (polygenes), and environmental influences on the expression of these genes.
106
In a gene mapping scientific laboratory, the ratio between 2 flies did not give the expected results of 1:1:1:1. Though 2 of the four possible genotype occurred at a higher frequency. What can be analyzed from these results?
it make sense if the two loci are on the same chromosome, and thus their inheritance is linked.
107
Absolute or total linkage of all loci is extremely rare or common? Why?
Rare/ because the chromosomes have a numbered amount of genes and not all gene can be on one
108
What is an homologous chromosomes?
Similar chromosomes
109
Can homologous chromosomes exchange corresponding segments during prophase 1 of meiosis?
yes
110
Do genes stay together when they are close together? What does that mean for the ones farther apart?
Yes/ they are more likely they are to separate during recombination.
111
The progeny resulting from crossing over appear in repeatable proportions what is that repetition called?
recombinant frequency.
112
What is chiasma?
It’s the point of contact, the physical link, between two chromatids belonging to homologous chromosomes. When their crossing.
113
Recombinant frequencies are greater for loci that are .... because a.....
...farther apart on the chromosomes because a chiasma is more likely to cut between genes that are far apart.
114
Recombinant frequencies for many pairs of linked genes can be used to create what?
genetic maps showing the arrangement of genes along the chromosome.
115
What are the unit used to measure distances between genes?
map units
116
One map unit correspond to a recombination frequency of ...? What is its unit called?
0.01///centimorgan (cM)
117
Is sex determined in different ways in different species? Give an exemple between grass hopers and mammals
yes///
* Grasshoppers: Females have two X chromosomes, males have one. The sperm determines the sex of the zygote.
* Mammals: females have two X chromosomes, males have X and Y. Sex of offspring is determined by the sperm.
118
Can disorders arise from abnormal sex chromosome constitutions ?
yes
119
Turner syndrome is characterized by what ?
| What do the sex genes look like?
its characterized by the XO condition and results in females who physically are slightly abnormal but mentally normal and usually sterile.
120
Klinefelter syndrome is characterized by what ?What do the sex genes look like?
it results in males who are taller than average and always sterile. /// XXY
121
If a XY individual without a small piece of the Y will be what? (Sex-determination)
phenotypically female
122
If a XX individual with a small piece of the Y will be what? (Sex-determination)
male
123
The fragment of Y chromosomes contains what? What is that gêne called?
the maleness-determining gene, named SRY
124
This SRY genes codes for what? If it’s present what develops? If not what develops? (It’s = the answer from the first question)
The SRY gene codes for a functional protein. If this protein is present, testes develop; if not, ovaries develop.
125
What is the gene present in the X Chromosomes? What does it produce?
DAX1, produces an anti- testis factor.
126
What is the role of the SRY genes in males?
its actually to inhibit the maleness inhibitor encoded by DAX1.
127
Between the Y and X chromosomes, which one as very few genes and which one as a great varieties of characters?
Y as a few (20) / x as many
128
Females with XX may have ..... genes?
heterozygous
129
Males have how many copies of of a gene ?
| What is called those genes?
only one copy of a gene and are called hemizygous.
130
The difference between XX and XY genes generate a special type of inheritance called?
sex-linked inheritance
131
Genes on the sex chromosomes don’t fallow what? They are governed by the ....?
Mendelian patterns. They are governed by loci on the sex chromosomes.
132
A pedigree analysis of X-linked recessive phenotype show ? (4)
▪The phenotype appears much more often in males than in females.
▪A male with the mutation can pass it only to his daughters.
▪Daughters who receive one mutant X are heterozygous carriers.
▪The mutant phenotype can skip a generation if the mutation is passed from a male to his daughter and then to her son.
133
A pedigree analysis of Y-linked phenotype show ? (1)
▪The trait is only passed from father to son.
134
What did Mendel want to study when he did a lab with peas?
heritable characters and traits.
135
What specific character that Mendel was looking specifically?
that had well-defined alternative traits and that was true-breeding///that occur through many generations of breeding individuals.
136
Mendel developed true-breeding strains to be used as….?
parental generation, designated P.
137
What is called the first progeny( kids/generation) from the parents cross?
first filial generation, designated F1.
138
What is called the progeny of the first filial generation (F1) when they cross w/ each other or themselves?
F2
139
A monohybrid cross involves what?
one character (seed shape) and different traits (spherical or wrinkled).
140
From his first experiment, what did Mendel see during it?
▪The F1 seeds were all spherical; the wrinkled trait failed to appear at all.
▪Because the spherical trait completely masks the wrinkled trait when true-breeding plants are crossed, the spherical trait is considered dominant and the wrinkled trait recessive.
141
What was the conclusions from Mendel’s result? (4)
▪The units responsible for inheritance are discrete particles that exist within an organism in pairs and separate during gamete formation; this is called the particulate theory.
▪Each pea has two units of inheritance for each character.
▪During production of gametes, only one of the pair for a given character passes to the gamete.
▪When fertilization occurs, the zygote gets one unit from each parent, restoring the pair.
142
What is called the theory that the units responsible for inheritance are discrete particles that exist within an organism in pairs and separate during gamete formation ?
particulate theory.
143
What are genes?
units of inheritance
144
What are alleles?
different forms of a gene
145
What are true-breeding individuals? (what do they have?)
have two copies of the same allele (i.e., they are homozygous; SS or ss).
146
Can some of the smooth-seeded plants be heterozygous?
Yes
147
The actual composition of the organism’s alleles for a gene is called?
genotype
148
The physical appearance of an organism is called ?
phenotype
149
What is called the first law of Mendel? And What does it imply?
the law of segregation: the two alleles of a gene separate when an individual makes gametes.
150
What does locus or loci mean?
Genes
151
How can you determine possible allelic combinations resulting from fertilization?(what can you use?)
Punnett square
152
What can a test cross determine and what is it of?
of an individual with a dominant trait with a true-breeding recessive (homozygous recessive) can determine the first individual’s genotype.
153
Mendel verified his hypothesis by doing what ?
performing a test cross.
154
In a test cross, If the unknown is heterozygous what does it mean for the progeny?
approximately half the progeny will have the dominant trait and half will have the recessive trait.
155
In a test cross, If the unknown is homozygous dominant what does it mean for the progeny?
all the progeny will have the dominant trait.
156
What is called Mendel’s second law and what does it state?
the law of independent assortment, states that alleles of different genes (e.g., Ss and Yy ) assort into gametes independently of each other.
157
What does the dihybrid cross produce as gametes(the #)?
four possible gametes that have one allele of each gene: SY, Sy, sY, and sy.
158
What is dihybrid crosses?
hybrid crosses involving additional characters.
159
How can you calculate the probabilities of the outcomes of dihybrid crosses?
multiply the outcomes from each of the individual monohybrid components.
* An F1 (dihybrid) cross of SsYy generates 1/4 SS, 1/2 Ss, 1/4 ss, and 1/4 YY, 1/2 Yy, 1/4 yy.
* For example: the probability of the SSYy genotype is the probability of the SS genotype (1/4), times the probability of the Yy genotype (1/2), which is 1/8 (1/4 x 1/2 = 1/8).
160
What happens in nondisjunction?
one member of a homologous pair of chromosomes fails to separate from the other, and both go to the same pole (anaphase I); or, sister chromatids fail to separate (anaphase II).
161
What is the consequence of the nondisjuction?(gametes )
These events lead to one gamete with an extra chromosome (may produce a trisomy) and the other gamete lacking that chromosome (may produce a monosomy)
162
What happens when fertilization that occurs with a normal haploid gamete in nondisjuction? (What does it results as?)
it results in aneuploidy and genetic abnormalities that are invariably harmful or lethal to the organism.
163
In mitotic metaphase what can be fixed in order to characterize the chromosomes?
Cells
164
What is karyotype?
the number, shapes, and sizes of the chromosomes in a cell.
165
Individual chromosomes can be recognized by ....?
length, position of centromere, and banding patterns.
166
While Darwin was evaluating the theory of evolution. he observed that slight variations among individuals can significantly affect ....(2)
❑the chance that a given individual will survive
❑the number of offspring it will produce.
167
What did Darwin call the differential reproductive success of individuals ?
natural selection
168
Why did Darwin used the term « natural selection » ?(how did come up w/ it?)
he was a pigeon breeder and was familiar with artificial selection in the breeding of domesticated animals.
169
In nature, we observe ..... ; the physical expression of genes?
phenotypes
170
Natural selection acts on what?
the phenotypic variation of the individuals within a population
171
What is a genotype ?
The genetic constitution that governs a trait
172
Évolution acts on what?
the genetic (or genotypic) variation of the population.
173
What are alleles?
Genes that have different forms
174
What is called the sum of all alleles in a population?
gene pool
175
Is it true that a single individual has only some of the alleles found in the population to which it belongs?
true
176
What does the gene pool contain that produces the differing phenotypes on which agents of evolution act?
Variations
177
What is a (Mendelian) population ?
A locally interbreeding group within a geographic population
178
What are the measure of a population’s genetic variation?
frequencies/relative proportions
179
How is an allele’s frequency (p or q) calculated?
by dividing the number of copies of the allele in a population by the sum of alleles in the population.
180
A pedigree analysis of X-linked dominant phenotypes show that? (4)
▪The trait is never passed from father to son.
▪All daughters of an affected male and a
normal female are affected.
▪All sons of an affected male and a normal female are normal.
▪Matings of affected females and normal males produce 1/2 the sons affected and 1/2 the daughters affected.
181
does Mitochondria, chloroplasts, and other plastids possess a small amount of DNA?
yes
182
From what parent , Mitochondria (and plastids) are passed on by?
the mother
183
A pedigree analysis of mitochondrial phenotypes show that? (2)
▪An affected mother passes the trait to all her children.
▪An affected father passes it to none of the children.
184
What is the genotype frequency?
its the number of individuals with the genotype divided by the total number of individuals in the population.
185
The two populations in this example have the same allele frequencies for A and a, but they are distributed differently. Will the genotype frequencies of the two population be the same or different?
different
186
What describes the genetic structure of some being?
The frequencies of different alleles at each locus AND the frequencies of different genotypes in a Mendelian population
187
What does it mean to be in Hardy– Weinberg equilibrium?
A population of sexually reproducing organisms in which allele and genotype frequencies do not change from generation to generation
188
What are the 5 assumptions that must be made to meet the Hardy– Weinberg equilibrium?
▪Mating is random.
▪Population size is very large or infinite.
▪There is no migration between populations.
▪There is no mutation.
▪Natural selection does not affect the alleles under consideration.
189
In other words what does it mean (Hardy– Weinberg equilibrium) after one generation of random mating? By extension what does mean about the evolution?
the genotype frequencies do not change//this means that no evolution was detected in this population from one generation to the next.
190
What is the Hardy– Weinberg equation?
p^2 + 2pq + q^2 = 1
191
What is an important message of the Hardy– Weinberg equilibrium ? (The alleles)
that allele frequencies remain the same from generation to generation, unless some agent acts to change them.
192
The Hardy– Weinberg equilibrium show what about a population? (Distribution of genotype)
it shows the distribution of genotypes that would be expected for a population at genetic equilibrium.
193
What does the Hardy– Weinberg equilibrium allow scientists to determine?
it allows scientists to determine whether evolutionary agents are operating and their identity (as evidenced by the pattern of deviation from the equilibrium).
194
What does evolutionary agents cause? How are they observed as?
it cause changes in the allele and genotype frequencies in a population.
195
What are the known evolutionary agents?
➢Mutation
➢Gene flow
➢Genetic drift
➢Nonrandom mating
➢Natural selection.
196
What is a mutation?
its the origin of genetic variation. A mutation is any change in an organism’s DNA.
197
How are mutations to be appeared as? (2)
* Most mutations appear to be random, and are harmful or neutral to their bearers.
* Some mutations can be advantageous.
198
What is the mutations rate ? What are they sufficient to create?
Mutation rates are low//they are sufficient to create considerable genetic variation within a population.
199
What is one condition of the Hardy– Weinberg equilibrium? What happens if there is one? (Happens on a single loci)
that there is no mutation// its usually so low that mutations result in only very small deviations from H-W expectations.
200
What is appropriate to dismiss?, if there is large deviations.
mutation as the cause and look for evidence of other evolutionary agents.
201
Gene flow results from.....?
when individuals migrate to another population and breed in their new location
202
What happens when immigrants migrate to another country? (Gene pool)
they may add new alleles to the gene pool of a population, or, they may change the frequencies of alleles already present if they come from a population with different allele frequencies.
203
What is the genetic drift?
its the random loss of individuals and the alleles they possess.
204
In very small population, genetic drift may...?
it may be strong enough to influence the direction of change of allele frequencies, even when other evolutionary agents are pushing the frequencies in a different direction.
205
If a genetic drift happens in a very large population, what happens to the organism? What is it called?
they may pass through occasional periods when only a small number of individuals survive (a population bottleneck).
206
Give an example of bottlenecks in populations in nature like animals? What are the reasons?
predation, habitat destruction, and disease may reduce the population to a very small size, resulting in low genetic variation.
207
What are the two types of genetic drift?
bottleneck effect and founder effect
208
What is seen when the founder effect happens ?
a few pioneering individuals leave the original population and colonize a new region creating a new population
209
Since they leave the original population to colonize a new region (founder effet) what happens to the alleles? (Impact on this new population)
the new population will not have all the alleles found among members of the original population. This, too, reduces genetic variation.
210
When does the non-random mating occur?
when individuals mate either more often with individuals of the same genotype OR more often with individuals of a different genotype. An example would be inbreeding.
211
What is inbreeding?
its the mating of organisms closely related by ancestry.
212
In non-random mating, what are the resulting proportions related to the Hardy– Weinberg equilibrium expectations?
The resulting proportions of genotypes in the following generation differ from H-W expectations.
213
What happens when an individual mate with other individuals of the same genotypes? (Homozygous, heterozygous)
homozygous genotypes are overrepresented and heterozygous genotypes are underrepresented in the next generation.
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Darwin attributed all differences in all life-forms to .... which means what to one phenotype?
natural selection; the advantage that one phenotype may have over another in a particular environment/situation.
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What is the result of natural selection?
adaptation
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How can an adaptation occur?
For adaptation to occur, individuals that differ in heritable traits must survive AND reproduce with different degrees of success.
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What happens when some individuals contribute more offspring to the generation next generation than others? And what is all of this called?
allele frequencies in the population change in a way that adapts individuals to the environments that influenced their success. This is natural selection.
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What is the fitness of phenotype?
The reproductive contribution of a phenotype to subsequent generations relative to the contributions of other phenotypes
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The fitness of a phenotype is determined by what ?
the average rates of survival AND reproduction of individuals with that phenotype.
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Most characters are influenced by alleles at ...and are more likely to ....?
more than one locus /// show quantitative rather then qualitative variation.
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Natural selection can act on characters with quantitative variation in three ways what ?
➢Stabilizing selection ➢Directional selection ➢Disruptive selection
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What does stabilizing selection preserve?
it preserves the characteristics of a population by favoring average individuals. Thus, genetic variation is reduced.
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When does stabilizing selection occur?
| Give example?
it occurs when the extremes of a population contribute relatively fewer offspring than the average members to the next generation.
Ex.: average human birth weight, average plant height, average litter/brood size, etc.
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What does directional selection change?
it changes the characteristics of a population by favoring individuals that vary in one direction from the mean of the population. Once again, genetic variation is reduced.
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When does directional selection occur?
| Give exemple?
it occurs when one extreme of a population contributes more offspring to the next generation.
Ex. longer-necked giraffes win more male-male fights for mates, darker-coated mice blend in on newly-formed volcanic substrate, etc.
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What does disruptive selection change?
it changes the characteristics of a population by favoring individuals that vary in both directions from the mean of the population. This tends to maintain overall variation in a population.
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When does disruptive selection occur?
| Give exemple?
it occurs when individuals at both extremes of a population are simultaneously favoured.
Ex.: black snails and white snails blend in among black and white rocks, both short- beaked and long-beaked hummingbirds eat from deep and shallow flowers, etc.
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In 1940 , Ernst Mayr proposed what?
the biological species concept
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What is the biological species concept? What does it mean/state?
Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.
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Determining if two populations are actually different species can be difficult why?
because speciation is often gradual
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What is speciation?
its the process by which one species splits into two species.
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Is it true that not all evolutionary changes result in new species?
true
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The critical process in the formation of new species is ?
the segregation of the gene pool of the ancestral species into two separate gene pools.
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How can speciation be facilitated?
by interruption of gene flow among populations.
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What is the allopatric (geographic)speciation?
Speciation that results when a population is divided by a geographic barrier
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Barriers can form when?
as continents drift, sea level changes, glaciers advance/retreat, climate changes.
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Is it true that if their environments are different, populations will evolve differently through natural selection. Genetic drift and mutation can also be factors?
true
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Is allopatric speciation is the dominant or recessive form of speciation?
dominant form of speciation
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Allopatric speciation may occur when? (Population cross)
hen some members of a population cross a barrier and form a new, isolated population
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Population established with Allopatric speciation differ genetically from the parent population because of what?
because of the founder effect
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A barrier’s effectiveness at preventing gene flow depend on what?
it depends on the size and mobility of the species in question.
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What is sympatric speciation?
A partition of a gene pool that occurs without physical separation
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The most common means of sympatric speciation is? (Duplication)
polyploidy—duplication of whole sets of chromosomes.
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Polyploidy arise in 2 ways what?
▪Autopolyploidy is chromosome duplication in a single species.
▪Allopolyploidy is the combining of chromosomes from two different species.
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When can autopolyploidy occur?
it can occur accidentally if two diploid gametes combine, resulting in a tetraploid individual.
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When can allopolyploidy arise?
it can arise when individuals of closely related species interbreed, or hybridize.
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Why are allopolyploidy usually fertile?
because each of the chromosomes has a nearly identical partner to pair with during meiosis.
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Polyploidy can create what? (Reproduction)
it can create new species of plants more easily than animals, because plants of many species can reproduce by self- fertilization.
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What results when a barrier to gene flow is established ?
the resulting daughter populations may diverge genetically.
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Is it true that Any genetic differences that accumulate in reproductively isolated populations over time reduces the probability that individuals can mate successfully when they come back into contact?
true
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If hybridization occurs and hybrids are less fit natural selection will result in what?
in reinforcement of mechanisms that will prevent this hybridization in the future
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What are the mechanisms that prevent hybridization?
❑Prezygotic isolating mechanisms
❑Postzygotic isolating mechanisms
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Prezygotic isolating mechanisms operate before or after fertilization?
before
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In Prezygotic isolating mechanisms , what happens to the habitat isolation and temporal isolation?
▪Spatial/Habitat isolation: live in different locations.
▪Temporal isolation: mating periods don’t overlap.
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In Prezygotic isolating mechanisms , what happens to the Behavioural isolation and mechanical isolation?
▪Behavioral isolation: individuals of one species may reject or fail to recognize individuals of other species as mating partners.
▪Mechanical isolation: have differences in size and shape of reproductive organs.
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In Prezygotic isolating mechanisms , what happens to the gametic isolation?
▪Gametic isolation: sperm of one species may not attach or penetrate egg of other species.
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Postzygotic isolating mechanisms operate before or after fertilization?
after
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In Postzygotic isolating mechanisms , what do does mechanisms mean?
- hybrid zygote abnormality
- low hybrid viability
- hybrid infertility
▪Hybrid zygote abnormality: fail to mature normally, either dying during development or have severe abnormalities.
▪Low hybrid viability: hybrids may survive less well than individuals resulting from matings within populations.
▪Hybrid infertility: may mature normally, but be infertile when they attempt to reproduce. Ex: Donkey + Horse→Mule
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Genes are made up of ..... and are expressed....as polypeptide?
DNA////in the phenotype
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What is the central dogma (main belief) of molecular biology?
DNA → RNA → protein.
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RNA viruses include or exclude DNA altogether, going directly from.....?
exclude
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In retroviruses, what is their rule of transcription ?(reversed or the same) Exemple?
reversed
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A gene is expressed in two steps what ?
* First, DNA is transcribed to RNA
| * then RNA is translated into protein.
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RNA is transcribed from a DNA template after the ....are exposed by....?
bases of DNA////unwinding of the double helix.
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What can act as a template for transcription?
In a given region of DNA, only one of the two strands
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What catalyze transcription from the template strand of DNA?
RNA polymerase
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The initiation of transcription requires that ....recognize and bind tightly to a promoter sequence on DNA.
RNA polymerase
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RNA elongates in a ...., antiparallel to the template DNA. ?
5’-to-3’ direction,
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What terminate transcription?
Special sequences and protein helpers
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The genetic code consists of ?
triplets of nucleotides (codons)
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Since there are 4 bases. How many codons?
64
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One mRNA codon indicates what?
the starting point of translation and codes for methionine.
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Three stop codons indicate?
the end of translation.
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The other 60 codons code only for what ?
particular amino acids
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Since there’s is only 20 different aminos acids the genetic code is called....?
redundant...that is, there is more than one codon for certain amino acids.
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A single codon has only one amino acids the genetic code is called....?
unambiguous(clear,not messy ,organized)
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What does it mean unambiguous?
not capable of being understood in two or more possible senses or ways (meaning each codon as 1 amino acids and will always have the same)
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In prokaryotes, translation begins ..... the mRNA is completed?
before
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In eukaryotes, transcription occurs.....and translation occurs.....?
in the nucleus//in the cytoplasm
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Translation requires what? (3)
tRNA’s, activating enzymes, and ribosomes.
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In translation, ..... are linked in codon-specified order in mRNA?
amino acids
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How is the aminos acid and mRNA linked (process)?
when the transfer RNA (tRNA) binds the correct amino acid, and has an anticodon complementary to the mRNA codon.
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What is The aminoacyl-tRNA synthetases ? And how is charged tRNAs formed?
A family of activating enzymes
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Where do the mRNA and the charged tRNA meet?
ribosome
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What triggers the beginning of translation?
An initiation complex consisting of an amino acid-charged tRNA and a small ribosomal subunit bound to mRNA
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Polypeptide grow from .....towards....? That corresponds to ?
N terminus toward the C terminus (corresponds to 5’-to- 3’of mRNA).
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Is it false that the ribosome move along the mRNA one codon at a time?
nope its true
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what is a mRNA?
messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.
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what is a tRNA?
(during the transcription process) /the new mRNA strand to become double-stranded by producing a complementary strand known as the transfer RNA (tRNA) strand.
