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Bio1 > UNIT 2 > Flashcards

UNIT 2 Flashcards

1
Q

What is nessesairy for reproduction, growth and repair/regeneration of an organism?

A

Cell division

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2
Q

Unicellular organisms use cell division primarily for what?

A

reproduction

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3
Q

For multicellular organisms, cell division is important for what ? (2 reasons)

A

reproduction, in growth and repair of tissues.

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4
Q

What results in two new cells that are exact copies of one another in prokaryotes?

A

binary fission

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5
Q

Prokaryotes have how many chromosomes usually?

A

one chromosome ,(a single molecule of DNA); usually circular.

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6
Q

In eukaryotes, the nuclei divide by what? (What methods ,How do it reproduce?)

A

mitosis or meiosis

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7
Q

What is mitosis?

A

division of somatic (non sex) cells

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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

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9
Q

What is meiosis?

A

division of germ (sex) cells

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10
Q

What does meiosis produce?

A

Production of eggs in the ovary or sperm in the testes; used for sexual reproduction

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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).

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12
Q

Interphase makes up how many pour-cent of cell cycle?

A

~90%

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13
Q

Interphase has how many sub-phase and how are they named?

A

has three sub-phases: G1, S, and G2.

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14
Q

What happens in the G1 (gap 1) phase ? And how does chromosomes look?

A

Cellular growth & maintenance; chromosomes are single, unreplicated structures

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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”

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16
Q

What happens in the S phase (synthesis) ? And how does chromosomes look?

A

DNA replicates; one chromosome becomes two sister chromatids

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17
Q

What happens in the G2 (gap 2) phase ?

A

Cellular growth & preparation for mitosis (i.e., duplication of centrosomes, etc.)

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18
Q

What is the M phase( mitosis)?

A

It is a nuclear division.

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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.

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20
Q

Mitosis makes up how many pour-cent of the cell cycle?

A

~10%

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21
Q

When does cytokinesis occur?

A

It is a cytoplasmic division, and may occur right after mitosis.

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22
Q

What stimulates the cell cycle?

A

Cyclin-Cdk complexes, growth factors, and hormones

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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.

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24
Q

In eukaryotic chromosomes DNA molecules are extensively….. in order to fit in the nucleus.

A

“packed”

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25
Q

How is the packing of the DNA molecules achieved?

A

by winding DNA molecules around histone proteins forming nucleosomes. This complex of DNA and histones is called chromatin.

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26
Q

What is just strands of chromatin?

A

Eukaryotic chromosomes

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27
Q

What protein around the DNA forms nucleosomes?

A

histone

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28
Q

What happens during the S phase ? And it’s “consequences “?

A

each chromosome must make a copy of itself./Each chromosome is now composed of two identical sister chromatids held together at the centromere.

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29
Q

As soon as mitosis begins what happens in the nucleus?

A

the chromosomes condense even more forming the characteristic shape of mitotic chromosomes.

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30
Q

What is the shape of the chromosomes when they condense?

A

mitotic chromosomes

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31
Q

What happens after the DNA replicates ?

A

the centrosome doubles.

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32
Q

A centrosome consist of what?

A

of two centrioles at right angles to each other.

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33
Q

When does the centrosome move to opposite ends of the nuclear envelope?

A

At G2 to M transition

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34
Q

What leads to the formation of the spidle structure?

A

These initiate formation of microtubules

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35
Q

What happens during prophase?(3 things) in mitosis

A

– 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.

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36
Q

What are the two type of micro tubules that the spindle has?

A
  • 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.
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37
Q

What happens during prometaphase?( mitosis//2)

A

– nuclear envelope & nucleolus disappear.

–chromosomes gradually pushed towards the middle of the cell.

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38
Q

What happens during metaphase? ( 2///mitosis)

A

–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.

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39
Q

What happens during anaphase? ( mitosis)

A

– each member of the pair of chromatids (now called a daughter chromosome) migrates to its pole along the microtubule track.

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40
Q

What happens during telophase? ( 4///mitosis)

A

– 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.

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41
Q

What is cytokinesis?

A

its the division of the cytoplasm; usually follows nuclear division.

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42
Q

In animals cell cytokinesis happens by ?

A

cytoplasm divides by plasma membrane furrowing (also called cleavage) caused by contraction of cytoplasmic microfilaments.

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43
Q

In plants cell cytokinesis is accomplished by?

A

cytokinesis is accomplished by vesicle fusion forming the cell plate (i.e., the beginning of the new cell wall).

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44
Q

What are centrosomes made up of?

A

2 centrioles at a perpendicular angle from each other

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45
Q

Asexual reproduction is based on what? how does it happen?

A

mitosis of the nucleus.

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46
Q

What are the two ways (asexually) for asexual organisms to reproduce?

A
  • It may be a unicellular organism reproducing itself

* Cells of multicellular organisms that break off to form a new individual

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47
Q

What are the offspring of asexual reproduction called? And why are they called that?

A

clones — genetically identical to the parent

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48
Q

If there is any variations asexually it results from what?

A

mutations

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49
Q

In sexual reproduction, the offsprings are identical or non identical to their parents?

A

non identical

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50
Q

Sexual reproduction results in what genetically?

A

in shuffling of genetic information in a population. No two individuals have exactly the same genes.

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51
Q

What is meiosis?

A

its the nuclear division that produces gametes that differ genetically from the parents, and also from each other.

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52
Q

What are gamete?

A

sexual cells, such as egg and sperm cells

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53
Q

What are the somatic cells? what are they or not specialized in? And what does it contain?

A

are body cells not specialized for reproduction///homologous (same size & shape; similar information) pairs of chromosomes with corresponding genes.

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54
Q

What can be called the pair of chromosomes in somatic cells?

A

diploid; 2n

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55
Q

What is called one of every pair of chromosomes ?

A

homolog

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56
Q

What do gamete contain?

A

they contain only one set of chromosomes (haploid; n), and are specialized for reproduction.

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57
Q

What goes into the haploid (single set of chromosomes)gamete? And what happens to the offspring?

A

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.

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58
Q

What is fertilization?

A

its the event when two haploid gametes (female egg & male sperm) fuse to form a diploid (2n) zygote cell.

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59
Q

When the two gametes fuse what is called the thing formed?

A

zygote

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60
Q

What are the différant sexual life cycles?

A

Haplontic life cycle,Alternation of generations and Diplontic life cycle

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61
Q

What kingdoms are part of the haplontic life cycle? How are gametes?

A

fungi and most protists; zygote is the only diploid stage.

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62
Q

What kingdoms are part of the alternation of generations? How are gametes?

A

plants and photosynthetic protists (i.e., algae); meiosis gives rise to haploid spores.

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63
Q

What kingdoms are part of the diplontic life cycles? How are gametes?

A

animals; gametes are the only haploid stage.

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64
Q

The meiosis consist of?( # of divisions)

A

2

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65
Q

The number of chromosomes goes from…. to….?

A

2 to 1

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66
Q

How many times are the DNA replicated in meiosis?

A

1

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67
Q

What are called the parent cells of the gamete? (Before meiosis)

A

Germ cells

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68
Q

The gametes are different or the same from the parent cell and each other?

A

different from the parent cell and from each other.

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69
Q

In meiosis, what happens during prophase 1?

A

homologous chromosomes pair up (synapsis), and material is exchanged by crossing-over (also called recombination) between non-sister chromatids of two adjacent homologs

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70
Q

In meiosis, what happens during prometaphase 1?

A

nuclear envelope & nucleolus disappear.

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71
Q

In meiosis, what happens during metaphase 1?

A

paired homologs now at the equatorial plate. Each chromosome has one kinetochore and associates with polar microtubules for one pole.

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72
Q

In meiosis, what happens during anaphase 1?

A

homologous chromosomes separate; daughter nuclei contain only one set of chromosomes. Each chromosome still consists of two chromatids.

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73
Q

In meiosis, what happens during telophase 1? (see image 3)

A

the nuclear envelope reaggregates; it’s followed by interphase called interkinesis.

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74
Q

DNA does it replicate before meiosis 1 or 2?

A

meiosis 2

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75
Q

In meiosis 2 what sisters separate ?

A

the sister chromatids separate.

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76
Q

What is the results of meiosis? (How much cells does it end up with)

A

The result of meiosis is four cells, each with a haploid chromosome content.

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77
Q

What ensures that the genetic composition of each haploid gamete is different from that of the parent and from that of the other gametes?

A

Both crossing over during prophase I -AND- the random selection of which homolog of a pair migrates to which pole during anaphase I

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78
Q

The more chromosome pairs there are in a diploid cell, the greater the ….?

A

the diversity of chromosome combinations generated by meiosis.

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79
Q

How can you calculate the probabilities of the outcomes of dihybrid crosses?

A

you have to multiply the outcomes from each of the individual monohybrid components.

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80
Q

What does autosomal inheritence mean?

A

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.

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81
Q

How does human geneticists evaluate the crosses of humans?

A

using pedigrees

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82
Q

What does the pedigrees show?

A

phenotype segregation in several generations of related individuals.

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83
Q

Why does human pedigrees do not show clear proportions ?

A

Since humans have such small numbers of offspring

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84
Q

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?

A

In other words, outcomes for small samples fail to follow the expected outcomes closely.

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85
Q

A pedigree analysis of the dominant allele for a given phenotype shows what? (3)

A

▪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.

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86
Q

A pedigree analysis of the recessive allele for a given phenotype shows what? (3)

A

▪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.

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87
Q

Why does different alleles exist?

A

because any gene is subject to mutation into a stable, heritable new form.

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88
Q

Can alleles mutates?

A

Yes, randomly

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89
Q

How is called the common allele in a population?

A

wild type

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90
Q

How are called the other allele present with a wild type?

A

mutant alleles

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91
Q

Mutant alleles may produce what?

A

a phenotype different from that of the wild-type allele.

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92
Q

How much alleles can a population have for a given gene?

A

more than two alleles

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93
Q

Even if more than two alleles exist in a population, any given individual can have….?

A

no more than two of them: one from the mother and one from the father.

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94
Q

What is the incomplete dominance ?

A

This mode of inheritance

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95
Q

What are the factors that show incomplete dominance?

A

Heterozygotes may show an intermediate phenotype which might seem to support the blending theory.

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96
Q

What “happens” in codominance? With example using the ABO blood 🩸?

A

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.

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97
Q

What are pleiotropy alleles?

A

are single alleles that have more than one distinguishable phenotypic effect.

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98
Q

pleiotropy alleles are caused by what ?

A

by the same protein produced by the same allele.

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99
Q

When does epistasis occur?

With an example?

A

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)

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100
Q

What are complementary genes?

A

In another form of epistasis, two genes are mutually dependent: the expression of each depends on the alleles of the other

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101
Q

What are polygenic inheritance ( quantitative trait loci ) ?

A

Complex inherited characteristics controlled by groups of several genes

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102
Q

In polygenic inheritance , each alleles _ or _ the phenotype?

A

intensifies or diminishes

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103
Q

In polygenic inheritance, variations are continuous (quantitative) or qualitative?

A

continuous (or quantitative)

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104
Q

What does locus or loci mean?

A

Gene

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105
Q

In polygenic inheritance, variations are due to what?(2 factors)

A

multiple genes with multiple alleles (polygenes), and environmental influences on the expression of these genes.

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106
Q

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?

A

it make sense if the two loci are on the same chromosome, and thus their inheritance is linked.

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107
Q

Absolute or total linkage of all loci is extremely rare or common? Why?

A

Rare/ because the chromosomes have a numbered amount of genes and not all gene can be on one

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108
Q

What is an homologous chromosomes?

A

Similar chromosomes

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109
Q

Can homologous chromosomes exchange corresponding segments during prophase 1 of meiosis?

A

yes

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110
Q

Do genes stay together when they are close together? What does that mean for the ones farther apart?

A

Yes/ they are more likely they are to separate during recombination.

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111
Q

The progeny resulting from crossing over appear in repeatable proportions what is that repetition called?

A

recombinant frequency.

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112
Q

What is chiasma?

A

It’s the point of contact, the physical link, between two chromatids belonging to homologous chromosomes. When their crossing.

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113
Q

Recombinant frequencies are greater for loci that are …. because a…..

A

…farther apart on the chromosomes because a chiasma is more likely to cut between genes that are far apart.

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114
Q

Recombinant frequencies for many pairs of linked genes can be used to create what?

A

genetic maps showing the arrangement of genes along the chromosome.

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115
Q

What are the unit used to measure distances between genes?

A

map units

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116
Q

One map unit correspond to a recombination frequency of …? What is its unit called?

A

0.01///centimorgan (cM)

117
Q

Is sex determined in different ways in different species? Give an exemple between grass hopers and mammals

A

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
Q

Can disorders arise from abnormal sex chromosome constitutions ?

A

yes

119
Q

Turner syndrome is characterized by what ?

What do the sex genes look like?

A

its characterized by the XO condition and results in females who physically are slightly abnormal but mentally normal and usually sterile.

120
Q

Klinefelter syndrome is characterized by what ?What do the sex genes look like?

A

it results in males who are taller than average and always sterile. /// XXY

121
Q

If a XY individual without a small piece of the Y will be what? (Sex-determination)

A

phenotypically female

122
Q

If a XX individual with a small piece of the Y will be what? (Sex-determination)

A

male

123
Q

The fragment of Y chromosomes contains what? What is that gêne called?

A

the maleness-determining gene, named SRY

124
Q

This SRY genes codes for what? If it’s present what develops? If not what develops? (It’s = the answer from the first question)

A

The SRY gene codes for a functional protein. If this protein is present, testes develop; if not, ovaries develop.

125
Q

What is the gene present in the X Chromosomes? What does it produce?

A

DAX1, produces an anti- testis factor.

126
Q

What is the role of the SRY genes in males?

A

its actually to inhibit the maleness inhibitor encoded by DAX1.

127
Q

Between the Y and X chromosomes, which one as very few genes and which one as a great varieties of characters?

A

Y as a few (20) / x as many

128
Q

Females with XX may have ….. genes?

A

heterozygous

129
Q

Males have how many copies of of a gene ?

What is called those genes?

A

only one copy of a gene and are called hemizygous.

130
Q

The difference between XX and XY genes generate a special type of inheritance called?

A

sex-linked inheritance

131
Q

Genes on the sex chromosomes don’t fallow what? They are governed by the ….?

A

Mendelian patterns. They are governed by loci on the sex chromosomes.

132
Q

A pedigree analysis of X-linked recessive phenotype show ? (4)

A

▪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
Q

A pedigree analysis of Y-linked phenotype show ? (1)

A

▪The trait is only passed from father to son.

134
Q

What did Mendel want to study when he did a lab with peas?

A

heritable characters and traits.

135
Q

What specific character that Mendel was looking specifically?

A

that had well-defined alternative traits and that was true-breeding///that occur through many generations of breeding individuals.

136
Q

Mendel developed true-breeding strains to be used as….?

A

parental generation, designated P.

137
Q

What is called the first progeny( kids/generation) from the parents cross?

A

first filial generation, designated F1.

138
Q

What is called the progeny of the first filial generation (F1) when they cross w/ each other or themselves?

A

F2

139
Q

A monohybrid cross involves what?

A

one character (seed shape) and different traits (spherical or wrinkled).

140
Q

From his first experiment, what did Mendel see during it?

A

▪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
Q

What was the conclusions from Mendel’s result? (4)

A

▪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
Q

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 ?

A

particulate theory.

143
Q

What are genes?

A

units of inheritance

144
Q

What are alleles?

A

different forms of a gene

145
Q

What are true-breeding individuals? (what do they have?)

A

have two copies of the same allele (i.e., they are homozygous; SS or ss).

146
Q

Can some of the smooth-seeded plants be heterozygous?

A

Yes

147
Q

The actual composition of the organism’s alleles for a gene is called?

A

genotype

148
Q

The physical appearance of an organism is called ?

A

phenotype

149
Q

What is called the first law of Mendel? And What does it imply?

A

the law of segregation: the two alleles of a gene separate when an individual makes gametes.

150
Q

What does locus or loci mean?

A

Genes

151
Q

How can you determine possible allelic combinations resulting from fertilization?(what can you use?)

A

Punnett square

152
Q

What can a test cross determine and what is it of?

A

of an individual with a dominant trait with a true-breeding recessive (homozygous recessive) can determine the first individual’s genotype.

153
Q

Mendel verified his hypothesis by doing what ?

A

performing a test cross.

154
Q

In a test cross, If the unknown is heterozygous what does it mean for the progeny?


A

approximately half the progeny will have the dominant trait and half will have the recessive trait.

155
Q

In a test cross, If the unknown is homozygous dominant what does it mean for the progeny?

A

all the progeny will have the dominant trait.

156
Q

What is called Mendel’s second law and what does it state?

A

the law of independent assortment, states that alleles of different genes (e.g., Ss and Yy ) assort into gametes independently of each other.

157
Q

What does the dihybrid cross produce as gametes(the #)?

A

four possible gametes that have one allele of each gene: SY, Sy, sY, and sy.

158
Q

What is dihybrid crosses?

A

hybrid crosses involving additional characters.

159
Q

How can you calculate the probabilities of the outcomes of dihybrid crosses?

A

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
Q

What happens in nondisjunction?

A

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
Q

What is the consequence of the nondisjuction?(gametes )

A

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
Q

What happens when fertilization that occurs with a normal haploid gamete in nondisjuction? (What does it results as?)

A

it results in aneuploidy and genetic abnormalities that are invariably harmful or lethal to the organism.

163
Q

In mitotic metaphase what can be fixed in order to characterize the chromosomes?

A

Cells

164
Q

What is karyotype?

A

the number, shapes, and sizes of the chromosomes in a cell.

165
Q

Individual chromosomes can be recognized by ….?

A

length, position of centromere, and banding patterns.

166
Q

While Darwin was evaluating the theory of evolution. he observed that slight variations among individuals can significantly affect ….(2)

A

❑the chance that a given individual will survive

❑the number of offspring it will produce.

167
Q

What did Darwin call the differential reproductive success of individuals ?

A

natural selection

168
Q

Why did Darwin used the term «natural selection» ?(how did come up w/ it?)

A

he was a pigeon breeder and was familiar with artificial selection in the breeding of domesticated animals.

169
Q

In nature, we observe ….. ; the physical expression of genes?

A

phenotypes

170
Q

Natural selection acts on what?

A

the phenotypic variation of the individuals within a population

171
Q

What is a genotype ?

A

The genetic constitution that governs a trait

172
Q

Évolution acts on what?

A

the genetic (or genotypic) variation of the population.

173
Q

What are alleles?

A

Genes that have different forms

174
Q

What is called the sum of all alleles in a population?

A

gene pool

175
Q

Is it true that a single individual has only some of the alleles found in the population to which it belongs?

A

true

176
Q

What does the gene pool contain that produces the differing phenotypes on which agents of evolution act?

A

Variations

177
Q

What is a (Mendelian) population ?

A

A locally interbreeding group within a geographic population

178
Q

What are the measure of a population’s genetic variation?

A

frequencies/relative proportions

179
Q

How is an allele’s frequency (p or q) calculated?

A

by dividing the number of copies of the allele in a population by the sum of alleles in the population.

180
Q

A pedigree analysis of X-linked dominant phenotypes show that? (4)

A

▪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
Q

does Mitochondria, chloroplasts, and other plastids possess a small amount of DNA?

A

yes

182
Q

From what parent , Mitochondria (and plastids) are passed on by?

A

the mother

183
Q

A pedigree analysis of mitochondrial phenotypes show that? (2)

A

▪An affected mother passes the trait to all her children.

▪An affected father passes it to none of the children.

184
Q

What is the genotype frequency?

A

its the number of individuals with the genotype divided by the total number of individuals in the population.

185
Q

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?

A

different

186
Q

What describes the genetic structure of some being?

A

The frequencies of different alleles at each locus AND the frequencies of different genotypes in a Mendelian population

187
Q

What does it mean to be in Hardy– Weinberg equilibrium?

A

A population of sexually reproducing organisms in which allele and genotype frequencies do not change from generation to generation

188
Q

What are the 5 assumptions that must be made to meet the Hardy– Weinberg equilibrium?

A

▪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
Q

In other words what does it mean (Hardy– Weinberg equilibrium) after one generation of random mating? By extension what does mean about the evolution?

A

the genotype frequencies do not change//this means that no evolution was detected in this population from one generation to the next.

190
Q

What is the Hardy– Weinberg equation?

A

p^2 + 2pq + q^2 = 1

191
Q

What is an important message of the Hardy– Weinberg equilibrium ? (The alleles)

A

that allele frequencies remain the same from generation to generation, unless some agent acts to change them.

192
Q

The Hardy– Weinberg equilibrium show what about a population? (Distribution of genotype)

A

it shows the distribution of genotypes that would be expected for a population at genetic equilibrium.

193
Q

What does the Hardy– Weinberg equilibrium allow scientists to determine?

A

it allows scientists to determine whether evolutionary agents are operating and their identity (as evidenced by the pattern of deviation from the equilibrium).

194
Q

What does evolutionary agents cause? How are they observed as?

A

it cause changes in the allele and genotype frequencies in a population.

195
Q

What are the known evolutionary agents?

A

➢Mutation

➢Gene flow

➢Genetic drift

➢Nonrandom mating

➢Natural selection.

196
Q

What is a mutation?

A

its the origin of genetic variation. A mutation is any change in an organism’s DNA.

197
Q

How are mutations to be appeared as? (2)

A
  • Most mutations appear to be random, and are harmful or neutral to their bearers.
  • Some mutations can be advantageous.
198
Q

What is the mutations rate ? What are they sufficient to create?

A

Mutation rates are low//they are sufficient to create considerable genetic variation within a population.

199
Q

What is one condition of the Hardy– Weinberg equilibrium? What happens if there is one? (Happens on a single loci)

A

that there is no mutation// its usually so low that mutations result in only very small deviations from H-W expectations.

200
Q

What is appropriate to dismiss?, if there is large deviations.

A

mutation as the cause and look for evidence of other evolutionary agents.

201
Q

Gene flow results from…..?

A

when individuals migrate to another population and breed in their new location

202
Q

What happens when immigrants migrate to another country? (Gene pool)

A

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
Q

What is the genetic drift?

A

its the random loss of individuals and the alleles they possess.

204
Q

In very small population, genetic drift may…?

A

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
Q

If a genetic drift happens in a very large population, what happens to the organism? What is it called?

A

they may pass through occasional periods when only a small number of individuals survive (a population bottleneck).

206
Q

Give an example of bottlenecks in populations in nature like animals? What are the reasons?

A

predation, habitat destruction, and disease may reduce the population to a very small size, resulting in low genetic variation.

207
Q

What are the two types of genetic drift?

A

bottleneck effect and founder effect

208
Q

What is seen when the founder effect happens ?

A

a few pioneering individuals leave the original population and colonize a new region creating a new population

209
Q

Since they leave the original population to colonize a new region (founder effet) what happens to the alleles? (Impact on this new population)

A

the new population will not have all the alleles found among members of the original population. This, too, reduces genetic variation.

210
Q

When does the non-random mating occur?

A

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
Q

What is inbreeding?

A

its the mating of organisms closely related by ancestry.

212
Q

In non-random mating, what are the resulting proportions related to the Hardy– Weinberg equilibrium expectations?

A

The resulting proportions of genotypes in the following generation differ from H-W expectations.

213
Q

What happens when an individual mate with other individuals of the same genotypes? (Homozygous, heterozygous)

A

homozygous genotypes are overrepresented and heterozygous genotypes are underrepresented in the next generation.

214
Q

Darwin attributed all differences in all life-forms to …. which means what to one phenotype?

A

natural selection; the advantage that one phenotype may have over another in a particular environment/situation.

215
Q

What is the result of natural selection?

A

adaptation

216
Q

How can an adaptation occur?

A

For adaptation to occur, individuals that differ in heritable traits must survive AND reproduce with different degrees of success.

217
Q

What happens when some individuals contribute more offspring to the generation next generation than others? And what is all of this called?

A

allele frequencies in the population change in a way that adapts individuals to the environments that influenced their success. This is natural selection.

218
Q

What is the fitness of phenotype?

A

The reproductive contribution of a phenotype to subsequent generations relative to the contributions of other phenotypes

219
Q

The fitness of a phenotype is determined by what ?

A

the average rates of survival AND reproduction of individuals with that phenotype.

220
Q

Most characters are influenced by alleles at …and are more likely to ….?

A

more than one locus /// show quantitative rather then qualitative variation.

221
Q

Natural selection can act on characters with quantitative variation in three ways what ?

A

➢Stabilizing selection ➢Directional selection ➢Disruptive selection

222
Q

What does stabilizing selection preserve?

A

it preserves the characteristics of a population by favoring average individuals. Thus, genetic variation is reduced.

223
Q

When does stabilizing selection occur?

Give example?

A

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.

224
Q

What does directional selection change?

A

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.

225
Q

When does directional selection occur?

Give exemple?

A

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.

226
Q

What does disruptive selection change?

A

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.

227
Q

When does disruptive selection occur?

Give exemple?

A

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.

228
Q

In 1940 , Ernst Mayr proposed what?

A

the biological species concept

229
Q

What is the biological species concept? What does it mean/state?

A

Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.

230
Q

Determining if two populations are actually different species can be difficult why?

A

because speciation is often gradual

231
Q

What is speciation?

A

its the process by which one species splits into two species.

232
Q

Is it true that not all evolutionary changes result in new species?

A

true

233
Q

The critical process in the formation of new species is ?

A

the segregation of the gene pool of the ancestral species into two separate gene pools.

234
Q

How can speciation be facilitated?

A

by interruption of gene flow among populations.

235
Q

What is the allopatric (geographic)speciation?

A

Speciation that results when a population is divided by a geographic barrier

236
Q

Barriers can form when?

A

as continents drift, sea level changes, glaciers advance/retreat, climate changes.

237
Q

Is it true that if their environments are different, populations will evolve differently through natural selection. Genetic drift and mutation can also be factors?

A

true

238
Q

Is allopatric speciation is the dominant or recessive form of speciation?

A

dominant form of speciation

239
Q

Allopatric speciation may occur when? (Population cross)

A

hen some members of a population cross a barrier and form a new, isolated population

240
Q

Population established with Allopatric speciation differ genetically from the parent population because of what?

A

because of the founder effect

241
Q

A barrier’s effectiveness at preventing gene flow depend on what?

A

it depends on the size and mobility of the species in question.

242
Q

What is sympatric speciation?

A

A partition of a gene pool that occurs without physical separation

243
Q

The most common means of sympatric speciation is? (Duplication)

A

polyploidy—duplication of whole sets of chromosomes.

244
Q

Polyploidy arise in 2 ways what?

A

▪Autopolyploidy is chromosome duplication in a single species.

▪Allopolyploidy is the combining of chromosomes from two different species.

245
Q

When can autopolyploidy occur?

A

it can occur accidentally if two diploid gametes combine, resulting in a tetraploid individual.

246
Q

When can allopolyploidy arise?

A

it can arise when individuals of closely related species interbreed, or hybridize.

247
Q

Why are allopolyploidy usually fertile?

A

because each of the chromosomes has a nearly identical partner to pair with during meiosis.

248
Q

Polyploidy can create what? (Reproduction)

A

it can create new species of plants more easily than animals, because plants of many species can reproduce by self- fertilization.

249
Q

What results when a barrier to gene flow is established ?

A

the resulting daughter populations may diverge genetically.

250
Q

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?

A

true

251
Q

If hybridization occurs and hybrids are less fit natural selection will result in what?

A

in reinforcement of mechanisms that will prevent this hybridization in the future

252
Q

What are the mechanisms that prevent hybridization?

A

❑Prezygotic isolating mechanisms

❑Postzygotic isolating mechanisms

253
Q

Prezygotic isolating mechanisms operate before or after fertilization?

A

before

254
Q

In Prezygotic isolating mechanisms , what happens to the habitat isolation and temporal isolation?

A

▪Spatial/Habitat isolation: live in different locations.

▪Temporal isolation: mating periods don’t overlap.

255
Q

In Prezygotic isolating mechanisms , what happens to the Behavioural isolation and mechanical isolation?

A

▪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.

256
Q

In Prezygotic isolating mechanisms , what happens to the gametic isolation?

A

▪Gametic isolation: sperm of one species may not attach or penetrate egg of other species.

257
Q

Postzygotic isolating mechanisms operate before or after fertilization?

A

after

258
Q

In Postzygotic isolating mechanisms , what do does mechanisms mean?

  • hybrid zygote abnormality
  • low hybrid viability
  • hybrid infertility
A

▪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

259
Q

Genes are made up of ….. and are expressed….as polypeptide?

A

DNA////in the phenotype

260
Q

What is the central dogma (main belief) of molecular biology?

A

DNA → RNA → protein.

261
Q

RNA viruses include or exclude DNA altogether, going directly from…..?

A

exclude

262
Q

In retroviruses, what is their rule of transcription ?(reversed or the same) Exemple?

A

reversed

263
Q

A gene is expressed in two steps what ?

A
  • First, DNA is transcribed to RNA

* then RNA is translated into protein.

264
Q

RNA is transcribed from a DNA template after the ….are exposed by….?

A

bases of DNA////unwinding of the double helix.

265
Q

What can act as a template for transcription?

A

In a given region of DNA, only one of the two strands

266
Q

What catalyze transcription from the template strand of DNA?

A

RNA polymerase

267
Q

The initiation of transcription requires that ….recognize and bind tightly to a promoter sequence on DNA.

A

RNA polymerase

268
Q

RNA elongates in a …., antiparallel to the template DNA. ?

A

5’-to-3’ direction,

269
Q

What terminate transcription?

A

Special sequences and protein helpers

270
Q

The genetic code consists of ?

A

triplets of nucleotides (codons)

271
Q

Since there are 4 bases. How many codons?

A

64

272
Q

One mRNA codon indicates what?

A

the starting point of translation and codes for methionine.

273
Q

Three stop codons indicate?

A

the end of translation.

274
Q

The other 60 codons code only for what ?

A

particular amino acids

275
Q

Since there’s is only 20 different aminos acids the genetic code is called….?

A

redundant…that is, there is more than one codon for certain amino acids.

276
Q

A single codon has only one amino acids the genetic code is called….?

A

unambiguous(clear,not messy ,organized)

277
Q

What does it mean unambiguous?

A

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)

278
Q

In prokaryotes, translation begins ….. the mRNA is completed?

A

before

279
Q

In eukaryotes, transcription occurs…..and translation occurs…..?

A

in the nucleus//in the cytoplasm

280
Q

Translation requires what? (3)

A

tRNA’s, activating enzymes, and ribosomes.

281
Q

In translation, ….. are linked in codon-specified order in mRNA?

A

amino acids

282
Q

How is the aminos acid and mRNA linked (process)?

A

when the transfer RNA (tRNA) binds the correct amino acid, and has an anticodon complementary to the mRNA codon.

283
Q

What is The aminoacyl-tRNA synthetases ? And how is charged tRNAs formed?

A

A family of activating enzymes

284
Q

Where do the mRNA and the charged tRNA meet?

A

ribosome

285
Q

What triggers the beginning of translation?

A

An initiation complex consisting of an amino acid-charged tRNA and a small ribosomal subunit bound to mRNA

286
Q

Polypeptide grow from …..towards….? That corresponds to ?

A

N terminus toward the C terminus (corresponds to 5’-to- 3’of mRNA).

287
Q

Is it false that the ribosome move along the mRNA one codon at a time?

A

nope its true

288
Q

what is a mRNA?

A

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.

289
Q

what is a tRNA?

A

(during the transcription process) /the new mRNA strand to become double-stranded by producing a complementary strand known as the transfer RNA (tRNA) strand.

Bio1 (3 decks)

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