Meiosis, Sexual/Asexual Reproduction, Microevolution

If a muscle cell of a typical organism has 32 chromosomes, how many chromosomes will be in a gamete of that same organism? A. 8 B. 16 C. 32 D. 64

B. 16

Sexual reproduction has some disadvantages. Among them are:

Finding a mate can be time-consuming and dangerous! Even favorable combinations of traits get reshuffled during meiosis.

What three stages are Meiosis I preceded by?

G1, S, G2

What happens in allopatric speciation?

Gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations

bottleneck effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.

Spores

Haploid cels that can produce a haploid organism or fuse with another spore to form a diploid cell

What are the two types of balancing selection?

Heterozygote advantage Frequency-dependent selection

What happens early in prophase I?

Homologous chromosomes are attached their tips to the nuclear envelope by proteins and as the nuclear envelope breaks down, the proteins of the homologous chromosomes bring the pair close to each other

Prometaphase I

Homologous chromosomes are attached to spindle microtubules at the fused kinetochore shared by the chromatids Chromosomes continue to condense and the nuclear envelope completely disappears

Metaphase I

Homologous chromosomes randomly assemble at the metaphase plate, where they have been maneuvered into place by the microtubules

Hybrid breakdown

Hybrid is fertile, but when they breed the next generation is sterile.

Prezygotic barriers block fertilization by:

Impeding different species from attempting to mate Preventing the successful completion of mating Hindering fertilization if mating is successful

Many species can reproduce either asexually or sexually. What might be the evolutionary significance of the switch from asexual to sexual reproduction that occurs in some organisms when the environment becomes unfavorable?

In asexual reproduction you produce a genetic clone of the organism. Thus there is no genetic variability. All the genes are the same. Sexual reproduction and crossing over in Prophase I of meiosis will allow for genetic variability to be produced. This is important evolutionary since this genetic variability will confer selective advantages/disadvantages on different individuals and will drive microevolution in order to adapt to adverse environmental changes.

What stage is DNA replicated in?

Interphase (S)

What is a spindle fiber attached to a kinetochore called?

Kinetochore microtubule

True or false: Groups are no clades if they don't include the ancestor node and all the descendants.

True

True or false: In Prometaphase I, the nuclear membrane has broken down entirely.

True

True or false: Organisms inherit genes, which are modified by evolutionary processes over time, resulting in the past and present diversity of life on Earth.

True

True or false: Sympatric speciation is not as common as allopatric.

True

True or false: The phylogenetic species concepts can be difficult to determine the degree of difference required for separate species.

True

In each somatic cell, the nucleus contains how many copies of each chromosome? What are they called?

Two Homologous chromosomes

What is a homologous pair?

Two chromosomes of the same type, containing copies of the same genes laid out in the same order but can code for different alleles of same gene

If two cells that combine each contain one set of chromosomes, the resulting cell will have?

Two sets of chromosomes

What is the chromosomal basis for sex determination in humans?

XX- female XY- male

Anaphase II

sister chromatids are pulled apart by the shortening of the kinetochore microtubules Non-kinetochore microtubules lengthen the cell

Prophase II

sister chromatids condense A new spindle begins to form The nuclear envelope starts to fragment

Metaphase II

sister chromatids line up at the metaphase plate

How are homologous chromosomes similar?

size, shape, and genetic content

The process of _________ bridges ______________ and _____________ and occurs when populations become genetically isolated from one another.

speciation microevolution macroevolution

The number of chiasmata varies according to ____________ and _____________ of chromosome.

species length

Sympatric speciation

species evolves into a new species without any barriers that separate the population

Relative Fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

Taxonomy

the ordered division and naming of organisms

Average heterozygocity

the percentage, on average, of a population's loci that are heterozygous in members of the population

Polyploidy

the presence of extra sets of chromosomes due to accidents during cell division

A human cell containing exactly 22 autosomes and a Y chromosome is A. a zygote B. a sperm C. an egg d. a somatic cell of a male human e. a somatic cell of a female human

B. A sperm

True or false: Lack of gene flow and reproductive isolation can lead to allopatric speciation.

False, when caused by the same mutation this can lead to sympatric speciation

For any gene with a dominant allele A and recessive allele a, consider a cross between AA and Aa. From this cross, the proportion of offspring expected to be homozygous dominant is _______ , the proportion of offspring expected to be homozygous recessive is _______ and the proportion of offspring expected to be heterozygous is ______ .

1/2 0 1/2

Every time crossing over occurs, ________ of the sister chromatids of a tetrad swap DNA, leading to _____% of the resulting gametes being recombinants.

1/2 50%

If the father doesn't have the trait, but the mother is heterozygous:

1/2 the daughters will be carriers and 1/2 the sons will have the trait

If the father has the trait and the mother is heterozygous:

1/2 the daughters will be carriers, 1/2 will have the trait, 1/2 the sons will have the trait

Which of the following is true of a species that has a chromosome number of 2n = 20? Select all that are true. A. At G2 of the cell cycle, a cell would contain 20 chromatids. B. The species must reproduce sexually C. The species is diploid. D. Each cell has 10 homologous pairs of chromosomes. E. 20 tetrads will form during prophase of meiosis.

C and D

A liver cell of a woodland hedgehog contains 88 chromosomes. Write in the appropriate number for each of the following hedgehog cells: a neuron has __________ chromosomes, sperm have ________ chromosomes, a skin cell just after S-phase of mitosis has _________ chromosomes, a pancreatic cell has ___________ homologous pairs of chromosomes, and a zygote has __________ chromosomes.

88 44 88 44 88

What is the result of the first meitotic division?

2 haploid cells

What are sister chromatids?

2 identical copies of DNA held together by a centromere

You have a bag of 1000 marbles, half of which are black and half of which are white (and they are thoroughly mixed up). You are going to select a marble, then your friend Bernt is going to select a marble. The chances that you both select a black marble are approximately ____%.

25% It states that if an outcome depends on more than one event (i.e. you getting the black marble AND Bernt getting the black marble), you figure out the probabilities of each one happening alone and multiply them together. Chance that you get black? 50%. Chance that Bernt gets a black marble? 50%. 50% x 50% = 25%. You'll use this in Mendelian genetics a lot.

TH Morgan's P generation was a red-eyed female x a white-eyed male. When Thomas Hunt Morgan bred the F1 flies together (F1 x F1), the phenotypes of the offspring showed a familiar 3:1 pattern and __________% of these F2 offspring had white eyes. This would suggest that the F1 parents were ____________.

25% heterozygotes

In the previous question, you considered a "testcross" between F1 heterozygotes in which the dominant GS alleles were on one of the homologous chromosomes, and the recessive gs alleles were on the other chromosome. In the previous scenario, these two alleles are linked. But now, consider if they were on different chromosomes. Using the same dihybrid testcross between this F1 and a homozygous recessive fish Predict the genotypes expected in their offspring and in what percentage. A. 25% GGSS, 50% GgSs, and 25% ggss B. 25% GgSs, 25% Ggss, 25% ggSs, and 25% ggss. C. 100% GgSs. D. 50% GGSS and 50% ggss

25% GgSs, 25% Ggss, 25% ggSs, and 25% ggss. If the genes were not linked, this would mean the two genes are on different chromosomes. Then due to independent assortment of chromosomes, the F1 heterozygotes could make GS, Gs, gS, and gs gametes. In the testcross between the F1 and the homozygous recessive fish, this would yield offspring of GgSs, Ggss, ggSs, and ggss in a 1:1:1:1 ratio.

What is the 2N number of chromosomes in humans?

2n=46

Consider tail length and coat color in a hypothetical population of pygmy camels. Tails are either short or long, and coats are either white or tan. How many different combinations of tail length and coat color are there in this population? In your answer do not include any words, just provide a numeric answer.

4

Each allele has ____ percent chance of going into a zygote.

50

In a dihybrid testcross, the recombination rate is _______ percent, due to independent assortment of chromosomes during metaphase I.

50%

You have a bag of 1000 marbles, half of which are black and half of which are white (and they are thoroughly mixed up). You are going to select a marble. The chances that you select a black marble are approximately ____%

50%

What is the first thing you need in order for speciation to occur?

A barrier to gene flow

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Frequency-dependent selection

A decline in the reproductive success of individuals that have a phenotype that has become too common in a population.

Locus

A gene's specific location along the length of the chromosome

Population

A group of individuals that belong to the same species and live in the same area

Clade

A group of species that includes an ancestral species and all its descendants.

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Prezygotic barriers

A reproductive barrier that impedes mating between species

Pleiotropy

A single gene having multiple effects on an individuals phenotype

Epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

In a hypothetical population of diploid beans from Beanland, there is a single gene locus that determines bean color B/b. The phenotypes of the beans, demonstrating incomplete dominance are black (BB), white (bb) or black-eyed (Bb). You have collected a sample of 10 individuals from one population. (2 BB, 3 bb, 5 Bb) A. What is the total number of alleles in the sample?

A. 20

If the DNA content of a diploid cell in the G-1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I will be ___. A. 2x B. x C. 0.5x D.0.25x

A. 2x

Consider a pea plant that is heterozygous at the flower color locus. Just for convenience, we'll abbreviate the two alleles "Q" and "q". When this plant makes gametes, each one will get either the Q allele or the q allele, but not both! Amazingly, Mendel figured this out through careful experimentation and patient observation. What did Mendel call this phenomenon? A. He called it the law of segregation. B. He called it Mendelian genetics. C. He called it the law of transmutation. D. He called it the law of independent assortment. E. He called it heredity.

A. Law of segregation

Mendel's series of experiments studying inheritance of flower color really gave him great insight. He deduced that there was a "heritable trait" that gave the offspring purple flowers, and a different "heritable trait" that gave the offspring white flowers. He called the purple trait "dominant" and the white trait "recessive". A. The "dominant" allele codes for a protein that leads to purple pigment, and one "purple" allele is sufficient to make the flower purple. B. If an organism is heterozygous and is purple, we call the purple allele the "dominant" allele. C. The dominant gene hides the recessive gene

A. The "dominant" allele codes for a protein that leads to purple pigment Heterozygotes have one allele that does not code for a functional protein, but it doesn't affect the color because the other allele does code for that protein - enough of it to make the flower purple.

A hypothetical gene on the X chromosome affects the color of the fur of pillowpigs, which is inherited in a complete-dominance pattern. The dominant phenotype is red, the recessive phenotype is tan. Two red pillowpigs are mated, and the female has four pillowpiglets -- two red and two tan. What do we know about this pillowpigs family? Select all that apply. A. The mother was heterozygous for the fur color trait. B. The father had a recessive allele for the fur color trait C. All of the offspring were male D. Two of the offspring were female E. The mother was homozygous for the fur color trait. F. At least two of the offspring were male.

A. The mother was heterozygous for the fur color trait. Correct! We know the father has a dominant allele because he's red. He does not have two copies of the dominant allele because it's on the X chromosome. Because there was at least one tan baby, this baby must not have any dominant allele. Therefore, the recessive allele the baby got must have come from the mother. But since she has the dominant phenotype, she must be heterozygous. E. The mother was homozygous for the fur color trait. F. At least two of the offspring were male.

Which of the following processes might produce a human zygote with 45 chromosomes? A. An error in meiotic anaphase occurring in either an egg or sperm B. A gene duplication during DNA replication C. Failure of the egg nucleus to be fertilized by the sperm D. Failure of an egg to complete meiosis II

A. an error in meitotic anaphase

At metaphase I, homologous chromosomes are connected only at what structures? A. chiasmata B. recombination nodules C. microtubules D. kinetochores

A. chiasmata

The two homologs of a pair separate and move toward opposite poles of a dividing cell during ___. A. meiosis II B. mitosis only C. meiosis I D. meiosis II and mitosis E. meiosis I and mitosis F. fertilization

A. meiosis 1

Which rule do you use if the outcome is possible via more than one process?

Addition rule

If the father has the trait and the mother is homozygous dominant for the trait:

All female offspring will be carriers

Gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

What four main concepts explain the ratio that Mendel discovered during his pea plant experiment?

Alleles (alternative versions) You get two alleles, one from each parent. One of the alleles is dominant and the other is recessive. The 2 alleles separated during gamete formation and end up in different gametes. This is called the law of segregation.

How many chiasma per chromosome must there be for proper separation of homologous during meiosis I?

At least 1

Consider two adjacent genes on chromosome #4, gene A (alleles A and a) and gene B (alleles B and b). An individual is Ab on the maternal copy and aB on the paternal copy. Given that they are adjacent, you can assume no crossing over will occur. What gamete genotypes can this individual make? A. AB, Ab, aB, and ab B. Ab and aB C. AABB, aabb, AaBb D. Aa and Bb E. AaBb only

B. Ab and aB

When conducting an experiment using a dihybrid cross, which of the following parental genotypes would be crossed? A. RR x GG B. RrGg x RrGg C. RRGG x rrgg D. Rr x Gg

B. RrGg x RrGg The "di" part signifies that there are two characters involved, (in this case, the R and the G). "Dihybrids" are individuals that are heterozygous for two characters. A "dihybrid cross" is a cross between two dihybrids.

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? A. Other male-specific factors influence eye color in flies. B. The gene involved is on the X chromosome. C. The gene involved is on an autosome, but only in males. D. The gene involved is on the Y chromosome.

B. The gene involved is on the X chromosome.

What structure is most important in forming the tetrads? A. centromere B. synaptonemal complex C. chiasma D. kinetochore

B. synaptonemal complex

Consider the same cell from the last question. The DNA content of a diploid cell in the G-1 phase of the cell cycle is x. Follow this cell's lineage through meiosis. What will the DNA content of a single cell at metaphase II of meiosis be? A. 0.25x B. x C. 0.5x D. 2x

B. x

Determine the parental generation if: The ratio of offspring is 3:1

Both parents are heterozygous

How does meiosis achieve its haploid chromosome number?

By undergoing one round of chromosome duplication and two rounds of nuclear division

In the previous question, there was a mating between a fish homozygous dominant (GGSS) for two linked characters and a fish homozygous recessive (ggss) for the same two linked characters. This is the P generation, and their offspring are the F1 generation. Now consider a "testcross" between an F1 fish from the above mating and a fish that is homozygous recessive for both traits. What percent of each genotype would be predicted in their offspring? A. 100% GgSs B. 25% GGSS, 25% ggss, 50% GgSs C. 50% GgSs and 50% ggss D. 25% GgSs, 25% Ggss, 25% ggSs, and 25% ggss

C. 50% GgSs and 50% ggss Parent generation (P) = GS GS x gs gs . I'm writing it this way instead of GGSS because I like to remind myself that the dominant alleles are LINKED. They are going to travel together on the same chromosome. And in the other parent, the recessive alleles are linked, meaning that the g will travel with the s on the same chromosome. One parent can donate only GS gametes, the other parent only donates gs gametes. F1 generation will be heterozygotes. Again, you can write this like GgSs, but I really want to remind myself that the two dominant traits are physically on the same chromosome, so in meiosis, they will go together into the same gamete. So I write this as GSgs. The F1 generation can therefore make either GS gamete or gs gamete. F1 dihibrid testcross: GS gs x gs gs (hom. rec. both traits) should yield offspring with genotypes of GSgs and gsgs in a 1:1 ratio.

When can crossing over be observed visually?

Can be observed visually after the exchange as chiasmata

You have been asked to record data on the phenotypes of this population, and you find that all the camels with a long tail also have a tan coat, and all the camels with a short tail have a white coat. On rare occasion, you will see a long-tailed white camel, or a short-tailed tan camel. But the vast majority is long/tan or short/white. What is a reasonable explanation for the predominance of these two phenotypes? Note: both colors and both tail lengths are equally fit for their environment, so there is no selective advantage to one over the other. A. The gene loci for coat color and tail length are on the same chromosome, but are not close together. B. The allele for tan coat and the allele for a long tail are on maternal chromosomes. C. The gene loci for coat color and tail length are close together on the same chromosome. D. Independent assortment is not a factor in pygmy camel genetics. E. The gene for tail length and the gene for coat color are on 2 chromosomes that travel together. F. Camels with long tails and tan coats are more tolerant of heat and more likely to survive.

C. The gene loci for coat color and tail length are close together on the same chromosome.

Thomas Hunt Morgan bred a red-eyed female fly with a white-eyed male fly. All the offspring had red eyes. What does this suggest about the eye-color character? A. The white allele (w) was lost during the breeding process. B. The white phenotype arises by chance and cannot be passed from one generation to another. C. The red allele (w+) is dominant. D. Male flies do not determine the phenotype of the offspring.

C. The red allele (w+) is dominant.

A particular gene "V" is on chromosome #3. In the population are three possible alleles - V1, V2, and V3. An individual that is homozygous V2V2 mates with an individual that is heterozygous V1V3. What are the possible genotypes of their offspring? A. V1V2V3 B. V1V2, V2V2, V1V3 C. V1V2, V2V3 D. V1V3V2V2

C. V1V2, V2V3 Because one of the parents is homozygous, this parent can only donate one allele (in this case, the V2 allele). The other parent is able to donate a V1 or V3 allele. So for any given offspring, there's a 50% chance they'll have the V1 allele, and a 50% chance they'll have a V3 allele. What are the chances they'll have a V2 allele? 100% chance, due to the V2V2 parent.

Which of the following is not true in regard to crossover? A. Spindle microtubules guide the transfer of DNA across the synaptonemal complex. B. Non-sister chromatids exchange genetic material. C. Chiasmata are formed. D. Recombination nodules mark the crossover point.

C. chiasmata are formed

The part of meiosis that is similar to mitosis is ________. A. meiosis I B. anaphase I C. meiosis II D. interkinesis

C. meiosis II

What phase of mitotic interphase is missing from meiotic interkinesis? A. G0 phase B. G1 phase C. S phase D. G2 phase

C. s phase

The Cavendish banana is currently threatened by extinction due to a fungus. This banana variety is triploid (3n) and can only reproduce through cloning by its cultivators. Given what you know about meiosis, explain how the banana's triploid number accounts for its inability to form normal gametes. Considering genetic diversity, discuss how the absence of sexual reproduction might makes this domesticated species vulnerable to infectious agents.

Cavendish banana being triploid creates unbalanced gametes because of random segregation of three homologous chromosomes, no matter how they align. A gamete produced by meiosis in such a triploid might receive two copies of some chromosome, three copies of other, no copy of other and so on. When these unbalanced gametes fuses with normal gamete, the resulting zygote has different number of chromosomes and this difference is often lethal. For this reason triploid do not usually produce viable gametes, so Cavendish banana is sterile and produce no seeds. Being unable to reproduce sexually, this species suffers from loss of genetic diversity, which will result in inability of this species to evolve in changing environmental conditions and become prone to diseases. Because this species is grown from clones rather than seed, there is very little genetic diversity among them. Since all the alleles in the population are the same, and susceptible to the disease, nearly all the banana can become susceptible to disease, and if any infectious agent happens to attack entire species may be wiped out. Since all the alleles in the population are same and mutation in any of the allele may make it susceptible to infection or disease and entire species may be at risk because they are all derived from the same individual by cloning.

Microevolution

Change in allele frequencies in a population over generations.

Telophase II and cytokinesis

Chromosomes arrive at the pols of the cell and decidedness Nuclear envelopes surround the four nuclei Cleavage furrows divide the two cells into four haploid cells

Prophase I

Chromosomes condense Nuclear envelope fragments Homologous chromosomes bind firmly together along their length, forming a tetrad Chiasmata form between non-sister chromatids Crossing ver occurs at the chiasmata Spindle fibers emerge from the centrosomes

Homologous chromosomes

Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.

Sexually-reproducing organisms create offspring that are different from one another and different from their parents. What are three sources of variation due to sexual reproduction?

Crossing Over Independent Assortment Random fertilization

Which of the following is true of crossing over? A. Segments of DNA are trade between unrelated chromosomes B. Crossing over occurs more in male gametes than female gametes C. Most homologue pairs do not have any crossover events. D. A chiasma indicates that a crossover has occurred.

D. A Chiasma indicates that a crossover has occurred A is incorrect because crossing over occurs between homologues chromosomes. B is incorrect because crossing over is not more likely to happen in male gametes than female gametes (they are equally capable of crossing over). C is incorrect because crossing over is very common. There can be multiple crossover event between homologous chromosomes. D is correct because a chiasma is a cross shaped structure that links homologues together. This is the location where pairs can trade genetic information.

Consider a character of horns on a jackalope. Horns are blunt or pointy, with blunt being the dominant trait. A jackalope with blunt horns could have the genotype of BB or Bb. How could you find out which one it is? A. Mate this jackalope with another blunt-horned jackalope and see what phenotypes the offspring have. B. Mate this jackalope with another jackalope that you know is homozygous dominant and see what phenotypes the offspring have. C. Mate this jackalope with another jackalope that you know is heterozygous and see what the phenotypes of the offspring are. D. Mate this jackalope with a pointy-horned jackalope and see what phenotypes the offspring have.

D. Mate this jackalope with a pointy-horned jackalope

In albinism, what is the molecular reason why heterozygotes have a "normal" phenotype? A. Presence of the dominant allele actually hides the presence of the recessive allele. B. A person must have both recessive alleles to show the trait. C. The recessive allele codes for a protein that makes the skin appear white, but two copies are needed to counteract the effects of the dominant allele D. The dominant allele codes for a functional protein, which allows for enough melanin to be produced such that the carrier appears normal even though they only have 1/2 the normal amount of melanin.

D. The dominant allele codes for a functional protein, which allows for enough melanin to be produced such that the carrier appears normal even though they only have 1/2 the normal amount of melanin.

At which stage of meiosis are sister chromatids separated from each other? A. prophase I B. prophase II C. anaphase I D. anaphase II

D. anaphase II

Meiosis produces ________ daughter cells. A. two haploid B. two diploid C. four haploid D. four diploid

D. four diploid

A button beetle has two unlinked genes, one for wing shape (W) and one for antenna length (A). Its genotype is WwAa. Which of the following genotypes for these two genes is possible in a gamete from this organism? A. W B. WwAa C. Ww D. wa

D. wa Mendel's law of segregation states that the two alleles for each heritable character (in this case, wing shape or antenna length) segregate during gamete formation and end up in different gametes. The law of independent assortment states that each pair of alleles from unlinked genes will assort independently of any other allele pair during gamete formation. Therefore, each gamete will receive one allele for wing shape and one allele for antenna length, resulting in the following possible genotypes of gametes produced by this organism: WA, Wa, wA, and wa.

Morphological species concept

Defines a species by structural features

Sexual dimorphism

Differences in physical characteristics between males and females of the same species.

Explain the Law of Segregation.

During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.

What happens during s phase of meiosis I?

Each chromosome is replicated to produce 2 identical copies called sister chromatids that are held together at the centromere by cohesion proteins and centrosomes also replicate and prepares cell to enter prophase I

Phylogeny

Evolutionary history of a species or group of species.

Reproductive isolation

Existence of biological factors that impede members of genetically distinct groups form producing viable fertile offspring Genetic differences, not geographic

True or False: Men can be carriers of a sex-linked gene.

False

True or False: Mutations that occurs and accumulate in separate population guarantee speciation.

False

True or False: The morphological species concepts lies on objective criteria.

False subjective

True or False: In mitosis the parent and daughter cells have different ploidy levels.

False Same policy levels (identical)

True or False: If traits tend to be inherited together, it's because they are located far from each other different chromosomes.

False, Close to each other on the same chromosome

True or False: Most animals and plants are haploid.

False, diploid

True or false: Polyploidy is more common in animals than plants.

False, more common in plants than animals

True or false: Homologous chromosomes are identical.

False, not identical. They contain slight differences in their genetic information, causing each gamete to have a unique genetic makeup.

In general, the genetic variation that comes from sexual reproduction is a benefit to sexually-reproducing populations. But which of the following scenarios would favor asexual reproduction?

Most individuals are well-suited to their stable environment. Good combinations of traits can be passed on wholesale with no danger of the traits being shuffled with every generation via meiosis and random fertilization. Parents pass on 100% of their genome to their offspring. The environment is harsh for seedlings but not for mature plants. Offspring often have a very difficult time getting established. A zygote (or a seedling, as is the case here) needs time and energy to grow, during which they are very vulnerable to the environment. A clone, however, can be created by mitosis of the parent, and can receive nutrition from that parent until they get disconnected. At this point the offspring will be more able to get the resources they need. The species is rare. A very uncommon species would have difficulty finding a mate. The ability to reproduce asexually might keep this species from going extinct.

Which rule do you use if 2 or more independent events must happen together or in a specific combination?

Multiplication rule

What does variation begin with?

Mutations are the original source of variation.

Directional selection

Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Balancing Selection

Natural selection that maintains stable frequencies of two or more phenotypic forms in a population.

What keep genetic variation in a population?

Neutral variation is genetic variation that does not confer a selective advantage or disadvantage. Diploidy and balancing selection keep alleles around.

What are the five assumptions of Hardy-Weinberg equilibrium?

No mutations. Random mating. No natural selection. Extremely large population size. No gene flow.

True or false: Morphological species concept puts an emphasis on breeding system.

No, breeding system is irrelevant

Is the law of independent assortment relevant when we are referring to linked genes? Why or why not?

No. Linked genes will often travel together if they are close together on the same chromosome.

What is the main difference between meiosis and mitosis?

Occurs in Meiosis I: Homologous chromosomes pairs become associated with each other are bound together with the synaptonemal complex, develop chiasmata and undergo crossover between sister chromatids and line up along the metaphase plate in tetrads with kinetochore fibers from opposite spindle poles attached to each kinetochore.

Diploid organisms inherit how many copies of each homologous chromosome from each parent?

One

Haploid

One set of chromosomes

Where are haploid cells found?

Only within structure that give rise to gametes or spores

Determine the parental generation if: 1/2 the offspring have the recessive phenotype and 1/2 have the dominant

Parents are heterozygous and homozygous recessive

The rule: "Individuals considered members of the same species should be more closely related to each other than they are to other species." is a basis of which speciation concept?

Phylogenetic

Name factors can reduce gene flow within one population.

Polyploidy (4n can't mate with 2n parents_ Habitat differentiation Sexual selection Pollinator preference

Fertilization

Process in sexual reproduction in which male and female reproductive cells join to form a new cell

A single crossover event between homologous non-sister chromatids leads to __________ _________ of equivalent DNA between a maternal and paternal chromosomal.

Reciprocal exchange

What is located at intervals along the synaptonemal complex?

Recombination nodules

What are non-sister chromatids?

Replicas of different chromosomes that are similar but not identical One comes from mother and one from father

What prevents gene flow between two closely-related species?

Reproductive isolation

Why doesn't natural selection create perfect organisms?

Selection can only act on existing variation (Mutations are random) Evolution is limited by historical constraints (what is inherited from parents) Adaptations are often compromises Chance, natural selection, and the changing environment often interact

Intersexual selection

Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.

Telophase I and Cytokinesis

Sister chromatids arrive at the poles of he cell and begins to decondense A nuclear envelope forms around each nucleus and the cytoplasm is divided by a cleavage furrow The result is two haploid cells Each cell contains one duplicated copy of each homologous chromosome pair

Biological Species concept

Species is a group of populations whose members have the potential to interbreed in nature and produce fertile offspring.

Anaphase I

Spindle microtubules pull the homogenous chromosomes apart Sister chromatids are still attached at the centromere

Chiasmata

The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis.

How are homologous chromosomes different?

The alleles for the traits they carry may be different

Cleavage furrow

The area of the cell membrane that pinches in and eventually separates the dividing cell, constriction of actin ring that leads to cytoplasmic division

What happens near the recombination nodules on each chromatid?

The double stranded DNA is cleaved and the cut ends are modified and a new connection is made between non-sister chromatids

Allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

What is the difference between a haploid and diploid cell?

The main difference between haploid and diploid cells is the number of chromosome sets found in the nucleus. Ploidy is the area of biology that refers to the number of chromosomes in a cell. Therefore, cells with two sets are diploid, and those with one set are haploid

Prometaphase II

The nuclear envelope disappears Spindle fibers engage the individual kinetochores on the sister chromatids

Absolute Fitness

The ratio of frequencies of a particular genotype from one generation to the next

specific epithet

The second part of a binomial, it refers to one species within a genus.

True or False: Females need 2 copies for recessive X-linked traits to be expressed.

True

True or False: In meiosis, the starting nucleus is always diploid and results in haploid nuclei.

True

True or False: Reproductive isolation can be classified by whether factors act before or after fertilization.

True

True or False: Reproductive isolation reinforces and protects the genetic differences that have built up between different population or species by limiting gene flow between them.

True

True or False: Selection alters the frequency distribution of heritable traits

True

True or False: Some plants and all fungi produce spores.

True

Polytomy

a branch point from which more than two descendant groups emerge

A human cell containing 22 autosomes and a Y chromosome is

a sperm

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Synaptonemal complex

a zipper-like structure composed of proteins, which connects two homologous chromosomes tightly along their lengths and supports the exchange of chromosomal segments between non-sister homologous chromosomes in a process called crossing over

Somatic cell

any cell of a living organism other than the reproductive cells.

What is the key event of pro metaphase I?

attachment of the spindle fiber microtubules to the kinetochore proteins at the centromeres

Node

branch point

Limitations of the Biological Species concept

cannot be applied to fossils or asexual organisms emphasizes absence of gene flow

In plants, a _______ _________ is formed during cell cytokinesis by ___________ __________ fusing at the metaphase plate.

cell plate golgi vesicles

Systematics

classifies organisms and determines their evolutionary relationships

Intrasexual selection

competition among individuals of one sex (often males) for mates of the opposite sex

What are the two sources of genetic variation?

crossover, random/independent assortment

Phylogenetic Species Concept

defines a species as the smallest group of individuals that share a common ancestor on a phylogenetic tree

Neutral variation

differences in DNA sequence that do not confer a selective advantage or disadvantage

Cytokinesis

division of the cytoplasm to form two separate daughter cells

q^2

frequency of homozygous recessive genotype

Reduced hybrid viability

genes of the different parent species may interact poorly, impairing the hybrid's development

Cells produced at the end of telophase II and cytokinesis are _____________ _________ because of the random assortment of paternal and homologs and because of the recombining of maternal and paternal segments of chromosomes that occurs during crossover.

gentically unique

Genus

group of closely related species; the first part of the scientific name in binomial nomenclature

Taxa

group or level of organization into which organisms are classified

Monophyletic group

group that consists of a single ancestral species and all its descendants and excludes any organisms that are not descended from that common ancestor

Spindle fibers

help pull apart the cell during replication and are made up of microtubules, grow from centrosomes placed at the opposite pole of the cell

The Northeastern Flubbergill is a fish with warts all over its body. The wart color is controlled by a single gene with two alleles. Warts are either green or white, with green dominant over white. Some Flubbergills have spines, and some do not. Presence of spines is also controlled by a single gene, with spines dominant over "no spines". The wart color gene and the spine gene are fairly close to each other on the same chromosome. A mating between a fish homozygous dominant for both traits and a fish homozygous recessive for both traits, will yield offspring that are _____.

heterozygotes with green warts and spines

2 x pq

heterozygous frequency

p^2

homozygous dominant frequency

Rooted tree

includes a branch to represent the last common ancestor of all taxa in the tree

Heterozygote advantage

individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes

Adaptation

inherited characteristics of organisms that enhance their survival and reproduction in specific environments

Recombination nodules

large protein assemblies that mark the points of later chiasmata and mediate the process of crossover or genetic recombination between non-sister chromatids

Diploidy

maintains genetic variation in the form of hidden recessive alleles (both parents are heterozygous for a certain trait)

Nucleotide variability

measured by comparing the DNA sequences of two individuals in a population and then averaging the data from many such comparisons

In some species, cells enter a brief interphase or interkinesis before entering __________ _____.

meiosis II

Kinetochore proteins

multiprotein complexes that bind the centromeres of a chromosome to the microtubules of the mitotic spindle

What is the n number of chromosome in humans?

n=23

Disruptive selection

natural selection in which individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle of the curve

In addition to fertilization, sexual reproduction includes a __________ division that ___________ the number of chromosome sets.

nuclear reduces

Ploidy level

number of sets of chromosomes in a cell

What happens at the end of prophase I?

pairs are only held together at chiasmata and are called tetrads because the 4 sister chromatids of each pair of homologous chromosomes are now visible

Gene flow between populations holds the ___________ of a species together.

phenotype

True-Breeding

plants that produce offspring with the same traits as their parents

What can sympatric speciation result from?

polyploidy, natural selection, or sexual selection

Postzygotic barriers

prevent the hybrid zygote from developing into a viable, fertile adult due to reduce hybrid viability, reduced hybrid fertility, hybrid breakdown

In which phase is the spindle fully formed?

prometaphase II

In which phase do chromosomes fragment into vesicles if the nuclear envelopes were formed?

prophase II

Cohesin Proteins

proteins that bind to the centromeres of sister chromatids and hold them together until anaphase II

Diploid

two sets of chromosomes (2n)

Reduction division

when the chiasmata resolve and the tetrad is split to each pole, the ploidy level for the future nuclei is reduced from two to one, also known as Meiosis I