Biology Review Test 1

1-15 What are the evolutionary advantages of reproducing sexually? What are the limitations?

-genetic variation (adaptations, natural selection) -courtship of 2 parents -long process -energy consuming

1-1 chromatid, use term correctly

1 strand in a chromosome, liked together by the centromere each contains a double helix of DNA sister chromatids - identical DNA molecules made after replication

Which of these best describes an "allele" A. a gene locus on the chromosome B. a specific version of the gene for a trait C. a duplicate found on both chromosomes in a pair

B

If a cell with 2n=60 chromosomes undergoes meiosis, but 1 chromosomal non-disjunction event occurs during meiosis 2, that is, members of 1 twin chromatid pair fail to separate normally, how many chromosomes will be in the 4 resulting daughter cells? A. 30, 30, 30, 30 B. 30, 30, 29, 29 C. 30, 30, 31, 31 D. 30, 30, 31, 29 E. 31, 31, 29, 29

D

Inbreeding increases the percentage of which genotypes in a population? A. Only homozygous dominant B. only homozygous recessive C. only heterozygous D. both homozygotes

D

The term "macroevolution" refers to evolution A. of large structures B. within a large population C. of groups of organisms above the species level D. of groups of organisms over a long time scale

C

1-18 If the 2 alleles present in a diploid individual have the same DNA sequence, is that individual homozygous or heterozygous for that trait?

Homozygous

1-1 chromosome, use term correctly

a DNA molecule with the respective proteins (histones)

1-1 homologous pair, use term correctly

set of 1 maternal and 1 paternal chromosome that carry the same gene loci and pair up during fertilization 2n = 23 (humans have 23 pairs) have different alleles

1-2 Is a homologous pair the same as a pair of twin chromatids?

No twin chromatids are part of 1 chromosome and are identical pieces of DNA homologs are not identical

1-14 What are the evolutionary advantages of reproducing asexually? What are the limitations?

-needs 1 parent (no courtship) -offspring are identical (so if parent is thriving so will offspring/low population density) -little energy -faster -no genetic variation

Misconceptions about evolution, what are they in these statements. 1. When their habitats changed over time, frogs evolved a different color because they needed to be brown 2. Evolution by natural selection is survival of the fittest. 3. Evolution by natural selection is a random process. 4. Evolution by natural selection tends to produce perfect organisms.

1. Needed to 2. But also reproduction 3. Not random 4. Not perfect (depends on environment)

1-30 Name the 5 main assumptions of Hardy-Weinberg equilibrium. Tell how violating any of those assumptions would cause the population (gene pool) to evolve and not stay in equilibrium.

1. No natural selection 2. No mutation 3. No gene flow 4. Large Population 5. Random Mating (interbreeding)

1-2 What are homologous chromosomes?

are 2 different chromosomes, 1 from mother and 1 from father carry same gene loci and pair up during fertilization usually the same size/length

1-4 If the diploid number (2n) for a species is 54, what is the haploid number (n) for that species?

n = 27

A cell (2n = 50) undergoes meiosis. The products are _____ cells, each with _____ chromosomes. A. 2 cells, each with 25 chromosomes B. 2 cells, each with 50 chromosomes C. 4 cells, each with 25 chromosomes D. 4 cells, each with 50 chromosomes

C

A chromosome contains? A. two-singles stranded DNA molecules B. one double-stranded DNA molecules C. two double-stranded DNA molecules D. many double-stranded DNA molecules

C

A population that is variable in fur color phenotypes changes its distribution over time, such that the average color stays the same but the variance (spread of values) decreases in the population. Which mode or combination of modes of selection would explain this? A. directional selection only B. disruptive selection only C. stabilizing selection only D. 2 of these would explain this E. any of A, B, or C would explain this

C

Assuming that there are only two alleles for a given gene locus, if the frequency of one allele in a population is 0.6, what is the frequency of the other allele? A. -0.6 B. 0 C. 0.4 D. 0.6 E. 1

C

Classical albinism results from a particular recessive allele. Which of the following are the expected phenotypes of offspring from an albino woman and a normally pigmented man who has an albino father? A. 3/4 normal 1/4 albino B. 3/4 albino 1/4 normal C. 1/2 normal 1/2 albino D. all normal E. all albino

C

Hemophilia is an X-linked recessive trait. A man without hemophilia marries a woman who is a carrier but not affect. What fraction of their daughters will be carriers? A. all B. 2/3 C. 1/2 D. 1/4 E. none

C

If the barrier is removed from the two populations that were formed by allopatric speciation, what characteristic would allow one to determine if the two populations had become separate species? A. different morphologies B. habitat specialization C. inability to interbreed D. competition for resources

C

In a certain species, n = 20 If one diploid cell in this species undergoes meiosis, the products will be A. 2 cells, each with 20 chromosomes B. 2 cells, each with 40 chromosomes C. 4 cells, each with 20 chromosomes D. 4 cells, each with 40 chromosomes

C

In cell division during meiosis, members of the same homologous pair separate from each other in _________, while the sister (twin) chromatids separate from each other in ___________. A. meiosis 1, meiosis 1 B. meiosis 2, meiosis 2 C. meiosis 1, meiosis 2 D. meiosis 2, meiosis 2

C

One hears the statement "Evolution all happens by chance." Which of the following statements is TRUE and helps to correct that misconception? A. Mutations do not happen by chance alone B. selection involves survival of the fittest C. Natural selection does not happen by chance D. Chance cannot produce perfect organisms

C

Red-green colorblindness is an X-linked recessive trait. Neither John nor Ann is colorblind, but Ann's father is colorblind. What fraction of the daughters of John and Ann are expected to be carriers for the trait? A. 0 (none) B. 1/4 C. 1/2 D. 3/4 E. all

C

Structures in different species are considered homologous if A. they have the same function in different species B. they have the same structure (shape etc) C. they are derived from the same ancestral structure D. two of these are true

C

The ultimate origin of genetic variation is A. genetic drift B. natural selection C. mutation D. a founder effect E. non-random mating

C

These processes can produce genetic variability: a. mutation, b. crossing over, c. independent assortment Rank them in terms of the amount of genetic variability they produce among the gametes made by a single individual. A. a most > b middle > c least B. b most > c middle > a least C. c most > b middle > a least D. c most > a middle > b least

C

What is a normal process that contributes to genetic variability during meiosis? A. independent assortment B. crossing over C. both A and B D. neither A nor B

C

When a chestnut-colored horse is mated with a cream-colored horse, all the offspring are palomino (incomplete dominance). When two palomino horses are mated, what proportion of their offspring would be expected to be palomino? A. 0 (none) B. 0.25 C. 0.50 D. 0.75 E. 1.0 (all)

C

Which of these would be an evolutionary advantage to having the X-chromosome inactivation system? A. it would decrease expression of one harmful X-linked traits B. it would decrease expressions of only recessive X-linked traits C. it would make the amount of expression of all X-linked traits about the same in males and females D. it would make the mutation rate of X-linked traits about the same as that of Y-linked traits

C

Which statement about an individual that is homozygous for a specific allele is NOT true? A. each of its cells possesses 2 copies of that allele B. each of the gametes it produces contains 1 copy of the allele C. both of its parents had to be homozygous for that allele D. it is true-breeding with respect to that allele (will pass that allele to all offspring)

C

In a population of 1000 diploid individuals the gene pool for a trait like eye color would consist of how many alleles? A. 500 B. 1000 C. 2000 D. another number

C 1000 x 2

1-22 a) use multiplication rule to determine the probability that a couple planning to have 2 children will have 2 sons b) A couple with 2 sons is expecting a new baby - what is the probability it will be a son?

1/2 x 1/2 = 1/4 1/2

1-6 If a cell with 2n = 40 chromosomes undergoes meiosis, but one non-disjunction event occurs during Meiosis 2, how many chromosomes will be in each 4 daughter cells?

20 20 19 21

A species' diploid chromosome number is 50 1. how many homologous pairs are there? 2. 2n = _______ and n = ________ 3. In G1 of the cell cycle, the nucleus of a typical cell of this species has _____ DNA molecules and ____ chromosomes 4. In G2, after DNA replication, the nucleus of this cell has ____ DNA molecules and ______ chromosomes.

25 50, 25 50, 50 100, 50

1-10 If a diploid cell has n pairs of chromosomes, how many different combinations of haploid chromosomes can be produced in meiosis of that cell? (ignore crossing over). Does independent assortment of homologous chromosomes during meiosis I produce a large amount of genetic variation, even without considering crossing-over and random fertilization?

2^n combinations Yes, it produces the largest amount of genetic variation

Hb^AHb^A w = 0.8 ________ offsprings ________ 5Hb^S alleles Hb^AHb^S w = 1 5 offsprings Hb^SHb^S w = 0.2 ________ offsprings ________ 5 Hb^S alleles

4 0 1 2

1-5 If a cell with a genome of 20 pairs of chromosomes undergoes normal meiosis, how many cells result and how many chromosomes are in each of the resulting cells?

4 cells, each with 20 chromosomes

Individuals of a particular species of flowering plant that lives only one year can produce red, white, or pink flowers depending on their genotype. Assume offspring have the same color as their parents. One year a certain population had 300 red-flowering plants, 500 white-flowering plants, and 800 pink-flowering plants. When the same population is censused the following year, the offspring present consist of 600 red-flowering, 900 white-flowering and 1000 pink-flowering plants. Which color provided the highest relative fitness? A. red B. white C. pink D. all are equal

A

There are two alleles and 3 genotypes for the C gene locus (incomplete dominance). Individuals with different genotypes vary in their relative fitness. If the relative fitness of C1C1 individuals is 1.0, the relative fitness of C1C2 individuals is 0.9, and the relative fitness of C2C2 individuals is 0.8, which of these should result in future generations? [Assume large population and random mating.] A. frequency of C1 will increase B. frequency of C2 will increase C. frequency of heterozygotes of C1C2 will increase D. frequency of both homozygotes will increase E. not enough information provided to predict

A

Which of these is true of allopatric speciation but is not true of all speciation processes? A. a geographic barrier B. genetic divergence occurs C. Reproductive incompatibility occurs

A

_______ in the mating cross Tt x TT, what is the probability of their offspring having genotype "tt"? A. 0 B. 0.25 C. 0.5 D. 0.75 E. 1

A

diploid chromosome number (2n) is 50 How many pairs of homologous chromosomes are there in this species? A. 25 B. 50 C. 100 D. another number

A

Predict what happens to the frequency of the sickle-cell globin allele (q) 1. in populations that move away from malaria areas (still get sickle cell anemia) 2. where sickle-cell anemia can be medically treated very successfully (with or without malaria) A. q will increase B. q will decrease C. no significant change

A A

In a certain species, n = 20. 1. "n" refers to which? A. haploid number B. Diploid number 2. How many chromosome pairs are there? A. 10 B. 20 C. 40 D. another number

A B

A normal male without hemophilia marries an affect female who has hemophilia. What fraction of their children will have 1 allele for hemophilia? A. all B. 3/4 C. 1/2 D. 1/4 E. none

A because it's a x-linked trait

A mouse shows the dominant black phenotype but has an unknown genotype. To do a test cross, you would mate this individual with which of these? A. Any black mouse B. Any brown mouse C. A mouse that you think has the same genotype D. Not enough information given here to set up a test cross

B

If humans had the same kind of life cycle as flowering plants then humans would have: A. Diploid sperm cells B. Multicellular haploid sperm C. Testes that had both meiosis and fertilization occurring in them D. Testes with petals

B

In areas of Africa in which malaria is prevalent, many human populations exist in which the allele that produces sickle-cell disease and the allele for normal red blood cells both occur at constant frequencies, despite the fact that sickle-cell anemia disease frequently causes death at an early age. This is an example of which of these? A. the founder effect B. heterozygous advantage C. mutation D. nonrandom mating E. gene flow

B

In mice, short hair is dominant to long hair. If a short-hair individual is mated with a long-hair individual and both long-hair and short-hair offspring result, then just from looking at the offspring you learn that: A. the short-hair individual was homozygous B. the short-hair individual was heterozygous C. the long-hair individual was homozygous D. the long-hair individual was heterozygous E. more offspring are required in order to decide

B

There is a large population of organisms. By chance, ten females and one male wander off and join another population. This is an example of: A. Genetic drift B. gene flow C. sexual selection D. artificial selection E. non-random mating

B

Very few protein-coding genes are on the Y chromosomes. Y-linked genes include the sry gene that expresses the testis-differentiation protein. A male with this gene will A. usually pass it on to his sons, but about 10% of the time also to a daughter B. only pass the gene to his sons C. only pass the gene to his daughters D. only pass the gene to his grandsons E. pass the gene to all of his children if the mother is a carrier

B

Which of the following is NOT a feature of microevolution? A. allele frequency changes B. new species are formed C. assumptions of Hardy-Weinberg are not met D. chance is sometimes involved

B

Which of these must be true for a female mammal to be a genetic mosaic for a particular X-linked trait? A. she must have more than 1 X chromosome B. she must be heterozygous for that trait C. both A and B must be true

B

Which of these sets of parents (blood type phenotype given) is probably not correctly matched to their child (by blood type) A. parents A and B, child AB B. parents A and O, child AB C. parents A and O, child O D. parents A and B, child O E. parents AB and B, child AB

B

Which parents gives the sex-determining trait to the child? A. mother B. father C. could be either parent D. both parents E. the stork

B

________ in the mating cross Rr x Rr, what fraction of the offspring will have the genotype "rr"? A. 0 B. 1/4 C. 1/2 D. 3/4 E. 1

B

A chromosome contains A. DNA from one of your parents on the left DNA and from the other parent on the right. B. DNA from only one of your parents

B Once combined it will have both parents' DNA, this one has only 1

There are 2 alleles for a certain gene locus, A and a. 70% of the alleles in a particular gene pool are A. What is the allele frequency of a? A. 0.20 B. 0.30 C. 0.50 D. 0.70

B p + q = 1

A rabbit population has a gene with 2 alleles, A1 and A2. If the allele frequency of A1 is 0.6, what percent of the population consists of individuals that have both alleles, A1 and A2? A. 0.36 B. 0.40 C. 0.48 D. 0.50 E. 0.70

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

1-11 What is crossing-over (recombination)? Does it occur in Meiosis 1, Meiosis 1, why?

Crossing Over (synapsis): maternal and paternal homologs exchange genetic information Only in Meiosis 1 during Prophase 1

A woman is heterozygous for the recessive X-linked gene for hemophilia. Her husband is not affected by hemophilia. What proportion of their daughters will be carriers for the trait? A. 0 B. 0.25 C. 0.33 D. 0.50 E. none of these

D

After a genetic bottleneck we are likely to see which? A. population remains small B. More of 1 phenotype because of natural selection C. More of 1 phenotype because of sexual selection D. Low frequency of heterozygous in population

D

In Manx cats, a gene showing incomplete dominance produces three phenotypes. Individuals that are homozygous for one allele have a normal cat posture and tail; individuals homozygous for the other allele are deformed and die as embryos; heterozygous individuals are Manx (humped rear and no tail). If two Manx cats are mated, what proportion of their surviving offspring should be Manx? A. 1/4 B. 1/3 C. 1/2 D. 2/3 E. 3/4

D

In a population of beetles, the frequency of the dominant allele A at a locus is 0.8. If the population has 400 individuals, what is the expected number of A alleles in the gene pool? A. 320 B. 400 C. 480 D. 640 E. 800

D

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following mechanisms likely explains the genetic uniqueness of this population? A. population bottleneck B. heterozygous advantage C. mutation D. founder effect

D

Which chromosomal event during meiosis both is true AND explains Mendel's law of independent assortment? A. all maternal chromosomes separate from all paternal chromosomes B. members of a homologous pair within a tetrad separate from one another C. twin chromatids separate from one another D. each homologous pair tetrad lines up and separates independently from other pairs E. the 4 members of 1 tetrad end up in 4 different meiotic products

D

Which of the following is true about the two members of a homologous pair of chromosomes? A. they are identical DNA molecules B. they form the 2 sides of 1 double helix C. they separate from one another during meiosis 2 D. they contain the same gene loci in the same order E. 2 of these are true

D

Which statement about a test cross is NOT true? A. it tests whether an unknown individual is homozygous or heterozygous B. The (unknown) test individual is crossed with a homozygous recessive individual C. If the (unknown) test individual is heterozygous, the progeny will show a 1:1 ratio D. If the (unknown) test individual is homozygous, the progeny will show a 3:1 ratio E. Test cross results are consistent with Mendel's model of inheritance

D

Why are males more often affected by sex-linked recessive traits than females? A. male hormones such as testosterone often alter the effects of mutations on the X chromosome. B. Female hormones such as estrogen often compensate for the effects of mutations on the X chromosome. C. X chromosomes in males generally have more mutations than X chromosomes in females D. Cells of males have only 1 X chromosome

D

What is a common normal process that contributes to genetic variability during mitosis? A. independent assortment B. mutation C. both A and B D. none

D A and B are in Meiosis

If 2 achondroplastic dwarfs have children, what fraction of their living offspring will also be dwarfs? A. 0 B. 1/4 C. 1/2 D. 2/3 E. 3/4

D dwarfs are hetero AA will die, embryonic lethal

Which of the following - happening differently on either side of the barrier - could contribute to genetic divergence? A. Different mutations B. Different natural selection by predators C. Different Sexual selection D. Two of the above E. All 3 of the above (A, B, C)

E

Which of the following is false concerning sister (twin) chromatids? A. the formation of sister chromatids doubles the amount of DNA in a cell B. sister chromatids consist of 2 identical copies of a single homolog C. sister chromatids are held together at the centromere D. sister chromatids are formed during the S phase of the cell cycle E. in meiosis sister chromatids separate from one another during meiosis 1

E

Which of the following would be an exception to the principle of independent assortment? A. crossing over B. Segregation of alleles C. co-dominant alleles D. lethal alleles E. linked genes

E

What is the probability (fraction) that if these heterozygote parents (both carriers) have 2 children, they will have 2 albino children? A. 0 B. 1/8 C. 1/4 D. 1/2 E. None of the above

E 1/4 x 1/4 = 1/16

1-7 Write out a general life cycle with arrows linking these terms: haploid (n), diploid (2n), meiosis, fertilization. Are the products of Meiosis haploid or diploid?

For an animal 2 gametes (n) -> Fertilization -> 2n (zygote) -> 2n (diploid multicellular organism) -> meiosis -> n meiosis produces a Haploid cell

1-17 Define and distinguish gene & allele, and genotype & phenotype

Gene: distinct units of heredity that influence traits by determining the structure of proteins manufactured in the cell allele: versions of a gene alternative forms of genes for a given trait at any one locus on the chromosome genotype: all the pairs of alleles constitute the individual's genotype (genetic composition, the specific alleles present) Phenotype: refers to the collection of structural, biochemical, and physiological features expressed in the individual's appearance

1-12 What is an evolutionary advantage of diploidy?

Having 2 sets of chromosomes can have an evolutionary advantage when adapting to the environment

1-16 How does having a sexual phase in the life cycle confer an evolutionary advantage to organisms in changing environments?

Having many different offsprings containing different genes and characteristics that better suit different environments (allows for adaptations)

1-23 Human ABO blood group phenotypes are determined by multiple alleles, specifically three alleles: IA, IB, (both dominant) and i (recessive). Use a Punnett square to determine the possible offspring phenotypes (ABO blood types) from a man with blood type A and a woman with blood type B. (Both of their fathers have type O blood)

I^Bi x I^Ai = I^AI^B I^Ai I^Bi ii

1-8 define sexual reproduction and asexual reproduction. how do they differ in comparison pf genetic traits between parent and offspring? at what points are mitosis and meiosis involved in each?

Sexual reproduction: meiosis and fertilization -requires 2 haploids to fertilize -genetic variation -offspring not identical DNA from parents -long process (courtship of 2 parents) -requires energy Asexual reproduction: mitosis only -no genetic variation - DNA identical to parent (clone) -1 parent needed (no courtship) -low population density (advantage) -faster

L M N O P Q R S Duplication Deletion Inversion

L M M N O P Q R S L N O P Q R S N M L O P Q R S

1-24 What are linked genes, and how are they an exception to the law of independent assortment?

Linked genes: genes whose loci are on the same chromosome and are therefore likely to be inherited together They do not separate during independent assortment because they travel together wherever the chromosome goes

1-3 How does Meiosis 1 differ from Meiosis 2? Do the 2 members of homologous pair separate from one another at MI or MII? At what point do identical chromatids separate from one another?

Meiosis 1: -produces 2 cells -homologs separate during anaphase I -crossing over (prophase I) -independent assortment (metaphase I) -23 pairs in humans Meiosis II: -produce 4 cells -twin chromatids separate (anaphase II) - 23 single chromosomes in humans

1-26 King Henry VIII divorced his first wife and beheaded his second wife because "they produced only daughters". Was Henry correct, in sex determination terms, in faulting them for not producing sons?

No, the father determines the sex. The mom can only give the X while the father must give a Y to have a boy

1-13 Distinguish asexual reproduction from sexual reproduction.

Same as 1-8 answers

1-20 What is a "test cross"? An individual with an unknown genotype shows a dominant trait in its phenotype. Tell how mating that individual in a "test cross" can determine whether it is homozygous dominant or heterozygous.

Test Cross: Mate organism with unknown genotype to known one with recessive traits (homozygote) Looking at it's offspring (a lot) to see their genotypes Aa means the organism had a dominant allele and is heterozygous example: black and brown mouse

1-28 How does a translocation differ from other altered chromosomal structures?

Translocation: involves 2 different (non-homologous chromosomes) A portion of a chromosome breaks off and reattaches to a different chromosome Deletion, duplication, and inversion involve 1 chromosome

A large population of green frogs lived in the green vegetation around a pond. Over time, the pond dried up and more vegetation tended to be brown. Years later the population by the process of natural selection, one step leading to the next. Be specific but brief. You do NOT need to write in complete sentences, a bullet-point list of short phrases is fine.

What you should have included for a complete answer: a. source of genetic variation; original mutation b. The environment changed somehow c. individuals with certain traits had greater fitness and greater reproductive success d. selective agent - what caused some individuals to survive and reproduce more? (predators) e. change in allele frequency in the population

1-29 What is a chromosome nondisjunction event that can happen to cause an egg cell with aneuploidy, such that when that egg is fertilized, the offspring is a child with Down Syndrome (trisomy 21)?

When homologous pairs don't separate during Meiosis 1 or sister chromatids don't separate during Meiosis 2 normal 1 less 1 too much Down syndrome will have an extra chromosome

1-25 What is the genetic (chromosomal) basis of sex determination in mammals?

XY is the method of sex determination in mammals XX females XY males Sex determined by father

1-9 In animal life cycles, do diploid cells undergo mitosis? In life cycles of the great majority of animals, including humans, do haploid cells undergo mitosis?

Yes (example: growing or healing wounds) No, only meiosis

1-1 DNA molecule, use term correctly

a double helix nucleic acid that carries genetic info double-stranded molecule

1-27 Red-green color blindness is an X-linked recessive trait. A non-colorblind male marries a non-colorblind woman whose father is colorblind. Draw the complete Punnett Square (including X and Y chromosomes) and predict (a) the percentage or fraction of their offspring that would be colorblind (b) the percentage or fraction of their sons that would be colorblind

a) 1/4 b) 1/2 The mother is a carrier X^CY• X^CX^c = X^CX^C X^CY X^CX^c X^cY

1-21 For each of the following tell what offspring phenotypes, and in what ratios are expected from a mating between 2 heterozygotes (carriers) a) simple dominance example: cystic fibrosis recessive trait (possible alleles F & f) b) incomplete dominance example: pink snapdragons (alleles CR,CW). c) co-dominance example: MN blood types (alleles M, N; possible blood type phenotypes M, N, MN)

a) offspring are: FF Ff Ff ff (3:1 phenotypic ratio) b) offspring are: CRCR, CRCW, CRCW, CWCW (1:2:1) c) offspring are: MM MN MN NN (1:2:1)

Which of the following best describe the evolutionary term "adaptive radiation"? A. One population evolve to adapt to a new environment B. Populations evolve to adapt to radiation after an exposure to X-rays C. Different species form from a single ancestral species by adaptation D. two of these fit as descriptions

c example: Finches

1-19 What is a monohybrid cross? Using Letters A and a denote alleles, give the genotypes of 2 individuals in a monohybrid cross. What is a dihybrid cross? (give an example using letters)

monohybrid cross: 1 characteristic/phenotype presented 3:1 Aa x Aa Dihybrid cross: 2 characteristics/phenotypes presented 9:3:3:1 AaBb x AaBb