MoleGen 4500
If thymine makes up 15% of the bases in a certain DNA sample, what percentage of the bases must be cytosine?
35%
Hemizygosity would most likely be associated with which of the following?
X-linked inheritance
You are doing lab work with a new species of beetle. You have isolated lines that breed true for either blue shells and long antenna, or green shells and short antenna. Crossing these lines yields F1 progeny with blue shells and long antenna. Crossing F1 progeny with beetles that have green shells and short antenna yield the following progeny: Which shell color and antenna length alleles are dominant? b. Are the shell color locus and antenna length locus linked? c. Check your answer to the previous question with the chi-square test. d. If the genes are linked, calculate the recombination frequency between them.
blue and long are dominant genes are linked recombination frequency is 33%
The stage at which "sister chromatids go to opposite poles" immediately follows which stage listed below?
mitotic metaphase
How many Barr bodies would you expect to see in an XXY individual?
1
Sister chromatids separate during what phase(s)?
Mitosis Anaphase, Meiosis anaphase 2
Choose the answer that lists--in order of appearance--all the cell types expected to be formed during oogenesis.
(b) oogonium, primary oocyte, secondary oocyte and first polar body, ootid and second polar body
Suppose that in sweet cherry a single gene controls fruit color [red (R-) is dominant to yellow (rr)] and a second gene controls bloom time [early bloom (E-) is dominant to late bloom (ee)]. A true breeding tree with red fruit and early bloom is crossed to a tree that has yellow fruit and blooms late. The resulting F1 is selfed to create a population of 500 F2 trees. The segregation of traits in this F2 population is show below: What is Mendel's Second Law? (ii) Do a Chi Square analysis to determine whether the results conform to Mendel's Second Law. (iii) If the results do not conform to this law, can you come up with an explanation for the lack of conformity?
(i) Independent assortment; that is, different gene pairs assort independently in gamete formation. (ii) X2 = ~258, df = three; The results are significantly different from what would be expected under Independent Assortment. (iii) The genes are linked (that is, they are close to one another on the same chromosome)
Other than genes, name three other regions of chromosomes? What are their functions? Which of them represent euchromatin? Heterochromatin?
-Centromere - the attachment point for spindle microtubules (heterochromatic) -Telomeres - natural ends, the tips of linear chromosomes that serve to stabilize the chromosome (Heterochromatic) -Origin of replication - where DNA synthesis begins (euchromatic)
Two forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their first daughter will have hemophilia?
0
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype?
0%
In a mating between individuals with the genotypes IAIB X IOIO, what percentage of the offspring are expected to have the O blood type?
0%
The woman is expecting a child with a man who is a "nonroller." What is the probability that their child will be a "roller"?
1/2
Two forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their first son will have hemophilia?
1/2
What is the probability of flipping a penny and a nickel and obtaining one head and one tail?
1/2
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AABBCCdd ?
1/256
Tony, who is not diseased, has a sister with cystic fibrosis (CF). Neither of his parents have CF.Tony is expecting a child with Tina. Tina's family history is unknown.
1/300
In the following cross, what proportion of individuals will have the Bombay phenotype?
1/4
One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: In this problem you must include the probability of having a daughter in your computation of the final probability.)
1/4
Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child. What is the probability that their next three children will be albino?
1/64
Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child. What is the probability that their next child will be an albino girl?
1/8
What is the probability of obtaining 3 heads in three flips of a fair coin?
1/8
If they live long enough, the penetrance of individuals carrying the Huntington's Disease allele will be what?
100%
In snapdragons, heterozygotes for one of the genes have pink flowers, whereas homozygotes have red or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers?
100%
10% recombination is equal to how many map units?
10mu
Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Assume that two fully heterozygous plants are crossed. Give the phenotypes (with frequencies) of the offspring.
12 (white):3(yellow):1(green)
If a typical somatic cell has 32 chromosomes, how many chromosomes are expected in each gamete of that organism?
16
In a healthy male, how many sperm cells would be expected to be formed from (a) 400 primary spermatocytes? (b) 400 secondary spermatocytes?
1600;800
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. WHat is the total number of telomeres in a rat cell in G2
168
If a double heterozygote (AaBb) is crossed with a fully recessive organism (aabb), what phenotypic ratio is expected in the offspring?
1:1:1:1
Assume that a cross is made between two organisms, both heterozygous for a gene that shows incomplete dominance. What phenotypic and genotypic ratios are expected in the offspring?
1:2:1
With incomplete dominance, a likely ratio resulting from a monohybrid cross would be
1:2:1
What types of phenotypic ratios are likely to occur in crosses when dealing with a single gene pair where all the genotypic combinations are of equal viability?
1:2:1, 3:1
Assume that a dihybrid cross (AaBb X AaBb) is made in which the gene loci are autosomal, independently assorting, and incompletely dominant. What phenotypic ratio would you expect from such a cross? Just provide the ratio, not the phenotypes.
1:2:1:2:4:2:1:2:1
Mitosis ends with _____, while meiosis ends with _____.
2 diploid cells; 4 haploid cells
Phenotypically wild F1 female Drosophila, whose mothers had light eyes (lt) and fathers had straw (stw) bristles produced the following offspring when crossed to homozygous light-straw males: What is the map distance
2 map units
What is the total number of chromosomes in a polar body cell from a rat?
21
If a typical somatic cell has 44 chromosomes, how many chromosomes are expected in each gamete of that organism?
22
How many haploid sets of chromosomes are present in a diploid individual cell with a chromosome number of: 46? 32?
23, 16
Two organisms, AABBCCDDEE and aabbccddee, are mated to produce an F1 that is self-fertilized. If the capital letters represent dominant, independently assorting alleles, how many different genotypes will occur in the F2?
243=3^5
Myrmecia pilosula actually consists of several virtually identical, closely related species of ants, with females having chromosome numbers of 18, 20, 32, 48, 60, 62, and 64. The males are haploid, and each gamete contains the n complement. Assume one crossed a female of species (A) with 32 chromosomes and a male species (B) with 9 chromosomes. How many chromosomes would one expect in the body (somatic) cells of the female offspring?
25
If a crossover event happened in one half of all tetrads, how many recombinant gametes would be produced?
25%
In an organism with 52 chromosomes, how many bivalents would be expected to form during meiosis?
26
A trihybrid cross is a cross between two individuals who are heterozygous for three genes. For example: AaBbCc x AaBbCc. Assuming these three genes are unlinked and assorting independently, what segregation ratio would be observed?
27:9:9:9:3:3:3:1
The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female?
2:1 male to female
If one is testing a goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the Chi-square analysis?
3
In one strand of DNA, the nucleotide sequence is 5'-ATGC-3'. The complementary sequence in the other strand must be:
3'-TACG-5'
Suppose you heard through various media of an animal alleged to be the hybrid of a rabbit and a cat. If the cat (Felis domesticus) has a diploid chromosome number of 30 and a rabbit (Oryctolagus cuniculus) has a diploid chromosome number of 46, what would be the expected chromosome number in the somatic tissues of this alleged hybrid?
38
What phenotypic ratios are likely to occur in crosses when dealing with two completely dominant, independently segregating gene pairs, when both parents are fully heterozygous?
3:1
How many different F2 genotypes would you expect in a cross with four heterozygous gene pairs?
3^4=81
here is about as much nuclear DNA in a primary spermatocyte as in ________
4
Human gametogeneis from one oogonium and one spermatagonium results in how many mature gametes of each?
4 male spermatids, 1 ovum
The ant, Myrmecia pilosula, is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words, 2n = 2. (Males are haploid and have just one chromosome.) For the purposes of this question, assume that a G1 somatic cell nucleus in a female Myrmecia pilosula contains 2 picograms of DNA. How much DNA would be expected in a Metaphase I cell of a female?
4 picograms
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males.
42,21
Klinefelter syndrome in humans, which leads to underdeveloped testes and sterility, is caused by which chromosomal condition?
47, XXY
Individuals with Klinefelter and Turner syndromes have how many chromosomes, respectively?
47,45
Assume that there are 12 map units between two loci in the mouse and that you are able to microscopically observe meiotic chromosomes in this organism. If you examined 200 primary oocytes, in how many would you expect to see a chiasma between the two loci mentioned above?
48
A recessive gene for red-green color blindness is located on the X chromosome in humans. Assume that a woman with normal vision (her father is color-blind) marries a color-blind male. What is the likelihood (give a percentage) that this couple's first son will be color-blind?
50%
In a mating between individuals with the genotypes IAIO X IOIO, what percentage of the offspring are expected to have the O blood type?
50%
When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
50%
In G1 of the cell cycle, the genus Ooompa lumpa has a DNA content (C) of 2.5 picograms. Following DNA synthesis (in G2 of the cell cycle) what will be the DNA content (in picograms) of the Oompa lumpa cell?
5pg
A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?
75%
in a three point mapping experiment how many genpotypes are expected
8
Assuming independent assortment, what proportion of the offspring of the cross AaBbCcDd X AabbCCdd will have the aabbccdd genotype?
8/256
Assume that two genes are 80 map units apart on chromosome II of Drosophila and that a cross is made between a doubly heterozygous female and a homozygous recessive male. What maximum percent recombination would be expected in the offspring of this type of cross?
80%
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be phenotypically ABCD ?
81/256
How many different F2 genotypes would you expect in a cross with four heterozygous gene pairs?
81=3^4
Assume that a dihybrid cross is made in which the genes' loci are autosomal, independently assorting, and incompletely dominant. How many different phenotypes are expected in the offspring?
9
Assuming Mendel's Second Law is correct, what is the expected segregation ratio for traits in a dihybrid cross?
9:3:3:1
Typical ratios resulting from epistatic interactions in dihybrid crosses would be
9:3:4, 9:7
What types of ratios are likely to occur in F2 crosses when one is dealing with two interacting, epistatic gene pairs?
9:7, 9:3:4, 12:3:1, 15:1
Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?
A color blind female
The primary structure of a protein is:
A linear chain of amino acids
Listed below are blood types for several children and their mothers. Give all possible genotypes and blood types for the father of each child.
A. B, O, A or AB BO, OO, AO, AA, AB B.BO, OO or AO B, O or A C. B, A BO, BB,AO or AA D. A,B BO,BB or AO
Which of the following parental genotypes will produce only heterozygous F1 offspring?
AA x aa
Given that loci A and B in Drosophila are sex-linked and 20 map units apart, what phenotypic frequencies would you expect in 100 offspring resulting from the following cross? (Assume A and B are dominant to a and b, respectively.) AaBb (cis) female X ab/Y male
AB=40 ab=40 Ab=10 aB=10
Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring. When the albino was crossed with a second black one, 4 black and 3 albino offspring were produced. What genetic explanation would apply to these data?
Albino = recessive; black = dominant
Assume that a man who carries an X-linked gene has children. Assuming normal meiosis and random combination of gametes, the man would pass this gene to
All of his daughters
At what stage of the meiotic cell cycle and during what chromosomal configuration does crossing over occur?
At the four-strand stage of meiosis, after synapsis of homologous chromosomes, and before the end of prophase I.
Two mice of the same species have different ear shapes. You find that one mouse, having normal shaped ears, was caught in a field in Kenya. The other mouse, with curled ears, was caught in the frozen tundra of Greenland. You have determined that both mice have identical genotypes at the gene loci controlling ear shape. How would you explain the differences in ear shape? Describe an experiment by which you could test your hypothesis. More (correct) detail will increase your likelihood of getting full credit.
Because both mice have the same genotype at the relevant loci controlling ear shape, there is most likely an effect of environment on phenotype. Because Kenya and Greenland have quite different climates (but also different food sources, humidity, sunlight intensities, etc.), it is possible that the very different temperature ranges within each region resulted in differential expression of identical genotypes for ear shape in each mouse—for example, differential expression of temperature-sensitive allele(s) involved in ear development. However, the phenotypic differences could also be a result of differences in diet, light conditions, exposure to chemicals, nutrition, or a range of other non-genetic factors.
Why are rare X-linked recessive diseases more common in males than in females?
Because females have two copies of the X chromosome and males have only one X chromosome
The attachment point on the chromosome for spindle microtubules is the
Centromere
What conditions are likely to apply if the progeny from the cross AaBb X AaBb appear in the 9:3:3:1 ratio?
Complete dominance, independent assortment, no gene interaction
Assume that a cross is made between AaBb and aabb plants and that all the offspring are either AaBb or aabb. These results are consistent with the following circumstance:
Complete linkage
Name one characteristic of X-linkage that is often used to identify X-linked genes in pedigree analysis.
Criss-cross pattern of inheritance-where all sons exhibit mutant mother phenotype, the phenotype largely or exclusively affects males.
During interphase of the cell cycle,
DNA content essentially doubles.
When cells withdraw from the continuous cell cycle and enter a "quiescent" phase, they are said to be in what stage?
G0
In peas, gray seed color is dominant to white. For the purposes of this question, assume that Mendel crossed two plants with gray seeds with each other and the following progeny were produced: 320 gray and 80 white.
Gg x Gg genotypic 1:2:1 phenotypic 3:1
Ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. What si the woman's genotype
Heterozygous
If an X-linked disorder is lethal to the affected individual prior to the age at which one reaches reproductive maturation, the lethality will be expressed only in males. Why?
Heterozygous females are carriers and do not express the disorder
What is the fundamental difference with respect to the chromatids between metaphase of mitosis and metaphase I of meiosis? How does the resulting cell differ in mitosis vs. meiosis I?
In mitosis, sister chromatids separate during metaphase. In meiosis 1, homologous chromosomes separate during metaphase. Meiosis 1 metahase is a reduction step resulting in haploid cells.
For the purposes of this question, assume that being Rh+ is a consequence of D and that Rh- individuals are dd. The ability to taste phenylthiocarbamide (PTC) is determined by the gene symbolized T (tt are nontasters). A female whose mother was Rh- has the MN blood group, is Rh+ and a nontaster of PTC, and is married to a man who is MM, Rh-, and a nontaster. List the possible genotypes of the children. Assume that all the loci discussed in this problem are autosomal and independently assorting.
MMDdtt, MMddtt, MNDdtt, MNddtt
The trait for medium-sized leaves in iris is determined by the genetic condition PP'. Plants with large leaves are PP, while plants with small leaves are P'P'. The trait for red flowers is controlled by the genes RR, pink by RR', and white by R'R'. A cross is made between two plants each with medium-sized leaves and pink flowers. If they produce 320 seedlings, what would be the expected numbers of the phenotypes below? Assume no linkage.
Medium red: 40 Small red:20 Large red:20 Large pink:40 Medium pink:80 small pink:40
Homologous chromosomes move toward opposite poles of the dividing cell during
Meiosis 1
These two terms generally refer to meiosis I or II. Enter the correct stage of meiosis in the box below each term.
Meiosis 1=reductional Meiosis 2=equational
After what meiotic stage (Meiosis I or II) would one expect monads to be formed?
Meiosis 2
Chromosomes are in unseparated, sister-chromatid form, at the end of which phase(s)?
Meiosis I prophase Meiosis I anaphase Meiosis II prophase Mitosis prophase
Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assume that you are microscopically examining the mitotic and meiotic cells of this organism. You note that in the female two chromosomal pairs are metacentric and that two pairs are acrocentric. What stage is represented in the drawing above?
Mitotic metaphase
Among dogs, short hair is dominant to long hair and dark coat color is dominant to white (albino) coat color. Assume that these two coat traits are caused by independently segregating gene pairs. For each of the crosses given below, write the most probable genotype (or genotypes if more than one answer is possible) for the parents. It is important that you select a realistic symbol set and define each symbol below.
Most probable genotype for parent are Llcc X Llcc.
Male mammals inherit an X chromosome from which of their parents? Their _____________.
Mother
Assuming a normal number of autosomes, what would be the sex of the following:
Mouse: male Drosophila: female
Assume that you are told that a particular organism, Drosophila, has the XO chromosome complement. You are also told that the autosomal complement is a normal 2n. You know that in humans the XO complement is female determining. Would you be correct in assuming that the Drosophila sex for XO is also female?
No humans and drosophilia are different
One form of deafness is caused by a rare autosomal recessive gene. In a mating involving a deaf man and a deaf woman, would you expect some of the children to have normal hearing? Explain your answer.
No. In a mating involving heterozygotes, three genotypic classes are expected in the offspring: fully dominant, fully recessive, and heterozygous.
The Chi-square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as
One less than the number of classes being compared
Trisomy 21 or Down syndrome occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome #21. Such individuals therefore have 47 chromosomes. Assume that a mating occurs between a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome? Justify your answer.
One-half of the offspring will be expected to have Down syndrome because of 2 X 1 segregation of chromosome #21 at anaphase I.
In deer mice, red eyes (r) is recessive to normal black eyes (R). Two mice with black eyes are crossed. They produce two offspring, one with red eyes and one with black eyes. Give the genotypes of parents and offspring of this cross.
Parent Genotypes: Rr x Rr
Assume that an organism has a diploid chromosome number of six. Two chromosomal pairs are telocentric, and the other pair is metacentric. Assume that the sex chromosomes are morphologically identical.
Primary oocyte (metaphase) Secondary spermatocyte (metaphase) Secondary oocyte (metaphase) First polar body (metaphase)
What conclusions did mendel make from his monohybrid cross?
Progeny inherit genetic factors from both parents. (2) Each individual possesses two factors (alleles) that control the appearance of each phenotypic trait. (3) The two alleles in each individual separate (segregate) during gametogenesis and are randomly distributed with equal probability of being distributed into the gametes. (4) From a cross between two true-breeding (homozygous) parents expressing different phenotypes for a given trait, traits that appeared unchanged in the F 1 heterozygous offspring were dominant, and traits that disappeared in F 1 heterozygous offspring were recessive
What are two features that distinguish a prokaryotic cell from a eukaryotic cell?
Prokaryotic: lack nucleus and membrane bound organelles. Store their genetic information in a region called a nucleoid, and lack an internal membrane system
discuss the similarities and differences between recombination and independent assortment
Recombination - the sorting of alleles into new combinations Independent assortment - in meiosis, each pair of homologous chromosomes assort independently of other homologous pairs. Recombination only shuffles already existing genetic variation and does not create new variation at the involved loci. Similarity - both result in an increase in genetic variation
The red kernel color in wheat is caused by the presence of at least one dominant allele from each of two independently segregating gene pairs (e.g., R-B-). Wheat plants with rrbb genotypes have white kernels, and plants with genotypes R-bb and rrB- have yellow kernels. If you cross a plant true breeding for red kernels with a plant true breeding for white kernels, a. what is the expected phenotype(s) and ratios of the F1 plants? b. what are the relative proportions of the phenotypic classes expected in the F2 progeny after selfing the F1 progeny?
Red 9:6:1
While doing field work in Madagascar, you discover a new dragonfly species that has either red (R) or clear (r) wings. Initial crosses indicate that R is dominant to r. You perform three crosses using three different sets of red-winged parents with unknown genotype and observe the following data: What is the most likely genotype for each pair of parents? b. Do you think there are a sufficient number of progeny to support each of your answers in the previous question?
Rr & rr
What is the mechanism that ensures Mendel's First Law of segregation?
Segregation of homologous chromosomes
While doing summer field work on a remote Indonesian island, you discover a new genus of lizard closely related to komodo dragons. You attempt to discover what sex determination system it uses by performing a series of controlled crosses on the island, using an isolated pair of lizards. Initially, all your crosses yield only males (in significant numbers). As fall begins and you prepare to leave the island, you find that your last cross yielded only females (in significant numbers). Suggest a mode of sex determination that explains this data.
Sex determination is influenced by temperature. Males are more likely to be produced in the summer when it is warmer, while females are more likely to be produced during the fall when it is cooler.
Which modes of inheritance are influenced by the sex of individuals. Select all that apply.
Sex limited, y-linked, x-linked
What does it mean if a human female oocyte is no longer arrested in metaphase II of meiosis?
She is pregnant
You observe continuous variation in tail length in a wild population of rats. Describe an experiment to determine whether this variation is an example of variable expressivity or continuous variation? HTML Editor Keyboard Shortcuts
Take male and female rats from each phenotypic extreme (shortest and longest tails). Interbreed short with short and long with long under controlled laboratory conditions for several generations. If this is polygenic inheritance, then you will be able to develop different homozygous lines for short and long tails. But, if after several generations each line continues to produce progeny classes exhibiting significant variance in tail length, you could assume variable expressivity is the primary basis for the variation because the genotypes for each extreme line are (theoretically) homozygous and isogenic. Therefore, variances in tail length observed within each line cannot be the result of variable polygenic genotypes.
Describe three different sex determination systems.
Temperature-dependent sex determination Ratio of X chromosomes to autosomes XX/XY determination
Human blood types are an example of codominance because:
The A and B alleles both express equally in individuals with both alleles.
You are conducting a cross using Drosophila melanogaster. The results of your cross indicate that the recombination frequency is very high. How do you feel about the accuracy of your map unit calculations based on this cross?
The calculations are not very accurate. The distance would be underestimated because double crossovers are not observed.
How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?
The daughter cells have the same number of chromosomes and the same amount of DNA.
An individual has the following genotype. Gene loci (A) and (B) are 15 cM apart. Indicate all the possible gametes that this individual can produce, and the proportions of expected progeny genotypes if a testcross is performed on this individual.
The gametes produced by an individual has the genotype Ab/aB are AB, aB, Ab, ab. Thus, the percent gametes produced are, AB (7.5%), aB (42.5%), Ab (42.5%), ab (7.5%).
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?
The gene involved is on the X chromosome Genetic distances within a given linkage group
What will be the probability of observing individuals exhibiting all of the dominant phenotypic traits in a pentahybrid (5 independently assorting gene loci) cross?
The probability of being expressed in the phenotype for each trait is 3/4, and the expression of each phenotype is an independent event --> (3/4)(3/4)(3/4)(3/4)(3/4) = 243/1024
For a particular plant, red flowers (A) are dominant over yellow flowers (a). An initial cross was made between a plant that was true-breeding for red flowers, and another plant true-breeding for yellow flowers. F1 progeny, all having red flowers, were allowed to form seeds (through self-fertilization), which were then planted to generate F2 progeny. Pollen from all the resulting F2 plants was pooled and used to fertilize true-breeding yellow plants. What proportion of the progeny resulting from this cross would be expected to have yellow flowers?
The proportion of the progeny resulting from this cross that is expected to have yellow flowers is ½ of the flowers.
You just bought two black guinea pigs from the pet store that are known to be heterozygous (Bb). You also know that black fur (BB) is dominant over white fur (bb), and that a lethal recessive allele is located only one cM away from the recessive b allele. You decide to start raising your own guinea pigs, but after mating these animals several times, you discover they produce only black progeny.
The recessive lethal allele is tightly linked to, and thus co-segregates with, the recessive b allele, which is lethal in the homozygous state ( bb ). 21 matings bb
The expected ratio of phenotypes among the progeny of a test cross is 1:1:1:1. Out of 200 total resulting progeny, 48 occur in one of the four phenotypic classes. Given this information, which of the following must also be true?
The value of observed - expected for this cell = -2
Which of the following species is considered a genetic model organism?
The worm, Caenorhabditis elegans
Prokaryotic chromosomes do not have telomeres because:
They are circular
Which of the following statements about homologous chromosomes are true?
They occur together in diploid cells.
Under what conditions does one expect a 1:1:1:1 phenotypic ratio among the offspring of a cross? What must be true about the parents? What must be true about the genes in question?
This occurs in a cross involving doubly heterozygous individuals crossed to fully recessive individuals. The genes involved assort independently of each other.
Why would it make sense for cyclin proteins to vary in concentration throughout the cell cycle?
Through phosphorylation, Cdks signal the cell that it is ready to pass into the next stage of the cell cycle acting as a check point.
In Drosophila, sex is determined by a balance between the number of haploid sets of autosomes and the number of ________.
X chromosome
What is the composition of a Barr body?
X chromosome
charachteristics of x linked recessive in pedigree
X-linked recessive traits will affect males predominantly and will be passed from an affected male through his unaffected daughter to his grandson. X-linked recessive traits are not passed from father to son.
Genes a, b, and c are known to be in linear order in an organism. A testcross is done that yields 20 double crossover progeny out of a total of 1000 offspring. Assume that there is no interference. (a) Type a genetic map showing the distances between these genes. Is there more than one possible map? (b) What would the distances be if there was 10% interference? (c) What number of double crossover progeny would be expected if there was interference of 15%?
a 20 mu b 10 mu c
Genetically speaking, brown eyes (B-) are dominant to blue eyes (bb). However, an individual can wear colored contacts in order to change his or her eye phenotype. Suppose a man with blue eyes (bb) marries a woman who appears to have blue eyes and together they have five children. Listed below are three possible outcomes. For each of the outcomes, predict the woman's genotype.
a) The woman naturally has brown eyes and is homozygous BB. b) The woman naturally has brown eyes and is heterozygous Bb. c) The woman naturally has blue eyes and is homozygous bb.
Extensive pedigree analysis on a characteristic shows all of the following: • the characteristic affects males and females equally. • two unaffected parents can have an affected child. • in families in which the parents are unaffected but the children are affected, 1/4 of the children are affected.
autosomal recessive
Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assuming that a somatic G2 nucleus contains about 8.0 picograms of DNA, how many picograms of nuclear DNA would you expect in: a) Mitotic metaphase b) a primary oocyte (metaphase) c) a secondary oocyte (metaphae) d) a first polar body (metaphase)
a-d:8,8,4,4
Given that loci A and B in Drosophila are sex-linked and 20 map units apart, what phenotypes would you expect in male and female offspring resulting from the following crosses? aabb female x AB Y male
all males = ab, all females = AB
What phenomenon describes a genetic trait that is expressed more strongly or earlier in development with each generation?
anticipation
Genetic distances within a given linkage group
are dependent on crossover frequencies between paired, non-sister chromatids. are measured in centiMorgans.
Provide an example of sex-influenced inheritance.
baldness patterns
The "distance" between two linked gene pairs can be expressed as a percentage. Name the unit based on percent recombination that was created in honour of the scientist who pioneered the use of fruit flies for genetic research.
centimorgan
The cellular organelles with inheritance independent of the nucleus are the _____________ and the ____________ . HTML Editor Keyboard Shortcuts
chloroplasts and mitochrondria
In anaphase
chromosomes move to opposite poles
Linked genes ____________.
co-segregate
In order to determine if mutations from different organisms that exhibit the same phenotype are allelic, which test would you perform?
complementation test
How does genetic recombination facilitate evolution?
creates more combinations of alleles for natural selection to act on
Two- and three-factor testcrosses can both be used to _____________ and _____________.
determine genotype map gene loci
Under what conditions does one expect a 9:3:3:1 phenotypic ratio among the offspring of a cross? What must be true about the parents? What must be true about the genes in question?
dihybrid cross (F2) with independently assorting, completely dominant genes
What is the relationship between the degree of crossing over and the distance between two genes?
direct
Phenotypic mosaicism for X-linked genes in female mammals can be caused by what?
dosage compensation involving the X chromosome
In the yawncat (a rare hypothetical animal), the dominant allele R causes solid tail color, and the recessive allele r results in white spots on a colored background. The black coat color allele B is dominant to the brown allele b, but these genes can only be expressed if the animal has an mm genotype at a third gene locus. Animals that are M- are yellow regardless of which allele from the B locus is present. A mating between a solid yellow-tailed male yawncat and a solid brown-tailed female yawncat produce 16 offspring with the following tail phenotypes: six solid yellow, two spotted yellow, three solid black, one spotted black, three solid brown, and one spotted brown.
female:mm bb Rr male:Mm Bb Rr 1/16
In the fruit fly, Drosophila melanogaster, a spineless (no wing bristles) female fly is mated to a male that is claret (dark eyes) and hairless (no thoracic bristles). Phenotypically wild-type F1 female progeny were mated to fully homozygous (mutant) males, and the following progeny (1000 total) were observed:
hairless gene is in the middle cl h +/cl h + and + + sp/+ + sp 10 and 30 mu
The difference between the homogametic sex and heterogametic sex is that __________________
he heterogametic sex determines the gender of the offspring
Because of the mechanism of sex determination, males of many species can be neither homozygous nor heterozygous. Such males are said to be:
hemizygous
Males with an X-linked gene are said to be ______________ for these X-linked genes.
hemizygous
Codominant alleles are expressed in individuals that are
heterozygous
A Barr body is
inactivated X chromosome, visible in the nucleus of a cell that is from a female mammal.
How do incomplete and co-dominance differ?
incomplete dominance= neither allele is dominant but are expressed. codominance= neither allele is dominant, but expression of alleles is observed as a distinct phenotype in heterozygous individual.
Assume that a cross is made between AaBb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: AaBb, Aabb, aaBb, aabb. These results are consistent with the following circumstance:
independent assortment
If a cyclin protein was produced at a constant level (instead of variably) througout the cell cycle what effect would you predict?
introduction of constant rate in a particular cyclin would either bring about an inappropriate cell cycle stage or turn off a stage prematurely or fail to come out of a stage. All of these would likely lead to apoptosis of the cell.
The following are features and characteristics of the DNA molecule except _________________
is used as genetic material by all organisms
When two genes fail to assort independently, the term normally applied is:
linkage
The genes for mahogany eyes and ebony body are approximately 25 map units apart on chromosome III in Drosophila. Assume that a mahogany-eyed female was mated to an ebony-bodied male and that the resulting F1 phenotypically wild-type females were mated to mahogany, ebony males. Of 1000 offspring, what would be the expected numbers of the following phenotypes:
mahogany = 375; ebony = 375; wild-type = 125; mahogany-ebony = 125
In a germ-line cell from a human male that is dividing, when do the X and Y chromosomes segregate?
meiosis 1, anaphase
A spontaneously aborted human embryo is characterized with respect to karyotype, and it is found to be normal except that it contains only one chromosome number two. This is an example of what type of aneuploidy?
monosomy or loss of a single chromosome
A situation where there are more than two alternative forms of a given gene would be called ________.
multiple alleles
If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?
n+1; n+1; n-1; n-1.
The phenomenon in which one crossover increases the likelihood of crossovers in nearby regions is called:
negative interference
In a three-point mapping experiment, what three general classes of offspring are expected (assuming crossovers occur)?
noncrossovers, single crossovers, double crossovers
In order to be functional, a chromosome requires all of the following except:
nucleomeres
describe two methods to study genetic inheritence
pedigree analysis and twin studies and adoption studies
In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________.
portion of the Y chromosome
Purple flower color and yellow seed color are dominant traits. An individual with purple flowers and yellow seeds is crossed to an individual with purple flowers and green seeds. The offspring of these two parents were as follows:
ppYy
Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assume that you are microscopically examining the mitotic and meiotic cells of this organism. You note that in the female two chromosomal pairs are metacentric and that two pairs are acrocentric.
primary oocyte (metaphase)
In studies of human genetics, usually a single individual brings the condition to the attention of a scientist or physician. When pedigrees are developed to illustrate transmission of the trait, what term does one use to refer to this individual?
proband
You have found a mutant of the p53 gene product that will affect the G1/S checkpoint. What would you predict would be the effect of this mutation and a potential consequence?
proliferation of the damaged cell---> tumor
Crossing over occurs during
prophase
In eukaryotes, chromosomes do not contain:
proteases
The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus would be called
segregation
Homologous chromosomes are those that can be matched by virtue of their similar structure and function within a nucleus. What chromosomes making up the human genome do not follow the same characteristics of homology?
sex chromosomes
Homologous chromosomes are those that can be matched by virtue of their similar structure and function within a nucleus. What chromosomes making up a genome do not follow the same characteristics of homology?
sex-determining chromosomes
synapsis
side by side alignment of homologous chromosomes
Describe how chromosomes are correctly transported to the cellular poles during mitosis. Name one class of DNA sequences and two classes of proteins that are involved in this process.
spindle fibers bind to kinetchores located on the centromeres of chromosomes. Centrioles migrate to the opposite sides of the cells and spindle fibers come out from them and connect to the kinetechores located on the centromeres of chromosomes. The spindle fibers then condense and pull sister chromatids towards opposite sides of the cell. Cytokinesis evntually occurs and the process is complete
2 scientisits
sutton and bolveri
Methods for determining the linkage group and genetic map in humans involve which of the following?
syntenic testing and lod score determination
In the G0 stage of the cell cycle, which of the following is true:
the cell exits the cell cycle
cytokinesis is
the formation of two cells at the end of mitosis in both plants and animals
in prokaryotes, replication begins at
the origin of replication
Embryonic stem cells are the subject of a great deal of research. What characteristic of embryonic stems cells accounts for this scientific interest?
they are potentially totipotent
In a Chi-square analysis, what condition causes one to reject (fail to accept) the null hypothesis?
usually when the probability value is less than 0.05
Phenotypically, what two general categories of offspring did Sturtevant and Morgan observe in the F2 generation of their fly crosses?
wild type and mutant
traits of autosomal recessive pedigree
will show both affected males and females arising with equal frequency from unaffected parents. The trait often appears to skip generations. Unaffected people with an affected parent will be carriers.
Hemizygosity would most likely be associated with which of the following?
x linked inheritance
Extensive pedigree analysis on a characteristic shows all the following: • if a woman with an affected father has children with an unaffected man, half of the sons and none of the daughters are affected. • affected females always have an affected father and an affected maternal grandfather. • the trait is never passed from father to son.
x-linked recessive