Chapter Two Flashcards
1
Q
Who is the father of genetics?
A
Gregor Johann Mendel
2
Q
In 1856, what did mendel do?
A
Began his studies of pea plants for 8 years., crossing thousands of pea plants in a garden.
3
Q
What is a cross?
A
A mating between two distinct individuals. An analysis of their offspring may be conducted to understand how traits are passed from parent to offspring.
4
Q
What is hybridization experiment?
A
- the mating of two organisms of the same species with different characteristics
- the phenomenon in which two single stranded molecules renature together to form a hybrid molecule.
5
Q
What are hybrids?
A
An offspring obtained from a hybridization experiment. A cell produced from a cell fusion experiment in which the two separate nuclei have fused to make a single nucleus.
6
Q
What did mendel chose as his experiment?
A
The garden pea- Pisum Sativum
7
Q
What was advantageous about the garden pea?
A
The species was available in several varieties including height, and appearance of their flowers, seeds and pods.
The ease of making crosses.
8
Q
The word gamate is used to describe what in Mendel’s experiments?
A
The haploid reproductive cells that fuse to form a zygote.
Male gametes are produced within pollen grains that form in the anthers.
Female gametes are produced within ovules that form in the ovaries.
9
Q
How does fertilization occur in garden peas?
A
A pollen grain lands on the stigma, which stimulates the growth of a pollen tube. This enables sperm cells to enter the stigma and migrate toward an ovule. Fertilization takes place when a sperm enters the micropyle, an opening in the ovulate wall, and fuses with an egg cell.
10
Q
In some experiments, Mendel wanted to carry out what?
A
Self-fertilization.
11
Q
What is self-fertilization?
A
Fertilization that involves the union of male and female gametes derived from the same parent.
12
Q
What is cross-fertilization?
A
It requires that the male and female gametes come from separate individuals.
13
Q
What are characters?
A
In genetics, a general characteristic such as eye color.
14
Q
What are Variants?
A
Individuals of the same species that exhibit different traits. An example is a tall and dwarf pea plant.
15
Q
What is true-breeding strain?
A
A strain of a particular species that continues to produce the same trait after several generations of self-fertilization (in plants) or inbreeding.
16
Q
What is another name for true-breeding strain?
A
True-breeding line
17
Q
What were the different characters Mendel found? What were the variants of the characters?
A
Height: Tall, Dwarf Flower color: Purple, White Flower position: Axial, Terminal Seed color: Yellow, Green Seed shape: Round, Wrinkled Pod color: Green, Yellow Pod shape: Smooth, Constricted.
18
Q
What do we mean when we say a strain is true breeding?
A
It maintains the same trait over the course of many generations.
19
Q
Experimental advantages of using pea plants include which of the following?
a. the came in several different varieties.
b. They were capable of self-fertiliation
c. They were easy to cross.
d. all of the above.
A
d. all of the above.
20
Q
The term cross refers to an experiment in which
a. gamates come from different individuals.
b. the gametes come from a single flower of the same individuals
c. the gamates come from different flowers of the same individual.
A
a. gamates come from different individuals.
21
Q
To avoid self-fertilizationin his pea plants, Mendel had to
a. spray the plants with a chemical that damaged the pollen
b. remove the anthers from the immature flowers.
c. grow the plants in a greenhouse that did not contain pollinators.
d. do all of the above.
A
b. remove the anthers from the immature flowers.
22
Q
What is a single-factor cross?
A
A cross in which an experimenter is following the outcome of only a single trait.
23
Q
What are monohybrids?
A
An individual produced from a single-factor cross in which the parents had different variants for a single character.
24
Q
What is an empirical approach?
A
A strategy in which experiments are designed to determine quantitative relationships as a way to derive laws that govern biological, chemical, or physical phenomena.
25
What are empirical laws?
Laws deduced from an empirical approach
26
How did Mendel's experiment begin?
True-breeding plants that differed in a single character.
27
What is parental generation?
In a genetic cross, the first generation in the experiment. In Mendel's studies, the parental generation was true-breeding with regard to particular traits.
28
What is another name for parental generation?
P generation
29
What constitues the F1 generation?
Crossing true-breeding parents to each other, called a P cross, produces the offspring that constitute the F1 Generation.
30
What is the F1 generation?
The offspring produced from a cross of the parental generation.
31
What is the F2 generation?
The offspring produced from a cross of the F1 generation.
32
What was Mendel's Goal?
To uncover the laws that inheritance pattern for a single character may follow quantitative natural laws.
33
What was Mendel's starting material?
True-breeding strains of pea plants that varied in only one of seven different characters.
34
Mendel's data argued strongly against what?
A blending mechanism of heredity.
35
What was Mendel's first proposal?
That one variant for a particular character is dominant over another recessive variant.
36
What is the definition of dominant?
An allele that determines the phenotype in the heterozygous condition.
37
What is the definition of recessive?
A trait or gene that is masked by the presence of a dominant trait or gene.
38
What was Mendel's second proposal?
The genetic determinants of traits are passed along as unit factors from generation to generation.
39
What is the particulate theory of inheritance?
A theory propsed by Mendel. It states that traits are inheritated as discrete units that remain unchanged as they are passed from parent to offspring.
40
What was the recurring pattern Mendel noticed?
Approximately a 3:1 ratio between the dominant and the recessive trait.
41
What was Mendel's third proposal?
Genes segretate from each other during the process that give rise to gametes.
42
A gene is defined as what?
A gene is a unit of heredity that may influence the outcome of an organism's traits.
43
What is Mendel's Law of Segregation?
The two copies of a gene segregate (or separate) from each other during transmission from parent to offspring.
44
What is homozygous?
A diploid individual that has two identical alleles of a particular gene.
homo means like
Zygo means pair
45
What is heterozygous?
A diploid individual that has different versions of the same gene.
46
What is genotype?
The genetic composition of an individual, especially in terms of the alleles for particular genes.
47
What is phenotype?
The observable traits of an organism
48
What is an easy way to predict the outcome of genetic crosses?
Use a punnett square
49
What is a Punnett Square?
A diagrammatic method in which the gametes that two parents can produce are aligned next to a square grid as a way to predict the types of offspring the parents will produce and in what proportions.
50
A pea plant is Tt. Which of the following statements is correct.
a. its genotype is Tt, and its phenotype is dwarf.
b. Its phenotype is Tt, and its genotype is dwarf.
c. Its genotype is Tt, and its phenotype is tall
d. Its phenotype is Tt, and its genotype is tall.
c. Its genotype is Tt, and its phenotype is tall
51
A Tt plant is crossed to a tt plant. What i the expected outcome for the ratio of offspring from this cross?
a. 3 tall: 1 dwarf
b. 1 tall: 1 dwarf
c. 1 tall: 3 dwarf
d. 2 tall: 1 dwarf
b. 1 tall: 1 dwarf
52
What are the two different hypotheses to explain how two different genes assort during gamete?
Linked hypothesis: the two genes always stay associated with each other.
Independent assortment hypothesis: the two different genes randomly segregate into haploid cells.
53
According to the linkage hypothesis of the Mendel's cross experiment, what is linked? Are two different genes linked, or are two different alleles of the same gene linked?
Two different genes are linked. The alleles of the same gene are not linked.
54
What was Mendel's protocol for two-factor cross?
Mendel began with two different strains of true-breeding pea plants that were different in seed shape and seed color. One plant was produced from seeds that were round and yellow; the other plant from seeds that were wrinkled and green. When these plants were crossed, the seeds, which contain the plant embryo, are considered part of the f1 generation. As expected the data revealed that F1 seeds displayed a phenotype of round and yellow. This was observed because round and yellow are dominant traints. It is the F2 generation that supports the independent-assortment model and refutes the linkage model.
55
What is another word for recombinant?
Nonparentals
56
What is Mendel's Law of Independent assortment?
Two different genes randomly assort their alleles during gamete formation (if they are not linked).
Or Two different genes randomly assort their alleles during the formation of haploid cells.
57
What is the expected ration for the independent assortment when a plant that is heterozygous for both genes is allowed to self-fertilize?
9:3:3:1
58
Why does independent assortment promote genetic variation?
It allows for new combinations of alleles among different genes to be found in future generations of offspring.
59
What is a consequence of the law of independent assortment?
A single individual can produce a vast array of genetically different gametes.
60
What is Genetic Recombination?
The process in which chromosomes are broken and then rejoined to forma novel genetic combination;
The process in which alleles are assorted and passed to offspring in combinations that are different from the parents.
61
What can be used to solve indpendent assortment problems?
A punnett square.
62
If a parent is Ttyy, how many different types of gametes can it make?
Two types: Ty and ty
63
What are the two methods for dealing with a large number of crossed-factors?
Multiplication method
| Forked-line method.
64
What is the multiplication method?
A method for solving independent assortment problems in which the probabilities of the outcome for each gene are multiplied together.
65
What is the forked-line method?
A method to solve indpendent assortment problems in which lines are drawn to connect particular genotypes.
66
What is a dihybrid testcross?
A cross in which an experimenter crosses an individual that is heterozygous for two genes to an individual that is homozygous recessive for the same two genes.
67
For a dihybrid testcross, what is the expected ratio?
1:1:1:1
68
What are examples of eukaryotic organisms?
```
Corn
Fruit Flies
Roundworms
Mice
Humans
```
69
What is a loss-of-function alleles?
An Alleles of a gene, that encodes an RNA or protein that is nonfunctional or compromised in function.
70
A pea plant has the genotypes rrYr. How many different types of gametes can it make and in what proportions?
a) 1. rr: 1 Yy
b) 1 rY: 1ry
c) 3 rY: 1 ry
d) 1 RY: 1 ry: 1 Ry: 1 ry
b) 1 rY: 1ry
71
A cross is made between a plant that is RrYy to a plant that is rrYy. What is the predicted outcome of the seed phenotypes?
a) 9 round, yellow: 3 round, green: 3 wrinkled yellow: 1 wrinkled green
b) 3 round, yellow: 3 round, green: 1 wrinkled, yellow: 1 wrinkled green.
c) 3 round, yellow: 1 round, green: 3 wrinkled, yellow: 1 wrinkled, green.
d) 1 round, yellow: 1 round, green: 1 wrinkled, yellow: 1 wrinkled green.
c) 3 round, yellow: 1 round, green: 3 wrinkled, yellow: 1 wrinkled, green.
72
In a population of wild squirrels, most of them have gray fur, but an occasional squirrel is completely white. If we let P and p represent dominant and recessive alleles of a gene that encodes an enzymes necessary for pigment formation, which of the following statements do you think is most likely to be correct?
a. The white squirrels are pp, and the p allele is a loss-of-function allele.
b. the gray squirrels are pp, and the p allele is a loss-of-fuction allele.
c. The white squirrels are PP, and the P allele is a loss-of-function allele.
d. The gray squirrels are PP, and the P allele is a loss-of-function allele.
a. The white squirrels are pp, and the p allele is a loss-of-function allele.
73
What are pedigrees?
Charts representing family relationships
74
What is pedigree analysis?
A genetic analysis using information contained within family trees. In this approach, the aim is to determine the type of inheritance pattern that a gene follows.
75
What are the two different meanings of horizontal lines in a pedigree?
They connect two individuals that have offspring together, and they connect all the offspring that are produced by the same two parents.
76
In a pedigree involving the transmission of a human trait or disease, affected individuals are depcited how?
By filled symbols that distinguish them from unaffected individuals.
77
Which of the following would not be observed in a pedigree if a genetic disorder was inherited in a recessive manner?
a. Two unaffected parents have an affected offspring.
b. two affected parents have an unaffected offspring
c. one affected and one unaffected parent have an unaffected offspring
d. all of the above are possible recessive disorder.
b. two affected parents have an unaffected offspring
78
What are the two mathematical operations to calculate probability of certain genes?
The product rule
| The binomial expansion equation.
79
What is the product rule used to solve?
Used in problems in which the outcomes are independent of each other.
80
What is the binomial expanion used for?
Used in problems having an unordered combination of outcomes.
81
What is probability?
The change that an event will occur in the future.
82
What is the formula for probability?
Probability=Number of times a particular outcome occurs/Total number of possible outcomes.
83
The accuracy of the probability prediction is dependent on what?
The size of the sample.
84
What is the random sampling error?
The deviation between the observed and expected outcomes due to change.
85
What happenes in larger samples?
The random sampling error is much smaller.
86
What is the product rule?
The probablity that two or more independent events will occur is equal to the products of their individual probabilities.
87
How does the product rule work?
First calculate the individual probability of this phenotype.
Then multiply the individual probabilities.
88
What is the binomial expansion equation?
P= (n!/x! (n-x)!) p^x q^(n-x)
89
What do the letters represent in the Binomial expansion equation?
p: the probability that the unordered outcome will occur.
n: total number of outcomes.
x: number of outcomes in one category
p: indivdual probability of x
q: individual probability of the other category
!: A factorial. The product of all integers from n down to 1. Example- 4!- 4x3x2x1
90
What are the steps for using the binomial expansion equation?
1. calculate the individual probabilities of the phenotypes.
2. determine the number of outcomes in category x versus the total number of outcomes.
3. Substitute the values of p, q, x and n in the binomial expansion equation.
91
What is used when more than two outcomes are possible?
A multinomial expansion equation.
92
What is the multinomial expansion equation?
P= (n!/a!b!c!...) p^a q^b r^c...
93
What do the letters represent in the multinomial expansion equation?
p: the probability that the unordered number of outcomes will occur.
n= total number of outcomes.
94
What is hypothesis testing?
Using statistical tests to determine data from experimentation are consistent with a hypothesis
95
What is the goodness of fit?
The degree to which the observed data and expected data are similar to each other. If the observed and predicted data are very similar, the goodness of fit is high.
96
What is a Null hypothesis?
A hypothesis that assumes there is no real difference between the observed and expected values.
97
What is one commonly used statistical method to determine goodness of fit?
Chi Square test
98
What is the chi square test?
This method can be used to analyze population data in which the members of the population fall into different categories.
99
What is the general formula for the chi square test?
X^2= Sigma[sum] ((O-E)^2)/E
100
What do the letters represent in the chi square test?
O: observed data in each category
E: expected data in each category based on the experimenter's hypothesis
101
What are the steps for using a chi square test?
1. Propose a hypothesis that allows us to calculate the expected values based on Mendel's laws.
2. Based on the hypothesis, calculate the expected values of the four phenotypes.
3. apply the chi square formula, using the data for the expected values that have been calculated.
4. interpret the calculated chi square value using a chi square table.
102
What are p values?
In a chi square table, the probability that the deviations between observed and expected values are due to random chance.
103
What is the degrees of freedom?
The number of categories that are independent of each other.
104
A cross is made between AA Bb Cc Dd and Aa Bb cc dd individuals. Rather than making a very large punnett square, which statistical operation could you use to solve this problem, and what would be the probability of an offspring that is AA bb Cc dd?
a. product rule, 1/32
b. product rule, 1/4
c. binomial expansion, 1/32
d. binomial expansion, 1/4
a. product rule, 1/32
105
In dogs, brown fur color (B) is dominant to white (b). A cross is made between two heterozygotes. If a litter contains six pups, what is the probability that half of them will be white?
a. 0.066 or 6.6%
b. 0.13 or 13%
c. 0.25 or 25%
d. 0.26 or 26 %
b. 0.13 or 13%
106
Which of the following operations could be used for hypothesis testing?
a. product rule
b. binomial expansion test
c. chi square test
d. all of the above.
c. chi square test.
107
What is the difference between cross-fertilization and self-fertilization?
Cross fertilization occcurs when the pollen and eggs come from different plants, self-fertilization , the come from the same plant.
108
With regard to genotypes, what is a true-breeding organisim?
A homozygote that has two copies of the same allele.
109
In your own words, describe Mendel's law of segregation. Do not use the word segregation in your answer.
Diploid organisms contain two copies of each type of gene. When they make gametes, only one copy of each gene is found in a gamete. Two alleles cannot stay together within the same gamete.
110
In a cross between a heterozygous tall pea plant and a dwarf plant, predict the ratios of the offspring's genotypes.
Genotypes: 1:1 Tt and tt
Phenotypes: 1:1 Tall and Dwarf
111
A cross is made between a pea plant that has constricted pods (a recessive trait; smoth is dominant) and is heterozygous for seed color (yellow is dominant to green) and a plant that is heterozygous for both pod texture and seed color. Construct a Punnett square that depicts this cross. What are the predicted outcomes of genotypes and phenotypes of the offspring?
c is the recessive allele for constricted pods; y is the dominant allele for yellow color. The cross is ccYy x CcYy. The genotypic ratio is 2 CcYY; 4 CcYy; 2 Ccyy; 4 ccYc; 2 ccyy. This is 2:4:2:2:4:2 ratio that can be reduced to 1:2:1:1:2:1 ratio.
The phenotypic ratio is 6 smooth pods, yellow seeds; 2 smooth pods, green seeds; 6 constricted pods, yellow seeds; 2 constricted pods, green seeds. That is 6:2:6:2 ratio which can be reduced to 3:1:3:1.
112
Describe the significance of nonparentals with regard to the law of independent assortment. In other words, explain how the appearance of nonparentals refutes a linkage hypothesis.
Offspring with a nonparental phenotype are consistent with the idea of independent assortment. If two different traits were always transmitted together as a unit, it would not be possible to get nonparental phenotypic combinations. For example, if a true-breeding parent had two dominant traits and was corssed to a true-breeding parent having the two recesive traits, the F2 generation could not have offspring with one recessive and one dominant phenotype. However, because independent assortment can occur, t is possible for F2 offspring to have one dominant and one recessive trait.
113
Ectrodactyly, als known as lobster claw syndrome, is a recessive disorder in humans. If a phenotypically unaffected couple produces an affected offspring, what are the following probabilities?
a. both parents are heterozygotes
b. an offspring is a heterozygote
c. the next three offspring will be phenotypically unaffected.
d. Any two out of the next three offsrping will be phenotypically unaffected.
a. 100%
b. 50% chance
c. 0.422 or 42.2%
d. 0.422 or 42.2%
114
In cocker spaniels, solid coat color is dominant over spotted coat color. If two heterozygous dogs were crossed to each other, what would be the probability of the following combinations of offspring?
a. a litter of five pups, four with solid fur and one with spotted fur.
b. a first litter of six pups, four with solid fur and two with spotted fur, and then a second litter of five pups, all with solid fur.
c. a first litter of five pups, the firstborn with solid fur, and then amont the next four, three with solid fur and one with spotted fur, and then a second litter of seven pups in which the firstborn is spotted, the second born is spotted, and the remaining five are composed of four solid and one spotted animal.
d. a litter of six pups, the firstborn with solid fur, the second born spotted, and among the remaining four pups, two with spotted fur and two with solid fur.
a. use the bionomial expansion where n=5, x=4, p=.75 q=.25. Answer: 0.396 or 39.6%
b. Use binomial. N=6, x=4, p=.75, q=0.25. For the second litter, n=5, x=5, p=.75, q=.25. Use product rule to multiple the first by the second. Answer: .07 or 7%
C. Use product rule. (.75 for the first pup) multipled by binomial where n=4, x=3, p=.75, q=.25. Answer first litter: .316. Second litter: Product rule: (.25) (.75) by binomial n=5, x=4, p=.75 q=.25. The probability of the second litter Answer: 0.025. The probability of these two occuring in this order is 0.008 or 0.8%
d. Product rule (.75) (.25) by binomial n=4, x=2, p=.75 q=.25. Answer: 0.040 pr 4%
115
In humans, the allele for brown eyes color (B) is dominant to blue eye color (b). If two heterozygous parents produce children, what are the following probabilities?
a. The first two children have blue eyes.
b. A total of four children, two with blue eyes and the other two with brown eyes.
C. The first child has blue eyes, and the next two have brown eyes.
a. Product rule (.25) (.25)=1/16
b. Use binomial n=4, p=1/4 q= 3/4 x=2
P=21%
C. Use product rule: (1/4) (3/4) (3/4)= .14 or 14%
116
A true-breeding tall plant was crossed to a dwarf plant. Tallness is a dominant trait. The F1 individuals were allowed to self-fertilize. What are the following probabilities for the F2 generation?
a. The first plant is dwarf
b. the first plant is dwarf or tall
c. the first three plants are tall
d. for any seven plants, three are tall and four are dwarf
e. the first plant is tall, and then amont the next four, two are tall and the other two are dwarf.
a. 1/4
b. 1 or 100%
c. (3/4)(3/4)(3/4)= .42 or 42%
d. n=7, p=3/4, q=1/4 x=3
P=0.58 or 5.8%
e. (3/4) by n=4, p=3/4, q=1/4 and x=2.
P=.21
Overall: .16 or 16%
117
An individual has the genotype of Aa Bb Cc and makes an abnormal gamete with the genotype AaBc. Does this gamete violate the law of independent assortment or the law of segregation (or both)?
It violate the law of segregation because two copies of one gene are in the gamete. The two alleles for the A gene did not segregate from each other.
118
A true-breeding tall pea plant was crossed to a true-breeding dwarf plant. What is the probability that an F1 individual will be true-breeding? What is the probability that an F1 individual will be a true-breeding tall pllant?
It is impossible for the F1 individuals to be true-breeding because they are all heterozygotes.
119
When an abnormal organism has three copies of a chromsome and therefore contains three copies of the genes on that chromsome, the alleles for each gene usually segregate so that a gamete will contain one or two copies of the gene. Let's suppose that an abnormal pea plant has three copies of the chromosome that carries the height gene. Its genotype is TTt. The plant is also heterozygous for the seed color gene, Yy, which is found on a different chromosome. With regard to both genes, howmany types of gametes can this plant make, and in what proportions? (assume that it is equally likely that a gamete will contain one or two copies of the height gene.)
2 TY, tY, 2 Ty, ty, TTY, TTY, 2 TtY, 2 Tty
You get 2 TY and 2 Ty because either of the two T alleles could combine with Y or y. Also, you get 2 TtY and 2 Tty because either of the two T alleles could combine with t and then combine with Y or y.
120
Wooly hair is a rare dominant trait found in people of scandinavian descent in which the hair resembles the wool of a sheep. A male with wooly hair, who has a mother with straight hair, moves to an island that is inhabited by people who are not of scandinavian descent. Assuming that no other scandinavians immigrate to the island, what is the probability that a great-grandchild of this male will have wooly hair?
The wooly-haired male is heterozygote, because he has the trait and his mother did not. Therefore, he has a 50 % chance of passing the wooly allele to his offspring; his offspring have a 50% of passing the allele to their offspring; and these grand children have a 50% chance of passing the allele to their offspring. Because this is an ordered sequence of independent event, we use the product rule. (.5) (.5) (.5)= .125 or 12.5%. Because no other scandinavians are on the island, the change is 87.5% for the offspring to be normal We use the binomial expansion equation to determine the likelihood that one out of eight great-grandchildren will have wooly hair, where n=8, x=1, p=0.125, q=0.875. Answer: .393 or 39.3%
121
A woman with achondroplasia ( a dominant form of dwarfism) and a phenotypically unaffected man have seven children, all of whom have achondroplasia. What is the probability of producing such a family if this women is a heterozygote? What is the probability that the woman is a heterozygote if her eighth child does not have this disorder?
Use product rule: (.5)^7= 0.78%
| the probability is 100% for the eighth child.
122
Albino coat color is a reccessive trait in guinea pigs. Researchers removed the ovaries from an albino female guinea pig and then transplanted ovaries from a true-breeding black quinea pig. They then mated this albino female to an albino male. The albino female produced three offspring. What were their coat colors?
Black fur. The ovaries from the albino female could produce eggs with only the black allele. The actual phenotype of the mother does not matter. Therefore all offspring would be heterozygotes and have black fur.
123
A tall pea plant with axial flowers was crossed to a dwarf plant with terminal flowers. Tall plants and axial flowers are dominant traits. The following offspring were obtained: 27 tall, axial flowers; 23 tall, terminal flowers; 28 dwarf, axial flowers; and 25 dwarf, terminal flowers. What are the genotypes of the parents?
The dwarf parent with terminal flowers must be homozygous for both genes, because it is expressing the recessive traits: ttaa, where t is the recessive dwarf allele, and a is the recessive allele for terminal flower. The phenotype of the other parent is dominant for both traits. However, because this parent was able to produce dwarf offspring with axial flowers, it must have been heterozygous for both genes: TtAa.
