MelendianMeiosis Flashcards
1
Q
What is the process by which offspring acquire genes from their parents?
A
Inheritance
2
Q
What type of cell division produces cells with half the number of chromosomes?
A
Meiosis
3
Q
What is genetic variation produced in sexual life cycles important for?
A
Evolution
4
Q
What are the specialized cells that undergo meiosis in humans?
A
Testes and ovaries
5
Q
What is the term for the coded information inherited from parents?
A
Genes
6
Q
What is the genetic program written in?
A
DNA
7
Q
How many chromosomes do human somatic cells contain?
A
46
8
Q
What is the single long DNA molecule in each chromosome associated with?
A
Proteins
9
Q
What is the location of a gene on a chromosome called?
A
Locus
10
Q
What type of reproduction produces genetically identical offspring?
A
Asexual reproduction
11
Q
What type of reproduction results in offspring with unique combinations of genes?
A
Sexual reproduction
12
Q
What is the term for an individual or group genetically identical to the parent?
A
Clone
13
Q
What is the diploid number of chromosomes in humans?
A
46 (2n = 46)
14
Q
What is the haploid number of chromosomes in humans?
A
23 (n = 23)
15
Q
What are the two types of chromosomes in humans?
A
Autosomes and sex chromosomes
16
Q
What are the sex chromosomes in human males?
A
X and Y
17
Q
What is the term for the ordered display of chromosomes?
A
Karyotype
18
Q
In a diploid cell, what do sister chromatids consist of?
A
Two identical copies
19
Q
What is the term for the process where male and female gametes unite?
A
Fertilization
20
Q
Fill in the blank: The genetic endowment of an organism is called its _______.
A
Genome
21
Q
True or False: Asexual reproduction involves the fusion of gametes.
A
False
22
Q
What happens to the number of chromosome sets during meiosis?
A
It is halved
23
Q
What is produced during fertilization in terms of chromosome number?
A
Diploid zygote
24
Q
What are gametes in humans?
A
Sperm and eggs
25
What is the haploid number of chromosomes in human gametes?
23
## Footnote
The haploid number is represented as n = 23.
26
What is the diploid number of chromosomes in human somatic cells?
46
## Footnote
The diploid number is represented as 2n = 46.
27
What type of cell division produces gametes?
Meiosis
28
What is the result of fertilization in terms of chromosome number?
Diploid zygote formed from two haploid sets
29
What is the primary function of meiosis?
To reduce the number of chromosome sets from two to one in gametes
30
In humans, what type of cells do not arise from mitosis?
Gametes
31
What prevents the doubling of chromosome number in sexually reproducing organisms?
Meiosis
32
What are the two main stages of the human life cycle in terms of ploidy?
Haploid and diploid
33
What is the multicellular diploid stage in plants called?
Sporophyte
34
What is produced by meiosis in the sporophyte?
Haploid spores
35
What type of life cycle alternates between multicellular haploid and diploid stages?
Alternation of generations
36
True or False: In most fungi, meiosis produces gametes.
False
37
What happens during prophase I of meiosis?
Homologous chromosomes pair up and crossing over occurs
38
What structure is formed by sister chromatids held together?
Centromere
39
What is independent assortment?
The arrangement of homologous chromosomes at the metaphase plate
40
What occurs during anaphase I of meiosis?
Homologous chromosomes separate and move toward opposite poles
41
What is the fate of the zygote after fertilization?
It divides by mitosis to form a multicellular organism
42
Fill in the blank: The division of the cytoplasm during meiosis is called _______.
Cytokinesis
43
What are the final products of meiosis?
Four genetically distinct haploid daughter cells
44
What is crossing over?
Exchange of genetic material between nonsister chromatids
45
In which phase do sister chromatids separate?
Anaphase II
46
What is the only diploid stage in certain fungi and some protists?
Single-celled zygote
47
What role do cohesins play during meiosis?
They hold sister chromatids together
48
What is the outcome of mitosis in terms of chromosome number?
Maintains chromosome number
49
What happens to chromosomes after interphase?
The chromosomes have been duplicated, and sister chromatids are held together by proteins called cohesins.
50
What is the function of cohesins in chromosome structure?
Cohesins hold sister chromatids together.
51
What occurs early in prophase I of meiosis?
The two members of a homologous pair associate loosely along their length.
52
What is synapsis?
The association of homologous chromosomes during prophase I.
53
What structure forms to hold homologs tightly together during synapsis?
The synaptonemal complex.
54
What happens to the DNA during crossing over?
The DNA of two nonsister chromatids is broken and joined to the corresponding segment of the nonsister chromatid.
55
What are chiasmata?
The points where crossing over has occurred.
56
What is the main difference between meiosis and mitosis regarding cell division outcomes?
Meiosis produces four genetically different cells, while mitosis produces two genetically identical cells.
57
What unique events occur during meiosis I?
Synapsis and crossing over, alignment of homologous pairs at the metaphase plate, and separation of homologs.
58
In which phase do homologous pairs align at the metaphase plate?
Metaphase I of meiosis.
59
What happens during anaphase I of meiosis?
The duplicated chromosomes of each homologous pair move toward opposite poles, but sister chromatids remain attached.
60
What is the outcome of meiosis II?
Separation of sister chromatids, producing four haploid daughter cells.
61
How does sister chromatid cohesion differ in meiosis compared to mitosis?
In meiosis, sister chromatid cohesion is released in two steps, while in mitosis, it lasts until the end of metaphase.
62
What is the role of crossing over in genetic variation?
It introduces genetic variability among gametes or spores.
63
What are the three mechanisms that contribute to genetic variation during sexual reproduction?
* Independent assortment of chromosomes
* Crossing over
* Random fertilization
64
Fill in the blank: Meiosis reduces the number of chromosome sets from ______ to ______.
two (diploid) to one (haploid).
65
True or False: Crossing over occurs during prophase of mitosis.
False.
66
What does the synaptonemal complex do?
It holds homologs tightly together during synapsis.
67
What is the significance of chiasmata during meiosis?
They hold homologs together as the spindle forms for the first meiotic division.
68
What occurs during the second meiotic division?
Sister chromatids separate.
69
What is the result of DNA replication in meiosis?
It occurs during interphase before meiosis I but not before meiosis II.
70
What is the role of mutations in genetic diversity?
They create different versions of genes, known as alleles.
71
What is the primary source of genetic variation among offspring in sexually reproducing species?
The behavior of chromosomes during meiosis and fertilization
## Footnote
This includes independent assortment, crossing over, and random fertilization.
72
What is independent assortment of chromosomes?
The random orientation of homologous chromosome pairs at metaphase I of meiosis
## Footnote
Each pair can orient with either its maternal or paternal homolog closer to a given pole.
73
How many possible combinations of maternal and paternal chromosomes can be produced by independent assortment in humans?
About 8.4 million combinations
## Footnote
This is calculated as 2^23, where 23 is the haploid number for humans.
74
What is the role of crossing over in genetic variation?
It produces recombinant chromosomes that carry genes from both parents
## Footnote
This results in new combinations of alleles.
75
What is the average number of crossover events per chromosome pair in humans during meiosis?
One to three crossover events
## Footnote
The number can vary depending on chromosome size and centromere position.
76
What does random fertilization contribute to genetic variation?
It adds to the genetic variability arising from meiosis
## Footnote
The fusion of gametes from different parents results in unique combinations.
77
How does natural selection relate to genetic variation in a population?
Natural selection favors individuals best suited to the environment, leading to the accumulation of beneficial genetic variations
## Footnote
This process enhances the population's ability to adapt to changing conditions.
78
What are mutations in the context of genetic variation?
The original source of different alleles
## Footnote
Mutations introduce new genetic material that can be mixed during meiosis.
79
Why is sexual reproduction considered advantageous despite its costs?
It generates genetic diversity, which can enhance adaptability in changing environments
## Footnote
This diversity can lead to better survival rates for offspring.
80
What is unique about bdelloid rotifers in terms of reproduction?
They have not reproduced sexually for over 50 million years
## Footnote
They utilize alternative mechanisms for generating genetic diversity.
81
What happens during synapsis in prophase I of meiosis?
Homologous chromosomes pair up and crossing over occurs
## Footnote
This leads to the formation of chiasmata.
82
What is the distinction between meiosis and mitosis?
Meiosis reduces chromosome sets from diploid to haploid, while mitosis maintains the diploid state
## Footnote
Meiosis involves two rounds of division, producing four haploid cells.
83
What is the result of anaphase I in meiosis?
Homologs separate, while sister chromatids remain joined at the centromere
## Footnote
This separation is crucial for reducing chromosome numbers.
84
Fill in the blank: The diploid number for fruit flies is 8, while for grasshoppers it is _____ .
46
85
True or False: If maternal and paternal chromatids have the same two alleles for every gene, crossing over will lead to genetic variation.
False
## Footnote
Crossing over requires different alleles to create variation.
86
What determines whether a person is female or male in humans?
The pair of sex chromosomes (XX for female, XY for male)
## Footnote
This is one of the 23 pairs of chromosomes in humans.
87
What is the significance of chiasmata during meiosis?
They hold homologous chromosomes together until anaphase I
## Footnote
This cohesion is essential for the proper segregation of chromosomes.
88
What occurs during metaphase I of meiosis?
Chromosomes line up as homologous pairs on the metaphase plate.
89
What happens during anaphase I of meiosis?
Homologs separate from each other; sister chromatids remain joined at the centromere.
90
What is the function of cohesins during meiosis?
Cohesins hold homologs together until anaphase I and are cleaved along the arms at anaphase I and at the centromeres in anaphase II.
91
What is synapsis?
The pairing of homologous chromosomes during prophase I.
92
What contributes to genetic variation in sexual reproduction?
Independent assortment of chromosomes, crossing over, and random fertilization.
93
What occurs during crossing over?
DNA of nonsister chromatids is broken and rejoined.
94
What is the raw material for evolution by natural selection?
Genetic variation.
95
What are the three events that contribute to genetic variation?
* Independent assortment during meiosis I
* Crossing over during meiosis I
* Random fertilization
96
True or False: Meiosis II separates sister chromatids.
True.
97
If the DNA content of a diploid cell in G1 phase is x, what is the DNA content at metaphase of meiosis I?
2x.
98
What is the result of Mendel's cross between true-breeding purple and white pea plants?
All F1 hybrids had purple flowers.
99
What is the Law of Segregation?
The principle that alleles segregate during gamete formation.
100
In Mendel's experiments, what was the F2 generation ratio of purple to white flowers?
Approximately 3:1.
101
What is a character in genetics?
A heritable feature that varies among individuals.
102
What is a trait in genetics?
An alternative version of a gene.
103
Fill in the blank: Mendel's approach to studying inheritance involved ________ true-breeding varieties.
[crossing]
104
What did Mendel conclude about the white flower trait in F1 hybrids?
The white flower trait was masked but did not disappear.
105
What characterizes the F1 generation in Mendel's experiments?
All plants had purple flowers.
106
What does the blending hypothesis suggest about inheritance?
Genetic material from parents mixes together.
107
What is the significance of large sample sizes in Mendel's experiments?
It allowed for accurate records and reliable conclusions.
108
What type of reproduction is the Cavendish banana undergoing?
Asexual reproduction.
109
Why is the Cavendish banana vulnerable to extinction?
It cannot form normal gametes due to its triploid number.
110
How does sexual reproduction contribute to genetic diversity?
By allowing for recombination of variant genes.
111
Fill in the blank: In meiosis, sister chromatids separate during ________.
[anaphase II]
112
What does random fertilization refer to in sexual reproduction?
The random combination of egg and sperm.
113
What is the expected flower color of the F1 hybrids from a cross between purple-flowered and white-flowered pea plants if blending inheritance were correct?
Pale purple flowers
## Footnote
This would be an intermediate trait between the P generation's purple and white flowers.
114
What ratio of flower color was observed in the F2 generation of Mendel's pea plant experiments?
Approximately 3:1
## Footnote
This ratio reflects the dominance of the purple flower trait over the white flower trait.
115
What does Mendel's conclusion about the F1 generation indicate regarding the recessive trait?
The recessive trait was masked, not destroyed
## Footnote
The white flower trait remained in the genetic makeup but was not expressed in the F1 generation.
116
What are the two versions of a gene called?
Alleles
## Footnote
Alleles account for variations in inherited characters, such as flower color in pea plants.
117
How many alleles for a character does an organism inherit from its parents?
Two alleles
## Footnote
One allele is inherited from each parent in a diploid organism.
118
What determines the appearance of an organism when two different alleles are present at a locus?
The dominant allele
## Footnote
The recessive allele has no noticeable effect on the organism's appearance.
119
What does the law of segregation state?
The two alleles for a heritable character segregate during gamete formation
## Footnote
This means each gamete receives only one allele from the pair present in the diploid organism.
120
What is the dominant trait for seed shape in Mendel's experiments?
Round seeds
## Footnote
The dominant trait is expressed in the F1 generation when a round seed variety is crossed with a wrinkled seed variety.
121
What is the expected ratio of round to wrinkled seeds in the F2 generation?
Approximately 3:1
## Footnote
This ratio is consistent with Mendel's observations across different traits.
122
Fill in the blank: Mendel's F1 plants had _______ flowers because the allele for that trait is dominant.
purple
## Footnote
The presence of the dominant purple flower allele determines the flower color in the F1 generation.
123
True or False: The white flower allele results in the synthesis of a functional protein.
False
## Footnote
The white-flower allele does not produce a functional protein, leading to the lack of purple pigment.
124
What does a Punnett square illustrate in Mendel's experiments?
The possible genetic combinations of offspring
## Footnote
It predicts the allele composition from the union of gametes from two parents.
125
What are the two alleles for flower color in pea plants?
* Purple-flower allele
* White-flower allele
## Footnote
These alleles represent the variations at the flower-color locus on the chromosomes.
126
What is the genetic makeup of true-breeding plants in Mendel's P generation?
Identical alleles (PP or pp)
## Footnote
True-breeding plants produce offspring that resemble themselves in appearance.
127
What happens to the gametes when an organism has identical alleles for a particular character?
All gametes receive the same allele
## Footnote
This results in offspring that always exhibit the same characteristic as their parents.
128
What is the significance of Mendelian patterns of inheritance in human traits?
Many human traits follow Mendelian patterns of inheritance.
129
What is a pedigree analysis?
A pedigree analysis traces a trait through generations of a family.
130
What does a dominant allele indicate in pedigree analysis?
Individuals lacking the trait must be homozygous recessive.
131
In the context of widow's peak, what is the genotype of individuals who lack this trait?
Homozygous recessive (ww).
132
What allele represents the widow's peak trait?
W (dominant allele).
133
What does the inability to taste PTC indicate about the trait's inheritance?
It is a recessive trait.
134
What allele represents the ability to taste PTC?
T (dominant allele).
135
How do geneticists use pedigrees to calculate probabilities of genotypes?
By analyzing family history for specific traits.
136
What is the probability of a child having a widow's peak from a Ww x Ww cross?
3/4 or 75%.
137
What is the probability that a child will be unable to taste PTC from a Tt x Tt cross?
1/4 or 25%.
138
What is a dihybrid cross?
A genetic cross involving two traits.
139
What is the predicted genotypic ratio for offspring from two heterozygous parents (Aa)?
1 AA : 2 Aa : 1 aa.
140
What is the most common lethal genetic disease in the United States?
Cystic fibrosis.
141
What causes cystic fibrosis?
A defect in the chloride ion transport protein.
142
What is the incidence of cystic fibrosis among people of European descent?
1 in 2,500.
143
What is the primary effect of sickle-cell disease?
Deformation of red blood cells due to abnormal hemoglobin.
144
How does sickle-cell disease affect blood vessels?
Sickled cells can clump and clog small blood vessels.
145
What is the carrier rate for the cystic fibrosis allele among Europeans?
1 in 25 (4%).
146
What is the effect of consanguineous matings on recessive traits?
Increases the probability of inheriting recessive traits.
147
What is albinism?
A recessive genetic disorder characterized by lack of pigmentation.
148
What is the chance that the sister without albinism is a carrier of the albinism allele?
2/3 chance.
149
What is the relationship between Mendelian traits and genetic disorders?
Simple Mendelian traits apply to genetic disorders as well.
150
What does the term 'carriers' refer to in genetics?
Individuals who transmit a recessive allele without showing symptoms.
151
What is the role of gene therapy in treating genetic disorders?
Research is ongoing to find cures for genetic disorders.
152
What is sickle-cell disease?
A genetic disorder that affects hemoglobin, leading to various symptoms including physical weakness, pain, organ damage, and potentially stroke or paralysis.
## Footnote
Regular blood transfusions can help prevent brain damage in children with sickle-cell disease.
153
What is the inheritance pattern of sickle-cell disease?
It is considered recessive, requiring two sickle-cell alleles for the disease to manifest.
## Footnote
The presence of one sickle-cell allele can affect the phenotype.
154
How are the sickle-cell alleles expressed at the organismal and molecular levels?
At the organismal level, the normal allele is incompletely dominant to the sickle-cell allele, while at the molecular level, the two alleles are codominant.
## Footnote
Both normal and abnormal hemoglobins are produced in heterozygotes.
155
What is sickle-cell trait?
A condition where an individual has one sickle-cell allele and is usually healthy but may experience symptoms during low blood oxygen levels.
## Footnote
Heterozygotes for sickle-cell trait are carriers.
156
What is the frequency of sickle-cell trait among African-Americans?
About one out of ten African-Americans have sickle-cell trait.
## Footnote
This is a high frequency of heterozygotes in a population with severe effects in homozygotes.
157
What is one evolutionary advantage of the sickle-cell allele?
Having a single copy of the sickle-cell allele reduces the frequency and severity of malaria attacks.
## Footnote
This is particularly beneficial in regions where malaria is common.
158
What is achondroplasia?
A form of dwarfism caused by a dominant allele, occurring in about one in every 25,000 people.
## Footnote
Individuals with achondroplasia are heterozygous and exhibit the dwarf phenotype.
159
What is the difference between lethal recessive and lethal dominant alleles?
Lethal recessive alleles are only lethal when homozygous, while lethal dominant alleles often cause death before reproductive age.
## Footnote
Lethal dominant alleles can be passed on if symptoms appear after reproductive age.
160
What is Huntington's disease?
A degenerative disease of the nervous system caused by a lethal dominant allele, with symptoms appearing between ages 35 to 45.
## Footnote
It affects about one in 10,000 people in the United States.
161
What are multifactorial disorders?
Diseases that have a genetic component plus significant environmental influences, such as heart disease and diabetes.
## Footnote
These disorders are often polygenic.
162
What role does lifestyle play in multifactorial disorders?
Lifestyle factors such as exercise and diet significantly influence the phenotype and risk for diseases like heart disease.
## Footnote
Individuals can manage their risk through healthy lifestyle choices.
163
What is the purpose of genetic counseling?
To assess the risk of genetic disorders before or during pregnancy based on family history.
## Footnote
Genetic counselors provide information to prospective parents.
164
What is the probability of a child having a recessive genetic disorder if both parents are carriers?
There is a 25% chance of the child having the disorder.
## Footnote
This is determined using a Punnett square for an Aa x Aa cross.
165
What are carrier tests?
Tests that identify whether individuals are heterozygous carriers of recessive alleles for genetic disorders.
## Footnote
Examples include tests for Tay Sachs disease, sickle-cell disease, and cystic fibrosis.
166
What is amniocentesis?
A diagnostic test where amniotic fluid is extracted to test for genetic disorders in the fetus.
## Footnote
It can be performed starting at the 15th or 16th week of pregnancy.
167
What is chorionic villus sampling (CVS)?
A diagnostic procedure that involves taking a sample of tissue from the placenta to analyze for genetic disorders.
## Footnote
CVS can be performed as early as the 10th or 11th week of pregnancy.
168
What is the Genetic Information Nondiscrimination Act?
An act that prohibits discrimination in employment or health insurance coverage based on genetic test results.
## Footnote
This act was established in 2008 to protect patients' rights.
169
What is the main advantage of chorionic villus sampling (CVS)?
CVS can be performed as early as the 10th or 11th week of pregnancy
## Footnote
CVS allows for early detection of genetic disorders.
170
What is the risk associated with amniocentesis and CVS?
Complications occur in a small percentage of cases, between 1 in 1,000 and 1 in 500
## Footnote
These risks include potential miscarriage.
171
Why are amniocentesis and CVS generally offered to women over age 35?
Due to their increased risk of bearing a child with Down syndrome or other chromosomal disorders.
172
What significant reduction in Tay-Sachs disease has been achieved since 1980?
The number of children born with Tay-Sachs disease has been reduced by 90%.
173
What common genetic disorder is screened for in newborns and what is its prevalence?
Phenylketonuria (PKU), occurring in about 1 in every 10,000-15,000 births in the United States.
174
What is the consequence of untreated PKU in newborns?
Severe intellectual disability due to accumulation of phenylalanine and its byproduct, phenylpyruvate.
175
What dietary restriction is necessary for managing PKU?
A diet low in phenylalanine, excluding substances like aspartame.
176
How many newborn genetic tests are there in the United States, and what do they often screen for?
Over 100 tests, many for metabolic disorders or enzyme deficiencies.
177
What is the impact of early detection of genetic disorders in newborns?
Improved chances for better life quality through early treatment.
178
What model do fetal and newborn screening for inherited diseases rely on?
The Mendelian model of inheritance.
179
What are the two laws of inheritance proposed by Gregor Mendel?
* Law of Segregation
* Law of Independent Assortment
180
What does the law of segregation state?
Genes have alternative forms, or alleles, that segregate during meiosis.
181
What is the expected phenotypic ratio from a monohybrid cross according to Mendel's law?
3:1 ratio of phenotypes.
182
What does the law of independent assortment state?
Alleles for different genes segregate into gametes independently.
183
What is the phenotypic ratio from a dihybrid cross?
9:3:3:1 ratio.
184
What are the multiplication and addition rules of probability in genetics?
* Multiplication rule: Probability of two events occurring together is the product of their individual probabilities.
* Addition rule: Probability of an event occurring in two or more mutually exclusive ways is the sum of their individual probabilities.
185
What is the significance of family pedigrees in genetics?
They can be used to deduce possible genotypes of individuals and make predictions about future offspring.
186
What is the difference between complete dominance and incomplete dominance?
* Complete dominance: Heterozygous phenotype same as homozygous dominant.
* Incomplete dominance: Heterozygous phenotype is intermediate between the two homozygous phenotypes.
187
What is a multifactorial character?
A polygenic character influenced by environmental factors.
188
What role do genetic counselors play in assessing genetic disorders?
They help couples determine the probability that their children will have genetic disorders.
189
What genetic testing methods are used for screening fetuses?
* Ultrasounds
* Blood tests
* Amniocentesis
* Chorionic villus sampling
190
What is the primary focus of genetic counseling?
To assess carrier status of recessive alleles associated with specific disorders.
191
What happens to dominant alleles in a population if affected individuals die before reproducing?
Dominant alleles may be eliminated from the population.
192
What are the characteristics of human diseases that are multifactorial?
They have both genetic and environmental components and do not follow simple Mendelian inheritance patterns.
193
What is the phenotype of an organism with a recessive trait?
Homozygous recessive genotype.
194
What does the term 'true-breeding' indicate regarding genotype?
The organism is homozygous for the trait.
195
What is the representation of dominant and recessive alleles?
Dominant allele is represented by uppercase letters and recessive allele by lowercase letters.
196
What are the possible genotypes for a dominant phenotype?
Homozygous dominant (PP) or heterozygous (Pp).
197
What genotype corresponds to a recessive phenotype?
Homozygous recessive (pp).
198
What does 'true-breeding' indicate about a genotype?
The genotype is homozygous.
199
How should a genetic cross be formatted?
[genotype] x [genotype].
200
What is the purpose of a Punnett square?
To determine the outcome of a genetic cross.
201
How do you set up a Punnett square?
Place the gametes of one parent at the top and those of the other on the left.
202
How many types of gametes can an individual with genotype AaBbCc produce?
8 types of gametes.
203
What is the expected number of different offspring from a cross of AaBbCc x AaBbCc?
64 different offspring.
204
What method can be used instead of a Punnett square for large crosses?
Use the rules of probability.
205
If the phenotypic ratio of offspring is 1:1, what does that indicate about the parents' genotypes?
The cross was between a heterozygote and a homozygous recessive.
206
What phenotypic ratio indicates that both parents are heterozygous?
3:1 ratio.
207
What ratio suggests that each parent is heterozygous for both genes?
9:3:3:1 ratio.
208
If both parents have a trait but their offspring do not, what can be inferred?
The trait must be recessive and the parents are both carriers.
209
What should you do first when analyzing a pedigree?
Label the genotypes of all known family members.
210
What is the probability of a child being normal if both parents are carriers of hemochromatosis?
Varies based on the specific outcomes considered.
211
In a tetrahybrid cross, what is the genotype of F1 individuals?
AaBbCcDd.
212
What is the probability of obtaining the genotype aabbccdd from AaBbCcDd?
1/256.
213
What is the expected phenotypic ratio when crossing heterozygous plants at two loci?
9:3:3:1.
214
What is the inheritance pattern of alkaptonuria?
Caused by a recessive allele.
215
How can you determine if a curl allele is dominant or recessive?
By performing a test cross.
216
What is the probability that Charles and Elaine will have a baby with cystic fibrosis?
Depends on the genotypes of Charles and Elaine.
217
What might be the effect of marrying later in life on late-acting dominant lethal alleles?
Increased frequency in the population.
218
What is the role of DNA in the continuity of life?
It carries heritable information ensuring trait perpetuation and variation.
219
What are alleles?
Alternative versions of a gene.
220
What is the phenotype of an organism?
Observable traits of an organism.
221
What is the genotype of an organism?
Genetic makeup of an organism.
222
What is a homozygote?
An organism with a pair of identical alleles for a gene.
223
What is a heterozygote?
An organism that has two different alleles for a gene.
224
What does Mendel's law of segregation state?
Alleles for a trait segregate into gametes such that half receive one allele and half receive the other.
225
What is a Punnett square used for?
To predict the genetic combinations of offspring from a cross.
226
Fill in the blank: In a testcross, an organism with an unknown genotype is crossed with a _______.
Homozygous individual expressing the recessive trait.
227
What is the expected phenotypic ratio in the F2 generation from a monohybrid cross?
3:1 ratio.
228
What are the two types of phenotypes for the flower color in pea plants?
* Purple flowers * White flowers
229
How can you determine if a purple-flowered plant is homozygous or heterozygous?
By performing a testcross with a white-flowered plant.
230
What is the expected phenotypic ratio from a dihybrid cross?
9:3:3:1 ratio.
231
True or False: A homozygous plant produces gametes with different alleles.
False.
232
What is meant by the term 'self-pollination'?
Pollination where an organism fertilizes itself.
233
What does it mean for an allele to be dominant?
It expresses its trait even if only one copy is present.
234
What does it mean for an allele to be recessive?
It expresses its trait only when two copies are present.
235
What is a monohybrid cross?
A cross between individuals that differ in one character.
236
What is the significance of Mendel's experiments?
They established the basic principles of inheritance.
237
What is the purpose of a testcross?
To reveal the genotype of an organism showing a dominant trait.
238
What are the four classes of gametes produced by dihybrid F1 plants?
* YR * Yr * yR * yr
239
Fill in the blank: An organism that has two different alleles for a gene is said to be _______.
Heterozygous.
240
What does the term 'breeding true' mean?
Homozygous plants produce offspring with the same traits.
241
What is the genotype of the F1 plants that exhibit yellow seeds with round shapes?
YyRr
242
What phenotypic ratio is observed in the F2 generation from Mendel's dihybrid experiments?
9:3:3:1
243
What does the law of independent assortment state?
Two or more genes assort independently during gamete formation.
244
Under what conditions does the law of independent assortment apply?
To genes located on different chromosomes or genes that are very far apart on the same chromosome.
245
What character traits did Mendel analyze in his pea plants?
Seed color, seed shape, and pod shape
246
Fill in the blank: Self-pollination is considered _______ reproduction.
sexual
247
How many offspring would be predicted to have terminal flowers and be dwarf from a cross of AaTt plants?
100
248
What is the probability of obtaining a heterozygous F2 plant from a monohybrid cross?
1/2
249
What are the two rules of probability mentioned for predicting genetic outcomes?
Multiplication rule and addition rule
250
True or False: The outcome of one coin toss affects the outcome of another toss.
False
251
What is the probability of both coins landing heads up when tossed simultaneously?
1/4
252
What is the probability of an F2 plant having wrinkled seeds (rr) in a monohybrid cross?
1/4
253
How do you calculate the probability of two independent events occurring together?
By multiplying their individual probabilities.
254
What would be the predicted offspring genotype of a trihybrid cross involving three characters?
Multiple combinations of dominant and recessive alleles
255
List the possible gametes produced by a pea plant heterozygous for seed color, seed shape, and pod shape (YyRr).
* YR
* Yr
* yR
* yr
256
What fraction of offspring from a cross of PpYyRr x ppyyrr are predicted to be homozygous recessive for at least two characters?
To be determined by probability calculations.
257
What is the expected proportion of homozygous dominant, homozygous recessive, and heterozygous offspring from an AA x Aa cross?
* Homozygous dominant: 1/2
* Homozygous recessive: 0
* Heterozygous: 1/2
258
What is the cross in the example given?
PpYyRr x Ppyyrr
259
What fraction of offspring from the cross is predicted to exhibit the recessive phenotypes for at least two of the three characters?
6/16 or 3/8
260
What is the term for the phenomenon where neither allele is completely dominant?
incomplete dominance
261
What is an example of incomplete dominance in flowers?
Red and white snapdragons produce pink flowers
262
How is the genotypic and phenotypic ratio for the F2 generation of snapdragons?
1:2:1
263
What is codominance?
When two alleles each affect the phenotype in distinguishable ways
264
What is an example of codominance in humans?
MN blood group
265
What does the term pleiotropy refer to?
A gene affecting multiple phenotypic characters
266
What is an example of a pleiotropic condition in humans?
Cystic fibrosis
267
What is epistasis?
When the phenotypic expression of a gene at one locus alters that of a gene at a second locus
268
In Labrador retrievers, what is the effect of the E gene?
Determines whether pigment will be deposited in the hair
269
What coat color results from a genotype of bb in Labrador retrievers?
Brown (chocolate) coat color
270
What coat color results when a Labrador is homozygous recessive for the E gene (ee)?
Yellow coat color
271
What is the relationship between dominant and recessive alleles?
Dominance is observed in phenotype, not due to interaction at the genotype level
272
Fill in the blank: The ABO blood groups are determined by multiple alleles, specifically _______.
IA, IB, and i
273
True or False: The recessive allele is always more common than the dominant allele.
False
274
What is the significance of the rules of probability in genetics?
They provide likelihood of various outcomes in genetic crosses
275
What is the importance of sample size in genetic predictions?
Larger sample sizes yield results closer to predictions
276
What is the expected phenotype ratio of offspring from a cross exhibiting incomplete dominance?
1 red: 2 pink: 1 white
277
What do heterozygotes produce in terms of enzyme molecules in Tay-Sachs disease?
Equal numbers of normal and dysfunctional enzyme molecules
278
What is an example of a character determined by one gene with two alleles?
Pea plant flower color
279
What is the typical outcome when F1 hybrids from incomplete dominance are interbred?
F2 generation with a 1:2:1 ratio
280
What are the two main situations involving multiple genes in determining a phenotype?
* Epistasis * Polygenic inheritance
281
What is the expected phenotypic ratio among F2 offspring of black Labs that are heterozygous for both genes?
9 black : 3 chocolate : 4 yellow
## Footnote
This ratio results from epistasis and represents a modification of the 9:3:3:1 ratio seen in Mendel's experiments.
282
What are quantitative characters?
Traits that vary in the population in gradations along a continuum
## Footnote
Examples include human skin color and height.
283
What is polygenic inheritance?
An additive effect of two or more genes on a single phenotypic character
## Footnote
This contrasts with pleiotropy, where one gene affects several characters.
284
How many genetic variations were found to affect height in a 2014 study?
Almost 700 genetic variations in over 180 genes
## Footnote
These variations were linked to genes involved in growth and other factors.
285
What is the total number of genes identified that affect human skin pigmentation?
378 genes
## Footnote
Many of these genes are involved in melanin production.
286
Fill in the blank: An individual with the genotype AABbcc would be very _______.
dark
## Footnote
This is based on a simplified model of polygenic inheritance.
287
What does the term multifactorial mean in genetics?
Many factors, both genetic and environmental, collectively influence phenotype.
288
What is the phenotypic ratio resulting from matings between AaBbCc heterozygotes?
1:6:15:20:15:6:1
## Footnote
This ratio reflects the cumulative effect of dark-skin alleles.
289
True or False: Environmental factors do not influence phenotypic expression.
False
## Footnote
Environmental conditions can significantly alter phenotypic outcomes.
290
What does a histogram show in the context of genetic data?
The distribution of numeric data, such as the number of dark-skin alleles.
291
What is the significance of Mendel's laws of segregation and independent assortment?
They explain heritable variations in terms of alleles passed from parents to offspring.
292
What is the distinction between incomplete dominance and epistasis?
Incomplete dominance involves blending traits, while epistasis involves one gene masking the effect of another.
293
If a man with type AB blood marries a woman with type O blood, what blood types would you expect in their children?
A and B
## Footnote
The expected fractions would be 50% A and 50% B.
294
What would the expected offspring phenotype be from a cross between a gray rooster and a black hen based on the previous data?
Gray, black, and white chicks
## Footnote
Based on the inheritance patterns observed.
295
What is the expected phenotypic variation for polygenic traits?
Broadest for polygenic characters
## Footnote
Environmental factors contribute to this variation.
296
How does the phenotypic range differ for the ABO blood group system compared to polygenic traits?
The phenotypic range is extremely narrow for ABO blood groups.
297
What is the concept that describes how many human traits follow specific inheritance patterns?
Mendelian inheritance
## Footnote
Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which describe how traits are passed from parents to offspring through dominant and recessive alleles.
298
True or False: All human traits are determined solely by Mendelian inheritance.
False
## Footnote
While many traits follow Mendelian inheritance, many others are influenced by multiple genes and environmental factors.
299
Fill in the blank: The principles of Mendelian inheritance were established by _______.
Gregor Mendel
## Footnote
Gregor Mendel is known as the father of genetics for his work on pea plants, which led to the formulation of the laws of inheritance.
300
What are the two types of alleles that Mendelian traits can have?
* Dominant alleles
* Recessive alleles
## Footnote
Dominant alleles mask the effects of recessive alleles in heterozygous individuals.
301
What does it mean for a trait to be expressed in a phenotype?
It means the trait is observable or measurable in an organism.
## Footnote
The phenotype is the physical expression of the genetic makeup (genotype) and can be influenced by environmental factors.
302
What is a genotype?
The genetic constitution of an individual.
## Footnote
The genotype determines the potential traits that an organism can express, but not all traits may be visible in the phenotype.
