Chapter 5 - Pedigrees and Populations Flashcards
(325 cards)
1
Q
What are pedigrees?
A
Family trees that track the inheritance of traits across generations.
2
Q
What do pedigrees help identify?
A
Whether a trait is autosomal or sex-linked.
3
Q
Define dominant traits in genetics.
A
Traits that show with one copy of the allele.
4
Q
Define recessive traits in genetics.
A
Traits that require two copies of the allele.
5
Q
What can be inferred by examining the pattern of traits in a pedigree?
A
The mode of inheritance.
6
Q
What is an example of a mode of inheritance?
A
X-linked recessive.
7
Q
How do pedigrees assist in genetic counseling?
A
They help determine the probability that an individual carries or expresses a trait.
8
Q
What is Hardy-Weinberg equilibrium (HWE)?
A
A state where allele and genotype frequencies do not change across generations.
9
Q
What assumptions are made in Hardy-Weinberg equilibrium?
A
No evolutionary forces are acting on the gene pool.
10
Q
What is the first condition for Hardy-Weinberg Equilibrium?
A
Random mating.
11
Q
What does βno mutationβ mean in the context of Hardy-Weinberg equilibrium?
A
DNA does not change.
12
Q
What does βno migrationβ imply for Hardy-Weinberg equilibrium?
A
No new alleles enter or leave the population.
13
Q
What is meant by βno selectionβ in Hardy-Weinberg equilibrium?
A
All genotypes have equal chance of survival/reproduction.
14
Q
What is the significance of βno genetic driftβ?
A
The population is large enough to avoid random changes.
15
Q
What is the Hardy-Weinberg formula?
A
πΒ² + 2ππ + πΒ² = 1 and π + π = 1.
16
Q
What does πΒ² represent in the Hardy-Weinberg formula?
A
Homozygous dominant genotype frequency.
17
Q
What does 2ππ represent in the Hardy-Weinberg formula?
A
Heterozygous genotype frequency.
18
Q
What does πΒ² represent in the Hardy-Weinberg formula?
A
Homozygous recessive genotype frequency.
19
Q
What do π and π represent in the Hardy-Weinberg formula?
A
Allele frequencies.
20
Q
Why is the Hardy-Weinberg formula useful?
A
It allows predicting allele/genotype frequencies from limited data.
21
Q
Fill in the blank: In Hardy-Weinberg equilibrium, allele and genotype frequencies do not change across _______.
A
generations.
22
Q
What is a pedigree analysis used for?
A
To determine the inheritance mode (autosomal or sex-linked, dominant or recessive) of a trait across generations.
23
Q
How can pedigrees be used if the mode of inheritance is known?
A
To calculate the probability of inheritance for specific genotypes in individuals.
24
Q
What is Hardy-Weinberg equilibrium?
A
A state where allele and genotype frequencies remain constant across generations in an ideal population.
25
What are the 5 conditions required for Hardy-Weinberg equilibrium?
* Random mating
* No mutation
* No migration
* No natural selection
* Large population size (no genetic drift)
26
What is the Hardy-Weinberg equation?
pΒ² + 2pq + qΒ² = 1 and p + q = 1
27
In the Hardy-Weinberg equation, what does 2pq represent?
The frequency of heterozygous individuals in the population.
28
What can the Hardy-Weinberg formula estimate with limited population data?
Allele and genotype frequencies.
29
What happens if any of the Hardy-Weinberg conditions are violated?
The population may evolve, and allele frequencies will change.
30
What is a pedigree chart?
A diagram that shows family relationships and the inheritance of specific traits across generations.
31
What is meant by the mode of inheritance?
The way a genetic trait or disorder is passed from one generation to the next (e.g., autosomal dominant, X-linked recessive).
32
What is genetic counseling?
A process where individuals receive information about genetic conditions, inheritance risks, and testing options.
33
What is incomplete penetrance?
When individuals carry a disease-causing allele but do not express the associated trait.
34
What is variable expressivity?
When individuals with the same genotype show different degrees or types of phenotype.
35
Who is the proband?
The first affected family member who seeks medical attention for a genetic disorder.
36
What does it mean if someone is affected?
They show signs or symptoms of a genetic trait or disorder.
37
What is a carrier?
A person who carries one copy of a recessive allele but does not exhibit symptoms.
38
What is autosomal dominant inheritance?
A trait that appears when only one copy of a mutant allele on a non-sex chromosome is present.
39
What is autosomal recessive inheritance?
A trait that appears only when two copies of a mutant allele on a non-sex chromosome are present.
40
What is X-linked dominant inheritance?
A dominant trait carried on the X chromosome that affects both sexes, but more severely in females.
41
What is X-linked recessive inheritance?
A recessive trait carried on the X chromosome, often seen in males who inherit only one X chromosome.
42
What is Y-linked inheritance?
A trait carried on the Y chromosome and passed from father to son only.
43
What does Y-linked mean?
Refers to genes found only on the Y chromosome.
44
What is mitochondrial inheritance (mtDNA)?
Inheritance of genes from mitochondrial DNA, which is passed from mother to all offspring.
45
What does sporadic mean in genetics?
A condition that arises by chance, not inherited from parents.
46
What is the product rule in probability?
The probability of two independent events both occurring is the product of their individual probabilities.
47
What is the sum rule in probability?
The probability of either of two mutually exclusive events occurring is the sum of their individual probabilities.
48
What is a population in genetics?
A group of interbreeding individuals sharing a common gene pool.
49
What does p + q = 1 represent?
The total frequency of the two alleles (dominant p and recessive q) in a population.
50
What is the Hardy-Weinberg formula?
pΒ² + 2pq + qΒ² = 1, representing genotype frequencies under equilibrium.
51
What does Hardy-Weinberg equilibrium describe?
A stable distribution of allele and genotype frequencies in a population not affected by evolutionary forces.
52
What is assortative mating?
Non-random mating where individuals with similar traits are more likely to mate.
53
What is random mating?
Mating that occurs by chance, not influenced by genotype or phenotype.
54
What is migration in population genetics?
The movement of individuals and their genes into or out of a population.
55
What is genetic drift?
Random changes in allele frequencies due to chance, especially in small populations.
56
What is the purpose of controlled crosses in genetics?
To identify how traits are inherited
## Footnote
Controlled crosses can be performed in organisms like pea plants or fruit flies but not in humans due to ethical restrictions.
57
What methods do geneticists use to study inheritance in humans?
Pedigree analysis and population studies
## Footnote
These methods help trace gene inheritance across generations and predict trait probabilities.
58
What is a pedigree?
A family tree that tracks the inheritance of traits
## Footnote
Circles represent females, squares represent males, and shaded shapes indicate affected individuals.
59
What do shaded shapes in a pedigree represent?
Affected individuals
## Footnote
This visual representation helps identify dominant, recessive, autosomal, or sex-linked inheritance.
60
What is a population in genetics?
A group of interbreeding individuals
## Footnote
Population studies help determine the commonality of certain alleles.
61
What formula is commonly used in population studies?
Hardy-Weinberg formula
## Footnote
This formula helps understand how genes behave in large groups over time.
62
What does an X-ray image of a hand typically indicate in genetics?
A genetic condition affecting bone development
## Footnote
An example is polydactyly, which involves having extra fingers.
63
How can inherited traits in humans be analyzed?
Via observation of families and populations
## Footnote
Unlike other organisms, test crosses cannot be conducted in humans.
64
Fill in the blank: A pedigree helps to reveal _______ inheritance.
Dominant, recessive, autosomal, or sex-linked
65
True or False: Population studies can help predict the probability of traits appearing in offspring.
True
66
Why canβt geneticists perform controlled matings in humans?
Due to ethical and practical limitations.
## Footnote
Ethical considerations prevent manipulation of human genetics in controlled mating scenarios.
67
What is a pedigree in genetics?
A chart showing family relationships and the inheritance of traits.
## Footnote
Pedigrees are crucial for visualizing genetic connections and trait transmission.
68
Why are pedigrees useful?
They help identify inheritance patterns like autosomal or sex-linked, dominant or recessive.
## Footnote
Understanding these patterns assists in predicting genetic disorders.
69
What is population genetics?
The study of gene distribution and changes within a population over time.
## Footnote
This field helps in understanding evolutionary processes and genetic diversity.
70
Why do geneticists study populations?
To estimate allele frequencies and understand genetic traits at a group level.
## Footnote
Population studies provide insights into the genetic health of populations.
71
What does the X-ray image of a hand in this section likely represent?
A visible inherited trait (like polydactyly) used to demonstrate how traits are passed without controlled experiments.
## Footnote
Such images can illustrate genetic variations that arise naturally.
72
What two tools are used when controlled mating is not possible?
Pedigree analysis and population genetics.
## Footnote
These tools allow for genetic assessment without direct manipulation of mating.
73
What are Pedigree Charts?
Diagrams that show how traits (especially diseases) are inherited across generations of a family
## Footnote
They map the phenotypes and sometimes genotypes of individuals.
74
What is the primary purpose of Pedigree Analysis?
To determine the mode of inheritance, predict the probability of offspring inheriting a disease, and analyze carrier status
## Footnote
This includes examining penetrance and family history of traits.
75
What is Genetic Counseling in the context of Pedigree Analysis?
The use of pedigree information to inform individuals about inherited risks
## Footnote
It helps families understand potential genetic disorders.
76
Define Mode of Inheritance.
How a trait is passed down (e.g., dominant/recessive, autosomal/sex-linked)
## Footnote
This determines how traits are transmitted through generations.
77
What does Incomplete Penetrance mean?
When someone has the gene but does not express the trait
## Footnote
They appear normal even though genetically affected.
78
Explain Variable Expressivity.
The severity or manner in which a trait is expressed varies between individuals
## Footnote
This can lead to different phenotypes in affected individuals.
79
Who is a Proband?
The first person in a family who brings a genetic disorder to attention
## Footnote
They are often the starting point for pedigree analysis.
80
What does 'Affected' mean in pedigree terms?
Someone who shows symptoms of the disease
## Footnote
Their symbol is completely filled in.
81
Define a Carrier in genetics.
A heterozygous individual who doesnβt show symptoms but can pass the trait
## Footnote
Often symbolized with a half-filled shape.
82
What symbol represents a female in Pedigree Charts?
Circle
## Footnote
This symbol helps quickly identify female individuals in the chart.
83
What symbol represents a male in Pedigree Charts?
Square
## Footnote
This symbol helps quickly identify male individuals in the chart.
84
What does a filled-in symbol indicate in a Pedigree Chart?
Affected
## Footnote
It signifies individuals who show symptoms of the disease.
85
What does a half-filled symbol represent in Pedigree Charts?
Carrier
## Footnote
It is sometimes used to indicate individuals who carry the trait without showing symptoms.
86
What does a diamond symbol indicate in Pedigree Charts?
Sex unknown
## Footnote
This symbol is used when the sex of the individual is not determined.
87
What does a double line signify in Pedigree Charts?
Consanguineous mating
## Footnote
It indicates mating between relatives.
88
What does a vertical line downward represent in Pedigree Charts?
Offspring
## Footnote
It shows the direct descendants of the individuals connected by a mating line.
89
What does a horizontal line between siblings indicate in Pedigree Charts?
Siblings
## Footnote
It connects brothers and sisters in the pedigree.
90
What is a pedigree chart used for?
To track the inheritance of genetic traits or diseases across generations.
## Footnote
Pedigree charts are essential tools in genetics for visualizing family relationships and trait transmission.
91
What is the purpose of pedigree analysis?
To determine inheritance patterns and calculate the probability of a trait appearing in offspring.
## Footnote
Pedigree analysis helps in understanding how traits are passed down through generations.
92
What is a proband?
The first person in a family to be identified with a genetic disorder and studied.
## Footnote
The proband serves as a starting point in pedigree analysis.
93
What symbol represents a female in a pedigree chart?
A circle.
## Footnote
This convention is widely accepted in genetic diagrams.
94
What symbol represents a male in a pedigree chart?
A square.
## Footnote
Males and females are visually differentiated in pedigree charts for clarity.
95
What does a filled-in symbol indicate in a pedigree chart?
The individual is affected by the trait.
## Footnote
Filled symbols clearly denote individuals with the condition being studied.
96
What does a half-filled symbol represent (when used)?
A carrier of the trait, usually heterozygous and unaffected.
## Footnote
This representation helps identify carriers in the family.
97
What is incomplete penetrance?
When an individual has the genotype for a trait but does not show the phenotype.
## Footnote
This concept highlights the complexity of genetic expression.
98
What is variable expressivity?
When the trait is expressed differently among individuals with the same genotype.
## Footnote
Variable expressivity can lead to a range of phenotypes in genetically identical individuals.
99
What does a double horizontal line between partners in a pedigree represent?
A consanguineous mating (mating between relatives).
## Footnote
This notation is crucial for understanding genetic risks associated with inbreeding.
100
Why are pedigrees important in human genetics?
Because controlled mating is not possible, pedigrees are used to infer inheritance patterns and risks.
## Footnote
They provide insights into genetic disorders in the absence of experimental breeding.
101
What does 'genetic counseling' involve in the context of pedigrees?
Using pedigree analysis to inform individuals about genetic risks and probabilities.
## Footnote
Genetic counseling is essential for families with hereditary conditions.
102
What is the first task when studying a pedigree of a disease or trait?
List all possible inheritance modes and identify which is most likely based on the pattern of affected individuals in the pedigree.
103
Why is inferring the mode of inheritance crucial?
It helps estimate the likelihood that future children will inherit the trait and aids in making clinical decisions and providing genetic counseling.
104
What does Autosomal Dominant inheritance mean?
One copy of the allele on a non-sex chromosome causes the trait and affects both sexes equally.
105
What is required for Autosomal Recessive inheritance?
Two copies of the allele on a non-sex chromosome are needed, and carriers are unaffected.
106
How does X-linked Dominant inheritance typically manifest?
One copy of the allele on the X chromosome causes the trait, often affecting more females.
107
What is the inheritance pattern for X-linked Recessive traits?
Two copies in females or one in males (XY) causes the trait, mostly affecting males.
108
Who is affected by Y-linked inheritance?
Only males are affected, as it is passed from father to son.
109
What is the significance of looking for sex bias in pedigree analysis?
It helps determine whether more males or females are affected, which can indicate the mode of inheritance.
110
What does checking transmission in pedigree analysis help rule out?
It helps rule out X-linked inheritance if fathers can pass the trait to sons.
111
In terms of dominance, what does it indicate if every affected person has an affected parent?
It suggests a dominant inheritance pattern.
112
What does it imply if traits skip generations in a pedigree?
It suggests a recessive inheritance pattern.
113
What is the first task when analyzing a pedigree with an unknown trait?
To determine which modes of inheritance are possible and most likely.
114
Why is identifying the mode of inheritance important?
It helps predict the probability of the trait appearing in future offspring.
115
What does AD stand for in inheritance?
Autosomal Dominant.
116
What does AR stand for in inheritance?
Autosomal Recessive.
117
What does XD stand for?
X-linked Dominant.
118
What does XR stand for?
X-linked Recessive.
119
What does Y-linked inheritance affect?
Only males, and it is passed from father to son.
120
What pattern in a pedigree suggests autosomal recessive inheritance?
The trait often skips generations and appears in siblings of unaffected parents.
121
What pattern suggests X-linked recessive inheritance?
Mostly males are affected; females are typically carriers.
122
Can fathers transmit X-linked traits to their sons?
No, because fathers pass Y chromosomes to sons, not X.
123
What is an autosomal dominant disease?
A disease caused by inheriting just one copy of a dominant allele located on an autosome.
124
How many mutated genes are needed to be affected by an autosomal dominant disease?
One mutated gene from either parent.
125
What does complete penetrance imply in autosomal dominant inheritance?
Every individual with the gene shows the trait.
126
What is a key feature of the inheritance pattern of autosomal dominant diseases?
Vertical transmission seen in every generation.
127
In autosomal dominant inheritance, how many parents of an affected individual are typically affected?
At least one parent is also affected.
128
Is the frequency of autosomal dominant diseases equal in males and females?
Yes, since the gene is autosomal.
129
Why are affected individuals typically heterozygous in autosomal dominant conditions?
Because the condition is rare, making it unlikely that both parents carry the same rare dominant condition.
130
Can unaffected individuals pass the trait to their offspring in autosomal dominant inheritance?
No, unaffected individuals do not pass the trait.
131
If an affected person is heterozygous, what is the chance of their children inheriting the condition?
50% chance.
132
Is it possible for an affected parent to have no affected children?
Yes, purely by chance.
133
In what type of families is the chance of an affected parent having no affected children higher?
In small families.
134
Name an example of an autosomal dominant condition.
* Achondroplastic dwarfism
* Polydactyly
135
What are pedigree clues for autosomal dominant conditions?
Affected individuals appear in every generation.
136
In autosomal dominant inheritance, which genders can be affected?
Both males and females.
137
What is the significance of skipping generations in autosomal dominant conditions?
No skipping of generations unless there's incomplete penetrance.
138
What causes an autosomal dominant disease?
A single copy of a dominant allele on a non-sex chromosome (autosome).
139
What does 'complete penetrance' mean in autosomal dominant traits?
Everyone with the allele shows the trait.
140
What is a hallmark of AD inheritance in a pedigree?
The disease appears in every generation (vertical inheritance).
141
Can an unaffected person pass on an autosomal dominant trait?
No, only affected individuals pass it on.
142
What is the probability that a heterozygous affected parent will pass on an AD allele?
50%.
143
Are AD traits more common in males or females?
Neither β both are equally affected.
144
Why are most AD individuals heterozygous?
Because the trait is rare, and two people with the same rare dominant condition are unlikely to mate.
145
Name two examples of human conditions with AD inheritance.
Achondroplastic dwarfism and polydactyly.
146
Can an affected individual have all unaffected children in an AD pedigree?
Yes, especially if they are heterozygous and chance favors inheritance of the normal allele.
147
What is XD Inheritance?
A gene causing the trait or disease is located on the X chromosome.
## Footnote
XD stands for X-linked Dominant.
148
How does the disease-causing allele behave in XD inheritance?
The disease-causing allele is dominant over the normal allele in females.
## Footnote
Only one copy of the mutant allele is needed for expression in both males and females.
149
Why do females and males experience XD inheritance differently?
Females (XX) can be heterozygous or homozygous for the dominant allele, while males (XY) have only one X chromosome.
## Footnote
A single disease-causing allele in males always results in the trait.
150
What is a key feature of the inheritance pattern in XD inheritance?
More females than males are typically affected.
## Footnote
This is because females have double the chance of inheriting the mutant X.
151
Is there father-to-son transmission in XD inheritance?
No, sons inherit their Y chromosome from their father, not X.
## Footnote
This is a defining characteristic of X-linked inheritance.
152
What happens when an affected male has children?
An affected male passes the mutant X to all his daughters, who will all be affected.
## Footnote
Sons do not inherit the X chromosome from their father.
153
What is the chance of an affected female passing the trait to her children?
Each child of an affected female has a 50% chance of inheriting the trait, regardless of sex.
## Footnote
This applies to both sons and daughters.
154
What diagnostic clue indicates that inheritance cannot be XD?
If a father passes a disease to his son, the inheritance cannot be XD.
## Footnote
This would suggest autosomal dominant (AD) instead.
155
Give a real-life example of a condition inherited in an XD pattern.
Some forms of rickets are inherited in an XD pattern.
## Footnote
This highlights the practical implications of XD inheritance.
156
What are the pedigree features of XD inheritance?
Both sexes affected, tends to affect more females than males.
## Footnote
Affected males do not pass the trait to sons, but all daughters are affected.
157
Where is the gene located in X-linked dominant inheritance?
On the X chromosome.
158
How many copies of the dominant allele are needed to express an XD trait in males?
One copy.
159
How many copies are needed for expression in females?
One copy (either heterozygous or homozygous).
160
Can a father pass an X-linked dominant trait to his son?
No β sons inherit the Y chromosome from their father.
161
What happens when a male with an XD trait has children?
All his daughters will be affected; sons will not inherit the trait.
162
Who is more likely to be affected in an XD pedigree, males or females?
Females β because they have two X chromosomes.
163
What pattern of inheritance eliminates XD as a possibility?
When a father passes the disease to his son.
164
What real-world disease might follow an XD inheritance?
Some forms of rickets.
165
What is AR Inheritance?
In autosomal recessive inheritance, a person must inherit two copies of a disease-causing allele (one from each parent) to be affected.
## Footnote
The gene is located on an autosome (non-sex chromosome).
166
What characterizes a carrier in AR Inheritance?
A carrier has one copy of the mutation but does not show symptoms.
167
What is a common feature of the parents of an affected individual in AR Inheritance?
Both parents of an affected individual are usually unaffected carriers.
168
In AR Inheritance, how does the inheritance pattern affect males and females?
Equal frequency in males and females.
169
Can unaffected parents have affected children in AR Inheritance?
Yes, unaffected parents can have affected children (a hallmark of AR).
170
What does it mean when a trait 'skips generations' in AR Inheritance?
The trait often 'skips generations'.
171
What is more likely in a pedigree for AR conditions?
More individuals in a pedigree are likely to be carriers than affected.
172
Why are AR conditions often rare?
AR conditions are often rare, so mating between carriers is more likely in consanguineous relationships (relatives).
173
Give an example of a disorder inherited in an autosomal recessive manner.
Phenylketonuria (PKU).
174
What is tested for in newborns related to AR Inheritance?
Newborns are tested at birth for PKU and other inborn errors of metabolism.
175
What are some clues in a pedigree for AR Inheritance?
Affected children from two unaffected parents; disease may seem to 'disappear' for generations; both sexes equally affected; horizontal pattern (affected siblings).
176
How many copies of the mutant allele are needed for AR disease expression?
Two copies β one from each parent.
177
Can two unaffected parents have an affected child in AR inheritance?
Yes, if both are carriers.
178
What is a carrier in AR inheritance?
A person with one mutant and one normal allele, showing no symptoms but able to pass the trait.
179
Does AR affect males and females equally?
Yes, because the gene is on a non-sex chromosome.
180
What is a common feature of AR pedigrees?
The trait may skip generations.
181
What real-world disease is inherited via AR?
Phenylketonuria (PKU).
182
Why are consanguineous matings more likely to show AR traits?
Relatives are more likely to carry the same rare allele.
183
What does the 'horizontal pattern' in AR pedigrees mean?
Multiple affected siblings in the same generation.
184
How can you distinguish AR from AD or XD in a pedigree?
In AR, unaffected parents can have affected offspring β not seen in AD or XD.
185
What is X-linked recessive inheritance?
The disease-causing gene is located on the X chromosome, and the trait is recessive.
186
Why are males more likely to be affected by X-linked recessive traits?
Males have only one X chromosome; if that X carries the mutant allele, they will express the disease.
187
What must females inherit to be affected by X-linked recessive traits?
Females must inherit two copies of the mutant allele, one from each parent.
188
How do males and females differ in their likelihood of being affected by X-linked recessive traits?
Males are affected more frequently than females; females are usually carriers.
189
What is a common way females pass on X-linked recessive traits?
Females pass the trait to their sons.
190
What is a key clue in pedigrees for X-linked recessive inheritance?
Affected males often come from carrier mothers.
191
Is there male-to-male transmission in X-linked recessive inheritance?
No, fathers give Y chromosomes to sons.
192
What rules out X-linked recessive inheritance in a pedigree?
An affected daughter from two unaffected parents rules out XR.
193
What classic example illustrates X-linked recessive inheritance?
Color blindness.
194
What test is often used to diagnose color blindness?
Ishihara plate.
195
What diagnostic insight suggests X-linked recessive inheritance is unlikely?
If a female is affected but her father is unaffected.
196
Fill in the blank: In X-linked recessive inheritance, the trait is _______.
recessive.
197
Why are males more frequently affected by XR disorders?
They have only one X chromosome β if it carries the mutant allele, they express the trait.
198
Can a female be affected by an XR disorder?
Yes, but she must inherit two mutant X chromosomes (one from each parent), which is rare.
199
What is a key clue in a pedigree that rules out XR inheritance?
An affected daughter with two unaffected parents.
200
Can fathers pass X-linked recessive traits to their sons?
No β they pass their Y chromosome to sons, not X.
201
What kind of transmission pattern is common in XR pedigrees?
Carrier mothers passing the trait to affected sons.
202
How does XR differ from AR and AD inheritance?
XR affects more males, while AR and AD affect both sexes equally.
203
What real-world condition often follows XR inheritance?
Color blindness.
204
What diagnostic tool is commonly used for color blindness?
The Ishihara Test.
205
What type of inheritance involves genes on the Y chromosome?
Y-linked inheritance
## Footnote
Y-linked inheritance is characterized by traits that are passed strictly from father to son and are only present in males.
206
Who is affected by Y-linked inheritance?
Only males are affected
## Footnote
Daughters do not inherit Y-linked traits as they do not receive a Y chromosome.
207
How is Y-linked inheritance passed on?
From father to son
## Footnote
This pattern of inheritance makes it the easiest to recognize, though it is rare due to few genes on the Y chromosome.
208
What is a real example of a Y-linked trait?
The hairy-ear-rim trait in some Indian families
## Footnote
Another example includes the Y-chromosome lineage of Genghis Khan, found in ~8% of men in parts of Asia.
209
What is Y-DNA used for?
Genealogy and evolutionary biology to trace male lineages
## Footnote
Y-DNA analysis helps in understanding ancestry and lineage.
210
What is the source of mitochondrial inheritance?
Inherited from the mother via the egg
## Footnote
Mitochondrial DNA is passed down through maternal lines.
211
Who can be affected by mitochondrial inheritance?
Both sexes can be affected
## Footnote
However, only females can pass it on to their children.
212
What can mutations in mitochondrial DNA cause?
Diseases, especially in energy-demanding tissues like muscles and nerves
## Footnote
Mitochondrial mutations can lead to various health issues.
213
What is mtDNA used for in research?
To trace maternal ancestry and evolutionary relationships
## Footnote
mtDNA is stable and shows maternal specificity, making it useful in studies.
214
Fill in the blank: Mitochondrial DNA is inherited from the _______.
mother
215
True or False: Y-linked inheritance can be passed to daughters.
False
## Footnote
Daughters do not inherit Y chromosomes, thus cannot inherit Y-linked traits.
216
Fill in the blank: The Y chromosome is present only in _______.
males
217
What is a common application of mtDNA in ecological studies?
Species identification
## Footnote
Its stability and maternal specificity make mtDNA useful for identifying species.
218
Who can be affected by Y-linked traits?
Only males.
219
How are Y-linked traits transmitted?
From father to son only.
220
Can females inherit or pass on Y-linked traits?
No, they do not have a Y chromosome.
221
What is an example of a Y-linked trait?
Hairy-ear-rim phenotype in some Indian families.
222
What makes Y-linked inheritance easy to identify?
The trait appears in all male descendants and no females.
223
What famous historical figure's Y chromosome is widely studied in genetics?
Genghis Khan.
224
Who passes on mitochondrial DNA?
The mother.
225
Can mitochondrial disorders affect both males and females?
Yes, but only females can pass them on.
226
Why donβt fathers pass on mitochondrial DNA?
Sperm mitochondria are typically not inherited; only the egg contributes mitochondria.
227
What kind of disorders are commonly linked to mitochondrial DNA mutations?
Disorders affecting high-energy systems like muscles and nerves.
228
What is mtDNA commonly used for in science?
Tracing maternal ancestry, studying evolution, and species identification.
229
What are the main contributing factors for many human diseases?
* Polygenic effects
* Environmental triggers
230
Define sporadic diseases.
Diseases that appear randomly and are not inherited from a parent.
231
What is a somatic mutation?
A mutation that occurs during a person's lifetime rather than being inherited.
232
True or False: Sporadic mutations can be passed down to the next generation.
False
233
What can mislead the perception of inherited diseases?
* Shared environmental exposure
* Coincidental onset due to non-genetic risk factors
234
What is ALS?
A neurodegenerative disorder that affects motor neurons.
235
What percentage of ALS cases follow an autosomal dominant inheritance pattern?
5β10%
236
What percentage of ALS cases are sporadic?
90β95%
237
What are the differences between inherited and sporadic ALS?
Different genes and proteins are implicated.
238
Name two historical figures known to have sporadic ALS.
* Stephen Hawking
* Lou Gehrig
239
Fill in the blank: A disease can appear to be inherited if it shows up in multiple family members due to _______.
[shared environmental exposure]
240
What is a sporadic disease?
A disease that arises from a new mutation or environmental factors, not inherited from a parent.
## Footnote
Sporadic diseases are often contrasted with inherited diseases, which are passed down through family genetics.
241
Can a sporadic disease appear in multiple family members?
Yes, due to shared environments or coincidental factors β not necessarily genetics.
## Footnote
This phenomenon can lead to confusion about the hereditary nature of the disease.
242
What are two factors that can complicate disease inheritance?
* Involvement of multiple genes
* Environmental exposures
## Footnote
These factors can make it difficult to determine the exact cause of a disease.
243
What proportion of ALS cases are inherited in an autosomal dominant pattern?
Approximately 5β10%.
## Footnote
This means that the majority of ALS cases are not inherited in this manner.
244
What proportion of ALS cases are sporadic?
About 90β95%.
## Footnote
This high percentage indicates that sporadic cases are much more common than inherited cases.
245
What causes most sporadic diseases?
Non-inherited mutations or environmental triggers.
## Footnote
These factors can include lifestyle choices, toxins, and random genetic changes.
246
Why might a disease seem inherited when itβs not?
Because multiple family members may share the same environment or toxins.
## Footnote
This can lead to a mistaken belief in a genetic link.
247
Who are two well-known people that suffered from sporadic ALS?
* Stephen Hawking
* Lou Gehrig
## Footnote
Their cases have raised awareness about the disease and its impact.
248
What is the significance of knowing a mode of inheritance in genetics?
Determines the likelihood that an individual carries a gene or will be affected by a genetic trait
## Footnote
Important for genetic counseling, predicting inheritance, and prospective parental planning.
249
What does the Product Rule (AND Rule) state?
Used when two independent events must both happen; multiply the probabilities of each event
## Footnote
Example: Probability of rolling a 5 three times is 1/6 Γ 1/6 Γ 1/6 = 1/216.
250
What does the Sum Rule (OR Rule) state?
Used when either of two events can happen; add their probabilities
## Footnote
Example: Probability of rolling a 5 or 6 is 1/6 + 1/6 = 1/3.
251
In an autosomal recessive inheritance scenario (Aa Γ Aa), what is the probability of a child being affected (aa)?
1/4
## Footnote
This is calculated as 1/2 Γ 1/2 = 1/4.
252
What are the genotype ratios for Aa Γ Aa?
1:2:1 β AA : Aa : aa
## Footnote
This indicates the proportions of different genotypes among offspring.
253
What is the phenotypic outcome of an Aa Γ Aa cross?
ΒΌ aa (affected), Β½ Aa (carriers), ΒΌ AA (unaffected non-carrier)
## Footnote
Reflects the distribution of phenotypes based on genotype ratios.
254
What is the chance that individual 6 is a carrier (Aa) given that their parents (individuals 1-4) likely are carriers?
2/3
## Footnote
Based on Mendelian ratios, excluding the homozygous recessive option (aa).
255
If individual 7 is unrelated and assumed not a carrier, what is the outcome for their children?
All children will be unaffected
## Footnote
This is based on the assumption that individual 7 does not carry the trait.
256
What is the probability that individual 12 is Aa?
1/3
## Footnote
Calculated as 2/3 Γ 1/2 = 1/3.
257
What is the combined probability that individual 14 is affected (aa)?
1/36
## Footnote
Derived from the probabilities of individuals 12 and 13 being Aa and the probability of aa from Aa Γ Aa.
258
What is the product rule in probability?
Multiply the probabilities of two independent events occurring.
## Footnote
The product rule is used when calculating the likelihood of multiple independent events happening together.
259
What is the sum rule in probability?
Add the probabilities of either of two events occurring.
## Footnote
The sum rule is applicable when considering mutually exclusive events.
260
In an Aa Γ Aa cross, what is the chance of an offspring being aa?
ΒΌ or 25%.
## Footnote
This is derived from a Punnett square analysis.
261
What is the chance that a child of two heterozygotes (Aa Γ Aa) is also a carrier (Aa)?
Β½ or 50%.
## Footnote
The possible genotypes from this cross are AA, Aa, Aa, and aa.
262
If an individualβs sibling is affected by an AR trait, what is the chance they are a carrier?
2/3 (assuming they are unaffected).
## Footnote
This is based on the assumption that the unaffected sibling has one affected parent.
263
How do you calculate the probability that a child from two carriers is affected by an AR disease?
Multiply the probability that each parent is a carrier Γ ΒΌ (from Aa Γ Aa producing aa).
## Footnote
This reflects the Mendelian inheritance pattern for autosomal recessive disorders.
264
What is the probability that individual 14 in Figure 5.4.11 is affected (aa)?
1/36.
## Footnote
This probability is calculated using the product of probabilities from the family tree analysis.
265
What is the frequency of the dominant allele represented by?
p
266
What is the frequency of the recessive allele represented by?
q
267
What is the relationship between p and q in a population?
p + q = 1
268
How many total alleles are there if the counts of genotypes are AA: 320, Aa: 160, aa: 20?
1000
269
How do you calculate the frequency of the dominant allele (p)?
p = (2 * AA + Aa) / total alleles
270
What is the formula to calculate the frequency of the recessive allele (q)?
q = (2 * aa + Aa) / total alleles
271
Calculate the frequency of the dominant allele (p) given AA: 320, Aa: 160, and total alleles: 1000.
0.8
272
Calculate the frequency of the recessive allele (q) given aa: 20, Aa: 160, and total alleles: 1000.
0.2
273
True or False: The formula q = 1 - p can be used to find the frequency of the recessive allele.
True
274
What is the genotype frequency formula for homozygous dominant (AA)?
p^2
275
What is the genotype frequency formula for heterozygous (Aa)?
2pq
276
What is the genotype frequency formula for homozygous recessive (aa)?
q^2
277
The equations for genotype frequencies are derived from which principle?
Hardy-Weinberg principle
278
What does 'p' represent in population genetics?
The frequency of the dominant allele (A).
279
What does 'q' represent in population genetics?
The frequency of the recessive allele (a).
280
What is the relationship between p and q?
p + q = 1.
281
How is the total number of alleles in a population calculated?
Multiply the number of individuals by 2 (each has 2 alleles).
282
What is the formula to calculate p using genotype frequencies?
p = (2 * (AA) + Aa) / total alleles.
283
What is the formula to calculate q using genotype frequencies?
q = (2 * (aa) + Aa) / total alleles.
284
If p = 0.8, what is q?
q = 1 β p = 0.2.
285
What genotype frequency does pΒ² represent?
The frequency of homozygous dominant individuals (AA).
286
What genotype frequency does 2pq represent?
The frequency of heterozygous individuals (Aa).
287
What genotype frequency does qΒ² represent?
The frequency of homozygous recessive individuals (aa).
288
What is the Hardy-Weinberg Formula?
πΒ² + 2ππ + πΒ² = 1
289
What does πΒ² represent in the Hardy-Weinberg Formula?
Frequency of homozygous dominant (AA)
290
What does 2ππ represent in the Hardy-Weinberg Formula?
Frequency of heterozygotes (Aa)
291
What does πΒ² represent in the Hardy-Weinberg Formula?
Frequency of homozygous recessive (aa)
292
What is the relationship between π and π in Hardy-Weinberg?
π + π = 1
293
What does π represent in the Hardy-Weinberg Formula?
Frequency of dominant allele (A)
294
What does π represent in the Hardy-Weinberg Formula?
Frequency of recessive allele (a)
295
If π = 0.8, what is π?
0.2
296
What is the frequency of homozygous dominant (AA) if π = 0.8?
0.64
297
What is the frequency of heterozygotes (Aa) if π = 0.8?
0.32
298
What is the frequency of homozygous recessive (aa) if π = 0.8?
0.04
299
What is the expected number of homozygous dominant (AA) in a population of 500 if 64% are AA?
320
300
What is Hardy-Weinberg Equilibrium?
A population where genotype frequencies stay constant across generations and allele frequencies don't change
301
What is one condition for Hardy-Weinberg Equilibrium?
Random mating
302
What is another condition for Hardy-Weinberg Equilibrium?
No natural selection
303
What is another condition for Hardy-Weinberg Equilibrium?
No migration
304
What is another condition for Hardy-Weinberg Equilibrium?
No mutation
305
What is another condition for Hardy-Weinberg Equilibrium?
Large population
306
What does deviation from Hardy-Weinberg assumptions suggest?
Evolutionary forces are acting (e.g., selection, mutation, drift)
307
If 0.04% of the population is homozygous recessive (aa), what is πΒ²?
0.0004
308
If πΒ² = 0.0004, what is π?
0.02
309
If π = 0.02, what is π?
0.98
310
What percentage of the population are carriers (Aa) if π = 0.98 and π = 0.02?
4%
311
What modes of inheritance are consistent with the pedigree?
Possible modes:
* AD (Autosomal Dominant) β Most likely
* AR (Autosomal Recessive) β If mother was a carrier and father was homozygous
* XR (X-linked Recessive) β If mother was carrier and father was affected
## Footnote
Not XD (X-linked Dominant) because a daughter inherited an unaffected allele from an affected father, which contradicts XD logic.
312
What additional data would help determine inheritance mode more clearly?
Examples:
* Whether paternal grandparents of affected individuals were affected
* If only paternal grandfather was affected, suggests XR
* Larger pedigree across multiple generations
* Genotyping or molecular testing
## Footnote
These additional data points can help clarify the mode of inheritance.
313
What's the most likely inheritance pattern in pedigree a?
AD (Autosomal Dominant)
## Footnote
Every affected individual has an affected parent and it is inherited in unrelated family lines.
314
What's the most likely inheritance pattern in pedigree b?
AR (Autosomal Recessive)
## Footnote
Affected children from unaffected parents indicate both parents are likely carriers.
315
What's the most likely inheritance pattern in pedigree c?
XR (X-linked Recessive)
## Footnote
More males affected; affected males inherit from unaffected (carrier) mothers with no male-to-male transmission.
316
What's the most likely inheritance pattern in pedigree d?
AR (Autosomal Recessive)
## Footnote
Multiple affected siblings from unaffected parents suggest AR; most affected individuals are male but no male-to-male pattern.
317
In a pedigree with a rare autosomal recessive disease, what are the genotypes of individuals aβj?
a, d, f β Affected individuals (aa)
b, c, e, g, h, i, j β Unaffected (likely AA if married in from general population)
## Footnote
Understanding genotypes in the context of pedigree analysis is crucial for genetic counseling.
318
If individual #1 is Aa (carrier), what is the chance #7 will be affected by AR disease?
1/64
## Footnote
Calculated by considering the probabilities of carriers in the preceding generations.
319
Given qΒ² = 0.01, calculate q (recessive allele frequency).
0.1
## Footnote
Calculated as β0.01.
320
Given qΒ² = 0.01, calculate p (dominant allele frequency).
0.9
## Footnote
Derived from the equation p = 1 - q.
321
Given qΒ² = 0.01, calculate 2pq (heterozygote frequency).
0.18
## Footnote
Calculated as 2(0.9)(0.1).
322
Given qΒ² = 0.01, calculate pΒ² (homozygous dominant).
0.81
## Footnote
Calculated as (0.9)Β².
323
Is the population in Hardy-Weinberg Equilibrium?
Not in Hardy-Weinberg Equilibrium
## Footnote
Observed genotypes do not match expected frequencies.
324
What are the expected frequencies if AA = 432 out of 1200?
Expected:
* AA = 432
* Aa = 576
* aa = 192
## Footnote
These values are derived from Hardy-Weinberg principles.
325
Why is this population not in Hardy-Weinberg Equilibrium?
Excess heterozygotes and fewer recessive homozygotes
## Footnote
This could be due to selection pressure against homozygous recessives or heterozygote advantage.
