BMD440: Human Genetics Exam II - Discussion Board Questions

T/F: Melanin protects against DNA damage from UV radiation, and exposure to the sun increases melanin synthesis

True

Which of the following statements about predicting the recurrence of a single-gene trait is true?

Mendel's laws cannot be used to predict the risk of recurrence

Which of the following is not caused by Wnt4 mutations?

Determined to be heterogametic sex at birth

A family with a history of early sleep onset is examined. Which of the following statements regarding the involvement of the Period 2 (PER2) gene in Familial Advanced Sleep Phase Syndrome (FASPS) is most accurate?

Mutation is the Per2 gene can lead to altered circadian rhythms, contributing to the early sleep onset observed in individuals with FASPS

Mutations in Wnt4 can cause the following characteristics EXCEPT:

Growth and formation of mammary gland

A population of chickens exhibits a sex-limited trait toward males. A researcher wants to understand the inheritance pattern of this trait. If a male chicken with the trait is crossed with a female without the trait, what would be the expected outcome?

Only male offspring will express the feather color trait

T/F: Height is not a polygenic trait

False

During the process of DNA repair, a cell may utilize the mechanism of homologous recombination to correct a double-strand break. Which of the following scenarios best illustrates the principle of homologous recombination?

A DNA segment from a sister chromatid is used as a template to repair a double-strand break in the damaged chromatid, resulting in an exact copy of the original sequence.

The presence of the ABO blood type is explained by what genetic phenomenon?

Codominance

A patient presents to the clinic complaining of being unable to sleep at regular times. They are always lethargic, irritable, and their decision making ability is substantially decreased. What could be the cause of these complaints?

They have DNA base mutation of the Period 2 gene on chromosome 2

In a family, not every generation has had cystic fibrosis since some individuals have been carriers. Both males and females have been equally affected by this disease. What does this indicate about cystic fibrosis?

Cystic fibrosis is an autosomal recessive disease

T/F: Polygenic traits often produce an all-or-none effect

False

T/F: Empiric risk decreases with disease severity, number of affected family members, and how closely related a person is with the affected person

False

Suzy has an appointment with her genetic counselor about the inheritance of her disorder Central Precocious Puberty. Suzy was informed that this disorder is always inherited from the father and does not skip generations. What type of disorder would this be?

Autosomal dominant

Of the following, which of these situations would MOST increase the risk of recessive allele expression?

Consanguinity

A new drug is being released targeting neurotransmitters in patients with depression, based on what we know about clinical depression, which of the following would be the most effective mechanism?

Target transcription factors for DNA that lead to a higher neurotransmitter expression, increasing neuronal concentration of Serotonin

Bob, a 38-year-old man, goes to the local geneticist in order to further understand the genetics in his family. Everyone in his family has flowing, curly hair except him, who is bald. Further genetic analysis reveals that Bob has a the same gene for good hair as his family, however, he also has a gene that encodes for baldness. Although he has normal hair genes similar to his family, the secondary gene "overpowers" the first gene. What phenomenon is being described here?

Epistasis

T/F: Purely polygenic traits, those that are not affected at all by the environment, are extremely common in nature

False

The heritability for clubfoot is 0.8. What does this mean?

The trait for clubfoot is mostly the result of gene action, but environmental factors could also contribute a little bit

5% of the Y chromosome is known as what? Hint: it contains 63 genes shared with the X chromosome

Pseudoautosomal regions (PAR1 and PAR2)

In a certain species of alien, two genes are known to affect whether or not they have wings. Having the dominant A trait means that the aliens will have wings. However, it has also been observed that those who have two recessive copies of the B gene will not have wings, even if their genotype shows that they have a copy of the dominant A trait. What kind of interaction is being described here?

Epistasis

Scientists are investigating 3 genes located on the same chromosome. They have found that the recombination between X and Y is 0.3, between Y and Z is 0.4, and that between X and Z is 0.1. What is the sequence of these three genes on the chromosome?

Z X Y (or Y X Z)

Femaleness is considered the ____ option.

Default

A couple has recently adopted a 6 month-old boy. They already have a 2 year-old boy. The difference in phenotype between the two children as they grow up will be mostly affected by the ________.

Genetics

Paul is scared of growing up because his dad, uncle, grandpa, and great-grandfather all have pattern baldness. Paul is in genetics right now and learned that pattern baldness is genetic and that the allele is dominant in one sex and recessive in the other. What kind of genetic inheritance is this?

Sex-Limited Traits

Natalie is a college student and is in need of money. She was walking along the Green at UAB and there was a table asking for volunteers for a research study. They said that she would receive $10,000 for a 15-year long study researching several different traits. What kind of research study is this?

Cohort study

T/F: The heritability of drug addiction is 0.01 to 0.02

False

A karyotype on a baby that was born. It was seen that the baby had an X and Y chromosome. What is the gender of a baby?

Male

T/F: a polygenic risk score is calculated from the number of risk alleles weighted by effect sizes calculated from the GWAS data

True

A patient presents with a mutation of the mitochondrial DNA. They have impaired vision as a symptom of their mutation. What mitochondrial DNA mutation do they have?

Lever optical atrophy

Using the pedigree below, what kind of disease would you expect to be tracking? And why is individual number 2 unaffected?

Mitochondrial Disorder, this disease is maternally inherited.

What is the correct order of steps when it comes to solving genetic problems?

1. Determine the genotype of the parents

2. Repeat for successive generations

3. List all genotypes and phenotypes of the traits

4. Unite all gametes in all combinations to reveal all possible genotypes

   1. Derive possible alleles in gametes

31542

A patient enters your office complaining that they no longer enjoy playing tennis, an activity that they used to frequently enjoy. They have low motivation and appetite, and they begin to cry. Which of the following disorders would you diagnose?

Major Depressive Disorder

Which of the following is NOT a limitation of Genome-Wide Association Studies?

None of the above

The pedigree above shows the presence of freckles through three generations of a family. Having freckles is an autosomal recessive trait controlled by a single gene. What is the genotype of individual II-3? 

Genotype Aa (heterozygote)

If individual III-5 marries a woman who is homozygous for not having freckles, what will be true of all their children?

All of their children will not have freckles. A cross between individual III-5 (aa) and someone who is homozygous for the dominant trait (AA) will yield all heterozygous children, and they will show the dominant phenotype. 

In a study of a particular plant species, researchers constructed a linkage map for three genes located on the same chromosome: Gene A, Gene B, and Gene C. After performing genetic crosses, the following recombination frequencies were observed:

Gene A and Gene B: 8%

Gene B and Gene C: 12%

Gene A and Gene C: 20%

Based on these recombination frequencies, which statement is most likely true about the arrangement of these genes on the chromosome?

Gene B is located between Gene A and Gene C.

T/F: X-linked chromosomes are always passed from father to daughter

False

T/F: X-linked recessive trait is always expressed in the male

True

Tom is genetically a male. However, he cannot produce androgens, which gives him a male appearance. Because of this, he shows female physical traits. What disorder is this?

Androgen insensitivity syndrome

Several patients at a hospital in one wing all have cystic fibrosis, and their families do not understand how some of them are suffering from more severe signs and symptoms, than others if all of them have the same condition, you have to explain to them the idea that cystic fibrosis has:

Complete penetrance and broad expressivity.

T/F: A genome-wide association study (GWAS) compare many genetic markers across the genome between two large groups of people

True

T/F: Trio analysis distinguishes carrier parents from de novo mutations in children

True

Which of the following statements correctly describes Schizophrenia?

Schizophrenia is a debilitating loss of the ability to organize thoughts and perceptions, which leads to a withdrawal from reality 

Which pattern of inheritance is typically associated with a single gene controlling a specific trait?

Autosomal recessive inheritance

What is a key characteristic of complex traits in genetics?

Influenced by multiple genes and environmental factors

Lisa's assigned sex at birth was female, yet when she starts going through puberty she does not develop breast or start menstruating. Instead she developed a deepened voice and muscles that make her appear masculine, even though she has not been lifting weights. Lisa gets checked up by a geneticist and discovers her biological sex is XY which led to the conclusion that she has a type of pseudohermaphroditism called 5-alpha reductase deficiency. Based on this information which of the following statements is true? Check all that apply? 

A) 5-alpha reductase deficiency is an autosomal recessive disorder.
B) Because there is a deficiency in 5-alpha reductase, testosterone can not be catalyzed into DHT.

C) Consanguinity can cause 5-alpha reductase deficiency. 

Which of the following is true about OCA2 genes?

If you have the dominant allele for OCA2 and a recessive allele for HERC2 then it will give blue eyes. 

T/F: Prevalence is the number of new cases during a specified time period

False

A male patient meets with a genetic counselor after to finding out about a chronic disease that has affected some males and females of every generation on his dad's side of the family. What best describes the mode of inheritance of this disease?

Autosomal Dominant

Most behavioral disorders are _____.

Polygenetic

Zeus had children with his sister Hera. Their child Ares has children with Aphrodite who is another “offspring” of Zeus. Given the large amount of consanguinity going on in this family, what type of Genome-Wide Association Study (GWAS) would you most likely run to for this family if the children of Ares and Aphrodite come to you for genetic counseling?

Homozygosity mapping

T/F: An individual with two of the same mutant recessive alleles for the same gene is a compound heterozygote.

False

Lisa is a 14-year-old girl who suffers from anorexia nervosa. Both of Lisa's parents are above 5'8. Her brother is 6'2. Due to Lisa's poor nutrition, her doctor measured her at just over 5 feet two inches tall. What kind of trait is most likely affecting Lisa's height?

Polygenic Trait

_________ is the rate a certain event occurs and ___________ is the number of individuals that have a particular disease at a specific time. 

Incidence, Prevalence

Preeclampsia is a complication that occurs during pregnancy. This disorder is characterized by high blood pressure, high levels of protein in urine, and swelling of the hands and feet. A recent study discovered that if a man's first wife has preeclampsia then the man's second wife had double the risk of developing the disorder. What could this indicate about preeclampsia?

Sex-limited trait

T/F: Incidence is the number of new cases during a specified time period

True

Which of the following is the physical manifestation of one’s genes?

Phenotype

To inherit a recessive disorder, a person usually must receive two abnormal genes, one from each parent. If both parents have one abnormal and one normal gene, neither parent has the disorder. However, each parent has a 50% chance of passing the abnormal gene to their children. Which of the following is the likelihood each child has of inheriting two normal genes?

25%

In humans, hemophilia is a sex-linked recessive trait. If a female who is a carrier for hemophilia marries a male with normal blood clotting. What fraction of the female children will be carriers?

50%

In 2000, there were approximately 2,076,969 male live births and 1,981,845 female live births in the United States. What is the sex ratio of this period? Round to the nearest hundredth.

1.05

A female inherits and passes down Rett syndrome to her son, who is severely affected by the trait. Rett syndrome would be a:

X-linked dominant trait

T/F: An X-linked dominant trait is always passed to all daughters but to no sons from their father?

True

A family comes into your clinic, and they would like a genetic analysis done to determine why only one of their four children was diagnosed with autism. Based on your knowledge of genetic analyses, which of the following analyses would be best, and what would the analysis likely find?

Trio analysis; there was a de novo mutation in the affected child

A plant biologist crossed two flowers: one red and one blue. This cross resulted in purple flowers. This is an example of  

Incomplete dominance

Layla has been experiencing frequent headaches and has been prescribed medication for it. Originally, 1 dose was enough to ease her pain. She now tells her doctor that she has to double her dose in order to feel relief from her headaches.  Layla is showing an increase in __.

Tolerance

Martha and John are a couple that have 2 daughters and 1 son. All three of their children have the same disease that their mother, Martha, has. All three children eventually have their own kids, and both daughter's children are also afflicted by the same disease that their mother's have. What is the mode of inheritance of this disease?

Mitochondrial DNA

T/F: The ability for anyone to grow a bear is a sex-influenced trait

False

T/F: Mendel's Second Law (Law of Independent Assortment) states that the inheritance of one gene will affect the chance of inheriting another gene.

False

A female patient in her late teens has been having difficulty paying attention in class, and she has also noticed a decline in her memory and understanding of topics in school. In taking the patient's history, it is discovered that she had fetal oxygen deprivation due to complications at birth. She is adopted, so she has no knowledge of her family history. Currently, she is expressing high levels of cytokine interleukin-8. What will this patient likely be diagnosed with?

Schizophrenia

Anna has three kids, two girls and one boy. Her son has a rare genetic disorder, but both of her daughters are unaffected and perfectly healthy. Her father and brother also have the disorder. This genetic mutation is the result of what inheritance pattern?

X-linked Recessive

Anna finds out she is pregnant with twins. Given that the father has no familial history of the disorder, what are the chances that she has a boy who doesn’t have the disorder and a girl who is a carrier? 

1/16

A colleague recently told you that cystic fibrosis and sickle cell disease occur in a similar way. Your other colleague laughs at the statement, saying "one disease effects the lungs, and the other effects the blood!" You disagree with the second colleague, stating that "genetically, they are quite similar." For clarification, what are you referring to?

Both genes are Mendelian genes, and also contain only a single nucleotide mutation

Which of the following conditions can be characterized by a decrease in enjoyment of favorite activities and an increase in fatigue?

Major Depressive Disorder

Which phenomenon has the phenotypic effect of “A heterozygote’s phenotype is distinct from and not intermediate between those of the two homozygotes.” 

Codominance

T/F: The rate of heritability predicts the degree of variation in a trait due to genetics. The closer to one that the trait is, the more the variability is the result of gene action. The farther from one the rate is, the more the variability is the result of environmental factors. The heritability rate for height is 0.8, meaning that environmental variance is responsible for the trait. 

False

T/F: The Period 2 gene allows a person to respond to day and night environmental cues

True

A male patient is concerned about having small testes and a high-pitched voice. Upon further testing, you find out that the patient has...

2 X chromosomes and the SRY gene present

Which of the following terms refers to the degree of variation in a trait due to genetics?

Heritability

Kallmann Syndrome, a hormonal disorder involving a poor sense of smell and delayed puberty, runs in Ashley's family. While Ashley is a carrier of the disease and is unaffected, her son is affected. Which of the following describes the trait for this disorder?

X-linked recessive trait

Eric has autism, but neither of his parents have autism. Scientists preform exome sequencing of Eric and his parents to identify mutant genes. Which approach of discovering genes involved in autism is described by this scenario? 

Trio analysis

Jacob goes to the doctor in search of a medication to help him treat his newly diagnosed major depressive disorder. His physician prescribes him Zoloft. His physician describes this drug as a SSRI. Which of the following statement best describes the explanation for why this drug is an effective treatment for Jacob? 

SRRIs are effective treatments for major depressive disorder because the block the reuptake of serotonin back into the pre-synaptic neuron, the more serotonin available in the synaptic cleft, the greater the chance of binding of it to receptors on the post synaptic neuron

T/F: In a monohybrid cross, the observed trait is recessive and the masked trait is dominant.

False

Amelia went to the clinic to get a health checkup. It appeared that she had been experiencing a phenomenon where one of the genes in her body were affecting the expression of another gene, and so she is missing the H antigen in her body. What is a possible explanation to this phenomenon?

Bombay phenotype

After conducting a genome-wide association study (GWAS) to investigate genetic factors associated with hypertension, a complex trait influenced by genetic and environmental factors, collecting data from monozygotic (MZ) and dizygotic (DZ) twins, a 62% concordance rate for hypertension in MZ twins and a 48% concordance rate in DZ twins tells us what about the heritability of hypertension?

As seen by the higher concordance in the MZ twins, hypertension has a significant genetic component

T/F: The heritability of autism is low, indicating that environmental factors are primarily responsible for the condition.

False