Question 1

________ is an example of a genetic disorder that is environmentally modifiable via diet.

Accepted Answer

Phenylketonuria (PKU) is a genetic disorder that affects the body's ability to metabolize an amino acid called phenylalanine. PKU can lead to intellectual disabilities and other health problems if untreated. However, PKU is considered an environmentally modifiable disorder because it can be managed with a strict diet low in phenylalanine. By avoiding high-protein foods and taking a special formula that provides the nutrients they need, people with PKU can live healthy lives without significant symptoms of the disorder.

Question 2

Joanna,a child born with the genetic condition PKU,may suffer mental retardation unless

Accepted Answer

PKU is a genetic disorder where the body is unable to break down phenylalanine, an amino acid found in many proteins. If left untreated, phenylalanine levels can build up in the body and cause brain damage and mental retardation. The best way to manage PKU is to restrict the intake of phenylalanine through a carefully controlled diet low in protein. This is the only treatment proven to prevent the development of neurological and cognitive symptoms. Gene therapy and drug therapy are not yet effective treatments for PKU. Restricting ribonucleic acid in the diet is not a treatment for PKU.

Question 3

Most pregnancies that involve a trisomy

Accepted Answer

Most pregnancies that involve a trisomy, which is an extra copy of a chromosome, result in spontaneous abortion, also known as a miscarriage. This occurs because the genetic abnormality is not compatible with life and the fetus cannot develop properly.

Question 4

Justin is a child with a sex chromosome abnormality.He and other children with this abnormality are more likely than children without sex chromosome abnormalities to show school and psychosocial problems

Accepted Answer

The answer of Justin is a child with a sex...

Question 5

Males are more likely than females to inherit sex-linked disorders because

Accepted Answer

Sex-linked disorders are often caused by a gene mutation on the X chromosome. Since males only inherit one X chromosome from their mother and a Y chromosome from their father, they do not have a second X chromosome to mask the effects of the abnormal X chromosome. On the other hand, females inherit two X chromosomes, so even if one X chromosome is abnormal, the other can often compensate for its effects.

Question 6

David has not yet shown signs of PKU and is already being treated.This is because his PKU was detected by

Accepted Answer

PKU is detected through a blood test that measures the levels of phenylalanine in the blood. It is important to start treatment early to prevent developmental delays and other complications. Therefore, David was likely diagnosed through a blood test and began treatment before showing signs of the condition.

Question 7

Individuals with trisomy 21 who live beyond the age of forty tend to develop the abnormal brain cells and behavioral symptoms associated with

Accepted Answer

Individuals with trisomy 21 have an increased risk of developing Alzheimer's disease as they age, and those who live beyond the age of forty tend to develop the abnormal brain cells and behavioral symptoms associated with this condition.

Question 8

The vast majority of babies born with Down syndrome have an extra ________ chromosome.

Accepted Answer

The answer of The vast majority of babies born with...

Question 9

Dr.Montenegro treats patients with PKU.She regularly answers questions related to the disease.Which of the following is not one of the concerns associated with PKU?

Accepted Answer

PKU (Phenylketonuria) is a metabolic disorder that requires strict dietary management to prevent intellectual disability and other complications. The concerns related to PKU management typically involve dietary restrictions, monitoring phenylalanine levels through blood tests, and the potential risks to offspring of mothers with PKU. Strenuous exercise is not directly related to the concerns of managing PKU itself, as the primary focus is on managing phenylalanine levels through diet and monitoring.

Question 10

An unusual feature of some genetic disorders is that their severity can increase from one generation to the next.This is known as the _______ phenomenon.

Accepted Answer

Anticipation is the phenomenon in which the severity of certain genetic disorders increases from one generation to the next. This is due to the expansion of trinucleotide repeats in the DNA, which can lead to progressively earlier onset and more severe symptoms. Examples of disorders that can exhibit anticipation include Huntington's disease, myotonic dystrophy, and some forms of familial cancer. Choices B, C, and D are not relevant to this phenomenon.

Question 11

The chances of having an infant born with Down syndrome

Accepted Answer

The chances of having an infant born with Down syndrome increase as maternal age increases. The risk is highest for women who are 35 years or older at the time of delivery. The risk increases exponentially with each year of maternal age. Paternal age does not affect the risk of having a child with Down syndrome significantly.

Question 12

The consequences of a recessive metabolic disorder such as PKU can be counteracted with a modification in dietary intake,making PKU a good example of

Accepted Answer

PKU is a recessive metabolic disorder caused by a mutation in the gene coding for phenylalanine hydroxylase, leading to the accumulation of phenylalanine and its toxic by-products in the blood and brain. The dietary modification involves restricting the intake of phenylalanine to prevent its build-up, which can cause intellectual disability, seizures, and behavioral problems. This illustrates how the individual's genotype (having two copies of the mutated gene) interacts with the environment (the intake of phenylalanine) to affect the phenotype (the symptoms of PKU). By modifying the environment (the diet), the harmful effects of the genotype can be reduced or eliminated, highlighting the interaction between the genotype and environment in determining the phenotype.

Question 13

Frederick was born with an anomaly on his X chromosome,but he displays no symptoms.If this mutation is passed on to his children,who is most likely to display full-blown fragile X syndrome according to the phenomenon of anticipation?

Accepted Answer

Fragile X syndrome is an X-linked dominant disorder, meaning that males (who have only one X chromosome) are more severely affected than females (who have two X chromosomes). In males, the mutation on the X chromosome is fully expressed, leading to the full-blown fragile X syndrome. In females, the mutation is partially expressed, leading to a milder form of the disorder known as fragile X premutation. However, the phenomenon of anticipation means that the severity of the disorder tends to increase with each generation. This is because the mutation on the X chromosome becomes more expanded with each generation, leading to a more severe form of the disorder. Therefore, Frederick's grandson is most likely to display full-blown fragile X syndrome, as the mutation on the X chromosome will have had more time to expand and become more severe.

Question 14

The condition known as ________ occurs when an extra chromosome is inherited.

Accepted Answer

Trisomy is the condition where an individual has an extra chromosome. It is commonly seen in conditions such as Down syndrome, where there is an extra copy of chromosome 21. Trigenesis is not a known medical condition, and Turner syndrome is a genetic condition where females are missing one X chromosome.

Question 15

Individuals with sex chromosome syndromes may be more vulnerable to ________ than children with a normal complement of sex chromosomes.

Accepted Answer

Children with sex chromosome syndromes may experience disruptions in caregiving patterns due to their condition, which may lead to emotional and behavioral problems. This vulnerability may be compounded by societal stigma and misunderstanding of these conditions, which may lead to reduced access to resources and support. These issues may be particularly salient for conditions such as Klinefelter syndrome, in which individuals have an extra X chromosome (XXY). However, there is no evidence to suggest that individuals with sex chromosome syndromes are more susceptible to Alzheimer's disease or dietary issues.

Question 16

The leading cause of mental retardation in males is ________,a disorder caused by a pinched region on the X chromosome.

Accepted Answer

Fragile X syndrome is a genetic disorder caused by a pinched region on the X chromosome. It is the leading cause of inherited mental retardation in males. Turner syndrome, Klinefelter syndrome, and recessive Y syndrome are also genetic disorders but do not cause the same type of mental retardation as fragile X syndrome.

Question 17

If a genetic disease is sex linked,it is likely that females will ________ and males will ________

Accepted Answer

If a genetic disease is sex linked, it means it is carried on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. If a female inherits one mutated X chromosome from either parent, she becomes a carrier of the disease. However, since she also receives a normal X chromosome from the other parent, she is usually protected from developing the disease. 
On the other hand, males have only one X chromosome, which means that if they inherit a mutated X chromosome from their mother, they will develop the disease because they do not have a second X chromosome to compensate. Therefore, females are more likely to be carriers of sex-linked genetic diseases, while males are more likely to have the disease. The correct answer is B, as females will be carriers, and males will have the disease.

Question 18

The Coopers just had a baby who tested positive for the recessive metabolic condition called PKU.Their pediatrician has instructed them to

Accepted Answer

The best choice is to restrict the baby's intake of milk and meats. PKU is an inherited metabolic disorder in which the body cannot properly process phenylalanine, an amino acid found in many foods, including milk and meats. Therefore, the baby needs to restrict intake of these foods to avoid complications. Gene therapy is not currently a viable option for treating PKU, and using milk instead of formula or monitoring the child's diet in adolescence would not address the immediate need to restrict intake in infancy.

Question 19

Which sex chromosome abnormality is impossible?

Accepted Answer

The combination YO is impossible because Y is always paired with another sex chromosome (either X or another Y) in males, and O is not a valid sex chromosome.

Question 20

Even with proper dietary controls,children with PKU may display

Accepted Answer

Despite dietary controls, children with PKU may still experience some growth and intellectual deficiencies due to the inability to metabolize phenylalanine properly. However, severe mental retardation is unlikely to occur as long as the condition is managed properly. Color blindness and depressed immune systems are not typically associated with PKU.

Quiz 3: Genetics and Heredity