Question 1

Blair has an autosomal abnormality.Her IQ is low and she has a number of distinctive physical features,including a protruding tongue and almond-shaped eyes.Based on this information,what syndrome does Blair have?

Accepted Answer

Blair exhibits physical characteristics commonly seen in people with Down syndrome, including a protruding tongue and almond-shaped eyes. Additionally, low IQ is also a common feature of Down syndrome. The other syndromes listed do not typically have these particular physical features.

Question 2

Suppose that you and your partner are both carriers for a genetic defect that causes a fatal metabolic disorder.Which prenatal testing procedure would give the earliest and most informative results regarding the health of your unborn child?

Accepted Answer

Chorionic villus sampling (CVS) is performed at 10-12 weeks of pregnancy and can detect genetic abnormalities in the fetus. It involves the removal of a small sample of the placenta and can provide results earlier than amniocentesis (which is usually done at 15-20 weeks). Germline gene analysis may also be informative, but it is not a prenatal testing procedure and would not provide information on the health of the unborn child. Ultrasound can detect physical abnormalities, but not genetic defects.

Question 3

Does a man with Supermale syndrome inherit it from his mother or father?

Accepted Answer

The answer of Does a man with Supermale syndrome inherit...

Question 4

Christos has a sex chromosome abnormality.He is taller than most of his friends,but otherwise his appearance is typical for a male.Although he and his wife tried unsuccessfully for several years to conceive a child,his wife is now pregnant.Based on this description,which syndrome does Christos have?

Accepted Answer

The answer of Christos has a sex chromosome abnormality.He is...

Question 5

Marjory is 45 years old and Jason is 51 years old.Marjory has just become pregnant and both are worried about having a child at their ages.Which prenatal screening procedure would their doctor most likely advise to rule out chromosomal abnormalities?

Accepted Answer

Amniocentesis is typically recommended for women over the age of 35 or those who may be at a higher risk for chromosomal abnormalities. This procedure involves taking a sample of amniotic fluid to test for genetic disorders. Ultrasounds may be used to detect physical abnormalities, but they cannot diagnose chromosomal disorders. Chorionic villus sampling (CVS) and maternal blood analysis may also be options, but they are typically reserved for higher risk pregnancies.

Question 6

According to the text,what is the cause of Down syndrome?

Accepted Answer

Down syndrome is caused by the presence of an extra 21st chromosome, also known as trisomy 21. This extra chromosome can come from either the mother or the father, but it is not caused by a dominant gene. Extra sex chromosomes, such as XXY or XXX, are associated with other chromosomal disorders, not Down syndrome.

Question 7

What procedure might a pregnant woman consider having performed to test for possible chromosomal or genetic defects in the fetus?

Accepted Answer

Amniocentesis is a procedure where a small sample of amniotic fluid is taken from the sac surrounding the fetus to test for chromosomal or genetic abnormalities. This test is typically done between weeks 15-20 of pregnancy and is considered invasive, but it is one of the most accurate ways to detect potential issues in the fetus. Ultrasound is a non-invasive technique used to monitor the development of the fetus but is not a conclusive way to test for chromosomal or genetic defects. Germline gene analysis and selective embryonic analysis are not typically used for routine testing during pregnancy.

Question 8

Which characteristic differentiates a man with Supermale syndrome from typical males?

Accepted Answer

Supermale syndrome, also known as 47,XYY syndrome, is a genetic disorder in which males have an additional copy of the Y chromosome. This results in taller stature than typical males, not necessarily in more intelligence or aggression. Therefore, the best choice is A.

Question 9

Which disorder is attributable to a chromosomal abnormality?

Accepted Answer

Down syndrome is caused by the presence of an extra chromosome 21, also known as trisomy 21. This chromosomal abnormality occurs spontaneously during cell division and leads to intellectual disability, distinct facial features, and other health problems. Muscular dystrophy is caused by mutations in specific genes, diabetes is a metabolic disorder caused by insulin resistance or deficiency, and cystic fibrosis is caused by mutations in the CFTR gene.

Question 10

Which of the following is ultrasound NOT used for?

Accepted Answer

Ultrasound is not commonly used to determine the presence of hereditary disorders. Instead, other tests such as amniocentesis or chorionic villus sampling (CVS) are used for this purpose. Ultrasound is, however, commonly used to detect multiple pregnancies, detect gross physical abnormalities, and determine the age of the fetus.

Question 11

Of the following methods for prenatal detection of genetic disorders,which one cannot be completed until early in the second trimester and can take an additional two weeks for test results?

Accepted Answer

Amniocentesis cannot be completed until early in the second trimester (around 15-20 weeks of pregnancy) and can take an additional two weeks for test results, compared to chorionic villus sampling which can be completed earlier in the first trimester. Ultrasound is used for visualization of the fetus but does not provide information on genetic disorders. Genetic imprinting is a phenomenon related to the expression of genes and is not a method for prenatal detection of genetic disorders.

Question 12

Down syndrome is a genetic disorder that illustrates how the expression of an individual's genetic code can be influenced by environmental conditions.What have researchers found regarding the treatment of Down syndrome?

Accepted Answer

While there is no cure for Down syndrome, researchers have found that the cognitive impairment can be reduced through early intervention. This often includes therapies, educational interventions, and support services. Special diets or genetic engineering are not currently viable options for treating Down syndrome. While early intervention can also improve physical outcomes, it is not a guaranteed reduction in physical characteristics associated with the disorder.

Question 13

Which of the following causes hereditary defects such as cystic fibrosis,phenylketonuria,and Tay-Sachs disease?

Accepted Answer

Hereditary defects such as cystic fibrosis, phenylketonuria, and Tay-Sachs disease are caused by recessive genes. This means that a person must inherit two copies of the mutated gene (one from each parent) to develop the disease.

Question 14

Some genetic disorders,such as Tay-Sachs disease,are always fatal,and yet these diseases occur in the offspring of two normal parents.How is this possible?

Accepted Answer

Disorders such as Tay-Sachs disease are typically caused by a recessive gene. This means that an individual must inherit two copies of the mutated gene (one from each parent) to develop the disorder. Even though both parents may be normal (heterozygous carriers), they can still pass on the mutated gene to their offspring. As a result, the offspring has a 25% chance of inheriting two copies of the mutated gene and developing the disorder.

Question 15

Antonio has a sex chromosome abnormality.He is taller than most of his friends and his body proportions are slightly feminized.He scored within the normal range on a recent intelligence test,although his score for the verbal scale was lower than average.Based on this description,which syndrome does Antonio have?

Accepted Answer

Antonio's height and feminized body proportions suggest he has Klinefelter's syndrome, which is caused by an extra X chromosome (XXY). The lower score on the verbal scale of the intelligence test is also consistent with this syndrome. Turner's syndrome (A) is caused by a missing or partially missing X chromosome (XO), while fragile-X (B) is a genetic disorder that can cause intellectual disability and behavioral challenges, but does not typically affect height or body proportions. Supermale (D) is a rare genetic condition in which a male has an extra Y chromosome (XYY), but it is not associated with feminization or other physical characteristics described for Antonio.

Question 16

In comparing amniocentesis and chorionic villus sampling (CVS),which is the most accurate statement?

Accepted Answer

CVS can be performed earlier in the pregnancy (usually between 10-13 weeks of gestation) compared to amniocentesis (typically performed between 15-20 weeks of gestation), but it is generally considered to have a slightly higher risk of causing miscarriage.

Question 17

Which of the following is caused by the uneven segregation of chromosomes?

Accepted Answer

Down syndrome, also known as trisomy 21, is caused by the unequal separation of chromosomes during meiosis, resulting in an individual having an extra copy of chromosome 21. This may occur due to non-disjunction or the failure of homologous chromosomes to separate properly during meiosis.

Question 18

Axel has a sex chromosome abnormality.He has severe mental retardation and shows some evidence of repetitive self-stimulatory behaviour.Based on this description,what disorder does Axel have?

Accepted Answer

Fragile-X syndrome is a sex chromosome abnormality that results in intellectual disability and repetitive self-stimulatory behavior. Supermale (A) is a rare condition in which a male has an extra Y chromosome, but this typically results in normal intellectual functioning. Turner's syndrome (C) is a condition in which a female is missing one X chromosome and can result in intellectual disability, but repetitive behavior is not a defining characteristic. Klinefelter's syndrome (D) is a condition in which a male has an extra X chromosome and can result in some developmental delays, but severe intellectual disability and repetitive behavior are not typically seen.

Question 19

Francine and her husband Jack are carriers of a genetic defect that results in a fatal metabolic disorder.Francine has just been told that she is pregnant.Which prenatal testing procedure would give Francine and Jack the earliest and most informative results regarding the health of their fetus?

Accepted Answer

Chorionic villus sampling (CVS) is the prenatal testing procedure that can give Francine and Jack the earliest and most informative results regarding the health of their fetus. This procedure involves collecting a sample of cells from the placenta, which contains the same genetic material as the developing fetus. This sample can be tested for the genetic defect that Francine and Jack carry, allowing them to make informed decisions about their pregnancy. Ultrasound may provide some information about the health of the fetus, but it cannot diagnose genetic disorders. Amniocentesis is another prenatal testing procedure, but it is typically performed later in pregnancy and does not provide results as early as CVS. Genetic imprinting is a genetic phenomenon that affects gene expression and is not a prenatal testing procedure.

Question 20

Which abnormality of the sex chromosomes is the major cause of mental retardation and is linked to infantile autism?

Accepted Answer

Fragile-X syndrome is caused by a mutation in the FMR1 gene, which leads to the inability to express certain proteins important for brain development and function. This syndrome is the most common genetic cause of mental retardation, affecting primarily males. It is also strongly linked to infantile autism, with up to 30% of individuals with fragile-X syndrome exhibiting autistic characteristics. Turner's syndrome and Klinefelter's syndrome are both chromosomal abnormalities that can affect physical development but do not typically result in mental retardation. Down syndrome is caused by an extra copy of chromosome 21 and can lead to intellectual disability, but it is not strongly linked to infantile autism.

Quiz 3: Hereditary Influences on Development