Question 1

Irving and Sarah were told by their fertility doctor that Irving's sperm contains 23 chromosomes.What does this indicate regarding Irving's ability to father children?

Accepted Answer

Irving's sperm containing 23 chromosomes is normal because human sperm cells (and egg cells) are haploid, meaning they contain half the number of chromosomes of somatic cells. This allows for the combination of 23 chromosomes from the sperm and 23 from the egg to create a zygote with the normal 46 chromosomes.

Question 2

Are most chromosomal abnormalities lethal or nonlethal?

Accepted Answer

Most chromosomal abnormalities are lethal and often result in spontaneous abortion, usually before the pregnancy is known. This is because significant deviations from the normal chromosome set disrupt crucial developmental processes.

Question 3

Once a baby is conceived, how can genetic abnormalities be detected?

Accepted Answer

There are multiple relatively low-risk procedures available for prenatal genetic testing, including blood tests, ultrasound, and non-invasive prenatal testing (NIPT), which can detect many types of genetic abnormalities without posing considerable risk to the fetus.

Question 4

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) can be performed earlier in the pregnancy (between the 10th and 12th weeks) than amniocentesis (usually performed in the second trimester, around 15-20 weeks) and provides genetic information about the fetus, allowing for early detection of genetic defects.

Question 5

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, which is a genetic condition and not related to the action of a dominant gene from either parent or the presence of extra sex chromosomes.

Question 6

What are polygenic traits determined by?

Accepted Answer

Polygenic traits are determined by the combined influence of many genes, each contributing a small effect to the outcome or phenotype. This contrasts with traits influenced by a single gene. Examples of polygenic traits include height, skin color, and eye color.

Question 7

Kyrin has several close relatives who are alcoholics, who are clinically depressed, or who suffer from schizophrenia.Kyrin has decided to have a vasectomy so that he will never father any children.He explains that his children would surely have a mental illness.Is Kyrin right?

Accepted Answer

Kyrin is overreacting because while there is a hereditary component to alcoholism, clinical depression, and schizophrenia, the presence of these disorders in relatives does not guarantee that his children would inherit them. The heritability of these conditions suggests an increased risk, not a certainty.

Question 8

Which disorder is attributable to a chromosomal abnormality?

Accepted Answer

Down syndrome is caused by a chromosomal abnormality, specifically the presence of an extra copy of chromosome 21.

Question 9

What is the complete set of cells in an organism known as?

Accepted Answer

The complete set of cells in an organism is referred to as its genome, which encompasses all the genetic material of that organism.

Question 10

If the differences in IQ scores in a population were entirely a result of genetic factors, what would you expect to find about the correlation in IQ scores for twin pairs?

Accepted Answer

If differences in IQ scores were entirely due to genetic factors, the correlation in IQ scores for monozygotic (identical) twins, who share 100% of their genes, would be the same regardless of whether they were reared together or apart, because their environments would have no effect on their IQ scores.

Question 11

According to Rowe and Plomin's research, what can you conclude if nonshared environmental influences are found to play a major role in the development of personality traits?

Accepted Answer

Rowe and Plomin's research indicates that nonshared environmental influences, which are differences in environment between individuals (even within the same family), play a significant role in the development of personality traits. This suggests that the unique experiences and environments individuals are exposed to contribute more to personality development than the shared or common experiences.

Question 12

Genetic uniqueness is ensured by a process during meiosis called crossing-over and by which other Mendelian principle?

Accepted Answer

Independent assortment, along with crossing-over during meiosis, ensures genetic uniqueness by allowing for the random distribution of maternal and paternal chromosomes to the gametes.

Question 13

Which trait illustrates the principle of codominance?

Accepted Answer

AB blood type is an example of codominance because both A and B alleles are expressed equally in the phenotype, resulting in a blood type that has both A and B antigens.

Question 14

Disorders such as hemophilia, some forms of night blindness, and two types of muscular dystrophy occur at different rates in males and females.Which statement best characterizes the pattern of these disorders in the two sexes?

Accepted Answer

These disorders are linked to genes on the X chromosome. Since males have only one X chromosome (XY), a single recessive allele for the disorder on the X chromosome will result in the disorder. Females have two X chromosomes (XX), so they would need two copies of the recessive allele to display the disorder, making it less likely for females to be affected.

Question 15

What does the mathematical index of heritability represent?

Accepted Answer

The index of heritability represents the extent to which genetic factors account for variations in a particular trait (such as IQ) within a population. It does not predict individual IQ scores based on family members' scores but rather assesses the overall influence of genetics on the variation of the trait in the population.

Question 16

What do the sperm and the ovum each contribute at conception?

Accepted Answer

Sperm and ovum each contribute 23 single chromosomes to the zygote at conception, combining to form a total of 46 chromosomes in the newly formed zygote.

Question 17

What new cell is formed when the sperm's genetic material fuses with the ovum's genetic material?

Accepted Answer

When the sperm's genetic material fuses with the ovum's genetic material, a zygote is formed. This is the initial cell created at conception, which eventually develops through various stages into a fetus.

Question 18

What does research with monozygotic twins on the role of heredity in mental illness indicate?

Accepted Answer

Research with monozygotic twins has shown that if one twin develops a mental illness, the other twin has an increased risk of developing the same disorder compared to the general population. However, it is also common for identical twins to be discordant for mental illnesses and behavioral disorders, meaning that even though they share the same genes, one twin may develop a mental illness while the other does not. This suggests a role for environmental factors and individual experiences in the development of these conditions alongside genetic predispositions.

Question 19

Genetic uniqueness is ensured by the Mendelian principle of independent assortment and by another process that occurs during meiosis.What is that process?

Accepted Answer

Crossing-over is the process that occurs during meiosis, specifically in prophase I, where homologous chromosomes exchange genetic material. This, along with the Mendelian principle of independent assortment, contributes to genetic diversity by ensuring that each gamete contains a unique set of genes.

Question 20

What occurs in the zygote as it moves through the fallopian tube toward the uterus?

Accepted Answer

As the zygote moves through the fallopian tube toward the uterus, it undergoes a series of mitotic cell divisions, a process known as cleavage. This increases the number of cells without increasing the overall size of the embryo.

Quiz 3: Hereditary Influences on Development