Question 1

Patsy and Terry are dizygotic twins.They

Accepted Answer

Dizygotic twins, also known as fraternal twins, come from two separate eggs fertilized by two different sperm. Therefore, they are no more genetically similar than ordinary siblings born at different times. While they may share some physical features, they are not guaranteed to look alike. The rate of development for dizygotic twins is not necessarily faster than single births, as it can vary based on individual factors.

Question 2

Research on sex chromosome disorders shows that

Accepted Answer

Research has found that both boys and girls with an extra X chromosome (47,XXX or 47,XXY) are at an increased risk for reading difficulties. Additionally, individuals with Turner syndrome (45,X) may experience verbal difficulties, but it is not a universal characteristic of the disorder. XYY syndrome has also been associated with increased aggression and antisocial behavior, but this is not true for all individuals with the disorder. Mental retardation is not a prevalent characteristic of sex chromosome disorders.

Question 3

Gilles has had frequent and high exposure to radiation in his occupation for the past ten years.Gilles's offspring are at greater risk for __________ than children whose fathers were not exposed to radiation.

Accepted Answer

High exposure to radiation has been linked to an increased risk of childhood cancer in offspring. The other options, cystic fibrosis, PKU, and hemophilia, are genetic disorders that are not specifically associated with radiation exposure.

Question 4

Fraternal twins are created when

Accepted Answer

Fraternal twins are created when two different ova are released and fertilized by two different sperm cells. This results in two zygotes, each with its own distinct genetic makeup.

Question 5

__________ help(s)explain why fragile X syndrome is expressed only when it is passed from the mother to the child.

Accepted Answer

Genomic imprinting helps explain why fragile X syndrome is only expressed when it is passed from the mother to the child. This is because the FMR1 gene, which causes fragile X syndrome, is located on the X chromosome. In females, one X chromosome is randomly inactivated in each cell to ensure that both copies of genes on the X chromosome are not expressed. However, in some cases, the FMR1 gene may still be active on the inactivated X chromosome when it is inherited from the mother due to a phenomenon called genomic imprinting. This can lead to the development of fragile X syndrome.

Question 6

Sickle cell anemia

Accepted Answer

Sickle cell anemia is an autosomal recessive disorder that occurs when a child inherits two copies of the sickle cell gene (HbS), one from each parent. It affects both males and females equally. It is not treated by a low-phenylalanine diet and is not present in many Jews of European descent.

Question 7

The twenty-first pair of chromosomes failed to separate during meiosis,so Aziz received three of these chromosomes rather than the normal two.Aziz has __________ syndrome.

Accepted Answer

Aziz has Down syndrome, which is caused by the presence of an extra copy of chromosome 21, a condition known as trisomy 21.

Question 8

Somatic mutation

Accepted Answer

Somatic mutations occur in the body cells and can lead to genetic mosaicism, where different parts of the body have different genetic makeups. This shows that an individual does not have a single permanent genotype. Somatic mutations do not typically occur in sex cells or in cells that give rise to gametes, and maternal age actually increases the risk of somatic mutations.

Question 9

Maya tested positive for PKU at birth and will __________ to have a normal lifespan.

Accepted Answer

PKU (phenylketonuria) is an inherited condition where the body cannot break down phenylalanine properly, leading to toxic build-up in the body. A low-phenylalanine diet is the standard treatment to manage PKU and prevent intellectual disabilities and other health problems. Hormone therapy, insulin injections, and blood transfusions are not related to the treatment of PKU.

Question 10

Studies of sex differences show that

Accepted Answer

Males have higher rates of miscarriage, infant death, and childhood death compared to females.

Question 11

In cases of X-linked inheritance,

Accepted Answer

In X-linked inheritance, the gene responsible for the disorder is located on the X chromosome. As females have two X chromosomes and males have one X and one Y chromosome, males are more likely to be affected by the disorder because they have only one copy of the X chromosome. If the X chromosome they inherit from their mother has the mutated gene, they will have the disorder. Females, on the other hand, are less likely to be affected because even if one of their X chromosomes has the mutated gene, the other X chromosome may have a normal copy, thereby masking the effects of the mutated gene.

Question 12

Personality characteristics are most likely determined by __________ inheritance.

Accepted Answer

Personality characteristics are determined by polygenic inheritance, which means they are influenced by multiple genes. It is not simply determined by a single gene, as in the case of dominant or recessive inheritance. Also, X-linked inheritance specifically refers to genes located on the X chromosome, which may not necessarily be related to personality characteristics.

Question 13

Which of the following is a recessive characteristic?

Accepted Answer

Red hair is a recessive characteristic, meaning both parents must carry the recessive gene for a child to inherit red hair. Curly hair, facial dimples, and double-jointedness are not necessarily recessive characteristics, as they can be influenced by multiple genes or factors.

Question 14

The sex of a new organism is determined by whether

Accepted Answer

The sex of a new organism is determined by whether an X-bearing sperm or a Y-bearing sperm fertilizes the ovum. The ovum always carries an X chromosome, so the sperm determines the sex.

Question 15

Abnormalities of the sex chromosomes

Accepted Answer

Abnormalities of the sex chromosomes usually lead to fewer problems than abnormalities of the autosomes because the body can often compensate for the extra or missing sex chromosome, whereas autosomal abnormalities often result in more severe developmental issues.

Question 16

In which of the following disorders does genomic imprinting operate on the sex chromosomes?

Accepted Answer

Genomic imprinting is known to occur on the sex chromosomes in fragile X syndrome. In this disorder, the FMR1 gene on the X chromosome is silenced due to methylation of cytosine residues in the promoter region. This results in a reduction or absence of the FMR1 protein, which is important for the development and function of the nervous system. The imprinting pattern of the FMR1 gene is dependent on the parent of origin, with expansion of CGG repeats on the maternal allele causing the disease. The other disorders listed do not involve genomic imprinting on the sex chromosomes.

Question 17

In dominant-recessive inheritance,the one allele that does not affect the child's characteristics is called

Accepted Answer

In dominant-recessive inheritance, the allele that does not affect the child's characteristics is called recessive. This allele is masked by the dominant allele when both are present in an individual's genotype. Only when an individual has two copies of the recessive allele will it be expressed in their phenotype.

Question 18

During their early years,children of single births often __________ than twins.

Accepted Answer

Single birth children typically receive more resources and attention from their parents, which can lead to better overall health. Twins may have to compete for resources and attention, which can lead to lower birth weights and possible health complications.

Question 19

Candace and Cassidy,like all monozygotic twins,

Accepted Answer

Monozygotic twins, also known as identical twins, are formed from one fertilized egg that splits into two embryos, meaning they have the same genetic makeup. The other choices are not necessarily true for all monozygotic twins.

Question 20

Identical twins are created when

Accepted Answer

Identical twins are created when a single fertilized egg (zygote) divides into two separate embryos. Each embryo develops its own placenta and amniotic sac, resulting in two genetically identical individuals. This process is known as monozygotic twinning.

Quiz 2: Genetic and Environmental Foundations