Question 1

Maricella was born several days ago, and her pediatrician has observed that she has almond-shaped eyes and a fold over her eyelids. In addition, her head, neck, and nose are smaller than other babies of her birth weight. It is most likely that Maricella has an extra of the _____ pair of chromosomes.

Accepted Answer

Maricella most likely has an extra chromosome on the 21st pair, which is known as Down syndrome. The almond-shaped eyes and fold over the eyelids, as well as the smaller features, are common physical characteristics of individuals with this chromosomal disorder.

Question 2

Kimberley is having a discussion with her friend Aasta about the genetic determinants of development. They cannot come to an agreement on what the functional units of heredity are. If they asked you to help them figure this out, what would you say?

Accepted Answer

Genes are the functional units of heredity. They are made of nucleotides but the sequence of these nucleotides in a gene determines the specific information that is inherited and passed down. Chromosomes are made of DNA and contain many genes, while ribosomes are organelles responsible for protein synthesis and not directly involved in the inheritance of genetic traits.

Question 3

David and Katie have always been close. In fact, they are so close that they shared the womb when their mother was pregnant with them. Given the information that you have already been given in this question, which of the following can you state conclusively?

Accepted Answer

David and Katie being twins is evident from the context of sharing the womb simultaneously, but the fact that they are of different genders (David being a male name and Katie being a female name) conclusively indicates they are dizygotic (fraternal) twins, as monozygotic (identical) twins would be of the same gender.

Question 4

Maricella was born several days ago, and her pediatrician has observed that she has almond-shaped eyes and a fold over her eyelids. In addition, her head, neck, and nose are smaller than other babies of her birth weight. With which of the following conditions would Maricella most likely be diagnosed?

Accepted Answer

The almond-shaped eyes, fold over the eyelids, and smaller head, neck, and nose are characteristic features of Down syndrome, a genetic disorder caused by the presence of an extra 21st chromosome. Turner's syndrome and Kleinfelter's syndrome involve abnormalities in the sex chromosomes (X and Y), which would not typically cause these specific physical features. Phenylketonuria is a metabolic disorder that can cause intellectual disability, but it does not present with the physical features described for Maricella.

Question 5

How many of the pairs of chromosomes in normal human cells are considered autosomes?

Accepted Answer

Autosomes are non-sex chromosomes, and humans have 22 pairs of them (44 total autosomes). This means that choice C, 22, is the correct answer.

Question 6

When you learned to speak English, you may have learned the following saying: "When two vowels go walking, the first does the talking." If we were to apply this rule to heterozygous genes, we would be most accurate if we said, "When two genes go walking, the ________ one does the talking."

Accepted Answer

In genetics, dominant alleles are responsible for producing the observable traits or phenotypes in an organism. When an individual has one dominant and one recessive allele of a gene, the dominant allele will always express itself and the recessive allele will be masked. This is why the dominant allele "does the talking" when two genes or alleles are present.

Question 7

Kathleen and Alphonse are expecting their first child, and are having a pleasant conversation about the sex of the baby. Kathleen says, "Well, as long as all of the chromosomes are X, we'll be having a girl!" Which of the following would be the best answer for Alphonse to give?

Accepted Answer

The sex of a baby is determined by one pair of chromosomes, specifically the sex chromosomes, which are XX for females and XY for males.

Question 8

Which of the following is NOT one of the chemical compounds that makes up a strand of DNA?

Accepted Answer

The correct name of the compound is "deoxyribose", which is a sugar molecule found in DNA. "Depranine" is not a real compound. The other options (adenine, thymine, and cytocine) are nitrogenous bases that make up the DNA code.

Question 9

Traits that are "either/or" phenotypes (e.g., being color blind or not being color blind, having a blood clotting disorder or not having a blood clotting disorder) are usually controlled by ________ genes.

Accepted Answer

Either/or phenotypes are controlled by single genes with alternative alleles that produce different phenotypes. This is known as Mendelian inheritance, where the genotype of an individual determines their phenotype for a particular trait. Polymorphic genes have multiple alleles, mutated genes have altered sequences that affect their function, and multiple genes control traits with continuous variation.

Question 10

When looking through a microscope at an entire set of human male chromosomes, how would you be able to differentiate an autosome pair from a sex chromosome pair?

Accepted Answer

The shape of the sex chromosomes would differ, whereas each autosome pair would look identical.

Question 11

When many genes work together to determine a characteristic, there may be a large range of phenotypes that are expressed. Why is this?

Accepted Answer

When multiple genes work together to determine a characteristic, there are many possible combinations of dominant and recessive alleles that can be expressed, leading to a wide range of phenotypes.

Question 12

Which maternal characteristic is most strongly associated with giving birth to a baby with Down syndrome?

Accepted Answer

The strongest maternal characteristic associated with giving birth to a baby with Down syndrome is higher maternal age, particularly in women over the age of 35. The likelihood of having a baby with Down syndrome increases as maternal age at pregnancy increases. Low levels of intelligence in the mother, alcohol consumption during pregnancy, and exposure to lead or mercury by the baby after birth are not directly linked to an increased risk of Down syndrome.

Question 13

If a physician informed you that your speech disorder was the result of problems on chromosomes 4, 7, and 15, you would rightly conclude that the disorder is always classifiable as

Accepted Answer

Chromosomes 4, 7, and 15 are not involved in determining dominance or recessiveness of a trait. Rather, they contain multiple genes that can contribute to a complex trait like a speech disorder, which would make it polygenic. Sex-linked would refer to a trait carried on a sex chromosome, which is not indicated in this scenario.

Question 14

Kendrie suffers from sickle cell anemia. She is not just a carrier of the illness, but she actually has the disease itself. Which of the following best describes Kendrie's red blood cell alleles?

Accepted Answer

Kendrie's red blood cell alleles are homozygous, meaning that both of her alleles for the sickle cell gene are the same (hemoglobin S). If she were heterozygous, she would only have one sickle cell gene and one normal gene (hemoglobin A) and would be a carrier of the disease but not have it herself. Genotypical and phenotypical are not accurate terms for describing the alleles themselves.

Question 15

Genotype is to phenotype as

Accepted Answer

Genotype refers to the genetic pattern or code, while phenotype refers to the physical, behavioral, and psychological features that result from that genetic pattern. Therefore, the relationship between genotype and phenotype is best represented by choice D - genetic pattern is to physical, behavioral, and psychological features. The other answer choices are not accurate representations of the relationship between genotype and phenotype.

Question 16

When Chester is conceived by his parents, he has the genetic instructions to grow up to be 6'1'' tall. During his childhood, however, he develops a digestive illness that significantly limits the amount of food he can eat, and he regularly fails to get enough vitamins in his diet. As a result, he grows up to be 5'11'' tall. In this example, a height of 6'1'' is Chester's ________ and a height of 5'11'' is Chester's ________.

Accepted Answer

Chester's genetic instructions (6'1'') represent his genotype, while his actual height (5'11'') due to environmental factors is his phenotype.

Question 17

How many chromosomes are found in the organism that results from the union of a sperm cell and an egg cell?

Accepted Answer

The organism resulting from the union of a sperm cell and an egg cell is a zygote, which has 46 chromosomes in humans. This is because each gamete (sperm and egg) contributes 23 chromosomes, resulting in a total of 46.

Question 18

Which type of allele is ignored when found in a heterozygous gene pair?

Accepted Answer

When a gene pair is heterozygous, the dominant allele is expressed while the recessive allele is ignored or masked. Therefore, the correct choice is D - recessive.

Question 19

Which of the following statements supports the proposition that the presence of an X chromosome appears to be necessary for life?

Accepted Answer

The statement "There are no chromosomal disorders wherein a person has only Y chromosomes" supports the idea that the presence of an X chromosome is necessary for life. This is because individuals with only Y chromosomes would lack essential genetic material carried on the X chromosome, which may lead to developmental or functional issues that could be life-threatening.

Question 20

How is it that DNA "knows" which specific amino acids, proteins, or enzymes to create?

Accepted Answer

The order of the four nucleotide bases (adenine, thymine, guanine, and cytosine) in the DNA sequence determines the sequence of amino acids in a protein. This is because the genetic code is based on a triplet code, where each set of three nucleotides (called a codon) codes for a specific amino acid. Therefore, the sequence of nucleotides in DNA ultimately determines the sequence of amino acids in proteins, which leads to the creation of specific enzymes and other cellular components.

Quiz 2: Biological Foundations: Heredity, Prenatal Development, and Birth