Which of the following is a component of a chromosome?
A. Centromere
B. Gamete
C. Homologue
D. Ribose
The protein disc that holds two sister chromatids together is what collectively makes a chromosome. A gene is a segment of DNA, deoxyribonucleic acid, which transmits information from parent to offspring. A single molecule of DNA has thousands of genes. A chromosome is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division.
Chromosomes have two components:
- Chromatids: two copies of each chromosome
- Centromeres: protein discs that attach the chromatids together
Human cells have 23 sets of different chromosomes. The two copies of each chromosome are called homologous chromosomes, or homologues. An offspring receives one homologue from each parent. When a cell contains two homologues of each chromosome, it is termed diploid (2n). A haploid (n) cell contains only one homologue of each chromosome. The only haploid cells humans have are the sperm and eggs cells known as gametes.
Therefore, the Correct Answer is A.
More Questions on TEAS 7 Science
-
Q #1: Mendel discovered the pattern associated with _____after developing a series of rules in genetics.
A. epigenetics
B. heredity
C. heterogeneity
D. taxonomy
Answer Explanation
Mendel was accurately able to predict the patterns of heredity by studying rules related to genetics. These rules helped shape his theory of heredity. Heredity is the characteristics offspring inherit from their parents.
From experiments with garden peas, Mendel developed a simple set of rules that accurately predicted patterns of heredity. He discovered that plants either self-pollinate or cross-pollinate, when the pollen from one plant fertilizes the pistil of another plant. He also discovered that traits are either dominant or recessive. Dominant traits are expressed, and recessive traits are hidden.
Mendel’s Theory of Heredity
To explain his results, Mendel proposed a theory that has become the foundation of the science of genetics. The theory has five elements:
- Parents do not transmit traits directly to their offspring. Rather, they pass on units of information called genes.
- For each trait, an individual has two factors: one from each parent. If the two factors have the same information, the individual is homozygous for that trait. If the two factors are different, the individual is heterozygous for that trait. Each copy of a factor, or gene, is called an allele.
- The alleles determine the physical appearance, or phenotype. The set of alleles an individual has is its genotype.
- An individual receives one allele from each parent.
- The presence of an allele does not guarantee that the trait will be expressed.
-
Q #2: Fertilization (the fusing of one sperm and an ovum) results in a(n) _____.
A. embryo
B. fetus
C. infant
D. zygote
Answer Explanation
Human intercourse consists of the male introducing sperm into the female’s reproductive system. Sperm may then pass through the female’s reproductive system to the Fallopian tubes where one sperm fertilizes an ovum, creating a zygote. The zygote passes out of the Fallopian tube and implants into the uterine wall to begin gestation. Over nine months, the zygote develops and grows into an embryo and then a fetus. An infant is the baby that is born.
-
Q #3: During the aging process, not all hormone levels decrease; some actually increase. Which of the following is a hormone that may increase as a person ages?
A. Cortisol
B. Insulin
C. Luteinizing
D. Thyroid
Answer Explanation
The aging process affects hormone activity in one of three ways: their secretion can decrease, remain unchanged, or increase.
Hormones that decrease secretion include the following:
- Estrogen (in women)
- Testosterone (in men)
- Growth hormone
- Melatonin
In women, the decline in estrogen levels leads to menopause. In men, testosterone levels usually decrease gradually. Decreased levels of growth hormone may lead to decreased muscle mass and strength. Decreased melatonin levels may play an important role in the loss of normal sleep-wake cycles (circadian rhythms) with aging.
Hormones that usually remain unchanged or slightly decrease include the following:
- Cortisol
- Insulin
- Thyroid hormones
Hormones that may increase secretions levels include the following:
Parathyroid hormone
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Norepinephrine
- Epinephrine, in the very old
-
Q #4: Which choice best describes homeostasis?
A. A functional system of the body
B. Blood flow to every cell in the body
C. A relatively constant environment within the body
D. Neural pathways that have integrated into the body
Answer Explanation
Homeostasis is the existence and maintenance of a relatively constant environment within the body. Each cell of the body is surrounded by a small amount of fluid, and the normal functions of each cell depend on the maintenance of its fluid environment within a narrow range of conditions, including temperature, volume, and chemical content. These conditions are known as variables. For example, body temperature is a variable that can increase in a hot environment or decrease in a cold environment.
There are two types of feedback mechanisms in the human body: negative and positive.
- Negative Feedback: Most systems of the body are regulated by negative feedback mechanisms, which maintain homeostasis. Negative means that any deviation from the set point is made smaller or is resisted. The maintenance of normal blood pressure is a negative-feedback mechanism. Normal blood pressure is important because it is responsible for moving blood from the heart to tissues.
- Positive Feedback: Positive-feedback mechanisms are not homeostatic and are rare in healthy individuals. Positive means that when a deviation from a normal value occurs, the response of the system is to make the deviation even greater. Positive feedback therefore usually creates a cycle leading away from homeostasis and, in some cases, results in death. Inadequate delivery of blood to cardiac muscle is an example of positive feedback.
-
Q #5: Which sequence describes the hierarchy level of biological organization?
A. Kingdom, phylum, class, order, family, genus, and species
B. Genus, class, kingdom, species, order, phylum, and family
C. Genus, class, kingdom, species, order, phylum, and family
D. Species, kingdom, genus, class, family, phylum, and order
Answer Explanation
Taxonomy is the process of classifying, describing, and naming organisms. There are seven levels in the Linnaean taxonomic system, starting with the broadest level, kingdom, and ending with the species level. For example, in the image the genus level contains two types of bears, but the species level shows one type. Additionally, organisms in each level are found in the level above it. For example, organisms in the order level are part of the class level. This classification system is based on physical similarities across living things. It does not account for molecular or genetic similarities.
-
Q #6: Which part of the digestive system comes before the stomach?
A. mouth
B. esophagus
C. ileum
D. colon
Answer Explanation
Oral Cavity is the first part of the digestive system. It is bounded by the lips and cheeks and contains the teeth and tongue. Its primary function is to masticate, or chew, and moisten the food.
Pharynx, or throat, connects the mouth to the esophagus.
Esophagus is a muscular tube about 25 centimeters long. Food travels down it to the cardiac sphincter of the stomach.
Pyloric sphincter. The exit of the stomach.
Small intestine is about 6 meters long and consists of three parts: duodenum, jejunum, and ileum.
Large intestine, consists of the cecum, colon, rectum, and anal canal. The cecum is located where the small and large intestine meet. The primary function of the large intestine is to compress the waste and collect any excess water that can be recycled.
Colon is about 1.5 to 1.8 meters long and consists of four parts: the ascending, transverse, descending, and sigmoid colon.
-
Q #7: What phase is the cell cycle part of?
A. Interphase
B. Metaphase
C. Prophase
D. Telophase
Answer Explanation
Before mitosis or meiosis occurs, interphase must happen. This is when the cell cycle takes place. The cell cycle is an organized process divided into two phases: interphase and the M (mitotic) phase. During interphase, the cell grows and copies its DNA. After the cell reaches the M phase, division of the two new cells can occur. The G1, S, and G2 phases make up interphase.
-
Q #8: A student notices a pattern of stripes on five tigers. Each of the five tigers has the same stripe pattern. Using his inductive reasoning, what does he logically assume based on this information?
A. The pattern continues to change over time.
B. Natural adaptations cause this pattern to occur
C. Each offspring will have the same stripe pattern
D. Ancestors of the tigers have different stripe patterns
Answer Explanation
Inductive reasoning involves making specific observations and using them to make broad statements. The student observes that all of the tigers have the same stripe pattern. He can use this observation to make the broad statement that all the tigers’ offspring will have the same stripe pattern.
Inductive reasoning involves drawing a general conclusion from specific observations. This form of reasoning is referred to as the “from the bottom up” approach. Information gathered from specific observations can be used to make a general conclusion about the topic under investigation. In other words, conclusions are based on observed patterns in data.
-
Q #9: The sequence of amino acids in a gene determines
A. the primary structure of a codon
B. the primary structure of a protein
C. the primary structure of a nucleotide
D. the primary structure of a nucleic acid.
Answer Explanation
The sequence of amino acids in a gene determines the primary structure of a protein. The components necessary for translation are located in the cytoplasm. Translation is the making of proteins by mRNA binding to a ribosome with the start codon that initiates the production of amino acids. A peptide bond forms and connects the amino acids together. The sequence of amino acids determines the protein’s structure, which determines its function.
-
Q #10: In the following single-replacement reaction, ______ replaces ______. Cl2+2NaI→2NaCl+I2
A. sodium, iodine
B. chlorine, iodine
C. chlorine, sodium
D. sodium, chlorine
Answer Explanation
In this reaction, chlorine (Cl2) is an element in the reaction that replaces iodine in the compound sodium iodide (NaI). This allows chlorine to form a compound with sodium (NaCl) and leaves iodine (I2) as an element.
Synthesis reactions involve two or more reactants (A and B) combining to form one product (AB). In the example provided, hydrogen (H2) and oxygen (O2) begin as separate elements. At the end of the reaction, the hydrogen and oxygen atoms are bonded in a molecule of water (H2O).
Decomposition reactions have only one reactant (AB) that breaks apart into two or more products (A and B). In the example above, hydrogen peroxide (H2O2) breaks apart into two smaller molecules: water (H2O) and oxygen (O2).
Single-replacement reactions involve two reactants, one compound (AB) and one element (C). In this type of reaction, one element replaces another to form a new compound (AC), leaving one element by itself (B). In the example, zinc replaces hydrogen in hydrochloric acid (HCl). As a result, zinc forms a compound with chlorine, zinc chloride (ZnCl2), and hydrogen (H2) is left by itself.
Double-replacement reactions involve two reactants, both of which are compounds made of two components (AB and CD). In the example, silver nitrate, composed of silver (Ag1+) and nitrate (NO31-) ions, reacts with sodium chloride, composed of sodium (Na1+) and chloride (Cl1-) ions. The nitrate and chloride ions switch places to produce two compounds that are different from those in the reactants.
Combustion reactions occur when fuels burn, and they involve specific reactants and products, as seen in the examples below. Some form of fuel that contains carbon and hydrogen is required. Examples of such fuels are methane, propane in a gas grill, butane in a lighter, and octane in gasoline. Notice that these fuels all react with oxygen, which is necessary for anything to burn. In all combustion reactions, carbon dioxide, water, and energy are produced. When something burns, energy is released, which can be felt as heat and seen as light.
