Heredity Honor

Science & Health

Requirements

1. What is heredity?

   Answer: Heredity is the transmission of characteristics (physical and biological) from parents to children, from generation to generation, through the genes contained in DNA. It is what makes descendants resemble their ancestors. — Heredity explains why we inherit traits from our parents — it is the basis of genetics.

2. Draw an animal cell and identify the following parts: plasma membrane, cytoplasm, nucleus, nuclear envelope, and ribosomes.
3. Explain the following:
   • What is a chromosome and where is it located?
   • What is a gene and where is it found?
   • What is an allele?
   • What is the difference between a dominant allele and a recessive allele?
   • Determine what type of allele you have for the following genetic traits (phenotypes): widow's peak, free earlobe, dimples, tongue rolling, myopia, being left-handed, and a cleft chin.
   • Using the Punnett square, predict the ratio of the following crosses: TT (tall) with tt (short); Tt (tall) with Tt (tall); Tt (tall) with tt (short).
   • What is mitosis? What is its function?
   • Draw a sequence of cells showing the process of mitosis, including: prophase, metaphase, anaphase, and telophase.
   • Explain how DNA is copied in the chromosome during this process.
   • What is meiosis? What is the difference between mitosis and meiosis?
   • Draw a sequence of cells showing the process of meiosis, including: interphase, prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, and telophase II.
   • Do the cells resulting from meiosis remain diploid? Explain.

   Answer: 1) What is a chromosome and where is it located? A chromosome is the filament formed by coiled and compacted DNA that carries the genes; it is located inside the NUCLEUS of the cell. 2) What is a gene and where is it found? A gene is a segment (stretch) of DNA that contains the information for a characteristic; it is found along the chromosomes, in the nucleus. 3) What is an allele? An allele is each of the alternative versions of the same gene, which occupy the same position on homologous chromosomes. 4) What is the difference between a dominant allele and a recessive allele? The dominant allele manifests itself even in a single dose (one copy is enough) and is represented by a capital letter; the recessive one only manifests itself in a double dose (two copies) and is represented by a lowercase letter. 5) Type of allele for each trait: widow's peak, free earlobe, dimples, tongue rolling, nearsightedness, and chin cleft are usually determined by a DOMINANT allele; being left-handed tends to be determined by a RECESSIVE allele. 6) Punnett square: TT (tall) x tt (short) → 100% Tt (all tall); Tt (tall) x Tt (tall) → 1 TT : 2 Tt : 1 tt, that is, 3 tall to 1 short (75% tall, 25% short); Tt (tall) x tt (short) → 1 Tt : 1 tt, that is, half tall and half short (50% / 50%). 7) What is mitosis? What is its function? Mitosis is the cell division that produces two daughter cells IDENTICAL to the mother cell, with the same number of chromosomes; its function is the growth, replacement, and repair of the body's tissues. 8) Sequence of mitosis (prophase, metaphase, anaphase, telophase): in the drawing, show — Prophase: the chromosomes condense and become visible, the nuclear membrane breaks down; Metaphase: the chromosomes line up at the center (equatorial plate) of the cell; Anaphase: the sister chromatids separate and migrate to opposite poles; Telophase: two new nuclei form and the cell divides into two. 9) How is the DNA copied in the chromosome during this process? Before division, the DNA double helix opens like a zipper and each strand serves as a template for the assembly of a new complementary strand (A with T, C with G), giving rise to two molecules identical to the original. 10) What is meiosis? What is the difference between mitosis and meiosis? Meiosis is the division that forms the gametes (reproductive cells) and generates four cells with HALF the number of chromosomes; it differs from mitosis in that mitosis generates 2 identical and diploid cells (for growth/repair), whereas meiosis generates 4 different and haploid cells (for reproduction), with two successive divisions. 11) Sequence of meiosis (Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II): in the drawing show — Interphase: the DNA is duplicated; Prophase I: homologous chromosomes pair up and may exchange pieces (crossing over); Metaphase I: the pairs of homologs line up at the center; Anaphase I: the homologs separate to the poles; Telophase I: two cells form with half the chromosomes; then, without new duplication, Prophase II, Metaphase II (chromosomes at the center), Anaphase II (sister chromatids separate), and Telophase II, ending in four daughter cells. 12) Do the cells resulting from meiosis remain diploid? Explain. No. The cells from meiosis are HAPLOID (they have half the number of chromosomes), because, in fertilization, the union of the male gamete with the female one restores the species' normal (diploid) number. — Chromosome, gene, allele, mitosis, and meiosis are the basis of how characteristics are transmitted and how cells multiply.

4. What are the nucleotides involved in the process of DNA replication? Describe how the replication of a DNA molecule occurs. Demonstrate your knowledge of this subject using a diagram or model.

   Answer: DNA nucleotides have a sugar (deoxyribose), a phosphate, and a nitrogenous base: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). In replication, the double helix opens up; each strand serves as a template and DNA polymerase fits in the complementary nucleotides (A with T, C with G), forming two identical molecules, each with one old strand and one new one (semiconservative replication). — The base-pairing rule (A-T, C-G) ensures that DNA is copied faithfully at each cell division.

5. What is a mutation? Using the diagram or model created in the previous question, illustrate the effect of a mutation on the genetic code.

   Answer: A mutation is any alteration in the DNA sequence (in the genetic code). It can occur due to a copying error or external agents (radiation, chemical substances). In the code, the substitution, loss, or insertion of a base changes the 'message', potentially altering the protein produced. Mutations can be neutral, harmful (causing diseases), or, rarely, advantageous. — A simple base substitution in DNA can change an entire protein — which is why mutation is a source of variation and, sometimes, of diseases.

6. Know at least five genetic disorders and tell a story about a famous person or someone you know who has one of these diseases.

   Answer: Five genetic disorders: Down syndrome (trisomy of chromosome 21), sickle cell anemia, cystic fibrosis, hemophilia, and color blindness. Historical example: hemophilia (the 'disease of kings') affected descendants of Queen Victoria of England, spreading throughout the European royal families. (It is also possible to tell the story of someone you know who lives with one of these disorders.) — Knowing about genetic disorders helps us understand, respect, and support the people who live with them.

7. Is genetics the only factor that contributes to your characteristics (physical, mental, social, and spiritual)? What other factors influence your life and your personality?

   Answer: No. Besides genetics, many factors influence life and personality: the environment (family, friends, school, culture), diet and health, lived experiences, education, personal choices, and, in the Christian view, spiritual life and the relationship with God. Heredity and environment act together in what we become. — We are not merely the product of our genes: environment, choices, and spiritual life profoundly shape who we are.

8. Find three quotations from the Bible or from the Spirit of Prophecy that relate to your answer to the previous question.