Results for "rosalind franklin"

biology 2.1Unit 2.1: Mitosis and Meiosis Introduction By the end of this section, you should be able to: Define a chromosome. Define DNA as the genetic material. Define genes. Describe the structure of chromosomes. Describe the components of DNA. Define mitosis and describe its stages. Define meiosis and describe its stages. Relate the events of meiosis to the formation of sex cells. Compare mitosis and meiosis. Chromosomes, Genes, and DNA Almost all the cells of your body—except for mature red blood cells—contain a nucleus, which acts as the control center of the cell. The nucleus holds all the information needed to make a new cell and, ultimately, a new individual. Inside the nucleus are chromosomes, thread-like structures that store genetic information passed from parents to offspring. Chromosomes are made up of DNA (deoxyribonucleic acid), a molecule that carries the instructions needed to make all the proteins in your body. Many of these proteins are enzymes, which control the production of other chemicals and affect everything about how your body functions. Each species has a specific number of chromosomes: Humans have 46 chromosomes (23 pairs). Tomatoes have 24 chromosomes (12 pairs). Elephants have 56 chromosomes (28 pairs). Half of your chromosomes come from your mother, and the other half from your father. These chromosomes are arranged in homologous pairs, meaning they contain matching sets of genes. A karyotype is a special photograph that arranges chromosomes into their pairs. In humans, 22 pairs of chromosomes are called autosomes, which control most body functions. The 23rd pair is the sex chromosomes, which determine whether you are male or female: Females have two X chromosomes (XX). Males have one X and one Y chromosome (XY). DNA Structure DNA is a long, twisted molecule shaped like a double helix (a spiraled ladder). Each strand of DNA is made up of smaller molecules called nucleotides, which consist of: A phosphate group A sugar (deoxyribose) A nitrogen base The four nitrogen bases in DNA are: Adenine (A) → Always pairs with Thymine (T) Cytosine (C) → Always pairs with Guanine (G) Genes are small segments of DNA that carry instructions for making proteins. The sequence of these bases acts like a biological code, directing the cell to create specific proteins. In 1953, James Watson and Francis Crick, using data from Rosalind Franklin’s X-ray photographs, discovered the double-helix structure of DNA. Their discovery led to a huge increase in genetic research, including the Human Genome Project, which mapped all human genes. Mitosis (Cell Division for Growth and Repair) All body cells (somatic cells) divide using mitosis, a type of cell division that creates two identical daughter cells. Mitosis is essential for: Growth (producing new cells). Tissue repair (replacing damaged or old cells). Asexual reproduction (producing offspring with identical DNA). Stages of Mitosis Interphase The cell prepares for division by copying its DNA. Chromosomes are not visible under a microscope. Prophase Chromosomes condense and become visible. The nuclear membrane breaks down. Metaphase Chromosomes line up in the center of the cell. Spindle fibers attach to each chromosome. Anaphase The spindle fibers pull the sister chromatids apart to opposite ends of the cell. Telophase A new nuclear membrane forms around each set of chromosomes. The cell is almost ready to split. Cytokinesis The cytoplasm divides, forming two identical daughter cells. Mitosis is constantly occurring in areas like your skin and bone marrow, where new cells are needed regularly. Meiosis (Cell Division for Reproduction) Unlike mitosis, meiosis occurs only in the reproductive organs (testes in males, ovaries in females) and produces gametes (sperm and egg cells). Gametes have half the number of chromosomes (haploid, n=23) so that when fertilization occurs, the new cell has the correct chromosome number (diploid, 2n=46). Stages of Meiosis Meiosis consists of two rounds of cell division, resulting in four non-identical cells. Meiosis I: Prophase I – Chromosomes pair up and exchange genetic material (crossing over). Metaphase I – Chromosome pairs line up in the center of the cell. Anaphase I – Chromosome pairs separate and move to opposite ends of the cell. Telophase I & Cytokinesis – The cell splits into two haploid daughter cells. Meiosis II (similar to mitosis): 5. Prophase II – Chromosomes condense again. 6. Metaphase II – Chromosomes line up in the center. 7. Anaphase II – Sister chromatids separate and move to opposite sides. 8. Telophase II & Cytokinesis – Four unique haploid gametes are formed. Each gamete is genetically different due to crossing over and random chromosome distribution. Mitosis vs. Meiosis: Key Differences Importance of Mitosis and Meiosis Mitosis ensures that cells grow, repair damage, and replace old cells. Meiosis allows genetic diversity, which is essential for evolution and survival. Summary Chromosomes carry genetic information in the form of DNA. Genes are sections of DNA that code for proteins. Mitosis produces two identical daughter cells for growth and repair. Meiosis creates four non-identical sex cells for reproduction. Mitosis ensures genetic stability, while meiosis introduces genetic diversity

Let’s break this down! I’ll give you a study guide covering asexual reproduction, sexual reproduction (in humans and plants), and Mendelian genetics — then I’ll create a test for you. ⸻ Study Guide for Asexual Reproduction, Sexual Reproduction, and Mendelian Genetics ⸻ I. Asexual Reproduction • Definition: Involves a single parent, producing offspring genetically identical to the parent (clones). • Types of Asexual Reproduction: • Binary Fission: Simple cell division (e.g., bacteria). • Budding: New organism grows from a bud on the parent (e.g., yeast, hydra). • Fragmentation/Regeneration: Organism splits, and each part grows into a new organism (e.g., starfish). • Vegetative Propagation: New plants grow from parts of the parent plant (e.g., runners in strawberries). • Parthenogenesis: Offspring develop from unfertilized eggs (e.g., some lizards, insects). • Pros and Cons: • Pros: Fast, no need for a mate, energy-efficient. • Cons: No genetic variation, susceptible to environmental changes. ⸻ II. Sexual Reproduction (Humans & Plants) Humans: • Process: • Gametes (sperm and egg) produced by meiosis. • Fertilization forms a zygote (diploid cell). • Male Reproductive System: Testes, epididymis, vas deferens, prostate, urethra, penis. • Female Reproductive System: Ovaries, fallopian tubes, uterus, cervix, vagina. • Hormonal Regulation: • Male: Testosterone (sperm production, secondary characteristics). • Female: Estrogen & progesterone (menstrual cycle, pregnancy). Plants: • Process: Alternation of generations (sporophyte & gametophyte stages). • Pollination: Transfer of pollen to stigma. • Fertilization: Sperm (from pollen) fuses with egg in ovule. • Structures: Stamen (male), carpel/pistil (female). • Seed & Fruit Development: Fertilized ovules become seeds; ovary becomes fruit. ⸻ III. Mendelian Genetics • Gregor Mendel’s Experiments: Pea plants, discovered inheritance patterns. • Key Concepts: • Genes & Alleles: Genes determine traits, alleles are gene variants. • Dominant vs. Recessive Alleles: Dominant alleles mask recessive ones. • Homozygous vs. Heterozygous: Same alleles (AA or aa) vs. different alleles (Aa). • Laws of Inheritance: • Law of Segregation: Allele pairs separate during gamete formation. • Law of Independent Assortment: Genes for different traits sort independently. • Genetic Crosses: Punnett squares, monohybrid/dihybrid crosses. • Probability & Ratios: Phenotypic/genotypic ratios. • Non-Mendelian Inheritance: Incomplete dominance, codominance, multiple alleles, polygenic traits, sex-linked traits. ⸻ AP Biology Practice Test Total Questions: 30 (Multiple Choice) Section 1: Asexual Reproduction (6 questions) 1. Which form of asexual reproduction involves an organism splitting into two identical cells? a) Budding b) Fragmentation c) Binary fission d) Parthenogenesis 2. Which organism commonly reproduces through budding? a) Bacteria b) Starfish c) Hydra d) Fern 3. A disadvantage of asexual reproduction is: a) Slow reproduction rate b) High genetic diversity c) Vulnerability to environmental changes d) Requirement of a mate 4. Which plant structure is involved in vegetative propagation? a) Petal b) Stigma c) Runner d) Anther 5. Parthenogenesis involves: a) Fertilized eggs developing into offspring b) Unfertilized eggs developing into offspring c) Fusion of gametes d) Regeneration of lost body parts 6. What is the primary benefit of asexual reproduction in stable environments? a) Genetic variation b) Rapid population growth c) Evolutionary adaptability d) Reduced mutation rates ⸻ Section 2: Sexual Reproduction (8 questions) 7. In humans, fertilization typically occurs in the: a) Uterus b) Vagina c) Ovary d) Fallopian tube 8. The male gamete in plants is contained in the: a) Ovule b) Anther c) Pollen grain d) Stigma 9. Which hormone triggers ovulation? a) Testosterone b) Progesterone c) Luteinizing hormone (LH) d) Estrogen 10. The female gametophyte in flowering plants is the: a) Ovary b) Pollen tube c) Embryo sac d) Sepal 11. Which part of the male reproductive system produces sperm? a) Epididymis b) Vas deferens c) Testes d) Prostate gland 12. The process where pollen is transferred from anther to stigma is: a) Germination b) Pollination c) Fertilization d) Sporulation 13. What structure develops into a seed after fertilization in plants? a) Ovule b) Ovary c) Stamen d) Pistil 14. Which term describes the fusion of egg and sperm to form a zygote? a) Gametogenesis b) Meiosis c) Fertilization d) Pollination ⸻ Section 3: Mendelian Genetics (16 questions) 15. Who is considered the “Father of Genetics”? a) Charles Darwin b) Gregor Mendel c) Rosalind Franklin d) James Watson 16. The physical expression of a trait is called: a) Genotype b) Phenotype c) Allele d) Chromosome 17. An organism with the genotype Aa is: a) Homozygous dominant b) Homozygous recessive c) Heterozygous d) Diploid 18. A Punnett square shows: a) The process of DNA replication b) Possible genetic combinations of offspring c) Chromosome number in gametes d) Evolutionary relationships 19. The expected phenotypic ratio for a monohybrid cross is: a) 1:2:1 b) 9:3:3:1 c) 3:1 d) 4:0 20. Which of Mendel’s laws states that allele pairs separate during gamete formation? a) Law of Independent Assortment b) Law of Segregation c) Law of Dominance d) Law of Inheritance 21. Incomplete dominance results in: a) Blended traits b) Both traits expressed equally c) One trait completely masking another d) A 9:3:3:1 ratio 22. A cross between two heterozygous individuals (Aa x Aa) produces what genotypic ratio? a) 3:1 b) 1:2:1 c) 9:3:3:1 d) 2:2 23-30

mayrice snd wilkins and rosalind franklin

Biology Unit 8 study guide, DNA replication, Scientists (s/r-strain) and (Rosalind Franklin + other scientists)

Rosalind Franklin and Maurice Wilkins

Chap 16 - Molecular basis of Inherita

CH 8: DNA Structure and Function (Pt1/2)

CH 8: DNA Replication (pt 2/2)