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Cellular Reproduction and DNA Offspring receive their traits from their parentsbut sometimes the child looks nothing like the parents Cellular Reproduction and DNA Offspring receive their traits from their parentsbut sometimes the child looks nothing like the parents Lamarkian biology- characteristics such as height, strength, and weight are determined by the activities of the parents. (FAIL.) The Father of Modern Genetics Gregor Mendel (1822-1884): an Austrian monk Gave first real explanation for how traits are passed on to offspring Conducted meticulous experiments on 29,000 pea plants Mendel's work was rejected during his lifetime, and it wasn't widely accepted until the 1930's and 1940's Genetics- the science that studies how characteristics get passed from parent to offspring Genes, Chromosomes, and DNA DNA governs an organism's traits and characteristics DNA's main function is to tell the cell what proteins to make Genes, Chromosomes, and DNA DNA governs an organism's traits and characteristics DNA's main function is to tell the cell what proteins to make Not every organism's traits are completely determined by a person's genes Genetic tendency- a range of possible characteristics set by DNA Genetic Tendencies People have a certain capacity for musical ability, or athletic ability Some people choose to fight against genetic predispositions such as alcoholism and obesity Consider an alcoholic whose father is also an alcoholic- you could argue that the son learned this through father, or that alcoholism is in his genes, or it's a combination of both Genetic Tendencies People have a certain capacity for musical ability, or athletic ability Some people choose to fight against genetic predispositions such as alcoholism and obesity Consider an alcoholic whose father is also an alcoholic- you could argue that the son learned this through father, or that alcoholism is in his genes, or it's a combination of both Gay rights activists are searching for a “gay gene” in order to justify their behavior However, many defects are transmitted through genes (eg. Down Syndrome, cystic fibrosis, color blindness) Even if a “gay gene” were found, a gene cannot force a person into a homosexual lifestyle- he is able to choose how to live, just like an alcoholic can choose not to drink alcohol Developmental Factors Characteristics completely from DNA: hair color, blood type DNA alone does not determine who you are or what you will become DNA provides the general framework within which you decide who you will become Developmental Factors Characteristics completely from DNA: hair color, blood type DNA alone does not determine who you are or what you will become DNA provides the general framework within which you decide who you will become Genetic factors- traits determined by DNA Environmental factors- nonbiological factors that are involved in a person's surroundings (family, friends, school, choices they make) Spiritual factors- factors in a person's life determined by the quality of their relationship with God There is still much debate over how much influence each of these factors has over a person's development Genes and DNA Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait Genes and DNA Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait The tasks that a cell can complete depend upon the proteins it produces If a cell produces certain proteins, it's a nerve cell, if it make other proteins, it's a blood cell Genes and DNA Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait The tasks that a cell can complete depend upon the proteins it produces If a cell produces certain proteins, it's a nerve cell, if it make other proteins, it's a blood cell A cell knows what proteins it should produce because the DNA tells it what to make DNA and RNA DNA and RNA DNA RNA Sugar: deoxyribose Sugar: ribose Structure: double helix Structure: single strand Nucleotides: adenine, guanine, cytosine, thymine Nucleotides: adenine, guanine, cytosine, thymine More stable, less likely to experience changes during duplication (less mutations) Less stable Protein Synthesis- Part 1: Transcription 1. Transcription- building an RNA strand from a section of DNA RNA copies DNA by attaching corresponding nucleotide bases RNA is like a camera that produces a negative image (light in places it should be dark) T- A C- G A- U Protein Synthesis- Part II: Translation 2. Translation: the process of translating the nucleotide bases into amino acid sequences Protein Synthesis- Part II: Translation 2. Translation: the process of translating the nucleotide bases into amino acid sequences Messenger RNA (mRNA)RNA that performs transcription and then goes to the ribosomes Protein Synthesis- Part II: Translation 2. Translation: the process of translating the nucleotide bases into amino acid sequences Messenger RNA (mRNA)RNA that performs transcription and then goes to the ribosomes Transfer RNA (tRNA)contains an anticodon bonded to an amino acid Anticodon- three nucleotide base sequence on tRNA Protein Synthesis- Part II: Translation Codon- a sequence of three nucleotide bases on mRNA that refers to specific amino acid Protein Synthesis- Part II: Translation Codon- a sequence of three nucleotide bases on mRNA that refers to specific amino acid Translation repeats until all amino acids that are called for by codons are linked together DNA → RNA → protein Protein Synthesis- Part II: Translation Codon- a sequence of three nucleotide bases on mRNA that refers to specific amino acid Translation repeats until all amino acids that are called for by codons are linked together DNA → RNA → protein A given amino acid can be “called for” by several different codons. eg. cysteine can be called by UGC or UGU However, a single codon cannot call for more than one amino acid (eg. UGU is only for cysteine) Protein Synthesis DNA and RNA Exons- part of DNA with instructions for making a protein Introns- separates exons, must be removed before it becomes mRNA DNA and RNA Exons- part of DNA with instructions for making a protein Introns- separates exons, must be removed before it becomes mRNA Introns are also known as “junk DNA” because they don't appear to serve any purpose DNA is very thin- .0000002mm If all the DNA from one cell we strung together end to end, it would be six feet long. All DNA in body: 67 billion miles (16x distance of Pluto to Sun) How DNA is Packaged Histones- proteins that act as spools which wind up small stretches of DNA Nucleosomes- beads of DNA wrapped around histone How DNA is Packaged Histones- proteins that act as spools which wind up small stretches of DNA Nucleosomes- beads of DNA wrapped around histone Chromosome- network of DNA coils and proteins In nucleus How DNA is Packaged Histones- proteins that act as spools which wind up small stretches of DNA Nucleosomes- beads of DNA wrapped around histone Chromosome- network of DNA coils and proteins In nucleus Chromatin- strands of chromosomes, RNA, and proteins Condensed chromosome- most compact version of DNA Humans: 46 chromosomes horse: 64, crayfish: 200 Mitosis and Interphase Mitosis- a process of asexual reproduction in eukaryotic cells Interphase- time interval between cellular reproduction Chromosomes not condensed Cell spends most of its time in this stage DNA remains in its chromatin form, except when making proteins Cell cycle- cycle between interphase and mitosis Mitosis -In order to reproduce, chromosomes must duplicate -Sister chromatids- duplicate chromosomes -The centrioles also duplicate, then mitosis starts 1. Prophase -duplicated chromosomes coil into their condensed form Centromere- the region that joins two sister chromatids -aster- microtubules extended from centrioles -as centrioles migrate, the microtubules grow, producing spindle fibers - Spindle fibers make up the mitotic spindle 2. Metaphase -chromosomes are lined up along equatorial plane 2. Metaphase -chromosomes are lined up along equatorial plane 3. Anaphase -microtubules separate the sister chromatids from each other -sister chromatids are pulled to opposite sides 2. Metaphase -chromosomes are lined up along equatorial plane 3. Anaphase -microtubules separate the sister chromatids from each other -sister chromatids are pulled to opposite sides 4. Telophase -spindle begins to disintergrate -plasma membrane begins to constrict along equatorial plane 4. Telophase -spindle begins to disintergrate -plasma membrane begins to constrict along equatorial plane -two cells begin to form -nuclear membrane forms around each chromosome - chromosomes uncoil from their condensed form back into chromatin -the end result is two identical daughter cells More About Mitosis •Each daughter cell gets at least one of each organelle •If the two cells have only one organelle between them, the organelle is split •DNA can build up or make new organelles as needed •The mitochondria has its own DNA so it can replicate itself More About Mitosis •Each daughter cell gets at least one of each organelle •If the two cells have only one organelle between them, the organelle is split •DNA can build up or make new organelles as needed •The mitochondria has its own DNA so it can replicate itself •Mitosis is a form of asexual reproduction •Every eukaryotic organism performs mitosis •Mitosis produces new cells as the organism grows, and replaces dead cells •Millions of red blood cells die every minute More About Mitosis • Plant mitosis: due to cell wall, the plasma membrane can’t constrict • Cellulose is formed in the middle, producing the cell well • Also no centrioles are in the plant cells Chromosomes Karyotype- the figure produced when chromosomes of a species during metaphase are arranged according to their homologous pairs -Homologous pairs- chromosomes that are very similar but not identical -Sex chromosomes- a pair of chromosomes which can be used to distinguish between the sexes - XX: female - XY: male Diploid and Haploid Cells •each homologue has exactly the same number of genes as its partner •For example, the gene for blood type can be found on chromosome #9- on one homologue, the gene might be for blood type A and on the other, O. •Diploid cell- a cell with chromosomes that come in homologous pairs •Haploid cell- a cell that has only one representative of each pair Diploid and Haploid Cells •Even species that have diploid cells will have some haploid cells •Diploid number (2n)total number of chromosomes in a diploid cell •46 for human •Haploid number- (n) number of homologous pairs in a diploid cell •23 for human Sexual Reproduction Meiosis – the process by which a diploid (2n) cell forms gametes (n) -each parent contributes 23 chromosomes -In meiosis, diploid cells get split into haploid cells called gametes -Gametes- haploid cells produced by diploid cells for purpose of sexual reproduction -Female: egg (ovum) Male: sperm -Two gametes join together to form a| diploid cell that has 23 homologous pairs of chromosomes- zygote Meiosis I Meiosis I- one diploid cell forms two haploid cells -two begin meiosis, cell must duplicate DNA and centrioles -Prophase I- centrioles move to opposite sides of cell -DNA is exchanged between homologous chromosomes (cross over) -Mitotic spindle forms -Metaphase I- single microtubule for each pair- chromatids stay intact Meiosis I Anaphase I- homologous pairs are pulled to either side Telophase I- plasma membrane constricts along equatorial plane -two haploid cells are formed -though each cell has 46 chromosomes, the cells are considered haploid because the chromosomes are paired with an exact duplicate, leaving 23 unique chromosomes Meiosis Prophase II- both cells have their centrioles duplicate and form a spindle Metaphase II- chromosomes line up along equatorial plane -chromosomes attach to each chromatid Anaphase II- the microtubules pull the chromosomes away from their duplicates Telophase II- plasma membrane constricts along equatorial plane, forming two pairs of haploid cells Mitosis vs. Meiosis Mitosis: one diploid cell forms two duplicate diploid cells Meiosis: diploid to haploid -One diploid cell forms 4 haploid cells Spermatogenesis -In males, meiosis produces sperm cells - At the end of meiosis II, flagella emerges on each of the four haploid cells Oogenesis Oogenesis: meiosis in females -at the end of telophase I, one of the two cells produced takes most of the cytoplasm and organelles -After meiosis II, one of the big cells from Meiosis I takes most of the cytoplasm and organelles -the end result is one large gamete (Egg cell) and three smaller polar bodies - when the sperm burrows into the egg, it forms a diploid cell called a zygote Viruses Virus- non-cellular infectious agent 1. has genetic material (RNA or DNA) inside a protective protein coat 2. cannot reproduce on its own -a virus hijacks a cell in order to reproduce -because a virus cannot reproduce on its own, it’s not alive Lytic Pathway 1. Virus attaches to bacterium 2. Virus injects own genetic material 3. Virus DNA instructs bacteria to make viral proteins and genetic material 4. Viruses form in cell 5. Cell ruptures, releasing several viruses Viruses •Some viruses, like HIV, can inject genes into the cell and lie dormant for several years before the lytic pathway starts •Viruses: chicken pox, flu, mumps, cold, mumps, measles, AIDS, cold sores, some forms of cancer •Viruses affect plants, animals, and bacteria The Immune System Phagocytic cells- purpose is to engulf and destroy pathogens (eg. White blood cells) Lymph nodes- a place for phagocytic cells to gather -lymph carries pathogens through the lymph nodes, where the phagocytic cells destroy them Antibodies- specialized proteins that aid in destroying infectious agents Antibodies -some antibodies can destroy many kinds of pathogens, others can only fight one kind -when the body is infected, it produces antibodies that will destroy the pathogen -the body remembers which antibodies will fight a particular disease Vaccine- a weakened or inactive version of a pathogen that stimulates the body’s production of antibodies which can aid in destroying a pathogen