Biology Study Note PDF

Genetics Terminology: Chromosome: A structure made of protein and DNA that carries genetic information and is located in the nucleus. Autosome: An autosome is any chromosome that isn’t a sex chromosome Sex Chromosome: Sister Chromatid: A Sister Chromatid is an identical copy of a chromosome made...

Genetics Terminology: Chromosome: A structure made of protein and DNA that carries genetic information and is located in the nucleus. Autosome: An autosome is any chromosome that isn’t a sex chromosome Sex Chromosome: Sister Chromatid: A Sister Chromatid is an identical copy of a chromosome made during DNA replication in the synthesis phase of interphase Centromere: A Centromere is part of the chromosome. It helps the cell divide during mitosis and meiosis, and the spindle fibers attach to it. Homologous Chromosomes: Homologous Chromosomes are a set of maternal and paternal chromosomes with the same genes that pair up during fertilization. DNA: Deoxyribonucleic acid is a structure made of two chains in a double helix shape that carries the genetic information to create life. The chains are made of nucleotides, Nucleotides are made up of a nitrogen base (adenine, thymine, cytosine, & guanine (A&T Bond, C&G Bond)), A sugar called Deoxyribose, and a phosphate group. A covalent bond between the nitrogenous bases holds the chains together. Genes: Genes are the basic unit of inheritance. Genes are made up of sequences of DNA arranged on specific parts of a chromosome. Diploid: Diploid describes a cell with two complete sets of chromosomes. All human cells are diploid except for the gametes, human body cells have a total of 46 chromosomes. Haploid: Haploid describes a cell with one set of chromosomes. Human gametes are haploid and have 23 chromosomes. Gamete: A gamete is a sex cell. A female Gamete is called an ova and a male gamete is called a sperm. Somatic cell: Body cells of an organism. (ie, any cell other than the sex cells) Nucleus: The Nucleus is a structure that contains the chromosomes and is often called the brain of the cell. Chromosomal Mutations: Chromosomal Mutations occur when there is a defect in the structure or amount of chromosomes in a cell. Numerical mutations are when there is a missing or extra chromosome within a cell, Trisomy there is one extra chromosome, monosomy there is one missing chromosome and polyploidy where you inherit more than one complete set of chromosomes. Structural Mutations are when the structure of a chromosome is not properly formed, Deletions are when part of the chromosome is missing, Amplifications are when the size of a chromosome is altered, inversions are when part of the chromosome is inverted, and translocation is when parts of a chromosome has been swapped with another chromosome. Real-world examples Trisomy 21 is the cause of Down syndrome. Turner syndrome is caused by monosomy. Mitosis: Mitosis is part of the cell cycle and is the process and duplicating the nucleus and creating a new somatic cell. There are four stages of mitosis, the first is the prophase in which the chromosomes condense themselves, and the chromosomes move along the equator. Metaphase is the second phase and the actions that occur within it are the spindle fibers connected to the chromosomes. In the third phase of anaphase, the spindle fibers pull the chromosomes in two creating two identical daughter chromosomes, the spindle fibers begin to pull the chromosomes to opposite sides of the cell. In telophase, the chromosomes reach opposite sides of the cell, and a new nuclear envelope begins to form. Meiosis: Meiosis is a reductive form of cell division that creates gametes also called gametogenesis(spermatogenesis in males results in 4 sperm cells, Oogenesis in females results in 1 egg & 3 polar bodies, Haploid sperm fertilizes a haploid egg to form a zygote.). The number of chromosomes is reduced from diploid to haploid(halved) during meiosis making haploid gametes. There are two parts of meiosis 1 and 2. In meiosis 1 one diploid cell makes two haploid cells by splitting a homologous chromosome. In Meiosis 2 each haploid divides again forming sister chromatids. Meiosis Phases: Prophase 1: The nuclear membrane dissolves and centrioles move to opposite sides, Chromosomes pair with homologous chromosomes creating tetrads. (4 sister chromatids make up a tetrad)Crossing over can occur at this point. Metaphase 1: Tetrads line up on the equator. A double line of chromosomes forms. Spindle fibers from centrioles attach to the centromeres. Anaphase 1: Chromosomes are pulled by spindle fibers towards the poles(opposite ends). Telophase 1: The nuclear membrane may reform. The cytoplasm divides after telophase forming two haploid daughter cells. Meiosis 2: (ressembles mitosis) Prophase 2: The centrioles are replicated. Centrioles move to opposite poles. Spindle fibers form and then attach to centromeres. Metaphase 2: Chromosomes move to the equator and form a single line. Anaphase 2: Sister chromatids are separated by the spindle fibers. They are moved to opposite poles of the cell. Telophase 2: Cytoplasm separates creating 4 haploid cells. Mendelian Genetics: Gregor Mendel was a scientist who experimented on pea plants and made major contributions to the science of inheritance and the passing on of traits. Mendelian genetics is about how parents pass traits onto their offspring. Medel described three principles for this type of inheritance. Law of dominance and uniformity, The dominant trait is the one that is shown unless there are only recessive genes. Law of segregation of genes, Only one of the two gene copies present is passed onto the gamete. Law of independent assortment, The allele from one gene will not affect the allele of another gene. Punnett Squares: A grid diagram is used to test for an offspring's different possible genotypes and their frequencies. Beyond Mendel Incomplete dominance: Two alleles of equal dominance are inherited and they form a new phenotype(ie, Red dominant + White dominant = Pink phenotype) Multiple alleles is a term used to describe when a genotype has more than 2 possible alleles. Codominance: When two different alleles are both expressed in the phenotype (Red+White = Red&White) Sex-linked traits: Sex-linked traits are genes that are located on the sex chromosomes. Examples: Hemophilia, and color blindness.