LS 12 Notes (DNA and Genetics)

LS 12 Notes (DNA and Genetics)

  • Genetics is the study of heredity
  • Gregor Mendel is considered to be the “Father of Genetics”. He was an Austrian monk who experimented with pea plants around 1853.
  • The basic laws of Mendelian genetics explain the transmission of most traits that can be inherited from _generation to generation.
  • The passing of traits and genes from one generation to the next is heredity.
  • Deoxyribonucleic acid is _DNA and it is the genetic material that is passed from parent to offspring and it carries the genetic code.
  • James Watson and Francis Crick made a model of the DNA molecule (double helix)
  • DNA is a double helix molecule.
  • DNA is a molecule that includes different components — sugars, nitrogenous bases, and phosphates. The arrangement of the nitrogenous bases within the double helix forms a chemical code.
  • The nitrogen bases are: adenine, guanine, cytosine and thymine.The bases pair up and adenine always pairs with thymine and guanine always pairs with cytosine
  • Chromosomes are strands of tightly wound DNA. Genes are sections of a chromosome that carry the code for a particular trait. An allele is an alternate form of a gene. A chromosome carries DNA and contains DNA
  • A gene is a segment of DNA on a chromosome that carries a specific trait
  • The information carried in the chromosomes of an organism is a genome-all the DNA in one cell of an organism.
  • Humans have 46 chromosomes, which is 23 pairs.
  • The letters capital X and capital Y represent sex chromosomes. XX represents female while XY represents male
  • A trait is a characteristic that is passed to offspring in genes
  • Alleles are different forms of a gene [example:tall (T) vs. short (t) for height]
  • Having two like gene or alleles, such as TT or tt is pure/purebred
  • Genoytpes are the genetic makeup represented by the letters of the alphabet (TT, Tt, tt)
  • Phenotype are the physical characteristics/appearance or what an organism “looks like” represented by words (tall, yellow, thin)
  • Homozygous-two identical alleles for a trait (TT or tt).This is similar to purebred which means offspring are the same as the parent
  • Heterozygous-two different alleles for a trait (Tt), also known as a hybrid
  • A Punnett Square is a model used to predict the possible combinations of inherited factors resulting from single trait crosses. (genetic crosses)Reginald Punnett came up with the square.Shows possible combination of parents and the offspring that would be created.
  • Dominant traits mask the expression (phenotype) of recessive traits. A genotype is the specific combination of dominant and recessive gene forms.
  • The dominant allele masks recessive alleles.It is represented by a capital letter (for example T). This trait will always show up if that allele is present.It will be written first in a Punnett Square.
  • A recessive allele is represented by a lower case letter and is the weaker of the two alleles
  • Codominance is where neither trait is either dominant or recessive.
  • Characteristics that are expressed through genes can be inherited. Characteristics that are acquired through environmental influences, such as injuries or practiced skills cannot be inherited.
  • Meiosis is the process that occurs in the formation of sex cells by which the number of chromosomes is reduced by half.
  • Mitosis is where the nucleus divides once and creates two new nuclei and 1 copy of the DNA goes to each daughter cell
  • You can inherit how you look from your parents, but you can’t inherit mannerism, skills, or abilities. Examples: sports skills, humor, clumsiness
  • Mutations are random events; they are changes in genes or chromosomes
  • Genetic disorders are abnormal conditions caused by mutations or changes in DNA (genes or chromosomes). This can happen during meiosis or can be passed down from parents.Some genetic mutations include:
    • Cystic Fibrosis-mucus fills up in the lungs and intestines, no cure (usually occurs in whites)
    • Sickle Cell-affects the blood and formation of blood cells, affects the hemoglobin, a protein in red blood cells, no cure (usually affects African Americans)
    • Huntington’s-found on dominant allele, you have a 50% chance of passing it to offspring, diagnosed after you turn 30, it is fatal because it breaks down your brain cells
    • Down Syndrome-you are born with an extra chromosome and it happens during meiosis
    • Hemophilia-blood clots slowly or not at all, it is a sex linked disorder-it is more common in males
  • Genetic engineering is where genes from one are put into the DNA of another and used for medication production, improve food sources, and cure genetic disorders.
  • In genetic engineering, the genetic code is manipulated to obtain a desired product/result.
  • Genetic engineering has numerous practical applications in medicine, agriculture, and biology.
  • Cloning is making a genetically identical copy of an organism that is created by using tissue of a single adult
  • Selective Breeding is creating organisms with desired traits, usually to improve production amounts or to resist disease
  • Inbreeding is crossing two individuals with identical or similar alleles
  • A series of contributions and discoveries led to the current level of genetic science.