Honors Biology Chapter 8 - DNA Structure and Function, Viruses, and Karyotypes
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-what structure DNA is organized into
-an eukaryotic one of these consists of one DNA molecule
-duplicated ones condense to look like the letter "X"
-human body cells are considered this because they have 2 sets of 23 chromosomes
-represented by the symbol "2n"
-two sets of chromosomes
-an image of the chromosomes of an individual
-shows all the chromosomes found in the diploid cells of the individual
-arranged in order according to size, centromere location, shape, and length
-one set of chromosomes
-uses the symbol "n"
-sex cells are considered this
-the building block of DNA and monomer of nucleic acids
-made of one sugar (deoxyribose), three phosphate groups, and a nitrogen base (adenine, thymine, cytosine, and guanine)
-structure determined in the early 1900s
-chromosomes that determine the sex of an individual
-Pair 23, differs in males and females -X and Y chromosomes (XX=female, XY=male)
-seals any gaps that remain between the bases of the "new" DNA
-the enzyme that helps glue DNA fragments (Okazaki fragments) together
-assemble new strands of DNA from nucleotides starting at the primers, using the parent strands as templates
-the enzyme that carries out DNA synthesis
-replicates DNA molecules to build a new strand of DNA
-process in which DNA makes a duplicate copy of itself
-occurs during the S phase of interphase
-must come BEFORE cell division, so each cell inherits a complete and identical copy of the parents' genetic info
-three major steps: binding of enzymes to existing DNA, unwinding of double helix, synthesis of new matching strand for each existing strand
-proceeds in a 5' to 3' direction
-the order in which the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T) are arranged in a strand of DNA
-varies tremendously among species
-DNA molecules can be 100's of millions nucleotides long
-after DNA replication occurs one strand of the DNA is parental (conserved) and the other is new because the parental DNA served as a template
-one half old and one half new
-permanent change in the DNA sequence of a cell's chromosome occurs when proofreading and repair mechanisms fail to solve an error
-can form in any type of cell
-ones that occur during egg or sperm formation can be passed on to offspring
-ones that alter DNA's instructions may have a harmful or lethal outcome
-most cancers begin with this
-not all are dangerous
-some give rise to variation in traits, a basis for evolution
-process in which cells become different in form and function
-a one way path
-once this occurs, most of a cell's DNA has been turned off
-a somatic cell is taken from an adult organism (contains master blueprint for new individuals)
-adult somatic cells will not start dividing to produce an embryo because the cell has already differentiated
-a cloning technique that can undifferentiate a somatic cell by turning its unused DNA back on
-an unfertilized egg's nucleus is replaced with the nucleus of a donor's somatic cell, the egg's cytoplasm reprograms the transplanted DNA to direct the development of an embryo, which is then implanted into a surrogate mother
-method of reproductive cloning used in 1997 to clone a lamb named Dolly
-isolated two different types of pneumonia from mice and grew them in his lab but only one of the strains caused pneumonia
-disease causing bacteria grew in smooth colonies, while the harmless one grew in rough colonies
-mice injected with disease causing bacteria developed pneumonia and died, mice injected with the harmless strain were fine
-wondered if the disease causing bacteria might produce poison, so isolated a culture of cells heated them to kill the bacteria and injected it into the mice
-the mice survived his heated solution, so the cause of pneumonia was NOT a chemical poison released by the disease causing bacteria
-mixed his heated disease causing bacteria with live harmless ones and injected that into the mice, the mice developed pneumonia and many died
-the heat killed bacteria had passed their disease causing ability to the harmless strain he called it TRANSFORMATION
-discovered that heat-killed, disease-causing bacteria can transform harmless bacteria into disease ones (transformation)
-thought that if they figured out what part of the virus entered the infected cell they could learn whether genes were made of protein or DNA
-grew viruses and cultures containing radioactive isotopes which acted as markers
-mixed the marked viruses with bacteria, waited a few minutes then separated the virus from the bacteria and tested the bacteria for radioactivity
-nearly all the radioactivity in the bacteria from phosphorus (32p), the marker, was found in DNA
-proved DNA was a component that passes information from one generation to the next (the first principle)
-worked with a bacteriophage
-carried out experiments to determine DNA (not protein) is the molecule that passes on the information to make new viruses inside a host
-5 carbon sugar
-three phosphate groups
-nitrogen containing base
-huge in length
-2 nanometers in diameter
-repeating patterns every 0.34 nanometers
-two chains of nucleotides running in opposite directions (antiparallel) coiled into a double helix
-sugar phosphate backbone created by covalent bonds which link the deoxyribose of one nucleotide to the phosphate of the next
-hydrogen bonds between the internal bases hold the two sides together
-can be 100's of millions of nucleotides long
-adenine
-thymine
-cytosine
-guanine
-adenine to thymine, with TWO hydrogen bonds
-cytosine to guanine, with THREE hydrogen bonds
-the sex of a perso
-how many autosomes a person has
-how many and what sex chromosomes a person has
-any chromosomal abnormalities (monosomy, trisomy) which lead to genetic disorders (down syndrome, turner syndrome, klinefelters)
Enzymes unwind
Helicase separates the two strands of DNA and single strand binding proteins bind to the DNA strands, keeping them separated
Primers base pair with the exposed DNA. Hybridization is a base pairing between strands and is driven by hydrogen bonds.
Starting at the primers, DNA polymerases assemble new strands of DNA from nucleotides, using the parent strands as templates.
DNA ligase seals any gaps that remain between the bases of the "new" DNA and okazaki fragments together
Each parental DNA serves as a template for the new strand of DNA. The new DNA molecule winds up. One strand of each is parental (conserved) and the other is new. DNA said to be semi-conservative.
-helicase: breaks through the hydrogen bonds between the nitrogen bases in DNA, unzipping/separating it
-DNA polymerase: assemble new strands of DNA from nucleotides using the parent strands as templates, replicates DNA molecules, carries out DNA synthesis
-DNA ligase: seals any gaps that remain between the bases and okazaki fragments of the "new" DNA
-Primase: short, single strand of DNA or RNA that serves as an attachment point for DNA polymerase (tells it where to start)
-ionizing radiation from X-rays, most UV light and gamma rays
-chemicals: DDT, Agent Orange, BPA
-radiation: sun, UV, X rays
-disease/infection: HPV, Hepatitis
-nucleus removed from both donor cells (a somatic cell and an egg cell), followed by nuclear transfer
-cell growth in tissue culture
-embryo implanted into surrogate mother
-surrogate mother gives birth to the clone
-when cells are different in form and function
-a one way path
-most of a cell's DNA is turned off after this
-the DNA has to be reprogrammed when used for cloning because of this
-somatic cells have already been through this
-body cells
-used in SCNT (what cloned a lamb named Dolly in 1997)
-already been through differentiation (obtaining specialized characteristics), possibly causing problems in clones
Somatic Cell Nuclear Transfer is a method of this which was used in 1997 to clone a lamb named Dolly
the structure of a class of proteins is a helix
-a full complement of hereditary information must be transmitted along with the molecule from one generation to the next
-cells of a given species all have the same amount of hereditary information
-it must be exempt from major change in order to function as a genetic bridge between generations
-it must be capable of encoding a huge amount of information required to build a new individual
-the amount of adenine and thymine were always equal, as were cytosine and guanine
-DNA of different species differs and its proportions of adenine and guanine
-binding of enzymes to existing DNA
-unwinding of double helix
-synthesis of matching strand for each existing strand
-the wrong base is added to a growing DNA strand
-a nucleotide gets lost, or an extra one slips in