Download Genetics and DNA Replication Notes

Genetics and DNA Replication Notes
Heredity – study of how traits are passed to offspring.
Genetics – study of genes and how traits are passed on to offspring.
Information needed to pass traits on to offspring is found in DNA – Deoxyribonucleic Acid
Nucleus
chromosomes
genes
DNA
Hereditary info is
stored in the nucleus
Genes code for different traits; one gene = one trait; alleles are genes for a trait but carry different
forms of the trait.
Gregor Mendel, “Father of Genetics”
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Studied pea plants in the 1800’s
Identified 7 distinct traits
one gene = one trait
Law of Dominance
One gene is inherited from each parent; sometimes one allele is dominant/expressed over the other
allele/recessive allele.
Genotype – the two gene combination carried by an organism for a particular trait; Example: Hh =
heterozygous
Phenotype – the physical trait that is expressed/shows on the outside of the organism; Example – H is
dominant trait of dark hair and the person with Hh genotype shows dark hair trait.
Punnett Square (may be referred to as a “test cross”– a method for determining the percent chance that
offspring will have a certain genotype and phenotype. (see practice sheets on Punnett Squares)
Capital/upper case letter = dominant gene
Little/Lower case letter = recessive gene
Show Results for…
Genotype as HD: Het: HR ratio in that order
Or 25% per square in the test cross that shows that genotype.
Phenotype as Dominant: Recessive ratio in that order
Or 25% per square in the test cross that shows that phenotype.
P stands for the Parent generation
F1 stands for the first set of offspring produced
F2 stands for the second generation produced by the F1 generation
*See other note packets on the Mendelian and Non-Mendelian laws of genetics*
(Deb Thompson’s packet and LE Regents review packet)
Polygenic traits – traits determined by multiple genes. For example, height is
determined by 12 or more genes.
Polygenic traits produce “parental” and “recombinant” genotypes and
phenotypes; parental – exist in the parents, recombinant – does not exist in the
parents.
Percentage of parental versus recombinant is evidence of crossing-over and gene
linkage on chromosomes.
FLOW CHART OF LIVING STRUCTURES
LARGEST ON LEFT TO SMALLEST ON RIGHT
CELLS
NUCLEUS
CHROMOSOMES
GENES
DNA
ORGANIC
COMPOUNDS
Reproduction of offspring;
genetic inheritance of traits
DNA
JOBS
Protein synthesis; production
of proteins needed for life
funtions, enzymes, hormones,
keratin (makes up hair, nails,
claws, hooves etc.)
DNA and Protein Synthesis
Watson and Crick (1950’s) given credit for developing the first 3-D model of double helix
structure of DNA; Rosalyn Franklin made discoveries before them that advanced their work.
Rosalyn Franklin and Maurice Wilkins (1970’s) developed x-ray crystallography and computer
pictures of DNA.
DNA structure are two ladders of nucleotides that twist when bonded together.
(see diagrams on next page)
Remember: nucleic acids (DNA & RNA) and
nucleotide structure; house, pool and car
Protein base pairing of…
Adenosine to Thymine, or Uracil (for RNA),
and
Cytosine to Guanine
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Double helix twisted ladder
Genetic material found in nucleus
Codes for traits
ALSO CODES FOR THE MAKING/SYNTHESIZING OF PROTEINS
DNA Replication
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Enzymes replicate DNA for…
 Cell growth
 Cell division
 Cell repair
Enzymes needed for replication…
1. Helicase – “unzips” the original DNA strands, the scissor.
2. Primase – “flags”or shows starting point for helicase’s work, the primer.
3. DNA polymerase – “builds” the new strand by attaching complementary bases
, the builder. (most important to know)
4. Ligase – “glues” new strands together, the gluer.
(see packet with text correlated diagrams and amoeba sisters video)
RNA (Ribonucleic acid)
 Necessary for protein synthesis
 Carries DNA code outside of the nucleus to the ribosomes (messenger-RNA/m-RNA)
 Matches amino acids with codons (transfer-RNA/t-RNA)
 Found in ribosomes (ribosomal-RNA/r-RNA)
(To study: What are the differences and similarities between DNA and RNA? Make a chart to
compare and contrast the two; think about type of sugar in each name, # of chromosome
strands in structure, pairing of bases.)
Protein Synthesis
(Remember that polypeptides are complex proteins & amino acids are connected by peptide
bonds)
 Occurs at the ribosomes
 DNA carries the original code for the sequence of amino acids that make up all proteins
needed by the organism
 RNA makes the information from the DNA available outside of the nucleus
o Transcription – the copying of the “script” from DNA to m-RNA in the nucleus
o m-RNA carries the “script” out of the nucleus to the cytoplasm surrounding
ribosomes; (RNA pairs Adenine with Uracil not Thymine)
o Translation – the t-RNA “translates” the script from the m-RNA into the chain of
amino acids in the cytoplasm, at the site of the ribosomes in the cytoplasm;
codon/set of 3 bases of m-RNA matches anticodon/set of 3 of t-RNA.
The anti-codon carries the correct amino acid to be added to the protein chain.
(see packet graphics and text corresponding diagrams)
Mnemonic: Doctor writes the script first (transcription); second, the pharmacist translates the
Dr.’s terrible handwriting to fill the script (translation.)
(To study, recreate the flow chart below or reorganize the information into a different type of
graphic organizer.)
transcription
DNA
in the
nucleus
mRNA
codon
Importance of Protein Synthesis
Need all of the following which are proteins or contain proteins…
 Enzymes – the catalysts necessary for all reactions in the human body
 Hormones – chemical messengers that are required for regulation
 Organelle/Cell/Tissue structure – component of organelles such as the cell membrane;
growth, maintenance of body systems such as muscular, skeletal, circulatory…
 Antibodies – the immune system components that protect from infection
 Energy – aid in ATP production
 Cell and organism reproduction – needed for replication of DNA
Mutations
- a change in the DNA order
- CAN BE POSITIVE, NEGATIVE OR NEUTRAL in terms of consequences for organism OR the
adaptation of the species for survival; (disease resistant plants, bacterial resistance to
antibiotics, genetically inherited disorders /Sickle cell anemia…)
- INCREASE IN VARIATION WITHIN A SPECIES = INCREASED CHANCE OF SPECIE’S SURVIVAL
- only mutations in DNA in gametes are passed on to offspring
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can be random errors during replication for both cell division or protein synthesis
can be environmentally induced, caused by “mutagens”; radiation is common source of
environmental mutations (x-rays, UV light, chemicals…)
Specifics Ways that Mutations Occur
Deletions, insertions and substitutions
(see packet for illustrations and examples)
Gene mutations involve a single base, or a few bases
Substitution – “point mutation”
One base changed Ex. ATA becomes AAA
Insertion – base added
Deletion – base is missing
*“frameshift” = caused by insertion and deletion and means all codon orders after
change now code for different amino acids; more serious mutation
Chromosome mutations involve whole pieces/sections of chromosomes
Deletion – missing section
Duplication – added section
Inversion – reversed section of 1 chromosome
Translocation – cross-over between 2 chromosomes; homologous don’t match
(To study create a T-chart comparing gene mutations to chromosome mutations.)
Diseases can be caused by mutations
Autosomal recessive – mutation is found in a non-sex chromosome/an autosome and is a
recessive trait.
Autosomal dominant – mutation is found in a non-sex chromomsome/an autosome and is a
dominant trait.
Sex-linked – condition or disease is inherited on the “X” or “Y” chromosome; most commonly
inherited on the “X”; EFFECTS MALES MOST OFTEN; examples are hemophilia, color blindness
and male pattern baldness.
Genetic Engineering (Chapter 13)
Genetic engineering means manipulating/changing genes or DNA on a molecular level.
Selective breeding - selecting/choosing the parents in order to produce desired/positive traits in the
offspring.
Inbreeding - is continued selective breeding, results in a decrease in genetic variation, and can result in an
unintended increase in undesired/negative traits in the population; Example = purebred dogs
Hybridization – breed to increase genetic variation, does not result in increase of negative traits; Example = Liger,
Goldendoodles/mixed breed dogs.
Examples of desired traits for economic purposes intelligent dogs, blue-eyed dogs, fast racehorses, cows that
give more milk or meat…HUMAN PURPOSES, often COMMERCIAL/ECONOMIC
Desired traits for evolutionary purposes give the members of the species better chance of survival…HAS TO DO
WITH NATURE AND NATURAL PROCESSES.
Gene splicing – replacement of DNA sequence in a bacterial cell with a DNA sequence from another organism,
usually human DNA in order to produce a needed protein; Example: production of insulin for use by diabetics.
Restriction enzyme – used to splice DNA, remove sections to be removed and implanted.
Recombinant DNA – from two different sources
(see packet and below for illustrations and examples)
Cell from a
human being
Bacteria
IMPORTANT
Example: human insulin
Cloning – production of an organism with the identical DNA of the parent organism.
The parent organism donates an autosomal cell whose nucleus is supplanted/put into the
ova/egg of another organism. A third surrogate organism is used to carry the ova with the 2n
chromosome count from the parent. (see packet for illustrations and examples)
Transformation – changing a species by transferring DNA from one specie’s genome to that of
another; creates a transgenic organism; Example: “glowing mice”- fluorescent characteristic
attached to other traits being tested (Alzheimer’s disease research, neurological research) so
that scientists can easily see if the DNA change has been accepted by the transgenic organism.
Gel Electrophoresis - procedure that separates DNA segments according to size; used to solve
crimes and for paternity tests.
Synthetic Biology – developing branch of biology that actually creates DNA codes to generate
organisms or organic matter.
Example – research is being done to produce rubber for products like car tires by manipulating the DNA
of rubber tree plants in order to synthesize rubber using microorganisms/bacteria. The DNA of the
rubber tree plant needed to be changed to speed up the protein synthesis process in microorganisms.
Pre-AP Curriculum
Pyrimidine bases are C and T
Purine bases are A and G
After DNA is “unzipped” by the helicase enzyme (scissor), the leading strand, 5’(read five prime)
to 3’, is copied by DNA polymerase (builder), which is helped by RNA primase (primer), and
adds complementary bases continuously.
The lagging strand, 3’ to 5’, has to work backward matching the bases in chunks called Okizaki
fragments.
DNA ligase (gluer) joins or zips up the strands after they have been matched with its
complement. This is a semiconservative replication process because each strand is matched
with its complement and the original strand is joined with the new strand created. NOT that the
two original strands are rejoined.
RNA polymerase builds mRNA in a similar manner that DNA polymerase builds the
complementary DNA strand during replication.
5’ to 3’ and the reverse refers to the position of the sugar molecules and the numbered carbon
that is facing toward the starting direction of the DNA strand.