Unit VII: Genetics

Unit VII: Genetics Understanding our genes and the ways they are passed to the next generation. Modern Genetics Basic Genetics

A. Basic Genetics Genetics = study of heredity understanding of how characteristics get passed from parent to offspring, generation to generation 1. Gregor Mendel Monk - studied pea plants in the 1800’s a) True breeding = _____________ b) Traits = specific characteristic Seed Shape – round or wrinkled Seed Color – yellow or green Seed Coat – gray or white Pod Shape – smooth or constricted Pod Color – green or yellow Flower Position – axial or terminal Flower Color – purple or white Plant Height – tall or short Trait Allele =

c) Generations P = parent generation – original plants F1 = first filial generation = offspring of the original plants F2 = second filial generation = offspring of F1 d) Crosses – for each trait Mendel crosses true breeding plants and makes observations of the offspring ex: P  Tall Pea Plant x Short Pea Plant F1 All tall pea plants All tall plants Only 1 characteristic showed in the F1 generation Why not a blend of the parent plants? _________ – cross between parents with different traits

e) Conclusions 1. biological inheritance is determined by factors that are passed from one generation to the next ____________ ____________ = different forms of genes 2. _____________________– some alleles are dominant over recessive alleles. The recessive trait will only show if the dominant trait is not present.

f) Segregation What about the F2 generation? What happens next? Were the recessive alleles still present in the pea plant? Cross - F1 x F1 Ex: Hybrid Tall Pea Plant x Hybrid Tall Pea Plant F2 – Mostly Tall; some Short; Short trait reappeared Some how the short trait _________ from the tall trait

1. __________________________________________ When gametes are formed during meiosis there is a segregation/separation of alleles on homologous chromosomes. As a result of fertilization, __________________________. As a consequence, _____________________ are likely to be produced. Short separated from tall

2. Probability and Inheritance a) ________ = genetic make up / two alleles of an individual ___________________ = same alleles (TT or tt) __________________ = different alleles (Tt) = Hybrid b) _______________ = physical characteristic (Tall or Short) Usually determined by the genotype – sometimes the ___________ can affect the phenotype. Can two organisms have the same phenotype but different genotypes?

c) Punnett Square representation of parental gametes and the different allelic combinations of the offspring ex: Cross: True breeding Tall x True breeding Short T T t t 1. Determine the genotypes of the parents 2. Determines the possible gametes of the parents 3. Write the gametes on the outside of the box 4. Combine the parents gametes Remember only 1 gamete from each parents T T t T t T t t T t T t All the offspring are genotype Tt – heterozygous The genotype tells the phenotype – Tt  Tall In the heterozygous the recessive allele is hidden

T t x T t ex: Cross: Heterozygous Tall x Heterozygous Tall What is the genotype ratio? What is the phenotype ratio? Through his knowledge of math and detailed record keeping, with 10,000s of pea plants Mendel always had this ratio in the phenotypes.

d) _________________________________ If the genes for two different traits are located on different Chromosomes (____________________ chromosomes), they segregate randomly during meiosis and, therefore, may be _________________________ of each other. What if the plants are tall with round seeds and short with wrinkled seeds what allelic combinations will occur in successive generations? Not only did Mendel look at single traits, he observed the probability of the inheritance of multiple traits at the same time.

the organisms are heterozygous for two traits. (Use letters that are easy to tell the difference) ex: Dihybrid Cross T R T r t R t r T R T T R R T T R r T t R R T t R r T r T T R r T T r r T t R r T t r r Phenotype Ratio: 9 Tall Round 3 Tall Wrinkled 3 Short Round 1 Short Wrinkled t R T t R R T t R r t t R R t t R r T t R r T t r r t t R r t t r r t r

3. Other Patterns of Inheritance Not all genes come with dominant and recessive alleles a) Incomplete Dominance – neither allele is dominant heterozygous results in a mix of characteristics ex: Flower Color in Snap Dragons R = red; W = white Red Flower x White Flower Genotype Ratio: Phenotype Ratio:

b) Codominance both alleles show in the phenotype some cells produce one allele other cells produce the other ex: Roan Colored Cattle R = red coat; W = white coat RW = Roan = Some red hair some white hair in the coat What is the probability that the offspring of two roan colored cattle would be roan colored?

c) Multiple Alleles genes that have more than two alleles the individual only has 2 alleles, but more than two exist in the population ex: Blood Types IA = type A; IB = type B; i = type O IA & IB are codominant but both are dominant over i Who is the Daddy? Bill is the father A woman with type A blood has a child with type O blood, but she is unsure of the father. Bob has type AB blood and Bill has type A blood. Who is the baby’s daddy?

d) Polygenic Traits traits produced by the interaction of many genes Show a wide range of phenotypes Ex: Skin color, Eye Color, Height e) _________________________ genes that occur on the sex chromosomes X and Y chromosomes  XX = female; XY = male X chromosome is larger and carries more genes Since males only have 1 X chromosome, what ever allele is on the chromosome shows up in the phenotype Females have two alleles for the gene ex: color blindness and hemophilia

Ex: Color Blindness A normal man and a woman that is a carrier for colorblindness have children. X Y x X Xn a) What is the chance they will have a colorblind child? b) If they are having a girl what is the chance she will be colorblind? A boy? Watch for the wording of the question

4. Human Inheritance a) Pedigree a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. easier to visualize relationships within families Pedigrees are often used to determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases.

b) Karyotype and Amniocentesis picture of chromosomes 22 pairs of autosomes, 1 pair of sex chromosomes Used to determine gender and chromosomal disorders

c) Human Genetic Diseases / Disorders 1) Albinism recessive allele lack pigment in skin, hair, eyes 2) ____________________ recessive allele excess mucus in lungs; increases susceptibility to infections; death in childhood unless treated 3) _____________________ (PKU) recessive allele accumulation of phenylalanine (amino acid) in tissue body can not break down the amino acid mental retardation if they eat phenylalanine

4) ________________ Disease recessive allele higher occurrence (1/100 vs 1/100,000) in Jewish families of eastern European ancestry lipid accumulation in brain cells, nervous system break down  death in early childhood 5) Achondroplasia Dwarfism dominant allele bones fuse and stop growth

6) ________________________ codominant allele red blood cells have a crescent shape misshapen hemoglobin can not carry O2 as well 7) Polydactyl dominant allele extra toes and fingers not always expressed 8) ____________________ chromosomal disorder extra 21st chromosome cause by nondisjunction

B. Modern Genetics 1. Griffiths’ Experiments – 1920s 2 Strains of bacteria One strain is deadly Even when killed, the deadly strain can pass something to the non-deadly strain to make it a killer!

2. Avery’s Experiments – 1940s Repeats Griffith’s experiments but adds enzymes that break down different compounds in the cells Not until he destroys DNA that the mice live! DNA = molecule that stores and transmits genetic information

3. Watson and Crick – 1950’s Used Rosalind Franklin’s x-ray pattern of DNA to build its 3-D structure Double helix with complimentary base pairs a) DNA Structure Nucleotides A = _______________ B = _______________ C = _______________ __________________________________________ From the human to the DNA – PBS Flash

DNA STRUCTURE MOVIE

4. DNA Replication a) Occurs inside the ______  during S phase of cell cycle b) DNA molecules separate into ___ strands, then produces two new complimentary strands following the rules of base pairing c) Each original strand serves as a __________ for the new strand

Original DNA DNA “Unzips” Enzymes fill in nucleotides A T G G C C T G G G C A T C C G T T A T C A T G G C C T G G G C A T C C G T T A T C T A C C G G A C C C G T A G G C A A T A G T A C C G G A C C C G T A G G C A A T A G

Easy Version of DNA Replication Check out this site on your own for a more detailed explantation More Complicated but explains the process really well. http://207.207.4.198/pub/flash/24/menu.swf

5. Protein Synthesis a) _________ = Ribo Nucleic Acid single stranded nucleic acid contains Ribose as the sugar not __________ as in DNA has the base _______ instead of _________ as in DNA Types of RNA _______ = messenger RNA  carries gene out of the nucleus _______ = ribosomal RNA  makes up ribosome _______ = transfer RNA  brings in amino acid

b) Transcription 1st step of protein synthesis; similar to replication DNA  ______________ Occurs in the ______________ “Unzip” DNA – uses 1 side of DNA as a template RNA polymerase fills in complimentary RNA bases mRNA detaches from DNA mRNA leaves nucleus Simple Trasncription Animation Just another Trancription animation

Original DNA DNA “Unzips” Enzymes fill in RNA nucleotides RNA breaks from DNA DNA reconnects T A C C G G A C C C G T A G G C A A T A G A T G G C C T G G G C A T C C G T T A T C A U G G C C U G G G C A U C C G U U A U C The groups of 3 bases on the mRNA is called a CODON The codon codes for specific amino acids when making a protein

c) Translation 2nd step of protein synthesis mRNA  ______  __________  ___________ occurs in the ______________ at the _______________ Ribosome reads ___________ on mRNA Matches the codon to an anticodon on tRNA Ribosome reads next codon and brings in next tRNA with matching anticodon Since tRNA is attached to Amino Acids – two amino acids are located next to each other This proximity allows the ____________________ Makes a peptide Repeats until mRNA says stop

More than 1 ribosome can attach to the mRNA at a time Makes multiple peptides Translation Animation

To see it in some more detail check out the following website on protein synthesis http://learn.genetics.utah.edu/content/begin/dna/ d) Protein Synthesis Overview e) Genes code for peptides generally a protein is the combination of more than 1 peptide Try this website as an interactive for replication and protein synthesis http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html

6. Mutations ___________ in the _________ sequence Some are ____________ Some are ____________ Most are _____________ Mutations are only passed to the next generation if they occur in _________ Mutations in somatic cells are not passed – acquired characteristics are not passed

a) Gene Mutations changes in a single gene 1) Point Mutations – involve just one nucleotide substitution = change one nucleotide for another ex: T A C G C G A C C C G A becomes T A C G C C A C C C G A the change may or may not change the amino acid

2) __________________ Mutations insertion or deletion of a single nucleotide changes the codons read by the ribosome usually affects _________ amino acids after the mutation ex: DNA: T A C C G G A C C C G A mRNA: A U G G C C U G G G C U Amino A: Met Ala Try Cys Insertion DNA: T A C GC G G A C C C G A mRNA: A U G C G C C U G G G C U Amino A: Met Arg Leu Gly The order of amino acids changed  changes protein (big time)

Ex: delete 1 letter THE FAT CAT ATE THE RAT  THE FTC ATA TET HER AT ???? Completely change everything after the deletion No longer makes sense The same thing happens with the protein The order of the letter (amino acids) determines the structure of the words and sentence (protein) One little mistake can completely change the meaning

b) Chromosomal Mutations changes the structure of a chromosome rearrange the genes on a chromosome 1) Deletion 2) Addition / Duplication 3) Inversion – rearrange the genes 4) Translocation – move a piece of a chromosome to a non homologous chromosome Chromosomal Mutations

c) Mutagenic Agents factors that cause mutations 1) Radiation – X-rays ultraviolet radioactive substances, and cosmic rays 2) Chemicals – formaldehyde, benzene, asbestos fibers THC nicotine

7. DNA Technology ways in which the knowledge of DNA can help benefit society a) Selective Breeding choosing specific traits in organisms, mating the organisms, and hoping some of the offspring have the combinations of the traits ex: dogs, cattle, crops selective breeding has been occurring for 1000s of years

b) Genetic Engineering recombinant DNA; transfer DNA from one organism to another isolate gene  cut DNA with restriction enzymes  combine DNA of organisms  place recombinant DNA in a new organism *restriction enzymes = cut DNA at very specific sequences

can be used to make a variety of products bacteria that can make: Insulin, Human Growth Hormone crops that resistant to disease and insects livestock with extra copies of growth hormone gene

c) Cloning making an exact genetic copy Remove the nucleus of an egg cell Use the nucleus of a body cell  Insert the nucleus into the egg cell  Grow the egg cell  Identical genetic copy of the body cell organism Click and Clone

d) Gel Electrophoresis making “DNA Fingerprints” use restriction enzyme to cut DNA into fragments  place DNA into a porous gel  electrify gel and DNA fragments move  small pieces move the farthest  DNA banding pattern = finger print Gel Electrophoresis - Learning Center Gel Electrophoresis Virtual Lab

e) Human Genome Project sequence all human DNA map and locate all the human genes  about 3,000,000,000 base pairs in order help to find and cure diseases Gene Therapy find defective gene and replace it with a healthy gene

Unit VII: Genetics