Gregor Mendel - father of Genetics and 18th century Austrian monk -studied pea plants, developed idea of traits and inheritance
Genetics - The study of heredity.
Heredity - The passing on of traits from an organism to its offspring.
Trait - characteristics of an organism
Genes – (allele) Units of heredity. One set from each parent.
Dominant - One gene dominates another. - ex: Brown eyes dominate blue eyes.
Recessive - Weaker trait; Ex.blue eyed genes are dominated by Brown eyed genes.
Purebred - Genes that are the same for a given traits. Ex. - 2 Brown eyed genes. BB
BB or Bb bb
Hybrid – Two different types of genes for a given trait. Example one (B) brown eyed gene and one blue (b) eyed gene. Bb
1 Incomplete Dominance - Neither gene in an allele masks the other. Ex : Red rose and white rose have pink offspring.
WW RW RR
Law of Segregation - One gene (chromosome) from each pair of parent’s genes goes to egg or sperm cell.
Independent Assortment - Each set of genes is independently inherited. - random sorting - Ex. Tallness gene is randomly assorted from eye color gene. *** Some genes that are close to each other on a DNA molecule do not follow this rule.
Principles of Modern Genetics
- Traits, or characteristics, are passed on from one generation to offspring.
- An organism inherits genes in pairs, one from each parent.
- Some genes are dominant and some are recessive.
- Dominant genes hide recessive genes.
- Some genes are not dominant or recessive; they blend traits, incomplete dominance.
2 Genetics and Probability
-Probability is the chance or likelihood that something will happen.
Punnett Squares - A chart showing the possible gene combinations (or chromosomes) in a cross between two organisms.
Phenotype - What the organism looks like. Ex. Brown Dog
Genotype - Gene makeup of organism.
Ex. Bb - A brown dog with one brown gene and one white gene.
BB - A brown dog with 2 brown genes.
bb – A white dog with 2 white genes
Question : Cross a white dog (bb) with a black dog (Bb).
B b
Phenotype = 50% Bb b 50% bb Bb b b
Genotype = 50% Brown Bb 50% white b b b
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Chromosomes
Chromosomes - rod-like shaped structures made of coiled DNA
Walther Flemming - (1882 , German) - discovered chromosomes
Walter Sutton - American 1902 : Discovered that chromosomes come in pairs. - Sperm and egg cells have half the normal number of chromosomes.
Theory of Heredity
- Genes are carried from parents to their offspring on chromosomes.
Meiosis - process of cell division producing sex cells - each cell has a haploid amount of chromosomes
Haploid - 1/2 the number of chromosomes (sex cells)
Diploid - normal number of chromosomes ( somatic or body cells )
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Thomas Hunt Morgan - American Zoologist discovered sex chromosomes in fruit flies.
Sex Chromosomes - X and Y chromosomes determine sex. - X is larger than Y
Male = XY Female XX
Hugo De Vries - Dutch Botanist discovered mutations in primroses.
Mutation - A change in a gene or a chromosome.
A mutation in a somatic cell only affects that organism. A mutation in a sex cell affects its offspring. Most mutations are harmful or neutral. Mutations happen when DNA is damaged. Causes (Mutagens) - X rays, UV rays, Pollutants, toxic chemicals, old age
Beneficial - Some mutations help an organism survive in an environment. A mutation in a plant that can produce a toxin that protects it from insects. A major force behind evolution.
5 Human Genetics
Y chromosome - Triggers the production of the male hormone testosterone. - Testosterone is a hormone that controls male secondary sexual characteristics. i.e. deep voice, Adam’s apple
Multiple Alleles - Some characteristics are control by more than two alleles. - example - blue, brown and green eyed genes
Blood Surface Proteins - Two alleles A , B ( O is lacking in all three ) - codominant - all are expressed
Mom- AB A B 50% = AA A AA AB 50% = AB A AA AB Dad - AA
Inherited Diseases - A mutation in a gene that codes for an important protein. - example : Sickle Cell Anemia- A mutation in the gene for hemoglobin. Cause red blood cell to have a sickle shape. S = gene mutation (sickle cell) A = Normal gene
A S 25%=Normal
AA AS A 50%= Carriers
S AS SS 25%= Sickle cell
6 Genetic Diseases - Mutations can hide in hybrids. - Some have benefits. Sickle cell- Carriers have some protection from malaria. Cystic Fibrosis - May have offered some resistance to typhoid.
Genetic Engineering - Future of modern medicine. - Actually correcting the problem “gene” that causes the disease.
Nature Vs Nurture- Heredity Vs Environment - Twin studies suggest a 40% nature and 60% nurture.
Sex-linked Traits- Traits that are on X chromosome. - color blindness, hemophilia
Pedigree - A family tree showing the frequency of a trait.
males females
Human Genetic Disorders
Nondisjunction - The failure of a chromosome pair to separate during meiosis. - Body (somatic) cells may have more or less than normal amount of chromosomes, usually lethal.
Karyotype - Shows the size, shape and number of chromosomes in an organism.
Down Syndrome: An extra chromosome (trisomy) on the 21 chromosome. Have various physical and developmental problems, and mental retardation.
7 DNA
Deoxyribonucleic Acid
- “ The Blueprints of Life” contains all the information to make an organism. - DNA stores and passes on genetic information from one generation to the next. - DNA is a large molecule.
James Watson and Francis Crick - Nobel prize winners for their discovery of the structure of DNA.
Rosalind Franklin and Maurice Wilkins - Used X rays to discover the shape of DNA.
Structure of DNA
- Double helix, looks like a twisted ladder.
- Each rung (step) is made of two nitrogen bases connected to each other.
Nitrogen bases
- Adenine (A), Thymine (T), Guanine (G), and Cytosine ( C )
Rules for Connection
A (adenine) only combines with T (thymine)
G ( guanine ) only combines with C ( cytosine )
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Reading Strand - Only one side of the ladder is read, the reading strand.
Complimentary strand - Opposite strand of reading strand. A copy incase reading is damaged.
DNA is read like a book. The words are codons. Codons are 3 nitrogen bases long. Ex: ATT or GTC Each codon codes for an amino acid. These amino acids made in ribosome make up proteins.
Genes code for Proteins
DNA Replication:
Replication: The DNA molecule unzips itself and is both sides are copied.
In interphase stage of Mitosis a complete copy is made.
RNA - Ribonucleic Acid
RNA is an opposite copy of DNA RNA is a messenger. It takes information out of nucleus to ribosomes. Does not contain thymine, uracil ( U ) connects with Adenine ( A )
9 Applied Genetics
Plant and Animal Breeding
Selective Breeding - crossing plants or animals with desirable traits to produce offspring with those traits.
Hybridization -Crossing two organisms (usually from the same or close species) with different variations of a trait. Examples - corn, rice, mules, dogs.
+ =
Inbreeding - Crossing animals or plants with similar genes. - Used to keeps animals or plants purebreds.
Genetic Engineering -The process in which genes are transferred from one organism to another or designed.
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Recombinant DNA
- Inserting a gene into another genome.
Plasmid - Free floating circular pieces of bacterial DNA.
Bacterial Transformation;
1) Cut Plasmid with a restriction enzyme. Break the circular DNA. Leaving two sticky ends.
2) Insert a gene. Human gene for insulin. Inserted into a plasmid
3) Force plasmid into bacteria cell. Placed in a bacteria.
4) Plasmid forces bacteria to make gene product. Bacteria produce insulin.
Products of Genetic Engineering
Medical - Using bacteria to make drugs, hormones, and enzymes.
- Correcting genetic diseases.
- Designing genes to combat disease.
11 Agriculture - Genetically altering plants for better produce.
- Genetically altering plants for disease prevention. Many plants that you buy in stores are genetically modified. - ex: tomatoes , corn, and wheat
Gel Electrophoresis - Running cut pieces of DNA on an agarose gel for analysis.
Restriction Enzymes - Enzymes that cut DNA at specific sites.
- Identifies an organism through its genes, used in forensics. ex: crime scenes, food analyses, and endangered species protection
PCR- Polymerase Chain Reaction - Making multiple copies of a segment of DNA. - forensics and the study of genes
12 Types of Gene Therapy
in vivo - “ in life ” - placing good genes in cells invitro - “ in glass ” - correcting the genetic disease inside a test tube in situ - “ in position ” - correcting the disease inside a cell in the body
Future of Genetics
Gene Therapy :
- inserting “good” genes in a virus virus infects human cell , inserts good gene
- inserting corrected genes into an actual cell
- finishing of the Human Genome Project
The Secret Code of Life
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