Genetics & Heredity An overview of the history & principles of genetics
Mitosis/Meiosis Animations • Living things are composed of cells. • Cells are specialized and can be grouped into 2 main groups. • 1.Somatic cells (body cells)- brain cells, blood cells, skin cells, etc. • 2.Gametes (sex cells) – Sperm (male) & Egg (female). • Mitosis – somatic cell division. A process that takes the original cell, copies the genetic information and ends up with 2 identical cells. • Meiosis – sex cell division. A process that takes the original cell reproduces the genetic information and divides twice producing 4 cells each with 1\2 the original cells genetic information.
What is genetics? • Genetics is the study of how organisms pass on information to their offspring • It also explains characteristics & certain diseases.
What is a trait? • A trait is a characteristic that is passed on from parent to offspring. • Traits include eye color, hair color, metabolism, left or right hand. • Acquired characteristics like strength & education are not passed on directly as traits.
Who discovered genetics? • Gregor Mendel was a monk from Austria that is called the “Father of genetics”. • He worked with pea plants. • He studied several traits in the peas. • 1.pod shape • 2. Pod color • 3. Seed shape • 4. Seed coat color • 5. Plant height • 6. Flower position • He was able to predict outcomes & noticed patterns.
Mendel’s Findings • He noticed that there were 2 versions of many traits. • He noticed that in certain crosses 1 of the traits showed up more than the other. • He set up experiments to cross plants to see if he could predict the traits. • Mendel crossed plants with different traits to create a 2nd generation of plants and all 2nd generation plants looked exactly like the parent plant with the dominant traits. • Mendel also crossed 2nd generation plants with each other and the recessive trait reappeared with a 3-1 dominant to recessive ratio. • Finally Mendel did a few backcrosses with the 2nd generation plants and their parent offspring to help predict which traits were dominant & recessive.
Mendel’s Findings (cont.) • He called the trait that showed up more a dominant trait. The more hidden trait he called a recessive trait. • Dominant trait – a trait that seems to hide or mask another trait. • In a cross a dominant trait is shown with a capital letter. • Recessive trait – a trait that is masked or hidden by a dominant trait. • A lower case letter in a cross shows a recessive trait
More of Mendel’s findings • There are three possible gene combinations. • 1. Homozygous (pure) dominant – 2 copies of the dominant gene. • 2. Homozygous recessive – 2 copies of the recessive gene. • 3. Heterozygous (Hybrid) – 1 copy of the dominant gene & 1 copy of the recessive gene.
What is a pedigree? • A pedigree is a diagram that shows the history of a trait in a family. • They are good indicators that certain traits or diseases are possible. • Males are squares. Females are circles. They are usually in order from oldest to youngest from left to right. • Colored parts show the trait being looked at. This pedigree show 3 generations
Punnett squares • A Punnett square is a method used to predict possible gene combinations. • Dominant genes are given capital letters. • Recessive genes are given lower case letters. • Ex Tall (T) is dominant over short (t) • Possible combinations TT,Tt,tt.
Genotype and Phenotype • Phenotype – describes the visible expression of genes. (What you see.) • Genotype - shows the actual gene combinations. (What you get). • Online lab
How are traits passed on? • Traits are passed from parents to offspring. • They are passed by objects known as chromosomes. • Chromosomes – structures within the nucleus of a cell that carry genes. • *****Chromosomes occur in pairs. • Genes are specific locations on chromosomes. • Organisms receive 1 copy of each gene for a trait from each parent.
Co dominance and Incomplete Dominance • Incomplete dominance – a situation where an organism gets 2 genes that are not dominant over each other. Both genes are expressed. • Ex. Cross a red flower & a white flower & get a pink flower. • Sickle cell anemia – a genetic disease that curves red blood cells into a sickle shape. It is very painful & often deadly. It shows incomplete dominance. • Co-dominance – a situation where an organism has 2 dominant genes & both are expressed. • Ex. Two different colored eyes or alternating white & red flowers. Also blood types. Incomplete dominance Co dominance Web lab Blood type game
Multiple Alleles/Co dominance and Blood Types • Multiple alleles - Any of a set of three or more alleles, or alternative states of a gene, only two of which can be present in a diploid organism. • Eye color, Hair color, & blood types are all cases of multiple alleles. • Blood type is also co dominance with A & B being co dominant and O being recessive.
What is DNA? • DNA stands for Deoxyribonucleic Acid • It is a long thread – like material located in the nucleus of cells. • It has a twisted ladder shape called a double helix. • The shape was discovered by James Watson & Francis Crick.
The Genetic Code • DNA is made of 4 nitrogen containing base. • They are adenine,guanine,cytosine,& thiamine. • The sequence of these bases in triplet pairs determine an individuals genetic code. • Example: TAG could make left handed, TTG could make right handed.
Human Genetics Humans have 46 chromosomes (23 pairs) 1 pair is the sex chromosomes. Females have XX Males have XY
Mutations • Mutations are changes in the genetic structure. • They can be DNA mutations or chromosome mutations. • Mutations may be harmful, helpful or neither. Conjoined twins are caused by a mutation which won’t allow fertilized eggs to split.
Gene Mutations Gene deletion Gene duplication Gene inversion Gene translocation
Chromosome Mutations Trisomy:3 copies where 2 should be. Monosomy: 1 copy where 2 should be
SICKLE CELL ANEMIA TAY SACHS DISEASE CYSTIC FIBROSIS THALASSEMIA DUCHENNE MUSCULAR DYSTROPHY. PHENYLKETONURIA (PKU) MARFAN SYNDROME PROGERIA TRISOMY 21 OR DOWN SYNDROME SPINA BIFIDA ACHONDROPLASIA(DWARFISM) HUNTINGTON'S DISEASE FRAGILE X SYNDROME HEMOPHILIA KLINEFELTER SYNDROME TURNER SYNDROME TRISOMY 18 OR EDWARD SYNDROME CRI DU CHAT CLEFT LIP/CLEFT PALATE TRISOMY 13 OR PATAU SYNDROME Blue Rubber Bleb Nevus Syndrome Prader-Willi Syndrome Waardenburg Syndrome Retinoblastoma Genetic diseases
Genetic Counseling • If couples have a history of genetic diseases they may wish to see a genetic counselor. • They are specialized doctors who use pedigrees, Punnett squares & genetic screenings to determine probabilities of disorders. • They then advise the couple of their findings & their options.
Genetic Engineering • Genetic Engineering involves mapping the genes of organisms & manipulating them. • Many of the ideas of genetic engineering are controversial because they involve controlling traits. • Cloning, gene splicing, & gene therapy are part of genetic engineering.
Gene Splicing • Gene splicing involves “cutting” an undesirable gene out of one organism & replacing it with a desirable gene from another. • The organisms must be compatible. • Examples: Frost & insect resistant plants & Beefalos. • A Beefalo is an angus cow that has the size gene of the American Bison (Buffalo) The animal in the front is a normal angus cow. The animal in the rear is an 8 month old Beefalo.
Cloning • Cloning is the process of using DNA to produce a genetic duplicate of an organism. • Not even identical twins are genetic duplicates. • Sheep & cows have been cloned. • Human cloning is illegal in the US. Click and clone mice