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GENETICS 1 What is Genetics? • The study of how traits are inherited through the interaction of alleles 2 Heredity • The passing of traits from parent to offspring 3 The Father of Genetics: Gregor Mendel • An Austrian monk who studied mathematics and science • Studied how traits pass from generation to generation • He thought it was possible to predict the kinds of flowers and fruit a plant would produce • Most of his work was done studying peas 4 Gregor Mendel • Mendel was the first to trace one trait through several generations • He also used mathematics and probability to explain heredity. • He is famous for his work with pea plants. Why did he choose peas? • The conclusions he came to was how traits pass from one generation to the next 5 Genetics of Pea Plants 1 6 Mendel’s Experiments • Peas….. • Purebred: parents always produced the same traits generation after generation – Example: tall pea plants • Crossing two plants with different expressions of the trait he found the new plants all looked like one of the parents • He called these HYBRIDS – Example: yellow and green purebreds produce all green peas 7 8 Principles Of Heredity 1. Traits are controlled by alleles on chromosomes 2. An allele may be dominant or recessive 3. When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate sex cells 9 Genes • located on chromosomes, -made up of DNA • control an organisms form and function • during meiosis, pairs of genes separate and each sex cell winds up with one form of a gene for each trait 10 Alleles • Different forms of a trait that a gene may have • Every sex cell has one allele for each trait • Example…. Earlobes Attached vs. Unattached 11 Alleles separate into separate sex cells during meiosis 12 Dominant / Recessive Traits • Dominant factor- trait that dominates or covers up short form (Use Upper case letter) • Recessive factor- trait that seems to disappear (Use lower case letter) 13 Alleles Determine Traits • Homozygous two alleles for a trait that are exactly the same TT or tt • Heterozygous two different alleles for a trait •Tt 14 Genotype The set of genes an organism has. Sometimes it refers to the entire Genome of an organism and sometimes it refers to the alleles. We use letters to represent the trait or alleles. Example: Bb (heterozygous black) tt (homozygous short) 15 Phenotype • Physical trait that shows as a result of a particular genotype • Example: curly ears • straight ears 16 Punnett Square • • • • A tool used to predict results in genetics Dominant allele….Capital letter (T) Recessive allele….small letter (t) The letters that represent the genetic make up are called: genotype • Example: Tt 17 Making a Punnett Square • The letters indicating the alleles donated by each parent are written along the top and side. One letter per box. 18 19 Probability • A science that helps you predict the chance that something will occur • Coin toss 50/50 probability • Studying large numbers increased Mendel’s chances of seeing a pattern 20 Sex Determination • Females produce eggs that have only an X chromosome (XX) • Males produce both X-containing sperm and Y-containing sperm (XY) • Sex of an offspring is determined by the male gamete since males have both the X and the Y chromosome 21 Boy or Girl? 22 • “Blended” or intermediate expression • Neither allele for a trait is dominant over another..both are expressed • red and white flowers produced Pink flowers 23 CR CW CRCW 24 Codominance When 2 dominant alleles are expressed at the same time 25 Multiple Alleles • Many traits are controlled by more than two alleles, or multiple alleles. • Blood types: A, B, AB and O • A and B are Dominant over O Human BLOOD TYPES Phenotype Genotype A AA or AO B BB or BO AB AB O OO 26 Polygenic Inheritance • Polygenic inheritance - a group of gene pairs act together to produce a single trait • Produces a wide variety of phenotypes – height – weight – body build – shape of eyes, lips and ear 27 Muta tions • Changes or errors that occur when DNA is copied inside a cell. – Chemicals, radiation and radioactive substances can also cause mutations • A mutation results in the change of genes • Mistakes in meiosis can result in an organism with more or less chromosomes than normal. • Incorrect chromosome number can cause chromosome disorders – Downs syndrome (an extra chromosome #21) 28 mental Impact • Gene expression can be influence by the environment – people at risk for skin cancer should avoid sun exposure – Himalayan rabbits can only express the allele for dark fur in low temperatures 30 Recessive Genetic Disorders • Occur when both parents pass on the recessive allele and both recessive allele must be inherited by the offspring –Cystic Fibrosis –Sickle Cell Anemia 31 Sex-linked Disorders An allele that is inherited on a sex chromosome • Color-blindness • inherited allele on the X chromosome that prevents from seeing certain colors 32 More Sex-linked Disorders • Hemophilia blood does not clot properly • Females are just carriers 33 A tool for following a trait through generations of a family 34 Importance of Pedigrees • Pedigrees are important tools geneticists use to understand how a trait is inherited • They can then predict the probability the offspring will be born with a trait • Extremely important in breeding animals or plants because livestock and plant crops are used as sources of food 35 Genetic Engineering • Scientists are experimenting with methods that allow them to go into cells to change or the arrangement of DNA • Used to produce large quantities of medicine, such as insulin • Also used to find new ways to provide people with more nutritious food 36 Genetic Engineering 37 Gene Therapy • Placing a normal allele in a cell that has a mutation • A virus is used as the vector to deliver the DNA 38 SELECTIVE BREEDING The selection of certain seeds or animals for reproduction in order to influence the traits inherited by the next generation. SELECTIVE BREEDING • The Liger is the result of breeding a female Tiger to a male Lion. • The liger has both stripes and spots. The stripes are inherited from its tiger parent and the spots from the lion parent. The Zebroid is the result of breeding a female Horse and a male Zebra. The Zedonk / Zonkey is the result of breeding a female Donkey and male Zebra. OKAPI Not selective breeding 42 The Human Genome Project • identify all the approximately 20,000 - 25,000 genes in human DNA, • determine the sequences of the 3 billion chemical base pairs that make up human DNA, • store this information in databases, • improve tools for data analysis, • transfer related technologies to the private sector, and • address the ethical, legal, and social issues (ELSI) that may arise from the project. • Work is still on-going 43