Genetics Chapters 9 and 12

Introduction to Genetics Genetics is the science of heredity and variation in living organisms. Every living thing has inherited a set of characteristics from its parent or parents. Traits – genetically determined variant of a characteristic Francis Crick's first sketch of the deoxyribonucleic acid double-helix

Introduction to Genetics At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called “genes”. This property was first observed by Gregor Mendel http://en.wikipedia.org/wiki/Genetics Chapter 12: Day One

Introduction to Genetics The molecular basis for genes is: deoxyribonucleic acid. Good thing to know. DNA Chapter 12: Day One http://en.wikipedia.org/wiki/Genetics

Gregor Mendel Called the father of genetics for his study of the inheritance of traits in pea plants. Augustinian priest and scientist Mendel showed that the inheritance of traits follows particular laws, which were later named after him. The significance of Mendel's work was not recognized until the turn of the 20th century. Its rediscovery prompted the foundation of the discipline of genetics. Chapter 11: Day Five Start Here http://en.wikipedia.org/wiki/Gregor_Mendel

Gregor Mendel Used garden peas and studied 7 specific traits These different varieties of peas are called true-breeding because they always pass on their traits to their offspring Chapter 11: Day Five http://en.wikipedia.org/wiki/Gregor_Mendel

Gregor Mendel Normally the flowers of pea plants self-pollinate: the pollen (male sex cells) and the ovum (female sex cells) come from the same flower pollen If Mendel’s true-breeding plants were allowed to self-pollinate, the plants would inherit all the characteristics from the plant that bore them ovum Chapter 11: Day Five

Gregor Mendel He studied 7 specific traits Each trait had 2 possible forms (alleles) Allele- one of a number of different forms of a gene

P generation Cross P generation Original true-breeding plants F1 generation Hybrid plants- offspring that have inherited 1 trait from each parent r r r r Chapter 11: Day Five

Why are the F2 hybrids all red? P generation Cross Why are the F2 hybrids all red? Mendel concluded that each P1 parent had 2 identical genes for each trait AND that 1 allele must be DOMINANT and the other RECESSIVE r r r r r r Chapter 11: Day Five

Genotype- the letter combinations showing possible alleles Identical alleles are homozygous Opposite alleles are heterozygous Phenotype is the form of the trait that shows up in what the organism looks like rr = homozygous white RR = homozygous red Rr = heterozygous red red white or Chapter 11: Day Five

3:1 ratio F1 generation F2 generation 3:1 ratio, why is that? r r r r Chapter 11: Day Five

When each F1 plant flowers and produces gametes, the 2 alleles segregate from each other so that each gamete carries only a single copy of each gene. Therefore, each F1 plant produces 2 types of gametes- those with the allele for redness and those with the allele for whiteness.

Mendel’s Results & Conclusions Law of Segregation – a pair of factors is segregated, or separated, during the formation of gametes Law of Independent Assortment - factors separate independently of one another during the formation of gametes

Gregor Mendel Review The inheritance of biological characteristics is determined by individual units known as genes. Genes are passed from parents to their offspring. The principle of dominance states -some alleles are dominant and some others are recessive. During gamete formation, alleles segregate from each other so that each gamete carries only a single copy of each gene. Principle of independent assortment –alleles segregate independently

Inheritance Pattern and Human Genetics Chapter 12

Chromosomes Sex chromosomes Autosomes Contain genes that determine the sex of an individual Autosomes All the other chromosomes This is old news.

Sex Determination

Sex-Linked Trait A trait that is coded for an allele on a sex chromosome Is something missing here? r Bigger, has more information Most X-linked alleles have no counterpart on the Y chromosome.

Dude, I ain’t going nowhere!! Linked Genes Pairs of genes that tend to be inherited together, found on same chromosome Don’t leave me, man!! Dude, I ain’t going nowhere!!

Chromosome Map A diagram that shows the linear order of genes on a chromosome.

Mutations A change in the nucleotide-base sequence. Involve an entire chromosome or a single nucleotide. Germ cell: Occurs in the organism’s gametes. Passed onto offspring. Somatic-cell: Take place in organism’s own body cell Lethal: Cause death.

Chromosome Mutations Deletion Inversion Translocation Nondisjunction Loss of a piece of chromosome Inversion Segment breaks off, flips, and reattaches Translocation Piece breaks off and reattaches to different chromosome Nondisjunction Chromosome fails to separate from its homologous partner during meiosis

Gene Mutations Point mutations Substitution Frameshift mutation Change that occurs within a single gene or other DNA segment Substitution One nucleotide replaces another Frameshift mutation Loss of nucleotides cause incorrect grouping of codons Insertion mutation One or more nucleotides are added to a gene, which can also result in a frameshift mutation See page 240

Pedigree A diagram that shows how a trait is inherited over several generations.

Genetic Traits and Disorders Genetic disorders Diseases or disabling conditions that have a genetic basis Complex characters Characters that are influenced strongly by the enviroment and by genes

Beyond Gregor Mendel Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes. Incomplete dominance Codominance Multiple alleles Polygenic traits

Polygenic Characteristics are influenced by several genes

Multiple Alleles Genes with 3 or more alleles

Codominance Both alleles are expressed

Incomplete Dominance A trait that is blended

Cloned glow in the dark cats. Genetic Engineering Genetic engineering, recombinant DNA technology, genetic modification/manipulation (GM) and gene splicing are terms that are applied to the direct manipulation of an organism's genes. Cloned glow in the dark cats. Chapter 13: Day Seven http://en.wikipedia.org/wiki/Genetic_engineering http://www.foxnews.com/images/330367/0_61_121207_cat.jpg

Genetic Engineering There are a number of ways through which genetic engineering is accomplished. Essentially, the process has four main steps. 1) Isolation of the gene of interest 2) Insertion of the gene into a vector 3) Transformation of cells of organism to be modified 4) Tests to isolate genetically modified organism (GMO) Chapter 13: Day Seven http://en.wikipedia.org/wiki/Genetic_engineering

Lab Assignment In your team, begin discussion on what you think genetic engineering is and your position on stem cell research. AFP / Getty Images Chapter 13: Day Seven Stop Here