BIO 105 1st Edition Lecture 9Genetics and Genetic Disorders Lecture Outline:I. Know why Gregor Mendel is significantII. Be able to differentiate between allelesIII. Know the characterisitcs of Mendel’s lawsIV. Know the types of Dominance RelationshipsV. Be able to read a Punnet squareVI. Know the different types of genetic disorders and their characteristics Gregor Mendel- Father of genetics, researched pea plants because of variation Alleles- different molecular forms of a geneEx: green, brown, and blue eye color (variations of a gene)-Dominant allele-masks a recessive allele that is paired with it- must be Recessive at BOTH alleles (or dominant not expressed) for Recessive allele to show-Phenotype- physical appearance determined by genes (Brown eye color)-Genotype- genetic makeup determined by genes- (BrBr, BrBl, BrGr)Allele Combinationns-Capital Letters = Dominant Trait-Lower Case = Recessive Trait-Homozygous- having two identical alleles at a locus Ex: AA or aa; Brown eyes vs. Brown eyes-Heterozygous- having two different alleles at a locus-Ex: Aa; Brown eyes vs. Green eyes Homologous Chromosomes- Are identical in length, size, shape, and gene sequence (like chromosome “21” from mom and chromosome “21” from dad make up your homologous pair of chromosome 21)**KNOW HOW TO READ A PUNNET SQUARE** Mendel’s Laws1. Mendel’s Theory of Segregationo An Individual inherits a unit of information (allele) about a trait from each parent carried on the 23 pairs or 46 chromosomeso During gamete formation (meiosis), the alleles segregate from each other in metaphase so they up in different gametes2. Mendel’s Law of Independent Assortmento Mendel concluded that the two “units” for the first trait were to be assorted intogametes (sperm and eggs) independently of the two “units” for the other traito Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis- mean each of the 46 chromosomes moves to a gamete independent of the other 45 chromosomes Dominance Relationships1. Complete dominance- pea plants (most common)2. Incomplete dominance- snapdragons3. Codominance- blood groups Incomplete Dominance- Heterozygotes show a distinctly different phenotype, not seen in homozygotes Co-dominance: ABO Blood Type- If either allele is present of the “dominant” alleles- BOTH are expressed o “O” = universal donor (ii)o “AB” = universal acceptor (AB) Epistasis- Interaction between gene pairs- for one phenotype- another phenotype must exist- Before Black or Brown color can be laid down in hair- the color (CC or Cc genes must be present)- Black (BB or Bb) is dominant to brown (bb)- if the color gene (CC or Cc) is NOT present (cc)- there will be NO color- fur will be white Pleiotropy- Alleles at a single locus may have effects on two or more traits- allele my impact several organs or traitso Marfan syndrome-impacts connective tissue, organs, joints, etc.o Cystic fibrosis- allele/ gene cause impact on lungs, kidneys, sweat, etc. (multiple sites) impacted from on gene Composition of Y Chromosome- Fewer than two dozen genes identified on Y chromosome (carries only 330 genes)- One is the master gene for male sex determination = SRY gene (sex-determining region of Y) Autosomal Recessive Inheritance Patterns- Most common genetic transmission type Autosomal Dominant Inheritance- Trait typically appears in every generation- Most homozygous combinations lethal (aborted or die before birth)- Heterozygotes show disease- example- Huntington’s disease (problem- disease shows in 30s after many have reproduced