Genetics The Study of Inherited Characteristics Meiosis in the Gonads makes gametes: Sperm Meiotic cell division Egg Chromosome DNA Code for Gene Segments of DNA Code Code for a trait Hair Color Eye Color Gene Segment For Hair color Trait Characteristic Feature Variations in a population 1
Dominant Trait Dominates Shows in the outward appearance Even when recessive trait is present BB or Albinism bb Recessive Trait hidden May be masked by a trait Alleles Letters of the alphabet Code for a trait One from father One from mother Dominant Allele: Upper Upper case letter of the alphabet Codes Codes for Recessive Allele: Lower Lower case letter of the alphabet Codes Codes for recessive Chromosomes in Nucleus Gene Segments For a Trait= A or a Monohybrid Cross Cross for one trait Example: Hair color Punnet Square B b B BB B BB 2
Genetic Genetic Cross= Mating F1= F1= 1 st filial generation F1 Generation Parents B BB B BB B b 2 nd nd Filial Generation- F2 of the cross between the children of an F1 Incest among F1 Only after pure x pure F1= F2= b b B b B B B b BB bb Phenotype Outward appearance Trait Trait that is shown looks brown (has b =white allele) Allele set True genetic Genotype makeup of the chromosome Homozygous: Pure condition 22 same case alleles BB= bb= = recessive Heterozygous: Hybrid Hybrid condition 22 different case alleles appears Mendelian Genetics Review: See Encarta CD-ROM 3
Incomplete dominance Incomplete Pink Carnation dominance Hybrid is a blend of Example: RR=red Rr=pink rr=white Co-dominance Both are displayed in the phenotype a combination per say Dihybrid Cross Cross with two Example: 1. Hair Color 2. Eye Color 2 types of Alleles (two ) parents Dihybrid Cross w/ both parents heterozygous RRYY: RRYy: RrYY: RRyy: RrYy: : Rryy: rryy: rryy: rryy 1 : 2 : 2 : 1 : 4 : 2 : 1 : 2 : 1 Polygenetic Traits Inheritance of trait that is controlled by 2 or more genes. Example: Plant Height has 3 genes (A, B, C)controlling the how tall a plant grows. AABBCC aabbcc Aabbcc AAbbcc AAcc AABBcc AABBCc 16 cm Each gene adds ~2cm to height of plant 4 cm Multiple Alleles More More than 2 alleles for a gene are possible for only one trait Example: Blood Type Blood type has 3 alleles I A ; I B ; i TYPES: A I A I A, I A i B I B I B, I B i AB I A I B O ii 4
Multiple Allele Example Problem Multiple Allele Problem I A i I B i A man heterozygous for blood type B marries a woman heterozygous for blood type A. What is the chance that their first offspring will have type O? A O AB B I A i ii I A I B I B i Given and Two Alleles: babies ID tags were lost, determine I B which baby i belongs to which parents: B = I B I B or I B Baby i 1 = Blood type I A O Baby 2 = Blood Type B I A I B I A i A = I A I A or I A i Mr. & Mrs. Doe have blood types A Mr. & Mrs. Jones have blood types A & B Cross: Hetero B x hetero A i I B i x I A i I B i ii X-Linked Traits Sex-linked Trait is on the sex chromosome XX= Female XY Male Ex:Red & white eyes Female= XX Add eye trait= X R X R or X R X r X r X r Male= XY Add eye trait= X R Y or X r Y Y is empty Karyotype http://gslc.genetics.utah.edu/units/disor ders/karyotype/ Chromosome Number Homologous Different # for different species Chromosomes Full set = 2N=Diploid are N= the sets of each # pairs pair 1 pair from mother 1 pair from father Humans= 23 pairs or 46 total Autosomes & Sex Chromosomes Autosomes = # 1-22 for all except sex Sex chromosomes= Pair # 23 XX(female) or XY(male) 5
Down Syndrome= 3 of #21 Klinefelter s = XXY Pedigree Charts Pedigree Chart -Cystic Fibrosis Male = Female= Sexual Union= Offspring= Change in DNA code Caused by: 1. Chemical damage 2. Errors in Replication 3. X-ray damage 4. UV damage Mutation A T G C A to A G C Changes Changes in the DNA code = = Changes in the final proteins made =Changes in the organism Mutation 6