Genetics The Work of Mendel Regents Biology 2007

Genetics & The Work of Mendel Regents Biology 2007 -2008

Gregor Mendel § Modern genetics began in the mid 1800 s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas used good experimental design u used mathematical analysis u § collected data & counted them u excellent example of scientific method Regents Biology

Regents Biology ? tanillop-fles all purple flowers result etanillop-ssorc u stnerap gnideerb eurt neht & dees desiar u stiart devresbo gnirpsffo dewolla u etanillop-fles ot txen devresbo & noitareneg stnalp aep der. B Mendel’s work Pollen transferred from white flower to stigma of purple flower

Mendel collected data for 7 pea traits Regents Biology

Looking closer at Mendel’s work 1 st = F 1 generation (hybrids) 2 nd = F 2 generation Regents Biology true-breeding purple-flower peas X true-breeding white-flower peas 100% purple-flower peas 75% purple-flower peas etanillop-fles Parents P 25% white-flower peas 100% 3: 1

What did Mendel’s findings mean? § Some traits mask others u purple & white flower colors are separate I’ll speak for traits that do not blend both of us! § purple x white ≠ light purple § purple masked white u dominant allele § functional protein w affects characteristic § masks other alleles u recessive allele § no noticeable effect § allele makes a Regents Biology non-functioning protein allele producing functional protein mutant allele malfunctioning protein homologous chromosomes

Genotype vs. phenotype § Difference between how an organism “looks” & its genetics u phenotype § description of an organism’s trait u genotype § description of an organism’s genetic makeup X P Explain Mendel’s results using …dominant & recessive …phenotype & genotype Regents Biology purple F 1 all purple white

Making crosses § Can represent alleles as letters flower color alleles →P or p u true-breeding purple-flower peas →PP u true-breeding white-flower peas →pp u purple F 1 Regents Biology PP x pp X P all purple white Pp

Law of Segregation § When gametes are formed, each gamete carries only 1 copy of the gene (allele) Gametes are haploid! egg Zygote sperm Regents Biology

Punnett squares Pp x Pp 1 st Aaaaah, phenotype & genotype can have different ratios generation (hybrids) % genotype male / sperm female / eggs P p PP Pp P PP Pp pp Regents Biology % phenotype 25% 75% 50% Pp pp 25% 1: 2: 1 3: 1

Any Questions? ? Regents Biology 2007 -2008