Download - GENETICS
GENETICS
What is heredity?• The passing on of characteristics (traits) from parents to offspring
• Genetics is the study of heredity
Gregor Mendel: ‘Father of Genetics’
• Most famous for his work on pea plants• He discovered different laws and
rules that explain factors affecting heredity.1. Law of Segregation 2. Law of Independent Assortment
Mendel Discovered..
• Each organism has two alleles for each trait•Alleles - different forms of the same gene (AA, aa, Aa)•Genes - located on chromosomes, they control how an organism develops (Brown or blonde hair)
Law of Segregation
• The two alleles for a trait must separate when gametes are formed• A parent randomly passes only one allele for each trait to each offspring (ex/ hair and eye color)
Law of Independent Assortment
• The genes for different traits are inherited independently
Rule of Dominance• The trait that is observed in the offspring is the dominant trait (uppercase: AA)
• The trait that disappears in the offspring is the recessive trait (aa: lowercase)
Phenotype & Genotype
• Phenotype - the way an organism looks• red hair or brown hair
• Genotype - the gene combination of an organism–AA or Aa or aa
Heterozygous & Homozygous
• Heterozygous - if the two alleles for a trait are different (Aa)
• Homozygous - if the two alleles for a trait are the same
(AA or aa)
Dihybrid vs Monohybrid
• Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee)
**Monohybrid Cross - Crossing parents who differ in only one trait
(AA with aa)
Questions...• How many alleles are there for each trait?•What is an allele?• How many alleles does a parent pass on to each offspring for each trait
Questions...• What do we call the trait that is
observed? • What case (upper or lower) is it
written in?• What about the one that
disappears? • What case is it written in?
Questions...•What is the phenotype?•What is the genotype?•What is homozygous?•What is heterozygous?•What is monohybrid crossing?
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