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InheritanceGenetic Information being
passed from one generation to the next
Gregor Mendel“Father of
Genetics”
Study of Genetics
• Mendel studied the trait of pea plant flowers and learned:– When both parent pea plants had
purple flowers, the offspring were purple
– When both parent pea plants had white flowers, the offspring were white
• He wondered what would happen if one parent pea plant had white flowers and the other had purple
What happened?•Mendel discovered that the
offspring where either ALL purple or ALL white– They were not as he
hypothesized – a light purple•He reasoned that the
offspring (baby pea plants) must be inheriting something from each parent that told them what color to be
The Cell• Story of inheritance
is told by the cell• Inside the nucleus is DNA – the inheritance messenger
• DNA is coiled into chromosomes which are the structures that carry the message of inheritance
•Nucleus contains chromosomes– Occur in
identical pairs
•Band on each chromosomes represents the allele
Genes and Alleles
•Two alleles on the paired chromosomes work together–These are a GENE
•A gene controls a trait
Genotype• Alleles are the code that determine
the trait
• Combination of alleles in an organism’s chromosomes is the
genotype– Lists the paired alleles for that organism– Examples: AA, ee, Tt
•Genetic make-up of an organism
Dominant and Recessive
•Not all alleles have an equal influence in determining traits
•Alleles with more influence are called DOMINANT ALLELES– Represented by UPPERCASE letters
(TT)
•Alleles with less influence are RECESSIVE– Represented by lowercase letters
(tt)
Phenotype•The physical result of an
organisms genotype– What an organism looks like
because of its genotype
Reflection page 60Reflection page 60