Presentation on theme: "Genetics. What do Bart, Lisa & Maggie all have in common? Why?"— Presentation transcript:
What do Bart, Lisa & Maggie all have in common? Why?
Traits can be… DOMINANT More likely to be seen Dominant overpowers the recessive traits. recessive Less likely to be seen Can sometimes be “hidden” within your genes. or
Most of these characters are the same species. But how are they different?
Genes – the instructions for traits We inherit our traits from our parents We get 23 chromosomes from Mom and 23 from Dad. This equals 46 chromosomes. Alleles every trait is decided by two alleles (one from Mom, and one from Dad) They can be dominant or recessive We represent these alleles with letters. Brown hair- dominant allele - B Blond hair- recessive allele - b
Alleles Examples –Curly hair – Dominant – C –Straight hair – recessive – c Examples –Dimples – Dominant – D –No dimples – recessive – d
Phenotype The appearance of the organism. PHENO is like PHOTO What you would be able to see in a photo? brown hair, curly hair, brown eyes, freckles, dimples, face shape spotted coat, short hair, long hair, floppy ears short ears
Genotype The genetic makeup of an organism. This is not visible, but inside their genes (DNA). Tongue rolling – dominant allele – T Not able to roll tongue- recessive - t Can roll tongue – TT, Tt Cannot roll tongue - tt
PUNNETT SQUARES First, make a box with 4 squares inside it Second, put both parents Alleles in the right spot. –Mom, Rr, can roll tongue –Dad, rr, can’t roll tongue R r rrrr
Bring down each letter Bring over each letter This will make 4 possible combinations R r rrrr RrRr RrRr r r PUNNETT SQUARES
What are the possible Genotypes? What are the possible phenotypes? Give a ratio for each PUNNETT SQUARES R r rrrr RrRr RrRr r r