How are genes inherited?

The parents Homer has straight hair Marge has curly hair

The families Is hair curliness controlled by genes or by the environment?

Homer Homer has straight hair Every cell in Homer has two sets of genes Homer’s has two straight hair genes We can show the straight hair gene with a capital S Homer’s genes: SS

Marge Marge has curly hair Every cell in Marge has two sets of genes Marge has two curly hair genes We can show the curly hair gene with a small s Marge’s genes: ss

Making a new Simpson Homer makes sperm Each sperm has one gene for hair type Homer only has straight hair genes So all of his sperm have straight hair genes Homer’s Sperm SS

Making a new Simpson Marge makes eggs Each egg has one gene for hair type Marge only has curly hair genes So all of her eggs have curly hair genes Marge’s Eggs ss

Making a new Simpson ss SS S S S S s s s s

Ss All of the Simpson babies have one gene for curly hair and one gene for straight hair So what type of hair do they have?

Making a new Simpson Ss THEY ALL HAVE STRAIGHT HAIR! The straight hair gene is DOMINANT Just one copy of this gene will give you that characteristic The curly hair gene is RECESSIVE You need two copies of the gene to have that characteristic

Liking donuts Homer likes donuts Every cell in his body has two donut genes. His genes are: D D Homer’s sperm D D

Liking donuts Marge doesn’t like donuts. Every cell in her body has two no donut genes Her genes are: d d Marge’s Eggs d d

Making a new Simpson dd DD D D D D d d d d

Dd Liking donuts is dominant Do the Simpson children like donuts?

Weight Marge has normal weight. Both of her weight gens are for normal genes Her genes are: N N Marge’s Eggs NN

Weight Homer does not have normal weight. He is obese. Both of his weight genes are for obesity (not normal weight) His genes are: n n Homer’s sperm nn

Making a new Simpson Nn Normal weight is dominant What weight do all the Simpson children have?

Practice Homer’s characteristic Homer’s genesMarge’s characteristic Marge’s genes Likes beerBBDoesn’t like beerbb Plays sportsSSDoesn’t play sportsss BurpsBBDoesn’t burpbb LazyLLNot lazyll Can’t danceddCan danceDD No musical abilitymmMusical abilityMM

The next generation? Lisa has straight hair Every cell in Lisa has two sets of genes Lisa has one gene for straight hair, which is dominant. She also has one gene for curly hair, which is recessive. Lisa’s genes: Ss

The next generation? Milhouse has straight hair Every cell in Milhouse has two sets of genes Milhouse has one gene for straight hair, which is dominant. He also has one gene for curly hair, which is recessive. Milhouse’s genes: Ss

The next generation? Milhouse’s genes: Ss Ss Ss Lisa’s genes: Ss

The next generation? Ss sS s S s S s s S S

The next generation SSssSs Straight hair is dominant How many children have straight hair? How many have curly hair?

The next generation Lisa’s characteristic Lisa’s genesMilhouse’s characteristic Milhouse’s genes Likes SchoolSsLike SchoolSs Good eyesightEEBad eyesightee BraveBbNot bravebb