Regents Biology Genetics Why do we look the way we do?

Regents Biology Inheritance of chromosomes  Egg + sperm  zygote egg sperm zygote fertilization mitosis & development meiosis

Regents Biology Inheritance of genes  On the chromosomes passed from Mom & Dad to offspring are genes  may be same information  may be different information eye color (blue or brown?) eye color (blue or brown?)

Regents Biology Effect of genes  Genes come in different versions  brown vs. blue eyes  brown vs. blonde hair  alleles

Regents Biology Genes affect what you look like X BB bb Bb Where did the blue eyes go??

Regents Biology Genes affect what you look like… X Bb bb Bb bb Why did the blue eyes stay??

Regents Biology Genes affect what you look like… X Bb BB or Bb bb Where did the blue eyes come from??

Regents Biology What did we show here?  Genes come in “versions”  brown vs. blue eye color  alleles  Alleles are inherited separately from each parent  brown & blue eye colors are separate & do not blend  either have brown or blue eyes, not a blend  Some alleles mask others  brown eye color masked blue

Regents Biology How does this work? eye color (brown?) hair color eye color (blue?)  Paired chromosomes have same kind of genes  but may be different alleles

Regents Biology Traits are inherited as separate units 1 from Mom 1 from Dad  For each trait, an organism inherits 2 copies of a gene, 1 from each parent  a diploid organism inherits 1 set of chromosomes from each parent  diploid = 2 sets of chromosomes homologous chromosomes

Regents Biology Making gametes BB= brown eyes bb= blues eyes Bb= brown eyes BBbbBbBb  brown is dominant over blue  blue is recessive to brown Remember meiosis! B B b b B b

Regents Biology How do we say it? BB= brown eyes bb= blues eyes Bb= brown eyes 2 of the same Homozygous 2 different Heterozygous BB B B bb b b BbBb B b homozygous dominant homozygous recessive

Regents Biology Punnett squares Bb x Bb male / sperm female / eggs X BB BbBbbb BbBb B b Bb

Regents Biology Genetics vs. appearance  There can be a difference between how an organism looks & its genetics  appearance or trait = phenotype  brown eyes vs. blue eyes  genetic makeup = genotype  BB, Bb, bb 2 people can have the same appearance but have different genetics: BB vs Bb

Regents Biology Genetics vs. appearance eye color (brown) eye color (brown) eye color (blue) eye color (brown) vs. BB B B Bb B b How were these brown eyes made?

Regents Biology Woof! Woof! Any Questions?