Chromosomes Genes DNA are found on is found within

Dominant Traits Hides or masks the effect of another trait Represented with a CAPITAL letter R Recessive Traits Trait hidden by a dominant trait Represented with a LOWER CASE letter r Alleles= different forms of a traits = alleles can be dominant or recessive

Tongue Rolling Free Ear Lobes Dark Hair Widow’s Peak Dimples Hitchhiker’s Thumb Light Hair Recessive TraitsDominant Traits No Dimples Brown eyes Blue, Green, Hazel Extra fingers/toes 20 fingers/toes Straight Thumb Straight Line Attached Lobes Non-rolling

Purebred = homozygous = same alleles (traits) = TT or tt Hybrid = heterozygous = mixed alleles (traits) = Tt

YY yYy y Homozygous for yellow seeds Homozygous for green seeds What is dominant/recessive? How do we fill in the parent boxes? Phenotype = PHYSICAL appearance of organism - Used to talk about what an organism looks like. Genotype= GENETIC makeup of organism - Used to talk about what type of genes an organism has

Who studied the genetics of pea plants for dominant and recessive traits? Who invented the tool used to predict the probability certain offspring would occur? How is a dominant trait represented in a Punnett square? Recessive? Is pink hair inherited or acquired? Answer these questions

Sex Chromosomes Males = XY Females = XX chance for offspring to be XY or XX. Humans = 46 chromosomes = 23 pairs 22 ch pairs = Alike in males and females 23rd ch pair = Sex Chromosomes

Sex-linked trait = trait controlled by a gene on a sex chromosome. Why is it sex-linked?  Found on the sex chromosome.  In males, there is no gene on the Y chromosome to hide the trait therefore the trait occurs more often in men. Examples of sex-linked traits:  color-blindness  baldness  hemophila

Twins Identical Twins – genetically Identical Zygote splits and develops as 2 seperate embryos. Both have exactly same genes. Fraternal Twins – not genetically identical Two (or more) different eggs fertilized by different sperm. Both have different genes.

Why is meiosis a necessary step in sexual reproduction? How many chromosomes does each human parent give to its offspring? ____ is produced by the union of 2 gametes. _____ cells have half the number of chromosomes as normal body cells.