Unit 7: Mendelian Genetics Mrs. Howland Biology 10 Rev. Jan 2016

ESSENTIAL QUESTIONS ~ ??? How is genetic information passed through generations? How do genes affect the characteristics of an organism?

UNIT OBJECTIVES: Students will be able to… Analyze Mendel’s experiments Make and interpret a Punnett Square Solve genetics problems Make and interpret a pedigree Make and interpret an karyotype Explain the significance of a hetrozygote advantage

Why do we look the way we do? We look like OURSELVES, but also a LITTLE BIT like our parents! (No, not twins, it’s the same kid!)

LOOKING BACK: Meiosis Recall that MEIOSIS is the process of cell division that results in 4 genetically unique daughter cells called GAMETES

LOOKING BACK: Meiosis GAMETES are combined (1 from father, 1 from mother) in fertilization step of sexual reproduction! GAMETES are the daughter cells produced during meiosis SPERM EGG ZYGOTE is the cell that forms as a result of sperm fertilizing an egg. DNA from both parents are combined

Law of INDEPENDENT ASSORTMENT What accounts for the differences and similarities in humans and other species? During METAPHASE and ANAPHASE of meiosis, there are 2 possible ways that the chromosomes can line up and separate  RESULTS in many different possibilities!

Gregor Mendel The “Father” of genetics LINK:

The Work of Gregor Mendel WHY PEAS? Can be crossed (bred) many times within a much shorter timespan than humans or other animals! FOUR (4) different characteristics that are easily observed: Height, pea color, pea shape, flower color

VOCABULARY! ALLELE: Different forms of a gene, located in same gene locus (location on chromosome) EXAMPLE: A gene can code for PEA COLOR. Two possible alleles for this gene may be GREEN or YELLOW

VOCABULARY! TRAIT: A specific characteristic EXAMPLE: Pea color, eye color, height CROSS-POLLINATION: Specific, controlled pollination Allowed Mendel to breed plants and control parents to compare inherited traits HYBRIDS: The offspring from crosses between parents that have different traits EXAMPLE: green pea plant (x) yellow pea plant

Mendel’s F1 Crosses P = the parents (the 2 plants that were crossed F1 = the first generation of offspring

When F1 plants reproduce by self-pollination F2 = offspring from F1 generation that self-pollinated

SEGREGATION When gametes are formed, alleles segregate from one another Each gamete carries a single allele for each gene

Mendel’s Pea Plants Mendel discovered that a hybrid cross resulted in 3 of one trait and 1 of the other in F2 generation (3:1 ratio or 75% and 25%)

Why did Mendel see these results? LINK:

CLASSWORK/HOMEWORK Color plate: Mendel’s Genetics (due at END OF CLASS) PACKET: (11.1) The Work of Gregor Mendel (due NEXT CLASS, P5=Tues 1/26, P1=Wed 1/27)

Learning the LINGO… Homozygous = Organisms that have TWO (2) of the same alleles for a gene HOMOZYGOUS

Learning the LINGO… Heterozygous = Organisms that have TWO (2) different alleles for a gene HETEROZYGOUS

Learning the LINGO… Genotype = Genetic makeup (the set of alleles) Phenotype = Physical traits (determined by alleles)

Genotype vs. Phenotype

Learning the LINGO… DOMINANT = Allele that is expressed, even if it is paired with a recessive allele Usually a CAPITAL letter: BB or Bb Recessive = Allele that is only expressed when paired with another recessive allele Usually a lower-case letter: bb

Dominant vs. Recessive

Punnett Square, Simple Cross

Punnett Square (Simple) EXAMPLE KEY: A = a =

Punnett Square: TRY THIS ONE! Which trait is DOMINANT? How do you know? Which trait is RECESSIVE? How do you know? KEY:

Looking at: TWO TRAITS DIHYBRID cross ~ a cross between offspring in the F1 generation that have different alleles for TWO traits Recall that LAW of INDEPENDENT ASSORTMENT states that alleles separate independently from one another Allele for 1 trait do not affect alleles for another trait

Determining Segregated Alleles for crosses with TWO TRAITS Use the FOIL method!! F = FIRST O = OUTSIDE I = INSIDE L = Last

Crossing TWO TRAITS - Dihybrid Punnett Squares are a lot bigger this time! EXAMPLE: Lab mice, 2 alleles for fur

Phenotypic Ratios ~ Dihybrid KEY: A = purplea = white B = tallb = short Ratio is 9:3:3:1

Try it! Complete this cross: