Review Questions1) What are the 4 bases that make up DNA? How do

they pair up?

2) Name 2 differences between Mitosis and Meiosis:

3) Why do we need mitosis? Why do we need meiosis?

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)A pairs with T; G pairs with C

• Mitosis produces 2 diploid cells; Genetically the same• 1 division; produces body cells• Meiosis produces 4 haploid cells; Genetically different• 2 divisions; produces gametes

• Mitosis repair the body, grow, and replace cells• Meiosis cut the number of chromosomes in half; makes more variation

Phase Quiz• Write which phase the cell is in:

1) 4)

2) 5)

3) 6)

Prophase

Metaphase

Metaphase I

Telophase

Anaphase

Telophase

Genes and Alleles

Genetic Terminology • What is a gene?

– Section of DNA that codes for a protein

– Give you characteristics:• Hair color, eye color, height

• What is an allele?– Different versions of a gene– Give you a specific type of

characteristic• Blue eyes, brown eyes, green eyes

• The combination of alleles for a gene is called a genotype

• Your physical appearance, based on a genotype, is called a phenotype– AA Red Flower– aa White flower

Dominate!• Allele are not created equal– An allele for one trait can

dominate another allele for the same trait

• Brown Eyes vs. Blue eyes– B = allele for brown eyes;

dominate allele– b= allele for blue eyes; recessive

alleleGenotype Phenotype

BB

bb

Bb

Brown Eyes

Blue Eyes

Brown Eyes

Homozygous Dominate

Homozygous Recessive

Heterozygous

Our Main Man Mendel!• Gregor Mendel father of

genetics; discovered trends in heredity 30 years before other scientists!

• Prior to Mendel what did people believe about inheritance?– Blending Theory all

genetic traits are equally mixed in offspring

– If this were true what would disappear?• Really tall, short, etc…

members of a population

246 cm

73.7 cm

Mendel’s Work• Secret to Mendel’s discovery

is his detailed record keeping and attention to the controlled experiment

• He work with Garden peas. Why?– Easy to grow– Easy to observe – Most traits (characteristics)

came in sets of two• White Flowers vs. Purple flowers• Yellow seeds vs. Green seeds• Smooth seeds vs. Wrinkled seeds

Crossing Peas• Mendel’s Experiment:1) Make pure breed plants– Purple flowers (PP)– White flowers (pp)

2) Mix gametes of two pure breed plants with different traits– Purple flowers X White flowers– Parental Cross; P generation– Produced only purple flowers

(Pp)

3) Mix gametes of offspring– Offspring= F1 generation– F1 Purple Flower X F1 Purple

Flower– Produced F2 generation– 3 Purple : 1 White ratio!

Mendel’s Three Theories• From the first cross all F1 flowers

are purple• From F1 cross F2 ratio is

3 purple: 1 white flower • Theories1) The parents must carry a pair of

factors (alleles) the control the inheritance of each trait– P purple flowers– p white flowers

2) If you have one of each allele, one will be dominate and one recessive– Pp purple flowers

3) Pairs of alleles are segregated into different gametes– Gamete has either P or p

What’s Your Genotype?• Comparing the phenotype of

you and your parents, you can know you genotype for some simple traits

• The phenotypes we will look at:– Tongue rolling dominant – Window’s Peak dominant – Cleft chin recessive – Attached earlobes recessive– Roman nose dominant– Dimples dominant

Review Questions1) What is the difference between a genotype and a

phenotype?

2) What are the terms for genotypes AA, aa, and Aa?

3) If a red flower (RR) is crossed with a white flower (rr), what will be the phenotype and genotype of the F1?

Genotype Alleles in DNA for a certain traitPhenotype The physical trait expressed by a genotype

• AA homozygous dominant• aa homozygous recessive• Aa heterozygous

• Phenotype Red flower Genotype Rr