Review Questions 1)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 allele GenotypePhenotype 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 F 1 flowers are purple From F 1 cross  F 2 ratio is 3 purple: 1 white flower Theories 1)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 Questions 1)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 trait Phenotype  The physical trait expressed by a genotype AA  homozygous dominant aa  homozygous recessive Aa  heterozygous Phenotype  Red flowerGenotype  Rr