Genetics & Gregor Mendel And his peas…….

We all have questions about where we came from and how we got the traits we have. 1)Look around you. Do you all look the same? 2)Who has a widow’s peak? Who has attached earlobes? Can you roll your tongue? 3)How did you get that way?

CHALLENGE QUESTION: Can you have a white haired baby rabbit when both its parents have brown hair???? Why or why not?

Mendel had questions too… Start Simple Stupid!!!! Gregor Mendel – ( ) an Austrian monk with the same questions who answered them by studying pea plants; earliest geneticist Why peas? Simple, not many traits, easy to control and manipulate, he was a gardener (scientist, mathematicist, and teacher too!)

Objectives: By the end of this lesson you should be able to: Describe how Mendel studied his pea plants Summarize Mendel’s ideas about inheritance Explain the principle of dominance Describe segregation Design a cross and predict the outcomes using a Punnett square

Pea plant vocabulary Fertilization – joining of sperm and egg to produce an embryo Pollination – the transfer of sperm from pollen to the female part of the flower

Types of pollinating Self pollination Cross Pollination Next class, you will Label and fill-in the parts on your very own flower sheets

What did Mendel do? He studied how pea plants inherited their traits by pollinating them himself and looking at the resulting children plant Traits – characteristics like seed color, plant height, seed shape, pod color OR….. Hair color, eye color, tongue curler…..

Your Reminder: How many traits do you have? You came from a sex cell (gamete) Sex cells are haploid –1n = 1 set of information –OR half You are made up of diploid cells –2n = 2 sets of chromosomes (1 from your mother and 1 from your father)

How did he observe plant traits? 1)First, he made true breeding pea plants He did this by allowing them to self pollinate over and over again until they repeatedly produced the same traits This way he was sure they were “pure” plants

2) He took the pure purple pea flowers and the pure white flowers and cross pollinated them

Parental generation = P purple x P white First filial generation, the offspring = All F1 are purple flowered pea plants The F1 generation are hybrid pea plants Hybrids – plants produced by crossing two different traits

Mendel’s first set of conclusions: 1)Inheritances is determined by traits passed from one generation to the next 2)The traits are determined by genes 3)Genes have contrasted forms called alleles Ex: The trait, flower color was determined by the parental genes that carried either the purple or white allele

Principle of dominance: States that some alleles are dominant and others are recessive Dominant = the version of an allele that will always exhibit its form if it is present What flower color is dominant? Recessive = the version of an allele that is hidden by the dominant allele and only present when the dominant allele is not What flower color is recessive?

Human Examples: Dominant Traits –Hanging Earlobes –Tongue Roller –Widow’s Peak Recessive Traits???

3 ) Next, Mendel wanted to know what happened to the white flower allele so he allowed the F1 generation to self pollinate F 1 x F 1 F 2 generation What do you think he saw? What color were these flowers? ¼ of the plants were white flowers ¾ of the plants were purple flowers

Mendel’s second set of conclusions: 1)Alleles separate from one another when gametes (egg and sperm) are formed HAPLOID CELLS (1n) 2)Alleles combine when an embyro is formed (egg and sperm combine) and contain a copy of the allele from each parent DIPLOID CELLS (2n)

Segregation: P generation = PP x pp (pure purple x pure white) F1 generation = Pp (all purple hybrids) Pp x Pp F2 generation = PP (purple) Pp (purple) pp (white) P is dominant p is recessive

Vocabulary terms to know: Homozygous = two of the same alleles; PP or pp Heterozygous = two different alleles;Pp Phenotypes = physical appearance of the characteristic; purple or white Genotype = the genetic makeup; PP, pp, or Pp

How did Mendel figure out all that we now know? Using probability - the likelihood that an event will occur How can you figure this out? Using Punnett Squares = shows the probability of each possible outcome that will result when a cross is made between two parents

Taste the paper…. What is it? What happened? What is your phenotype? Do you know your genotype? If not, how could you determine it?

Example #1 on Plant Height T = tall t = short Mom = T T tttt Dad = All possible kids belong here

Example #1 on Plant Height T = tall t = short Mom = T T tttt Dad = Tt All offspring at heterozygous tall Phenotype = tall Genotype = 4 Tt (heterozygous)

Example #2 – Your turn Use two of the offspring as parents T = tall t = short TT Tt tt Mom = T t TtTt Dad = Phenotype = 3 tall: 1 short Genotype = 1 tt: 2 Tt: 1 TT 1 homozygous short 2 heterozygous tall 1 homozygous tall

Example # 3 – Eye color 1. What are the possible eye colors of children if a homozygous brown eyed female and a homozygous blue eyed male have kids? Mom = BB bbbb Bb Phenotype = all brown eyes Genotype = 4 Bb heterozygous

Now try….. 1)What are the possible offspring if the mom is heterozygous brown eyes and the dad is blue eyes 2)What are the possible offspring if the mom and dad are both heterozygous brown eyes? 3)Can you have heterozygous blue eyes?