Mendel’s Genetics Monohybrid Cross

Gregor Mendel As discussed last class, he was an Austrian monk He worked at St. Thomas Monastery He studied both mathematics and botany

Why did he actually Succeed? He chose the appropriate organism to study He designed and performed his experiments correctly Analysis of the data was done properly

The Patient The common ______ also known as Pisum sativium It was chosen for 4 reasons It was _________ available Easy to _____and mature The sex organs are entirely ________ in the flower Different varieties had different ________

Purebred What is a purebred organism? __________________________________________________________ Why was this important to Mendel and his pea plants? This is because he used purebred plants to conduct all of his experiments

How did he make sure? How did Mendel make sure that his organisms (pea plant) were pure bred? He bred them as everyone else bred plants, and he looked at _____ ______ at a time He selected from the ________, only the plants that had the trait that he was looking for He then bred them together (________) and then he continued this for several generations until no more of the other trait showed up

What happened Next? He repeated this for all the other traits until he had pure bred plants with each trait.

The first of the Crosses So what did he end up doing next? He started to _______________ He designated the parents as the ____ generations and crossed a true-breeding _____pea plant, with a true-breeding ______ pea plant The offspring were of course the F1 generation and he also denoted them as __________

That F1 Generation What do you think he saw? What was the phenotype of the plants? ____________________________ What is this type of crossing called?

Creatively Creatively the name given to this type of cross is _____________ It is a _______ cross between two purebred plants giving us a hybrid species

What did his experiment look like?

That’s the Phenotype We have now seen the phenotype All of the F1 generations plants were _____ What do you think the genotype must be of the offspring? First we have to learn some more terms

Terms ___________________ (TT) – Two alleles for a trait that are the same as a result of pure breeding ___________________ – Having two alleles for a trait that are different ___________________ - Two alleles for a trait that are the same as a result of pure breeding

The First Cross PF1 Tall Short

Lets back track Yesterday we looked at the different combinations of alleles that an individual can have We also talked about dominance and recessiveness What did we say the dominant allele was? What about the recessive allele

What were the parents? The parent that was tall had a double _______ allele The parent that was short had a double _______ allele Both of these parents were homozygous

When he Crossed When the parents were crossed, the F1 generation was completely ____________ They all expressed the dominant trait, but why? __________________________________________________________

So the First cross is done, what about the second?

Second Cross Genotype

Mendelian Ratio As Mendel completed the experiment, he found that ____of the offspring of the F1 cross were the ________ (tall) and ____ were the _______ (short) The Ratio of _____ is known as the _________________

Based on observations, Why did this happen? Each parent in his F1 Generation starts with two hereditary “factors.” One factor is _______ and the other ________ The factors separate out in the and only one of the two factors contribute to the phenotype of the offspring

Why did this happen? The offspring inherit ____ factor from ____ and ____ from ____. If the dominant factor is present, it will be _______, even if the recessive one is present The recessive factors will be expressed ___ if the recessive factors are present

The first Law of heredity His results gave rise to his first law The law of Segregation

The law of segregation His law of segregation states: __________ _________________________________ These factors segregate in the gametes (after meiosis) Mendel did not know that his factors were actually genes, we know this today

What do we call this?

Punnett Square

What do they do for us? Well, they are used by geneticists so that they can _________ the expected ratio (__________) and to suggest possible combinations of _______ in the offspring They also tell us something about the __________ (the appearance of a trait in an organism)

So we saw TT x tt And for that cross we ended up having a ratio of? All were Heterozygous (100% - 0%) What about when we cross the F1 x F1 generations?

F1 X F1 What’s the ratio when we are talking about phenotype? 3:1 as well, three of the offspring will present the dominant gene while the fourth will present the recessive gene What about the genotype ratio? _______________________________________________________________________________________

Example

Class Work Read Pages 202 -212 Complete Questions 205 #1, 5, 6