Which statements about cell division are CORRECT? A. statements 1 and 3 B. statements 1 and 4 C. statements 2 and 3 D. statements 2 and 4

Today we will learn: b Who is the father of Genetics? b What is heredity? b What are traits? b Phenotypes vs Genotypes b Homozygous vs heterozygous

Mendel’s Laws of ___Genetics Why we look the way we look... ontent/begin/traits/ ontent/begin/traits/

What is heredity? b The passing on of characteristics (traits) from parents to offspring b _Genetics__ is the study of heredity

5 Gregor Mendel Austrian monkAustrian monk Considered the “father of genetics”Considered the “father of genetics” The first person to succeed in predicting how traits would be transferred from one generation to anotherThe first person to succeed in predicting how traits would be transferred from one generation to another –using the garden pea plant

Mendel used peas... b They reproduce sexually b They have two distinct, male and female, sex cells called _gametes_. b Their traits are easy to isolate

Mendel crossed them b _fertilization_ - the uniting of male and female gametes b Cross - combining gametes from parents with different traits

8 Types of pollination/fertilization Cross-pollination self-pollination

Questions b What did Mendel cross? b What are traits? b What are gametes? b What is fertilization? b What is heredity? b What is genetics?

What Did Mendel Find? b He discovered different laws and _rules_ that explain factors affecting heredity.

Rule of Unit Factors b Each organism has two _genes_ for each trait –Alleles - different forms of the same gene –Genes - located on chromosomes, they control how an organism develops

Rule of Dominance b The trait that is observed in the offspring is the dominant trait (uppercase) b The trait that disappears in the offspring is the recessive trait (lowercase)

Law of Segregation b The two alleles for a trait must separate when gametes are formed. b A parent randomly passes only one allele for each trait to each offspring.

Law of Independent Assortment b The genes for different traits are inherited independently of each other.

Genes and Dominance b Mendel came to two conclusions: 1.Factors that are passed/inherited from one generation to the next determine inheritance. 2.The Principle of Dominance - states that some alleles are dominant and some are recessive.

Questions... b How many alleles are there for each trait? b What is an allele? b How many alleles does a parent pass on to each offspring for each trait

Questions... b What do we call the trait that is observed? b What case (upper or lower) is it written in? b What about the one that disappears? b What case is it written in?

Phenotype & Genotype b phenotype - the way an organism looks –red hair or brown hair b genotype - the gene combination of an organism –AA or Aa or aa

Heterozygous & Homozygous b Heterozygous - if the two alleles for a trait are different (Aa) b _Homozygous - if the two alleles for a trait are the same (AA or aa)

Dihybrid vs Monohybrid b Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee) b Monohybrid Cross - crossing parents who differ in only one trait (AA with aa)

Questions... b What is the phenotype? b What is the genotype? b What is homozygous? b What is heterozygous? b What is monohybrid crossing?

Which genotype is heterozygous for two traits? A. ggTt B. GgTt C. GgTT D. GGTT

Punnett Square b Developed by Reginald _Punnett_. b A diagram used to show the probability or chances of a certain trait being passed from one generation to another.

Probability b The likelihood of a particular event occurring. Probability b Can be expressed as a fraction or a percent. b Example: coin flip.

What is a PUNNETT SQUARE? b A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine b A way to show phenotype & genotype  A chart that shows all the possible combinations of alleles that can result when genes are crossed

Using a PUNNETT SQUARE To set up a Punnett square, draw a large square, and then divide it into 4 equal sections (also squares). It should look something like this:

Using a PUNNETT SQUARE b Letters stand for dominant and recessive alleles b An uppercase letter stands for a dominant allele b Lowercase letters stand for recessive alleles

Using a PUNNETT SQUARE Finally, take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this:

Using a PUNNETT SQUARE b The two-letter combinations are the possible genotypes of offspring. b They are: Rr, Rr, rr, and rr genotypes b From this it is possible to determine the probability (chance) that a flower will have a red phenotype (2/4 or 50%) or a white phenotype (2/4 or 50%)

Reading Punnett squares b Allele letters are placed above and to the left of the square b Offspring are placed in the square. b Capital letters (Y) represent dominant alleles. b Lower case letters (y) represent recessive alleles.

What can you tell me from this punnet square?

Punnett square review:

What is independent assortment? bCbCbCbChromosomes/genes separate independently bdbdbdbduring the bfbfbfbformation of bgbgbgbgametes.

The dihybrid cross b Punnett square on board:

Putting it all together! T = Tall Plants Mom and Dad are both heterozygous t = short plant Male gametes T t Female Gametes T t T TtTt tTtT t Genotypic ratio: Phenotypic ratio:

Let’s Practice! hill.com/sites/ /student_view0/chapter5/m ath_practice.html

How well did you do today? b Which parts of this Punnett square would contain the genotype that results in the expression of only the recessive phenotype? A. parts 1 and 2 B. parts 1 and 4 C. parts 2 and 3 D. parts 3 and 4