Wednesday 4/9/14 AIM: Why is Gregor Mendel the father of genetics? DO NOW: How many chromosomes do you have and where do they come from? What would happen if you had an extra chromosome and why? HOMEWORK: Text read pages 267-70. Reading check pages 267 and 268, q 1 and 2 pages 270

What is genetics?

Genetics The study of inherited traits Chromosomes are the units of inheritance Chromosomes carry genes Genes are the specific direction or code for your physical trait Genes: code for proteins Proteins cause chemical reactions Chemical reactions lead to physical traits

Where do your inherited traits come from? Your dads sperm and your moms egg

Homologous chromosome Similar in size shape and genetic content Homologous chromosomes pair up at fertilization n+n=2n

Remember Zygote gets one complete set of chromosomes from the egg And one complete set of chromosomes from the sperm Bringing together homologous chromosomes

Haploid + haploid = diploid

Human Chromosomes Total we have 23 pairs 2(23)=46 22 of those pairs are called autosomes The 23 pair is the sex chromosomes

Sex Chromosomes XX female XY male

Y chromsome Carries the SRY gene SRY: sex determining region If the SRY gene is turned on, then gonads develop into testis and fetus becomes male If not then gonads become ovaries

AIM: How does the structure of DNA relate to its function? DO NOW: How many chromosomes do each of your cells have? How many genes does each of your cells have? How many nuclei does each of your cells have? Homework: text read pages 293,296,297 and 299. Answer Reading questions 293,296,297

Somatic or body cells have 46 chromosomes Examples of somatic cells Cardiac cells lung cells brain cells Skin cells muscle cells gall bladder cells Tracheal cells esophagal cells liver cells Gametes or sex cells have 23 chromosomes Male-sperm Female-ova or egg There are thousands of genes in each cell There is one nucleus in each cell that houses the chromosomes which carry genes on them Each cell expresses specific genes to make them specialized

So how do we know anything about genetics and homologous chromosomes?

Gregor Mendel Father of genetics Looked at the pea plant Specifically 7 visible traits Followed their inheritance over many generations HE KNEW NOTHING ABOUT GENES!!!!!

Mendel was lucky Each of the 7 traits Mendel observed was only present in 1 of 2 possible forms Ex: Plant color was either purple or white Pea shape was either round or wrinkled Mendel used this when performing his experiments.

Thursday 4/10/14 AIM: How did Gregor Mendel develop his basic laws of heredity? DO NOW: What is genetics? How do we know anything about genetics? HOMEWORK: Textbook read pages 276-277. do the reading check on page 277

Genetics The study of inherited traits Chromosomes are the units of inheritance Chromosomes carry genes Genes are the specific direction or code for your physical trait Genes: code for proteins Proteins cause chemical reactions Chemical reactions lead to physical traits

AIM: How did Mendel develop his basic laws of heredity? DO NOW: What is the difference between self fertilization and cross fertilization? HOMEWORK: textbook read pages 267-270. 1-Explain the difference between true breeding and hybrid. 2- Define P generation, first filial generation and second filial generation.’ 3- Explain why Mendel studied pea plants

Gregor Mendel’s experiments: Fertilization Self-fertilization: egg in the flower is fertilized by the sperm of the same flower Cross-fertilization: sperm from a foreign plant fertilizes an egg

Gregor Mendel Used both the processes of self fertilization and cross fertilization to experiment on pea plants This helped him develop his basic laws of heredity

Definitions True breed or pure breed: plants with a trait such as purple flowers that is always inherited by all offspring Can only produce one type of gamete HYBRID: The offspring of a cross fertilization 2 parents similar to sexual reproduction Can produce different types of gametes

Definitions continued Monohybrid cross: tracks one trait at a time Ex: flower color Dihybrid cross:

Mendel’s work Self fertilized true breed parents for many generations All offspring gave the same results Cross fertilized true breeds to get an F1 generation Self fertilized the F1 and observed the F2 generation

Mendel’s Experiment Parent Generation (P1): Purple true breed X White true breed First Filial (F1) 100% Purple flowers Self fertilize Second Filial (F2) 75% Purple: 25% White 3:1 ratio

Why were all the F1 generation flowers purple? Purple Trait is obviously dominant over the white trait The white trait was hidden but not gone

Why were some of the F2 generation part purple and part white? The F1 parent was carrying the white trait but it was masked or hidden. White is recessive to purple

Just from looking at these results, what can Mendel conclude?

Mendel’s Conclusions from a monohybrid cross 1- Copies of inherited traits must be separated when gametes are formed 2- When present in 2 forms one form is dominant over the other 3- the recessive trait will show itself when present in two copies

Tuesday 4/22/14

From these experiments, Mendel concluded: Traits are determined by physical unit that come in pairs (he did not know these would later be called alleles) Gametes separate and carry only 1 allele(copy) for each gene The particular allele that ends up in a gamete is caused by chance One allele is dominant and one recessive True-breeding organisms have the 2 copies of the same allele (homozygous)

AIM: How can we predict the possible genotypes and phenotypes of offspring? DO NOW: 2- if I cross fertilized a true breed green seed pea plant by a true breed yellow seed pea plant, what phenotypes do I expect to get? HOMEWORK: Textbook read pages 272-273. answer questions 1,2,3 on page 275

Create a list 7 traits observed by Gregor Mendel 1- Flower color 2- Plant size 3- Flower position 4-Seed color 5- shape of pod 6- Pod color 7- Seed shape Each of these traits has a dominant and a recessive phenotype

Seed color Dominant phenotype: green Recessive phenotype: yellow Genotype Phenotype GG Gg gg

Mendel had no idea about the following We know we get 2 copies of genes 1 from sperm 1 from egg Allele: is a copy of a gene Homologous chromosomes carry alleles

Monohybrid Cross Tracked one (mono) trait at a time

Mendel’s work Cross fertilized two true breed parents that displayed opposite traits.(P or Parental generation) All First filial or F1 offspring were purple

What happened to the white color?

Self-fertilized F1 Second filial or F2 generation yielded about ¼ white and ¾ purple So the white flower color was not lost just masked

Self-fertilized F2 Saw that all white flowered F2 yielded all white F3 but the purple still yielded 3:1 ratio of purple to white Therefore the white allele was not lost but rather hidden or masked by the purple allele

From these experiments, Mendel concluded: Traits are determined by physical unit that come in pairs (he did not know these would later be called alleles) Gametes separate and carry only 1 allele for each gene The particular allele that ends up in a gamete is caused by chance One allele is dominant and one recessive True-breeding organisms have the 2 copies of the same allele

Thursday 4/24/14 AIM: why did Mendel decide to perform a dihybrid cross? DO NOW: Let A represent the allele coding for terminal flowers and a axial flowers. Complete the following table: HOMEWORK: text read pages 274-275. answer questions 3 and 4 page 275 Genotype Phenotype AA Homozygous dominant terminal Aa Heterogygous aa Homozygous recessive axial

Mendel’s Law of dominance When two different alleles are present, the dominant alleles gives the resulting phenotype and masks the trait of the recessive allele However the recessive allele is still present Homozygous Dominant and heterozygous organisms display the same phenotype Recessive alleles are only displayed when present in 2 copies Homozygous recessive

Mendel’s Law of segregation Pairs of alleles on homologous chromosomes separate from each other during gamete formation Gametes receive only one allele from a homologous pair. Fertilization produces offspring with a copy of one allele from mom and one from dad

Mendel’s Hypothesis were consistent with his results 2 plants that look alike may actually carry different combinations of alleles Genotype: the combination of alleles carried by an organism Homozygous Dominant: AA Heterozygous: Aa Homozygous recessive: aa Phenotype: The physically observable feature So a homozygous dominant individual and a heterozygous individual will display the same phenotype but have different genotypes The only way for the recessive phenotype is observed is if the individual is homozygous recessive

Mendel was not satisfied He wanted to see if alleles could be inherited together He asked himself are all round seeds yellow? Are all green seeds wrinkled? He looked at two traits at the same time Dihybrid cross Ex: seed shape and seed color His results were inconclusive which means all round seeds were not yellow all wrinkled seeds were not green

In order to investigate, Mendel performed a dihybrid cross Dihybrid cross: crossed plants that differed in more than one trait Specifically Mendel looked at seed shape and seed color

Cross Fertilization Homozygous Dominant Homozygous recessive ALL heterozygous Dominant shape Recessive color Dominant color Recessive shape Both Dominant traits Both recessive traits

R-round r-wrinkled Y-Yellow y-green

Friday 4/25/14

Mendel’s dihybrid cross P: true breed RRYY(Round Yellow) x rryy(wrinkled green) All F1: RrYy (Round Yellow) Allowed F1 to self-fertilize which yielded the following phenotypic ratio F2: 9:3:3:1 ratio of Round Yellow: Round green: wr Yellow: wr,green

F1: Self Fertilization

F1: self fertilization

Display of all possible genotypes

Law of independent assortment Multiple traits are inherited independently of each other because alleles of genes are distributed independently during gamete formation Genes found on different chromosomes assort independently of each other during gamete formation Genes are inherited independently

What was the major question Mendel was trying to answer when he performed his dihybrid cross? Mendel asked himself if two characteristics were inherited together. Specifically is seed color inherited with seed shape?

Testcross Cross fertilize a dominant phenotype plant with a homozygote recessive plant WHY? Purpose is to analyze the ratio of the offspring This will tell us the parents genotype (homozygous dominant or heterozygous)

What do we call this type of cross ad why would we perform it?

Test cross Determines the genotype of a dominant displayed phenotype

Testcross The only way to display the recessive phenotype is to have a homozygous recessive genotype After performing a testcross, If the f1 offspring display ALL dominant phenotypes then I know the Parent genotype is homozygous Dominant. If the offspring display 50% dominant phenotype and 50% recessive than the Parental genotype is heterozygous