February 10, 2011

Make Sure you have your Notebook Checked for 9 Grades Posted Read and Define 10.1 Vocabulary Notes 10.1

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Mendelelian Genetics

http://sps.k12.ar.us/massengale/pwpt_biology.htm

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Gregor Mendel (1822-1884) Responsible for the Laws governing Inheritance of Traits 3

Gregor Johann Mendel



Austrian monk



Studied the inheritance of traits in pea plants



Developed the laws of inheritance



Mendel's work was not recognized until the turn of the 20th century 4

Gregor Johann Mendel



Between 1856 and 1863, Mendel cultivated and tested some pea plants 28,000



He found that the plants' offspring retained traits of the parents



Called the of Genetics" “Father 5

Site of Gregor Mendel’s experimental garden in the Czech Republic 6

Particulate Inheritance



Mendel stated that physical traits are inherited as “particles”



Mendel did not know that the “particles” were actually Chromosomes & DNA 7

Genetic Terminology

  

Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity 8

Types of Genetic Crosses

 

Monohybrid cross involving a single trait e.g. flower color cross Dihybrid cross cross involving two traits e.g. flower color & plant height 9

Punnett Square

Used to help solve genetics problems 10

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Designer “Genes”

  

Alleles two forms of a gene (dominant & recessive) Dominant stronger of two genes expressed in the hybrid; represented by a capital letter (R) Recessive gene that shows up less often in a cross; represented by a lowercase letter (r) 12

More Terminology

 

Genotype for a trait gene combination (e.g. RR, Rr, rr) Phenotype genotype the physical feature resulting from a (e.g. red, white) 13

Genotype & Phenotype in Flowers Genotype of alleles: R = red flower r = yellow flower All genes occur in pairs, so 2 alleles affect a characteristic Possible combinations are: Genotypes Phenotypes RR R r rr RED RED YELLOW 14

Genotypes

 

Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure Heterozygous genotype - gene combination of one dominant & one recessive allele ( e.g. Rr); also called hybrid 15

Genes and Environment Determine Characteristics 16

February 22, 2011

Vocab #3 pre-test… Check off on Monohybrid Principles of Genetics Notes 10.1

Monohybrid Worksheet Make sure to read chapter and understand Monohybrid concepts and vocabulary

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Mendel’s Pea Plant Experiments

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Why peas,

Pisum sativum

?

 

Can be grown in a small area Produce lots of offspring



Produce pure when allowed to self-pollinate several generations



Can be plants artificially cross-pollinated 19

Reproduction in Flowering Plants Pollen contains sperm Produced by the stamen Ovary contains eggs Found inside the flower Pollen carries sperm to the eggs for fertilization

Self-fertilization Cross-fertilization

can occur in the same flower can occur between flowers 20

Mendel’s Experimental Methods

Mendel hand-pollinated flowers using a paintbrush He could snip the stamens self-pollination He traced traits through the generations to prevent several 21

How Mendel Began

Mendel produced pure strains by allowing the plants to self pollinate for several generations 22

Eight Pea Plant Traits

Seed shape Seed Color Pod Shape Pod Color

--- Round --- Green

Seed Coat Color Flower position

(R) ---- Yellow (G) ---Axial (Y) --- Smooth (S) (A) or Wrinkled (r) or Green (y) or wrinkled or Yellow (g) ---Gray (G) or White or Terminal (a)

Plant Height

--- Tall (T) or Short (t)

Flower color

--- Purple (P) or white (p) (s) (g) 23

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Mendel’s Experimental Results

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Did the observed ratio match the theoretical ratio?

The theoretical or expected ratio of plants producing round or wrinkled seeds is 3 round :1 wrinkled Mendel’s observed ratio was 2.96:1 The discrepancy is due to statistical error The larger the sample the results approximate to the theoretical ratio the more nearly 27

Generation “Gap”

Parental P 1 Generation = the parental

.

F 1 generation = the first-generation offspring in a breeding experiment. (1st filial generation) From breeding individuals from the P generation 1 F 2 generation offspring in a breeding experiment. (2nd filial generation) From breeding individuals from the F generation = the second-generation 1 28

Following the Generations

Cross 2 Pure Plants TT x tt Results in all Hybrids Tt Cross 2 Hybrids get 3 Tall & 1 Short TT, Tt, tt 29

Monohybrid Crosses

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Mendel’s Law of Genetics

Reproduction produces different combinations of genes Many variations within each kind of life Great variations possible in skin, hair, eye color, facial structure, body size

P

1

Monohybrid Cross

Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Wrinkled seeds RR x rr R R r Rr Rr r Rr Rr Genotype: Rr

Phenotype:

Round Genotypic Ratio: All alike Phenotypic Ratio: All alike 32

P

1

Monohybrid Cross Review

   

Homozygous dominant x Homozygous recessive Offspring (hybrids) all Heterozygous Offspring called F 1 generation Genotypic & Phenotypic ratio is ALIKE ALL 33

F

1

Monohybrid Cross

Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Round seeds Rr x Rr R r R RR Rr r Rr rr Genotype: RR, Rr, rr

Phenotype:

Round & wrinkled G.Ratio: P.Ratio: 1:2:1 3:1 34

F

1

Monohybrid Cross Review

    

Heterozygous x heterozygous Offspring: 25% Homozygous dominant RR 50% Heterozygous 25% Homozygous Recessive Offspring called Genotypic ratio is Phenotypic Ratio F 2 Rr generation 1:2:1 is 3:1 rr 35

What Do the Peas Look Like?

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…And Now the Test Cross

Mendel then crossed a hybrid This is known as an F 2 cross There are two possible pure & a from his F 2 generation or test testcrosses: Homozygous dominant x Hybrid Homozygous recessive x Hybrid 37

F

2

Monohybrid Cross (1

Trait: Seed Shape Alleles: R – Round r – Wrinkled st

)

Cross: Round seeds x Round seeds RR x Rr R R R RR RR r Rr Rr Genotype: RR, Rr

Phenotype:

Round Genotypic Ratio: 1:1 Phenotypic Ratio: All alike 38

F

2

Monohybrid Cross (2nd)

Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Wrinkled seeds x Round seeds rr x Rr r r R Rr Rr r rr rr Genotype: Rr, rr

Phenotype:

Wrinkled Round & G. Ratio: 1:1 P.Ratio: 1:1 39

F

2

Monohybrid Cross Review

   

Homozygous x heterozygous(hybrid) Offspring: 50% Homozygous RR or rr 50% Heterozygous Phenotypic Ratio Rr is 1:1 Called Test Cross because the offspring have SAME genotype as parents 40

Practice Your Crosses

Work the P

1

, F

1

, and both F

2

Crosses for each of the other Seven Pea Plant Traits

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February 23, 2011

?? Of day – Left side Differentiated between the P 1, F1 and F 2 cross.

Review Monohybrid crosses Monohybrid Worksheet HOMEWORK: PSLab 10.1

Read Chapter 10!!

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February 24, 2011

Correct Mono Hybrid Worksheet Notes Dihybrid Principles of Genetics Flipping…

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Mendel’s Laws

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Results of Monohybrid Crosses Inheritable Phenotype factors or genes responsible for all heritable characteristics is based on are Genotype Each trait is based on two genes , one from the mother and the other from the father True-breeding individuals are homozygous ( both alleles) are the same 45

Law of Dominance

In a cross of parents that are pure for contrasting traits the next generation.

, only one form of the trait will appear in All the offspring will be heterozygous and express only the dominant trait.

RR x rr yields all Rr (round seeds) 46

Law of Dominance

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Law of Segregation

During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.

Alleles for a trait are then "recombined" at fertilization traits of the offspring .

, producing the genotype for the 48

Applying the Law of Segregation 49

Law of Independent Assortment

Alleles for another.

different

traits are distributed to sex cells (& offspring) independently of one This law can be illustrated using

dihybrid crosses

.

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Dihybrid Cross

A breeding experiment that tracks the inheritance of two traits .

Mendel’s “Law of Independent Assortment” a. Each pair of alleles segregates independently during gamete formation b. Formula: 2 n (n = # of heterozygotes) 51

Question: How many gametes will be produced for the following allele arrangements?

Remember: 2 n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq 52

Answer:

1. RrYy: 2 n = 2 2 = 4 gametes RY Ry rY ry 2. AaBbCCDd: 2 n = 2 3 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3. MmNnOoPPQQRrssTtQq: 2 n gametes = 2 6 = 64 53

Dihybrid Cross

Traits: Seed shape & Seed color Alleles: R round r wrinkled Y yellow y green RrYy x RrYy RY Ry rY ry RY Ry rY ry All possible gamete combinations 54

RY Ry rY ry

Dihybrid Cross

RY Ry rY ry 55

Dihybrid Cross

RY Ry rY ry RY RRYY RRYy RrYY RrYy Ry RRYy RRyy RrYy Rryy rY RrYY RrYy rrYY ry RrYy Rryy rrYy rrYy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio 56

Dihybrid Cross

Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 57

Test Cross

A mating between an individual of unknown genotype and a homozygous recessive individual.

Example: bbC__ x bbcc BB = brown eyes Bb = brown eyes bb = blue eyes CC = curly hair Cc = curly hair cc = straight hair bc bC b___ 58

Test Cross

Possible results: bC bc bbCc bb C c or bC bc bbCc bb c c 59

Biology 3/4/11

Pass Out Papers.

Science Vocab #4 Notes on 10.2

Vocab and PS Lab 10.2

Make sure I have Mono, Di hybrid and Principles of Genetics worksheet

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Summary of Mendel’s laws

LAW PARENT CROSS OFFSPRING DOMINANCE SEGREGATION TT x tt tall x short Tt x Tt tall x tall 100% Tt tall 75% tall 25% short INDEPENDENT ASSORTMENT RrGg x RrGg round & green x round & green 9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods 61

10.2 Meiosis

Chromosomes thousand or more genes located on a chromosome Diploid Cell 2n contains a pair of chromosomes one from the male and one from the female Haploid Cell n-cell with one of each kind of chromosome

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Homologous chromosomes

contain genes for the same trait, in the same order

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Zygote – fertilized egg which has a 2n diploid number of chromosomes Sexual reproduction – figure 10.11 , doubling of chromosomes and then halving the DNA is located on chromosomes, these chromosomes are made up of 2 halves called sister chromatids and are exact copies held together by a centromere

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March 7, 2011 ?? Of the Day: Differentiate between a diploid and haploid cell.

STAMP ON VOCAB 10.2

Vocab Pretest #5 Notes on Meiosis PS Lab 10.2

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Meiosis is divided into 2 separate divisions: Meiosis I

– begins with one 2n diploid cell

Meiosis II

– ends with 4 n haploid cells, called sex cells or gametes

Sperm Egg

– male gametes – female gametes

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Meiosis – cell division allows for offspring to have the same number of chromosomes as their parents (Mitosis would be double) Meiosis/Mitosis Animation

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March 9, 2011

Finish Meiosis Notes Meiosis Stages - Draw out all stages and describe each stage Meiosis Activity All Learning Targets due and finish up summaries of notebooks Add 2 level questions to notes Test Thursday!!

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Phases of Meiosis

Interphase –cell is reproducing its chromosomes and has 2 identical sister chromatids held together by a centromere Prophase I – each pair of homologous chromosomes ( 2 sister chromatids) come together, matched gene by gene to form a 4 part structure called a tetrad Crossing Over – exchange of genetic material between homologous chromosomes, this results in new combinations of alleles on a chromosome

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Metaphase I

Centromere of each chromosome becomes attached to a spindle fiber Spindle fibers pull the tetrads into the middle of the equator of the spindle Homologous chromosome line up side by side as tetrads (in mitosis they line up independently)

Anaphase I

Homologous chromosomes each with its 2 chromatids separate move to opposite ends of the cell Centromeres holding the sister chromatids do not split (as in mitosis)

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This ensures that each new cell will receive only one chromosome from each homologous pair

Telophase I

Spindle is broken down, chromosomes uncoil Cytoplasm divides to yield 2 new cells Each cell has only half the genetic info of the original cell but it is in only 1 chromosome so we still need another cell division Meiosis II – identical to mitosis

Prophase II

Spindle forms in each of the 2 new cells & the spindle fibers attach to the chromosomes

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Metaphase II

Chromosomes (still made up of sister chromatids), are pulled to the center of the cell and line up randomly at the equator

Anaphase II

Centromere of each chromosome splits Sister chromatids split and move to opposite poles

Telophase II

Nuclei reform Spindles break down Cytoplasm divides

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Genetic Recombination-

Allows for variation in organisms Each of the pairs of chromosomes can line up at the cells equator 2 different ways Humans 23 chromosomes 2 23 Times this by 2 parents 2 23 X2 23

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Mistakes in

Meiosis –

Nondisjunction

Non Disjunction

when the chromosomes don’t separate properly

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Trisomy

extra chromosome Downs syndrome http://www.ds-health.com/images/trisomy.gif

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Triploidy – complete extra “set” of homologous chromosomes can be beneficial in agriculture

http://://www.tokyo-med.ac.jp/genet/cki-e.htm&h=28

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Monosomy

one less chromosome Turners syndrome (X)

http://://www.tokyo-med.ac.jp/genet/cki-e.htm&h=28

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