Mendel’s Law of Heredity

Starter http://learn.genetics.utah.edu/content/inheritance/observable/

Objectives Define a trait and what codes for it. Describe Mendel’s first experiment and his conclusion

Review Match the following words to the picture. Homologous chromosomes (Tetrad) Sister Chromatids Chromatin Chromosome

Review Where in the cell are chromosomes found? In the nucleus What types of cells are you making in meiosis? Sex cells: egg and sperm

Gregor Mendel Studied genetics 1st to succeed in predicting how traits are transferred from 1 generation to the next Used pea plants in experiments Reproduces sexually

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Experiments Mendel performed cross-breeding experiments Used “true-breeding” plants Chose varieties that differed in only one trait (monohybrid cross) A true-breeding individual is pure for a certain trait. He comes after several generations having the same trait Mendelian Inheritance

Monohybrid cross Tested one trait Height: tall and short

P1 (Parental generation) Tall Plant X Short Plant

Discuss with a partner if the offspring will be tall, short, or both.

F1 (First) Generation All tall

Biology, 9th ed,Sylvia Mader Chapter 11 Characteristics Trait *Dominant *Recessive Stem length Tall Short Pod shape Inflated Constricted Seed shape Round Wrinkled Seed color Yellow Green Flower position Axial Terminal Flower color Purple White Pod color Green Yellow Mendelian Inheritance

Mendel called the trait that appeared the dominant trait Mendel called the trait that appeared the dominant trait. The trait that seemed to fade into the background was called the recessive trait.

http://learn.genetics.utah.edu/content/inheritance/intro/ http://learn.genetics.utah.edu/content/inheritance/traits/

You should see a 2

You should see a 5

Everyone should have seen a 16

You should see a 42

You should see a 7

You should see a 29

You should see a 6

You should see a 57

You should see a 10

Normal colour vision will see a 5. An individual with Red/Green (the most common) colour blindness will see a 2.

Objectives Describe Mendel’s second experiment and his conclusion Perform a simple cross using a punnet square

What did Mendel conclude after his first experiment?

Crossed the F1 generation with itself Tall Plant X Tall Plant

Discuss with a partner if the offspring will be tall, short, or both.

F2 (Second) Generation 3 tall: 1 short

After his observations, Mendel knew that there must be two sets of instructions for each characteristic. There was no other way to explain it. This idea was a long time before the discovery of DNA He didn’t even have a microscope!!

His Conclusion Each organism has 2 factors (genes) that control each of its traits Different forms of a gene= alleles Example the plant has 1 allele for tall and 1 for short Where do the alleles come from? 1 from mother, 1 from father Tall ♀ Same chromosome with different alleles ♂ Short

Put the words into the write column: Brown eye color height Eye color Blond hair hair color short Black hair Round nose Nose shape Alleles (specific) Genes (general)

Dominant vs. Recessive Observed trait (always wins!) Use a capital letter Trait is not seen (masked) Use a lowercase letter Example for the trait HEIGHT (T) T = Tall t = Short Dominant Recessive Example 2 for the trait CURLY HAIR (C) C = Curly hair c = straight hair Dominant Recessive

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio T = tall plant 3 tall t = short plant 1 short TT tt Mendelian Inheritance

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #39 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio T = tall plant 3 tall P generation t = short plant 1 short TT tt 39

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #40 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio P generation T = tall plant 3 tall t = short plant 1 short TT tt P gametes T t 40

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #41 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio P generation T = tall plant 3 tall t = short plant 1 short TT tt P gametes T t tt F1 generation Tt 41

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #42 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio P generation TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T sperm t 42

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #43 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation Allele Key Phenotypic Ratio TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T TT sperm t 43

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #44 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. F1 generation Allele key Phenotypic Ratio TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T TT Tt sperm t 44

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #45 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation Allele Key Phenotypic Ratio TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T TT Tt sperm t Tt 45

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #46 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation TT tt P gametes T t F1 generation Tt eggs F1 gametes T t T sperm TT Tt F2 generation t Tt tt Offspring Allele Key Phenotypic Ratio T = tall plant 46 3 tall t = short plant 1 short

P1 (Parental generation) TT tt Tall Plant X Short Plant Is t dominant or recessive? t T Is T dominant or recessive? Recessive Dominant Tt Is this tall or short? Tall

Genotype (gene combination) Phenotype (looks and behavior) Homozygous (same alleles) TT= homozygous dominant Tall tt= homozygous recessive Short Heterozygous (different alleles) Tt

Tt Tt Tt Tt TT tt F1 (First) Generation X Law of segregation Heterozygous Heterozygous Tt Tt X Law of segregation Homozygous Heterozygous Heterozygous Homozygous Tt Tt TT tt

Punnett Squares!

Step 1: Read the problem carefully. Problem: In pea plants, tall is dominant to short. Mendel sprinkled the pollen of a homozygous dominant plant on the pistil of a heterozygous plant. What were the phenotypes of the offspring.

Step 2: Make a key that lists the traits (alleles) and their symbols. Choose a letter: T What trait is dominant? T = Tall What trait is recessive? t = short

Step 3: Show the genotypes of the parents you are crossing. Is the father (pollen) homozygous dominant, homozygous recessive, or heterozygous? TT Is the mother (pistol) homozygous dominant, homozygous recessive, or heterozygous? Tt Thus, you will get TT x Tt

Step 4: Draw a punnett square with 4 boxes for a monohybrid cross or 16 boxes for a dihybrid cross. Are we testing 1 trait or 2 traits in the problem? 1 trait Dihybrid (2 traits) Monohybrid (1 trait)

Step 5: Figure out what types of gametes can be formed by the female and write them on the top side of the punnett square inside circles (to represent eggs). Problem: genotype of female plant is Tt so gametes can be T or t T t

Step 6: Figure out what types of gametes can be formed by the male and write them on the left side of the punnett sqaure inside circles with tails (to represent sperm/ pollen) Problem: genotype of male plant is TT so gametes can only be T. T t T T

Step 7: Fill in each box of the punnett sqaure which represent the zygotes or offspring of the parents. T t T TT Tt Tt TT T

Step 8: Determine the genotypic ratio of the offspring. What are the allele pairs? TT and Tt Determine the ratio. Genotypic ratio = 2TT:2Tt = TT:Tt = 1:1

Step 9: Determine the phenotypic ratio of the offspring. Look at the genotypes of the offspring: 2TT and 2 Tt Phenotypic ratio = all tall

Step 10: Make sure you answered any specific questions asked in the problem and box in your final answer. Problem: What were the phenotypes of the offspring? All Tall

Practice #1: Snow White loves her black hair but she married Prince Charming who has brown hair. Black is dominant to brown. If Snow White is heterozygous and Prince Charming is homozygous, what is the probability that they will have children with black hair?

Problem #2: The Transformer Bumblebee falls in love with a Lexus IS Problem #2: The Transformer Bumblebee falls in love with a Lexus IS. The ability to transform is recessive. If Bumblebee and the homozygous dominant Lexus have gobots, what is the probability that their kids will be able to transform?

Problem #3: Hitchiker’s thumb is dominant Problem #3: Hitchiker’s thumb is dominant. Shrek has hitchhiker’s thumb and Fiona does not. If 2 of their children have hitchiker’s thumb and 2 do not, then is Shrek homozygous or heterozygous for the trait?