Mendelian Patterns of Inheritance

Mendelian Patterns of Inheritance

Mendelian Patterns of Inheritance Chapter 11 Heredity Heredity- passing of traits from parent to offspring Traits- characteristics that are inherited hair color, height, blood type, susceptibility to a certain disease (diabetes, depression, obesity, breast

cancer) Genetics- the study of heredity Gregor Mendel Austrian monk who formulated fundamental laws of heredity in early 1860s Studied science and mathematics at University of Vienna Conducted breeding experiments

with the garden pea (Pisum sativum) Gathered and documented mathematical data from his experiments Mendels Experiments Garden Pea Easy to cultivate Short generation time Cross-pollination by hand

Mendels Experiments Self-Pollination Involves having the pollen (male sperm) be directly deposited on the female section of the flower Cross- Pollination Requires the

removal of the male stamen (makes pollen) on 1st flower and transferring the pollen from a different flower to the first one Blending Inheritance Prior to Mendel, most breeders believed parents of contrasting

appearance always produce offspring of intermediate appearance No knowledge of cells/chromosomes Based on the idea that offspring have traits of both parents Reappearance of traits attributed to genetic instability Mendels Experiments Studied mathematical trends in breeding patterns Looked at simple discrete traits

Mendels experiments helped him formulate the particulate theory of inheritance Inheritance involves reshuffling of genes from generation to generation One-Trait Inheritance Mendel performed cross-breeding experiments between true-breeding

plants True-breeding parents with a certain trait consistently pass that trait to every offspring (homozygous) Chose varieties that differed in only one trait (monohybrid cross) Results of Mendels cross of true breeding short with a true breeding tall pea plant Mendel saw the same results in different traits One-Trait Inheritance

Performed reciprocal crosses individuals pollinate one another Parental generation = P First generation offspring = F1 Second generation offspring = F2 Formulated law of segregation Law of Segregation Each individual has two factors for

each trait The factors segregate during gamete formation Each gamete contains only one factor from each pair of factors Fertilization gives each new individual two factors for each trait Law of Segregation Mendels Monohybrid Cross Mendels Monohybrid Cross

Alleles on homologous chromosomes These alternative forms of a gene that code for a trait are called alleles. There are 2 alleles for each trait; 1 allele for a trait is from mom and 1 allele is from dad. Homologous Chromosomes Principle of Dominance

Dominant allele (capital letter) masks the expression of the recessive allele (lowercase) Alleles occur on a homologous pair of chromosomes at a particular gene locus (location of gene on the chromosome) Homozygous = identical alleles (TT, tt) Heterozygous = different alleles (Tt) Genotype Vs. Phenotype

Genotype Refers to the alleles an individual receives at fertilization If alleles are identical, genotype is homozygous If alleles are different, genotype is heterozygous Phenotype Refers to the physical appearance of the individual

Practice In humans, the ability to taste the bitterness of PTC paper is dominant (T) to not being able to taste the bitterness of PTC paper (t). GENOTYPE GENOTYPE IN SCIENCE TERMS PHENOTYPE

Punnett Square All possible genotypes of sperm are lined up on one axis, and all possible genotypes of eggs are lined up on the other axis Every possible combination of alleles (zygote genotypes) placed within the squares

Formative Assessment Get your clickers! Alternate forms of a gene are called Chromosomes B. Alleles C. Gametes D. Heterozygotes A.

91% 5% s ot e et es Ga m Al

le le s 0% He te ro zy g Ch r

om os om es 5% Only one ________ allele is needed in order for that trait to be expressed in the phenotype. 95%

Recessive B. Dominant C. Heterozygous D. Homozygous A. oz yg ou s 0%

Ho m ou s He te ro zy g t 0%

Do m in an Re c es s iv e 5%

Which of the following genotypes is homozygous recessive? RR 2. Rr 3. rr 1. 96% 4% 1

0% 2 3 The genotype TT is Homozygous recessive 2. Homozygous dominant 3. Heterozygous 1.

100% 0% 1 0% 2 3 Which of the following genotypes is heterozygous? BB 2. Bb

3. bb 1. 100% 0% 1 0% 2 3 Brown eyes (B) are dominant over blue

eyes (b). Mr. Mallin has blue eyes. What is his genotype? 100% BB 2. Bb 3. bb 1. 0% 1 0% 2

3 Brown eyes (B) are dominant over blue eyes (b). Channing Tatum has brown eyes. What is his genotype? 91% BB 2. Bb 3. bb 4. BB or Bb 1.

9% 0% 1 2 0% 3 4 Brown eyes (B) are dominant over blue eyes (b). Assume Mr. Ward is homozygous dominant for brown eyes.

What is his sons phenotype? 1. Brown eyes 83% 2. Blue eyes 3. Bb 4. BB 17% 0% 1 2 0% 3

4 Free earlobes (E) are dominant over attached earlobes (e). Ms. Palmeris phenotype is free earlobes and her genotype is heterozygous (Ee). Which of these statements is true? 1. 2. 3.

Both of her parents have attached ear lobes At least one of her parents has free earlobes Both of her parents are homozygous recessive 91% 9% 0%

1 2 3 If a persons genotype is EE, what percentage of their gametes (produced by meiosis) would contain the recessive allele? A. 100% B. 50% 92% C. 25%

D. 0% 8% 0% 0% 25 % 50 % 10

0% 0% The previous question is a direct application of which of Mendels laws? A. Law of in d

ep en de nt as Ho s.. . m oz yg ou sD

o. .. La w of Se gr Pr eg in ati cip on le

of Do m in an ce 9% La w of

of D. 32% 23% w C. independent

assortment Law of Homozygous Dominance Law of Segregation Principle of Dominance La B. 36%

Testcross A monohybrid testcross is used to determine if an individual with the dominant phenotype is homozygous dominant or heterozygous for a particular trait Individuals with recessive phenotype always have the homozygous recessive genotype However, Individuals with dominant phenotype have indeterminate genotype May be homozygous dominant, or Heterozygous

Testcross Dihybrid Cross Dihybrid Cross Two-Trait Testcross A two-trait testcross is used to determine if an individual is homozygous dominant or heterozygous for either of the two traits Two-Trait Testcross

Law of Independent Pairs of allelesAssortment for different traits separate independently of one another during gamete formation (meiosis). In other words the inheritance of one trait has no influence on the inheritance of another trait.

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