Intro to Genetics

Genetics Student Expectation: B 6.F Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance. Readiness Standard

Gregor Mendel Austrian monk born 1822 Lived in a monastery and taught high school Experimented with pea plants by cross breeding plants with different characteristics and studying results. Known as the father of Genetics

Mendel’s Principles Law of Inheritance – Characteristics or traits are inherited by individual units known as “genes”.

Vocabulary Gene – the sequence of DNA that codes for a protein and thus determines a trait. Example – a gene will determine plant height in peas.

Mendel’s Principles Law of Segregation - states that during the formation of reproductive cells (gametes), pairs of hereditary factors (genes) for a specific trait separate so that offspring receive one factor from each parent.

Vocabulary Allele – one of a number of different forms of a gene. Example: this flower carries an allele for white and an allele for purple flowers

Mendel’s Principles Law of Independent Assortment - states that chance deter- mines which factor for a particular trait is inherited.

Mendel’s Principles Law of Dominance – states that when 2 or more forms of a gene exist (alleles), some forms are dominant and others are recessive

Dominant/Recessive Hitch Hikers Thumb Normal Thumb

Dominant/Recessive Free Earlobes Attached Earlobes

Dominant/Recessive

Polydactyly is Dominant!!

Dominant/Recessive Other examples of dominant traits: Dimples Tongue Rolling Freckles Curly hair (may be more than one gene)

Dominant/Recessive Shapes for Pea seeds R = round (Dominant) r = wrinkled (recessive) Genotype Phenotype RR Round homozygous dominant Rr Round heterozygous dominant rr wrinkled homozygous recessive

Monohybrid Crosses

Monohybrid Crosses

Monohybrid Crosses Practice some monohybrid crosses BB x BB BB x Bb What are the genotypic ratios? What are the phenotypic ratios?

Dihybrid Crosses

Non Mendelian Genetics Exceptions to Mendel’s Principles: Not all genes show simple patterns of dominant and recessive alleles The majority of genes have more than two alleles. Many traits are controlled by more than one gene.

Non Mendelian Genetics Incomplete Dominance - When one allele is not dominant over the other but the heterozygous offspring produce an intermediate (3rd) phenotype. Neither fully expressed. Example: Red (RR) x white (rr) = Pink (Rr)

Non Mendelian Genetics Co-dominance - Both alleles contribute to the phenotype. Both are expressed at the same time. Example: Brown BB x White WW = brown and white - BW

Non Mendelian Genetics Multiple Alleles - More than 2 possible alleles exist – not “either/or”. Only 2 expressed at a time. Example: Blood Type iA, iB, iAiB, ii Blood Type Genotype Can Receive Blood From A iAi = AO iAiA = AA A or O B iBi = BO iBiB = BB B or O AB iAiB A, B, AB, O O ii = OO

Multiple Alleles – Blood Types

Non Mendelian Genetics Polygenic Traits - Traits controlled by several genes often on multiple chromosomes. Examples: Skin Color Eye Color

Polygenic Traits Skin Color

Non Mendelian Genetics Sex Linked Traits - Genes that are carried by the sex chromosomes. Read More: http://anthro.palomar.edu/biobasis/bio_4.htm

Journal Work In your journal you will work the following punnett squares. This will be a graded assignment. You must re-write or abbreviate the questions and you must show your work and circle or hi-lite your answers.

Journal Work Problem 1 Identify each of the following as: Homozygous dominant, homozygous recessive or heterozygous. A. bb B. Hybrid C. TT D. Gg E. Purebred

Journal Work - Problem 2 Dominant/Recessive Monohybrid Cross Draw a Punnett square and provide the genotypic and phenotypic information. I = Not allergic to Iodine i – allergic to iodine Ii x II Genotypic ratios Phenotypic ratios Ii x ii Genotypic ratios

Journal Work - Problem 3 Dominant/Recessive Monohybrid Cross Two elephants are crossed and the resulting offspring have 50% large ears and 50% small ears. E = large ears e = small ears What are the genotypes of the parent? SHOW YOUR PUNNETT SQUARE.

Journal Work - Problem 4 Dominant/Recessive Monohybrid Cross A black rabbit is crossed with a white rabbit. 100% of the offspring are heterozygous for color. B = black b = white What are the genotypes of the parent? What are the phenotype percents for the offspring? SHOW YOUR PUNNETT SQUARE.

Journal Work - Problem 5 Dominant/Recessive Monohybrid Cross Cross a homozygous fuzzy bear with a hairless bear. F = fuzzy f – hairless What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work - Problem 6 Dominant/Recessive Monohybrid Cross Cross a heterozygous purple-flowered plant with a plant that has white flowers. P = purple p – white What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 7 Dominant/Recessive Dihybrid Cross: Y – yellow peas P – purple flowers T-tall plant y – green peas p – white flowers t – short plant Cross two heterozygous tall, heterozygous yellow pea plants. What are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 8 Dominant/Recessive Dihybrid Cross: Y – yellow peas P – purple flowers T-tall plant y – green peas p – white flower t – short plant Cross a short, purple flower plant that is homozygous for color with a short, purple flower plant that is heterozygous for color. Whate are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 9 Dominant/Recessive Dihybrid Cross: Y – yellow peas P – purple flowers T-tall plant y – green peas p – white flower t – short plant Cross a heterozygous purple flowered, green pea plant with a plant that has white flowers and is heterozygous for pea color. What are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 10 Incomplete Dominance - Monohybrid Cross: In snapdragons, red and white are both dominant. When they cross, they produce a pink flower. R – red R’ – white Cross a homozygous red and a homozygous white snapdragon. What are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 11 Co - Dominance - Monohybrid Cross: In a certain type of chicken, black and white feather share dominance. When they cross they produce chickens with both black and white feathers. B - black B’ - white Cross a homozygous black and a homozygous white chicken. Whate are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 12 Incomplete and Co - Dominance - Dihybrid Cross: In Fuzzy Trolls, Blue and Purple hair are both dominant. A hybrid genotype produces blue and purple stripes. Yellow skin and Red skin are both dominant. A hybrid genotype produces orange skin. B – Blue hair Y – yellow skin B’ – Purple hair Y’ Red skin A troll with purple hair and red skin reproduces with a troll with blue hair and orange skin. What are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 13 Multiple Alleles Monohybrid Cross: Blood Type: Cross a heterozygous Type A with a heterozygous Type B. Whate are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios? Blood Type Genotype Can Receive Blood From A iAi = AO iAiA = AA A or O B iBi = BO iBiB = BB B or O AB iAiB A, B, AB, O O ii = OO

Journal Work – Problem 14 Sex Linked - Monohybrid Cross: A female who is a carrier for baldness marries a man with normal hair patterns H – Normal hair pattern h – bald What are the parent genotypes? What are the F1 genotypic ratios? What are the F1 phenotypic ratios?