Allele Genotype vs. Phenotype Flashcard Warm-up For any trait, such as hair color, there are different forms of the protein that create the different hair colors. Each different form is called an allele. We use capital letters to represent dominant alleles and lower case letters to represent the recessive alleles. Genotype vs. Phenotype Genotype is the genetic makeup (AA, Aa, or aa) Phenotype is the physical trait, a result of the genotype

Where did my traits come from?? Unit 10- Genetics Where did my traits come from??

Inheritance of chromosomes Egg + sperm  zygote egg meiosis zygote mitosis & development fertilization sperm

Traits: physical or physiological characteristics; like eye color, or blood type Phenotype: individual’s observable trait; brown hair

Genes: Portion of DNA that make proteins that control our traits and are found on chromosomes. Chromosomes exist in pairs, one from sperm one from egg. Alleles: different versions of genes; blue eye gene, brown eye gene; we use letters to represent alleles Alleles are inherited separately from each parent.

How does this work? Paired chromosomes have same kind of genes but may be different alleles eye color (blue?) eye color (brown?) hair color

Genes affect what you look like X bb BB Bb Bb Bb Bb Where did the blue eyes go??

Genes affect what you look like… X bb Bb Bb Bb bb bb Why did the blue eyes stay??

What is a genotype and how do we write it? Genotype: the genetic makeup (the alleles you received from mom and dad) Examples of genotypes: Homozygous: Identical copies; AA – homozygous dominant aa - homozygous recessive Dominant genes mask or hide recessive Heterozygous: one dominant and one recessive; Aa 2 people can have the same appearance but have different genetics: BB vs Bb

Mendelian Genetics: Gregor Mendel : Father of Genetics Studied pea plants--- 1866 Why pea plants?

Mendel’s Principles Three Principles: 1. Principle of Dominance: dominant alleles can mask/ hide recessive alleles Homozygous dominant: AA; Dominant trait is expressed Heterozygous: Aa; dominant masks/hides recessive and is expressed Homozygous recessive: aa; recessive trait is expressed 2. Principle of Segregation: to separate, each parent can only pass on one allele per trait 3. Principle of Independent Assortment: genes on separate chromosomes are passed on independently from one another.

Principle of Segragation

Principle of Independent Assortment

Punnett squares B b BB Bb B b Bb bb Bb x Bb male / sperm female / eggs

Flashcard Warm-up Mendel’s Principles of Inheritance: Use your notes from yesterday to write down and briefly EXPLAIN the three principles

Punnett Squares Monohybrid cross: a Punnett square involving only one trait; 4 boxes Dihybrid cross: a punnett square involving two traits; 16 boxes

Flashcard Warm-Up Trait: Free earlobes- dominant = F Attached earlobes- recessive = f A woman has free earlobes, what are two possible genotypes she might have? The genotype for a man is Ff, what is his phenotype? What is a gene?

Incompletely Dominant Flashcard Warm-up Codominant If two alleles are codominant, they are equally strong. Both alleles would be seen in the phenotype. An example is crossing a black chicken with a white chicken and the offspring having both black and white feathers. Incompletely Dominant Neither allele is dominant, so when both alleles are present they mix or blend. These alleles are written with ONE letter that has a prime ‘

Non Mendelian Genetics: Codominance: Both alleles are equally dominant and will be expressed Phenotype: 3 possibilities Genotype: 2 Capital letters; BB, WW, or BW Red hair is dominant RR Roan is a mixture of red and white hair- RW White hair is dominant WW

Codominant Example: Cross a black cow with a white cow. Both hair colors are dominant.

Incomplete Dominance Phenotype: neither allele is completely dominant to mask the other Genotype: heterozygous RR’ results in a blended phenotype , capital letters for both traits and use a prime ‘ symbol for one RR RR’ R’R’

Incomplete Dominance Example Cross a white flowered plant with a pink flower. Both white and red are incompletely dominant.

Ticket Out the Door A) If feather color in a species of birds in codominant, cross a white bird with a black and white spotted bird. List all possible phenotypes. B) If fur color is incompletely dominant, cross a gray fur dog with a black dog. List all possible phenotypes.

Polygenic trait Flashcard Warm-up Sex chromosomes trait determined by many genes, results in a wide range of phenotypes Examples include height, skin color, hair color Sex chromosomes For humans, the last set of chromosomes are the sex chromosomes that determine the gender. Females have two X chromosomes and males have one X and one Y. Examples of sex-linked traits are colorblindness and hemophilia, these traits are carried on the X chromosome.

Multiple Alleles: more than two alleles exist for a trait Blood Type: Phenotype: Type A, AB, B, O Genotype: IAIA or IAi IAIB IBIB or IBi ii

Blood donation clotting clotting clotting clotting clotting clotting

Blood Type Example Cross a heterozygous type A mom with a Type O dad. What is the chance they have a child with Type O blood?

Sex Linked: trait found on the X sex chromosome Phenotype: Female – less likely but can show a sex-linked trait Genotype: XA XA, XA Xa , XaXa Phenotype: Male – sex-linked traits show up more because they have XY sex chromosomes, Genotype: XA Y, XaY No male carriers for a sex-linked trait

Sex-linked Example Cross a colorblind dad with a mom who is a carrier. What is the chance of this couple having a son who is not colorblind?

Polygenetic Traits that depend on many genes and create a range of phenotypes. Ex. Height, skin color NO PUNNETT SQUARE!

Human skin color AaBbCc x AaBbCc can produce a wide range of shades most children = intermediate skin color some can be very light & very dark

Nature vs. Nurture: Nature is heredity – your DNA Nurture is your environment The debate: Which has a greater influence? Example: We use identical twins to study the effects of the environment on genes.

Ticket Out the Door 1. A sex-linked trait is found on the __ chromosome. 2. Cross a mom with type AB blood with a dad who is type O. List all possible phenotypes.