Genetics and Inheritance Chapter 11 (page 262)

What makes you you? DNA DNA is a system of codes that controls every aspect of your life (how you look, how you act, etc.) DNA is like the instruction manual to keep you working.

DNA  gene Gene = one section of DNA that controls one specific trait. (Examples: Hairline gene, earlobe gene, etc.)

DNA  gene  chromosome Chromosome = 1 strand of DNA that is condensed/squeezed into a rod shape

DNA  gene  chromosome

Every living things inherits traits, or characteristics, from its parents. How are these traits passed from one generation to the next? The answer lies in the study of genetics.

Essential Question:

Genetics Definition = The branch of biology that studies heredity. (Heredity = biological inheritance)

~Austrian monk ~In charge of the monastery garden ~Experimented with pea plants Gregor Mendel “Father of Genetics” Gregor Mendel

Mendel observed seven traits that are easily recognized and apparently only occur in one of two forms:

Mendel knew an important fact of his pea plants: The flowers have both male and female reproductive parts.

Pollination SELF-POLLINATIONPea plants contain both male and female parts, so they can produce seeds by… SELF-POLLINATION Fertilization of a plant’s egg cells by the pollen of another plant =CROSS-POLLINATION

1. Gene- a section of DNA that controls a specific trait 2. Allele – alternative form of a GENE 3. Trait—a characteristic of a species determined by specific genes Terminology:

4. Dominant gene—the presence of this type of gene will mask/hide the other gene 5. Recessive gene—this gene is hidden by the other gene unless there are two copies of the recessive form.

Video from: genetics-hortensia-jimenez-diaz

Mendel’s Results and Conclusions: 1. Biological characteristics are determined by genes. (Genes are passed from parents to their offspring.)

2.Some forms (alleles) of a gene may be dominant and others may be recessive. Mendel’s Results and Conclusions:

3.In most sexually reproducing organisms, each adult has two copies of each gene—one from each parent. These genes are segregated/separated from each other when gametes are formed. (Law of Segregation) Mendel’s Results and Conclusions:

4.The alleles for different genes usually segregate independently of one another. (Law of Independent Assortment) Mendel’s Results and Conclusions:

6. HYBRID – offspring of parents with different traits Terminology continued:

Terminology Con’t… 9. Genotype – the genetic makeup of an organism an organism (ie. AA, Aa, aa) 10. Phenotype – the physical appearance of an organism (ie. Hair color, eye color, etc.) (ie. Hair color, eye color, etc.)

Monohybrid Crosses A cross between individuals that involves ONE pair of contrasting traits

Punnett Squares!!! = tool used to determine the probability of offspring of a cross between two parents

= DOMINANT = recessive Can be used to predict & compare the genetic variations that will result from a cross = DOMINANT (capital letter) = recessive (lower case) MonoHybrid Cross

= DOMINANT = recessive Can be used to predict & compare the genetic variations that will result from a cross = DOMINANT (capital letter) = recessive (lower case) HOMOzygous = organisms that have 2 IDENTICAL alleles for the same trait HETEROzygous = organisms that have 2 DIFFERENT alleles for the same trait

Segregatio n The likely hood that a particular event will occur

Test Cross To determine the GENOTYPE of an organism expressing the dominant phenotype. Testcross= a mating between an individual with an unknown genotype and an individual that is HOMOZYGOS RECESSIVE. – Look at offspring to determine parent genotype Example: Labrador Retriever –B- back fur –b= chocolate brown fur Black lab X chocolate lab B___ X bb

Test Cross Example In humans, long eyelashes is (E) is dominant short eyelashes (e). A man with long eyelashes marries a woman with short eyelashes and they have three children, two of whom have long eyelashes and one of whom has short eyelashes. Draw the Punnett squares that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children?

Dihybrid Crosses A cross between individuals that involves TWO pairs of contrasting traits

One allele can completely hide the other (Mendel traits) 1. Complete Dominance

Flower Color in Snapdragon 2. Incomplete Dominance (blending)

Incomplete dominance in humans

3. Codominance (both traits are seen—spotting) RR = red hair rr = white hair Rr = roan (red AND white hairs present)

Codominance and multiple alleles Most common blood type

One trait is controlled by multiple genes 4. Polygenetic Examples: Height, skin color

5. Pleiotropy --In humans these usually present themselves with disease. Example: sickle cell disease One gene affects multiple traits