Genetics are awesomeeee.

Structure of DNA Each DNA molecule is made up of two very long polymers Double helix: is the shape Nucleotides: are the building blocks – deoxyribose ( a 5 carbon sugar) – phosphate group – nitrogenous base

DNA double helix

Nitrogenous bases There are four different nitrogenous bases thymine (T), cytosine (C), adenine (A), and guanine (G) These four bases are the foundation of the genetic code. These chemicals act as the cell's memory, instructing it on how to synthesize enzymes and other proteins. These four nucleotides encode everything an organism needs to live and protects this information with incredible accuracy.

In a human being DNA is broken down onto 46 separate chromosomes Each chromosome has about 160 million nucleotide pairs This massive amount of information is stored and replicated almost flawlessly!

DNA Replication INTERPHASE: Before a cell divides, its DNA is replicated Semi Conservative replication: Two strands of a DNA molecule are separated, each ONE can be used as a template to produce a complementary strand. Each template and its new complement together then form a new DNA double helix, identical to the original.

Before replication can occur, the length of the DNA double helix about to be copied must be unwound. INTERPHASE The two strands must be separated, much like the two sides of a zippper: helicase The enzyme DNA polymerase then moves along the exposed DNA strand, joining newly arrived nucleotides into a new DNA strand that is complementary to the template.

Meiosis I STEP ONE MEIOSIS I: This is basically like the PMATI of a regular mitosis. Pairs of chromosomes are lined up at the center of the cell and then (separated) and pulled to each side. Meiosis is a bit different because there is something called crossing-over. This crossing over is an exchange of genes from 1 homologous chromosome to the other (genes from the chromosome you got from mom go onto the chromosome you got from dad. The genes are mixed up, not resulting in a perfect duplicate like mitosis. This is why your children will not look exactly like their Nana or Grandpa…. They will look like a combo.

The cell divides, leaving two new cells with a pair of chromosomes each. Normally the cell would begin to go about its business of living and slowly duplicate the chromosomes for another mitotic division. Since this is meiosis, there is a very short interphase and division begins again. The DNA is not doubled

Meiosis II STEP TWO MEIOSIS II: In Metaphase II all of the chromosomes line up along the center of the cell Anaphase II shows the chromosomes split and move to opposite sides of the cell. They don't divide up the DNA between the new cells Each daughter cell will get one-half of the DNA The cell membrane begins to pinch. When it's all over, you are left with four haploid cells that are called gametes. The eventual purpose of the gametes will be to find other gametes with which they can combine. When they do, they will form a new organism.

Mendel’s First Law Mendel's First Law is the law of "Segregation of Characteristics.” Humans are Diploid. This means you get two alleles for each trait. You get one allele from mom and one allele from dad. This law basically says that you can only get ONE allele from mom. Only ONE from dad. In eye color B Brown is dominant. Blue (b) is recessive. If mom has Brown eyes she could be BB or Bb. She can only pass ONE allele on in her egg.

Independent assortment Mendel's Second Law is the law of "Independent Assortment". This says that for two characteristics the genes are inherited independently. Example: Your shoe size and hair color are not inherited together. Meaning: people with black hair do NOT necessarily have Big Feet.

- If mom had the genotype AaBb she would make four kinds of gametes(eggs): they would contain the combinations of either AB, Ab, aB or ab. A is dominant (big feet): a is recessive (little ft) B is dominant (black hair):b is recessive(blond) So, mom would pass on either: Big feet & black hair (AB), big feet and blonde hair (Ab) Little feet and black hair (aB) Little feet and blonde hair (ab)

Punnett Square A punnett square is used to predict an expected outcome of a particular cross or breeding experiment.

Non Mendelian Genetics Some traits are not passed on the way the traits Mendel studied were. – Incomplete dominance – Co dominance – Multiple alleles

Incomplete Dominance Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a combined phenotype.

Codominance A condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other.

Multiple Alleles Any set of three or more alleles or alternative states of a gene. Only two of which can be present in an organism at a time. Responsible for differences in expressions of a given trait. Example: brown eyes v. green eyes.