Genetics & DNA Unit D

Genetics and DNA  During the 1860’s an Austrian monk and botanist named Gregor Mendel discovered that “factors” determine inheritance in pea plants.

 Another scientist named Walter Sutton made the connection between these factors and chromosomes..

DNA  The genetic material itself is called DNA or Deoxyribonucleic Acid.  It is located in the nucleus of the cell.

 Although scientists knew it existed, it was not until Francis Crick and James Watson proposed a Double-helix structure (what we describe as a twisted ladder) for the molecule that we know carries the genetic code of life.

 A gene is a unit of information that can be passed to offspring. (The ‘factors” that Mendel discovered!)  It is a segment of DNA.  Genes help determine whether your hair is straight or your eyes are blue.  Genes make hens white or speckled and gives frogs smooth skin.  It also makes roses smell sweet.

 DNA holds the secret code to make and maintain proteins that perform most of life’s functions.  Scientists today can transfer genes through genetic engineering. It can be transferred via direct injection or by inserting the DNA.

 All of you….  Your bones and muscles are all made of cells!

 In the nucleus of almost every cell are the complete instructions for making you!  Those instructions are found in 23 pairs of chromosomes or 46 total.  This complete set of instructions is called your genome.

 Each set of chromosomes, half from our mother and half from your father, contain one tightly packed strand of DNA.

 A nucleotide contains a base molecule Adenine, thymine, cytosine, and guanine, a sugar molecule, and a phosphate molecule.

 This ladder is made up of a series of letters (A,T, C, & G) that represent the chemicals Adenine, Thymine, Cytosine, an Guanine..  One pair of letters is called the base pair.  Adenine always pairs with Thymine and Cytosine always pairs with Guanine.  These nucleotides then, forms a gene that codes for a protein.

 Each strand of DNA may contain several thousand genes.  Some genes are thousands of bases long; others are millions of bases long.  The goal of the human genome project is to determine the complete sequence of the human genome.  This means to put billions of A’s, T’s, C’s, and G’s in the correct order!

Genes, Plants, People, & Animals  How do genes differ between…. People? Plants? Animals? They DON”T!

Genes in animals….  Think for a minute about what genes in animals tell us…

Genes in Plants…  What are some things that genes in plants tell us?

Genes in People…..  What do genes tell us about us?

Types of Genes  Genes can be  DOMINANT  RECESSIVE

DOMINANT GENES  Dominant genes are expressed in offspring not matter what gene the other parent contributes.  For example: Dominant for blue eyes…offspring will have blue eyes.

RECESSIVE GENES  Recessive genes are expressed in offspring only if both parents contribute a recessive.

 Characteristics that are inherited are called traits.  A dominant trait is an observable trait that masks the recessive form of a trait.  A recessive trait can be masked by the dominant form of the trait.  Two organisms can look alike but have different underlying gene combinations. They way an organism looks and behaves makes up it phenotype.

 The phenotype of a tall plant is tall, regardless of the genes it contains.  The gene combination that an organism contains is known as its genotype.  You cannot always know an organism’s genotype by simply looking at its phenotype!  New varieties of cultivated plants and domesticated animals have resulted from selective breeding for particular traits.