 Genetic material found in the nucleus of eukaryotic cells; in the cytoplasm of prokaryotes (no nucleus)  A library of genetic information (genes) located in the nucleus of eukaryotic cells  Made up of one long DNA molecule wrapped around chunks of protein

 Organisms have 2 different types of cells  Body (somatic) cells: skin, liver, brain These cells each have a Complete Set of chromosomes (46, or 23 pairs)  Sex cells (gametes): sperm and egg  Because sperm and egg need to meet and combine their chromosomes to form a new individual, they have ½ the number of chromosomes as body cells (23)

Normal Human Karyotype:  46 chromosomes  23 pairs  44 autosomes  22 pairs  2 sex chromosomes  1 pair  XX = female  XY = male

“TRISOMY 21”

 A Double helix ladder of connected nucleotides forming a sugar-phosphate “backbone” and nitrogen base “steps”  Each nucleotide of DNA consists of:  A sugar “deoxyribose”  A phosphate  A nitrogenous base:  AdenineThymine  CytosineGuanine

 Double-helix/spiral ladder  Sugar-phosphate “backbone”  Bases are rungs of ladder  Long sequences of bases make up genes

 Bacteria make a copy of their DNA strand  Then splits in two, creating two bacteria.

 Mitosis: Division of a cell into BODY cells. (Body cells = Somatic = liver, brain, skin, etc) First, DNA is copied, then the nucleus of eukaryotic cells divide, each new nucleus has a complete set of chromosomes. (Really, mitosis = nuclear division)  Cytokinesis: Cell Division. The eukaryotic cell divides into two cells, each with its own nucleus ***These two parts of the cell cycle are often combined and called ‘mitosis’

 Mitosis + Cytokinesis = 2 new cells with the same genetic information as the original cell

KEY TERMS:  Haploid Cells: The number of chromosomes in a sex cell n = 23 in humans (Sex cells = Gametes = sperm, egg)  Diploid Cells: The number of chromosomes in a somatic cell 2n = 46 in humans

 The division of a cell into sex cells. The number of chromosomes in the nucleus is halved. (46 to 23)

2n=46 human sex cell diploid (2n) n=23 sperm haploid (n) Crossing-over occurs at this stage 4 genetically different gametes are produced

homologous pairs This causes genetic variation Tetrad Tetrad, homol. pairs together

 Nondisjunction is when the chromosomes don’t split evenly in meiosis, resulting in too many or too few chromosomes in the sperm or egg.  Examples of diseases/conditions caused by non-disjuction:  Down’s Syndrome = 47  Turner’s Syndrome = 45  Klinefelter’s Syndrome = 47 nction%20Meiosis%20I.htm

Protein Synthesis: How DNA turns the base sequence into proteins DNA  RNA  Protein

 1.The Double Helix ‘unzips’  2. A matching(complementary) strand is made of each side, making two molecules of DNA

Copying DNA before the nucleus divides and before cell division

 As the ‘original copy’ of ALL the cells genetic information, DNA cannot leave the nucleus  DNA has ALL the genetic material, and cells only need to use specific information  So a ‘working copy’ is made that can leave the nucleus and make the needed proteins for the cells to function.

DNA holds the instructions for the manufacturing of protein. This is done through protein synthesis -the making of proteins from the instructions coded by the sequence of bases in the DNA 1. Transcription: In the nucleus, the genetic info is ‘copied’ from DNA to RNA in code. 2. Translation: The RNA leaves the nucleus and the code is translated on ribosomes to make specific proteins for gene expression

1865 Paper Published by Gregor Mendel based on his research with garden peas 1. Principle of Dominance and Recessiveness: There are alternate forms of genes called alleles. One factor in a pair of genes may mask the effect of another. Dominant allele: When only ONE of the alleles affects the trait. (Use a CAPITAL letter) Recessive allele: the allele that is NOT expressed if there is a dominant allele present. (Use a small letter).

1865 Paper Published by Gregor Menel based on his research with garden peas Homozygous – an individual who has the same alleles for a trait. Ex. 2 genes for cystic fibrosis (BB = homozygous dominant or bb = homozygous recessive) Heterozygous – an individual who has different alleles for a trait. Ex. One gene for cystic fibrosis, one for normal (Bb)

 Genotype – the genetic makeup of an organism“Genes” The many different alleles that an organism can possess: BB or Bb or bb  Phenotype – the external appearance of an organism. An organisms physical appearance, determined by it’s alleles “Photo” Genetics Terminology

Generations Parent generation = P Offspring of P generation = F1 Offspring of F1 generation = F2 Cross a homozygous dominant purple flower with a homozygous recessive white flower. Give the F1 genotype and phenotype percents. Purple = PP, white = pp

Sex-linked inheritance Males and females inherit some diseases with different frequency.  This is because the Y-chromosomes have fewer genes, and with only one X for males, there are no heterozygotes.  Examples: hemophilia and color-blindness Punnett squares that separate the chances of males and females getting diseases How males and females inherit: X N Y or X n Y X N X N or X N X n or X n X n

Pedigree Charts Pedigree charts follow a genetic mutation/disease through several generations of a family. You can determine what chance offspring has of having a disease based on family history and Punnett Square. The main diseases that are tracked this way are:  Tay-sachs  Huntingtons  Colorblindness  Hemophilia  Cystic fibrosis

Basic Symbols

PHENOTYPES Clear = unaffected Shaded = affected GENOTYPES Not usually indicated, but often can be determined by the phenotypes How to read a pedigree

Pedigree: recessive genetic disorder 1. An individual who is affected may have parents who are unaffected. 2. ALL children of 2 affected parents are affected

Pedigree: Dominant Inheritance 1.Every affected individual has at least one affected parent 2. Affected who mate with an unaffected have a 50% chance to pass the trait. 3. Two affected MAY have unaffected children

Sex-Linked Recessive males get their X from their mother fathers pass their X to daughters only females express it only if they get a copy from both parents. expressed in males if present recessive in females Outsider rule for recessives (only affects females in sex- linked situations): normal outsiders are assumed to be homozygous.

#1 – sickle-cell Autosomal Recessive (nn)

#4 - colorblindness X-linked Recessive (X n )

The factors for different traits are sorted into the gametes independent of each other. S = Smooth pea Y = Yellow Color 1.Determine all possible combinations of alleles in the gametes for each parent. DiHybrid Cross: Independent Assortment

DiHybrid Crosses 2. List the gametes for Parent 1 along one edge of the punnett square, and the gametes for Parent 2 along the other edge

DiHybrid Cross 3. Fill out the squares with the alleles from Parent 2 The result is the prediction of all possible combinations of genotypes for the offspring of the dihybrid cross, SsYy x SsYy.

A phenotypic ratio of 9:3:3:1 is predicted for the offspring of a SsYy x SsYy dihybrid cross. 9 spherical yellow : 3 spherical green : 3 wrinkled yellow : 1 wrinkled, green