Chapter 5 Heredity

Ch 5.1 - Genetics Heredity – the passing of traits from parents to offspring 1. Genes on chromosomes control the traits that show up in an organism 2. The different forms of a trait a gene may have are alleles

The Human Genome (Project 1990-2003)

3. Each sex cell contains one allele for that trait 4. The study of how traits are inherited is genetics

B. Gregor Mendel – “Father of Genetcs” 1 B. Gregor Mendel – “Father of Genetcs” 1. Mendel was the first to use mathematics of probability to explain heredity and to trace one trait for several generations

2. Allele – the different variations of a trait that genes carry a) Dominant allele – covers up or dominates the other trait b) Recessive allele – the trait that doesn’t show up or seems to disappear c) Hybrid – receives different genetic information for a trait from each parent

3. Probability – helps predict what an offspring will inherit 4. Punnett square – tool to help predict what an offspring will inherit a) Uppercase letters stand for dominant alleles b) Lowercase letters stand for recessive alleles

5. Genotype – the genetic makeup of an organism (represented by the letters) a) Homozygous – an organism with 2 alleles for one trait that are the same (TT or tt) b) Heterozygous – an organism with 2 alleles for one trait that are different (Tt)

6. Phenotype – the way an organism looks or behaves as a result of its genotype

In peas, the color yellow is dominat (Y) to Example: In peas, the color yellow is dominat (Y) to the color green which is recessive (y) Find the probabilities of what genes the offspring of 2 heterozygous parent plants would inherit Genotype: Phenotype:

Ch 5.2 – Genetics Since Mendel A. Incomplete Dominance 1. Neither allele is dominant for a trait 2.The phenotype produced is intermediate between the 2 inherited traits

Ex: four o’clocks red flowers x white flowers = pink

B. Multiple Alleles 1. More than 2 alleles control a trait 2 B. Multiple Alleles 1. More than 2 alleles control a trait 2. Can produce 3 or more phenotypes

Ex: Blood types Alleles – A,B, and O Phenotypes – Type A, Type B, Type AB and Type O

C. Polygenic Inheritance 1 C. Polygenic Inheritance 1. A group of genes act together to produce a trait which creates a great variety of phenotypes 2. Many human traits are controlled in this way

Ex: hair color, eye color, skin color, height

D. Mutations – genes that are copied incorrectly 1 D. Mutations – genes that are copied incorrectly 1. Can be harmful, beneficial or have no effect 2. Chromosome disorders – caused by inheriting too many or too few chromosomes

Ex: Down(‘s) Syndrome – extra copy of chromosome 21 Named for English physician J. Langdon Down who described the condition in 1866 Life Goes On actor Chris Burke

E. Recessive Genetic Disorders 1 E. Recessive Genetic Disorders 1. If both parents have a recessive allele for a disorder they can pass it on to their child 2. Because the parents are heterozygous they show no symptoms themselves

C = no cystic fibrosis C C CC Cc Cc c = has cystic fibrosis c c cc Ex: Cystic Fibrosis C = no cystic fibrosis c = has cystic fibrosis C c C CC Cc Cc c cc 25% chance child could inherit this disease

F. Sex Determination 1. One pair of chromosomes (called X and Y chrom’s) are responsible for the sex of an organism 2. Female egg cells- carry X chromosomes Male sperm cells- half have X & half have Y

3. If two X’s are inherited: XX = female If one X and one Y are inherited: XY = male 50% chance boy XX XY X 50% chance girl X XX XY

G. Sex-linked Disorders – disorders that can be inherited by genes on the X or Y chromosomes Ex: color blindness

Ch 5.3 – Advances in Genetics A. Genetic Engineering – changing the arrangement of DNA that makes up a gene 1. Recombinant DNA a) inserts useful DNA segment into bacteria cell b) Insulin for diabetic patients is produced in this way

2. Gene Therapy a) Inserts normal DNA into a virus which can then infect human cells and reproduce more copies of it b) Also done in plants by inserting genes with desired traits

B. Pedigree – a tool used to show patterns of genetic inheritance and follow traits through a family Affected Male Unaffected Male Affected Female Unaffected Female