Gregor Mendel Known as the Father of Modern Genetics Austrian monk Studied garden pea plants

Heredity: the passing of traits from parents to offspring (kids) –Can be complicated Ex: Why does your brother have different features than you? Ex: Why do some family members look alike while others look completely different?

Trait: a distinguishing quality that can be passed from one generation to another. -Ex. Eye color, Hair color, height, weight, skin color, facial features, body structure Genes: pieces of DNA that carry hereditary information on them.

Dominant trait: a trait observed when at least one dominant gene for a characteristic is inherited. Example: Bb or BB (capital letters represent dominant) Recessive trait: a trait that is apparent only when two recessive genes for the same characteristic are inherited. Example: bb (lower case letters represent recessive)

Genotype: inherited combination of actual genes Ex. Bb, LL, tt Phenotype: the organism’s physical appearance Ex. Blue eyes, brown hair

Purebred: both genes are alike –Also called homozygous –bb, TT, DD Hybrid: genes are different –Also called heterozygous –Bb, Tt, Dd

Incomplete Dominance When one trait is not completely dominant over another. Each gene has its own degree of influence. The hybrid genotype would yield a new phenotype. For example, in snapdragons, red flowers are incompletely dominant over white. The hybrid is pink. So the genotype RR would yield red flowers, WW would yield white flowers, and RW or WR would yield pink flowers.

Punnett Square Square used to visually show all possible gene combinations

Tall Plant (Tt) X Short Plant (tt) Tt t t Tt tt 50 % Tall 50 % Short

Tall Plant (TT) X Short Plant (tt) TT t t TtTt TtTt TtTt TtTt 100 % Tall 0 % Short`

Probability: chance that an event will occur –After solving Punnett squares, questions will often ask you to predict the probability of one of the traits. –Ex: What’s the chance of a child having blue eyes? –Expressed as: Percentages 0%, 25%, 50%, 75%, or 100% Ratios (0/4) (1/4) (2/4) (3/4) (4/4)

How are traits passed? Sexual Reproduction Asexual Reproduction

Sexual Reproduction Need 2 parent cells to reproduce (1 male and 1 female) Ex. Humans and most animals Offspring will have a combination of traits from both parents (genetic diversity)

Sexual Reproduction Advantages Adapts to changing environments more quickly If parents have a disease there is still a chance the offspring will be healthy Disadvantages Parents can be carriers and be healthy but there are no guarantees the offspring will be healthy Takes longer (because a mate is required) Less reliable

Asexual Reproduction 1 parent needed to reproduce Ex. Earthworms, fungi, many plants, bacteria, body cells Offspring is exact clone of parent (genetic continuity)

Asexual Reproduction Advantages Faster and easier to reproduce If parent is healthy then offspring will be healthy If parent has a disease it will likely die before reproducing Disadvantages If parent has a disease or mutation then the offspring will have it too No genetic variation, so unfavorable conditions in the environment could wipe out an entire population Insufficient resources due to quick population growth and overcrowding

Mutations A substitution or change in DNA Could be random error or caused by physical or chemical agents Occur when there is a change in the order of bases in an organism’s DNA A “mutagen” is anything (physical or chemical) that causes a mutation in DNA (Ex. High energy radiation from x-rays and ultraviolet radiation, asbestos and chemicals in cigarette smoke)

Mutations cont. We inherit hundreds of mutations from our parents. The human body cell has to have an entire set of 46 chromosomes (or 23 pairs) in order to grow and function. When mistakes are made during DNA replication and cell division, most of the time repair enzymes and other proofing mechanisms decrease the error rate in the end.

Genetic Disorders Result from an inherited disruption in an organism’s DNA. Inherited disruptions can take several forms including a change in the number of chromosomes and the deletion or duplication of entire chromosomes or parts of chromosomes. Mainly, alteration of a single specific gene is responsible for a disorder. Some genetic disorders result from several genetic alterations occurring simultaneously.

Genetic Disorders Diseases resulting from gene alterations cause a wide variety of physical malfunctions and developmental problems. Ex. hemophilia, cystic fibrosis, sickle cell anemia, Down’s syndrome, Tay- Sachs disease, Huntington’s disease

Down Syndrome

Sex linked traits If a gene is found only on the X chromosome and not on the Y chromosome, it is said to be a sex linked trait. Because the gene controlling the trait is located on the sex chromosome, sex linkage is linked to the gender of the individual. The result is that females will have two copies of the gene while males would only have one.

Sex linked traits cont. If the gene is recessive, then males only need one such recessive gene to have the sex linked trait rather than the normal two recessive genes for non sex linked traits. This is why males exhibit some traits more frequently than females.

Examples of Sex linked traits Red-green colorblindness Male Pattern baldness Hemophilia Duchenne Muscular Dystrophy

Human Genome Project Completed in 2003, the Human Genome Project (HGP) was a 13-year project coordinated by the U.S. Department of Energy and the National Institutes of Health Some of the project goals were: identify all the approximately 20,000-25,000 genes in human DNA determine the sequences of the 3 billion chemical base pairs that make up human DNA store this information in databases

Ethical Issues Discussion: What is the line between medical treatment and enhancement?