Heredity

Heredity

• the passing of physical characteristics from parents to offspring

Trait

• a characteristic that an organism can pass on to its offspring through its genes.

Offspring

• The product of reproduction; a new organism produced by one or more parents (ex. Human baby)

Chromosome

• DNA tightly coiled and rod shaped ~ location of genes

Gene

A segment of DNA located on a chromosome that controls some aspect of how cell or living things grow and develop

Allele

• alternate form of a gene for a trait; two or more forms of the same gene, they may be dominant or recessive.

• For example, brown and blue eyes are two different alleles for eye color. We have 2 alleles for any, one trait, one from our mother and one from our father. They may be the same form of the gene (homozygous) or two different forms (heterozygous).

Dominant

• stronger trait; overrides or covers up the recessive trait. In a gene pair (Rr) the dominant allele overrides the effects of the recessive allele

Dominantly Inherited Disorders

• Achondroplasia, a form of dwarfism with an incidence of one case among every 10,000 people. Heterozygous individuals have the dwarf phenotype

• Huntington’s disease, a degenerative disease of the nervous system, is caused by a lethal dominant allele that has no obvious phenotypic effect until the individual is about 35 to 45 years old.

Recessive

• weaker trait; covered up or hidden by the dominant trait, In a gene pair (rr) the effects of a recessive allele will be hidden if a dominant allele is present

• Ex: sickle cell anemia

Disorders Inherited as Recessive Traits

• Over a thousand human genetic disorders are known to have Mendelian inheritance patterns. Each of these disorders is inherited as a dominant or recessive trait controlled by a single gene. Most human genetic disorders are recessive.

Disorders Inherited as Recessive Traits

• Sickle-cell disease, which affects one out of 400 African Americans. Sickle-cell disease is caused by the substitution of a single amino acid in the hemoglobin protein of red blood cells

Homozygous

• an organism that has 2 identical alleles for a trait. An individual may be homozygous dominant (AA) or homozygous recessive (aa). Individuals who are homozygous for a trait are also referred to as homozygotes.

Heterozygous

• a genotype consisting of two different alleles of a gene for a particular trait. An individual that is heterozygous (Aa) is also referred to as hybrids.

Punnett Square

• a tool to predict the chances of a trait by using the allele combinations.

How Punnett squares work

Now you try….

Gregor Mendel~ Father of Genetics

• Austrian Monk.• Experimented with “pea plants”.• Used pea plants because:– They were available– They reproduced quickly– They showed obvious differences in the traits

Understood that there was something that carried traits from one generation to the next- “FACTOR”.

Gregor Mendel• Mendel's Plant Breeding Experiments

• Gregor Mendel was one of the first to apply an experimental approach to the question of inheritance.

• For seven years, Mendel bred pea plants and recorded inheritance patterns in the offspring.

• Particulate Hypothesis of Inheritance • Parents pass on to their offspring

separate and distinct factors (today called genes) that are responsible for inherited traits.

Mendel was fortunate he chose the Garden Pea

• Mendel probably chose to work with peas because they are available in many varieties.

• The use of peas also gave Mendel strict control over which plants mated.

• Fortunately, the pea traits are distinct and were clearly contrasting.

To test the particulate hypothesis, Mendel crossed true-breeding plants that had two distinct and contrasting traits—for example, purple or white flowers.

Mendel cross-fertilized his plants by hand. Why is it important to control which plants would serve as the parents?

Pea Generations

For each monohybrid cross, Mendel cross-fertilized true-breeding plants that were different in just one character—in this case, flower color. He then allowed the hybrids (the F1 generation) to self-fertilize.

Typical breeding experiment

• P generation (parental generation)

• F1 generation (first filial generation, the word filial from the Latin word for "son") are the hybrid offspring.

• Allowing these F1 hybrids to self-pollinate produces:

• F2 generation (second filial generation).

• It is the analysis of this that lead to an understanding of genetic crosses.

Mendel studies seven characteristics in the garden pea

Statistics indicated a pattern.

What is Genetics

• The study of how traits are inherited and passed down from parents to offspring

How is it possible to maintain such genetic continuity?

Martin Sheen

Charlie SheenEmilio Estevez

How is it possible to maintain such genetic continuity?

How are Genes passed down?

• In sexual reproduction both parents pass the genes for specific traits to their offspring. Each parent donates 23 chromosomes for a total of 46. The father giving 50% and mother giving 50%. Genes that both parents have will code dominant in offspring. Ex. Both parents carrying the dominant trait for black hair will result in a black haired offspring.

What is a genetic trait?

A genetic trait is a characteristic controlled by genes that result in specific characteristics such as eye color and hair color.

Where are genes located?

Centromere

The centromere is the structure formed when two chromatids join

Chromatids

Are two identical parts of a chromosome when two join it becomes a tetrad (meaning 4parts)

Tetrad

A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids

What is a genotype?

A genotype is an organisms make up ~ all the alleles inherited for specific traitsExample: Bb, DD, Rr, Aa

What is a phenotype?

The phenotype is the outward appearance and behavior of an organism resulting from genes passed down from both parents.Hair and eye color freckles

What is an acquired trait?

~An acquired trait is a trait that can NOT be passed down genetically.Examples include:• Temper• Behavior• Attitude• Habits

What is an inherited trait?

An inherited trait is a trait that is passed down to offspring from one generation to the next. You have no control over the outcome.Example:Eye colorHair colorHeightThe ability to roll your tongue

What is a generation?

A generation is the average length of time between the birth of parents and the birth of their childrenExample:• You all your siblings and cousins born to your

aunts and uncles equate one generation. Your parents , your aunts and uncles and their cousins equate one generation

What is DNA ?

• genetic material of an organism, Deoxyribonucleic Acid, chemical that contains the instructions for cells to make the necessary protein. It has a structure like a twisted ladder made up of nucleotides.

DNA

• DNA is often called the blueprint of life.

• In simple terms, DNA contains the instructions for making proteins within the cell.