Genetics and Heredity

Heredity and Genetics⦿Heredity is the

passing of traits from parents to offspring.

⦿Genetics is the overall study of genes and heredity. Kind of like how Biology is the study of living things.

⦿CELL: Basic unit of all living matter (Adult = over 10

trillion cells)

NUCLEUS: Central point of cell / contains genetic coding for maintaining life systems and issuing commands for growth & reproduction

CYTOPLASM: Substance of a cell outside of the nucleus

CHROMOSOMES:

46 in each Nucleus (23 pairs)

GENES: bands on chromosomes (thousands of genes)

DNA on genes (billions of DNA)

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⦿How many chromosomes are there in each cell?

⦿46 CHROMOSOMES or 23 PAIRS

⦿How many chromosomes are in Reproductive (egg & sperm) or Germ cells?

⦿23 CHROMOSOMES • (combined = the 46 chromosomes)

CELL DIVISION

⦿MITOSIS: Cell divides by copying the

DNA - cell splits - new cell with normal number of chromosomes (Cell growth & repair)

⦿MEIOSIS: a type of cell division that results in four daughter cells each with half the number of chromosomes of the parents call

Creates 1/2 sets of chromosomes

• Women = 23 Men = 23 Combined = 46

⦿Female Sex Cells XX (Ovum or Egg)

⦿Male Sex Cells XY (Sperm)

⦿Baby Girl = XX Baby Boy = XY • Conception is the union of an OVUM and the SPERM

⦿Gender is determined by the father! • Someone should have told King Henry VIII!

⦿DOMINATE Gene: More powerful - trait seen

in person ⦿RECESSIVE Gene: Weaker and hides in the

background. Trait can only determine when two of them are present - may show up in future generations.

⦿CARRIER: Has a recessive gene that is not visible ⦿ Trait: A genetically determined characteristic

⦿SEX-LINKED: Mother passes the recessive X to son • Color-blind male receives the trait from his mother. • The mother is usually not color-blind herself.

⦿ B = BROWN eyes (dominate) b = BLUE eyes (recessive)

⦿ BB = BROWN eyes ⦿ bb = BLUE eyes ⦿ Bb = BROWN eyes but carry the recessive BLUE eye gene

Who is Gregor Mendel?

⦿Gregor Mendel is known as the father of Heredity. He was an eastern European monk and studied pea plants.

⦿Gregor Mendel was born in 1822 in the Czech Republic.

⦿Gregor Mendel had an “interesting” childhood.

Gregor Mendel’s Research

⦿Mendel found that certain characteristics of pea plants were passed on from the parent plants to the offspring. These characteristics or genetic traits were caused by factors that we now call genes.

Traits and Genes

⦿ Traits are simply characteristics that an organism has. Gregor Mendel experimented with observable traits or characteristics.

⦿ Each trait can be is controlled by at least two genes. Traits can be dominant or recessive depending upon the genes that make them up.

Traits and Genes

⦿Dominant Traits-The strongest trait, this trait is always visible if there is at least one dominant gene.

⦿ Recessive Trait-The weakest trait, this trait is often not visible. For a recessive trait to show up it has to be expressed by two recessive genes.

Genetic Inherited Traits

⦿ The following is a list of genetically inherited traits you get from your parents.

⦿Color Blindness

⦿Cystic Fibrosis

⦿Down Syndrome

⦿Hemophillia

⦿ Sickle Cell Disease

⦿ Some forms of Cancer

⦿ Being Bald

Rules of Heredity

⦿ We use the letters of the alphabet as gene symbols to represent genes.

⦿ Every characteristics is caused by at least two genes.

⦿ Gene symbols are chosen by using the first letter of the strongest or dominant trait for both genes. For example if the dominant trait for a flower as to be yellow the gene symbol would be Y.

Rules of Heredity

⦿A capital letter is used for the strong trait (gene) and a lower cased letter is used for the weak trait.

⦿A strong trait is called dominant and a weak one is called recessive.

Rules of Heredity

⦿Whenever a dominant gene is present, it shows itself, but it takes two recessive genes (together) to show themselves.

⦿When two genes are exactly the same for a trait, they are called purebred. When they are not the same they are called hybrid.

Rules of Heredity

⦿ The phenotype refers to the visible expression of the genes, or what can be seen with the naked eye.

⦿ The genotype is the actual gene make-up of the organism.

⦿ Blending, co-dominance, or incomplete dominance all refer to genes where neither gene is dominant or recessive.

Important Heredity Terms

⦿Alleles are the different forms of genes. Two alleles for each gene are inherited, one from each parent.

⦿Genotype is the actual gene make-up. Both of the alleles together. Example TT, Tt, or tt.

Important Heredity Terms⦿ Phenotype is what you can

see or the visible expression of genes. Like brown eyes, being tall, ear size, etc.

⦿ Purebred is when the genes are the same for a trait. Organisms that are purebred often times have the same trait show up in each new generation. Another word for purebred is homozygous.

⦿ Individuals can be homozygous dominant or homozygous recessive.

Important Heredity Terms

⦿ Hybrid is when genes are mixed. This is when individuals have on dominant and one recessive gene. The dominant gene or trait expresses itself and shows up. Another term for hybrid is heterozygous.

⦿ Probability is the mathematical chance that something will happen.

Important Heredity Terms

⦿ Incomplete dominance or co-dominance is a rare instance when no gene dominates and a mixture of the two traits shows up as the trait of the offspring. For instance, in roses, a red rose crossed with a white rose produces a pink rose.

Genetics is Changing

⦿We often times use Punnett Squares to organize all the possible combinations of offspring from particular parents.

Using Punnett Squares

⦿ In flowers yellow is dominant over white. A white homozygous recessive flower is crossed with a yellow homozygous flower.

⦿ What are the genotypes and phenotype probabilities for this hybrid x purebred cross?

⦿ Let’s start with the basics…………

Cracking the Code of Life

⦿PBS Video

⦿1. Instructions for a Human Being.

⦿3. One Wrong Letter