GeneticsGenetics

Genetics

Genetics is the study of inheritance, how certain traits are passed from one Generation to the next. Early people did not understand that genetics as wellAs environment shape each individual.

Gregory Mendel is considered the “Father” of genetics. He was born in Germany1n 1822. He studied philosophy and physics and entered a religious order in 1843.He continued his education through the church. He was an avid gardener and the Variation in pea plants peaked his educated mind. He studied how the plants Passed traits like plant size and pea texture to the next generation. His math andPhysics helped him plan experiments to determine what was going on. He died in 1884 and his findings were mostly forgotten. In the early 1900’s interest in producingBetter agricultural product caused his experiments to be rediscovered. Basic genetics is often called Mendelian Inheritance.

Animal cell part review

1. Cell membrane: limits the cytoplasm withIn the cell.

2. Pinocytic vesicle: small bleb or openingTo the outside on the cell wall

3. Cytoplasm: transparent, semi-fluid sub-Stance in which other organelles float.

4. Endoplasmic reticulum: membrane usedFor transportation, metabolizing lipid, linedWith RNA5. Golgi bodies: stacks of saucer shaped Disks, involved in synthesis of carbohydrates

6. Centrosome : near nucleus involved withFormation of spindle during cell division.

7. Lysosomes: spherical bodies which contain digestive enzymes.

8. Mitochondria: The center for respiratory metabolism in the cell

9. Vacuole: Small spheres which are concerned with storage and excretion.

10. Nucleus: central body of the cell contains a nuclear sap (karyolymph)

11. Nucleus: a dense body contains RNA This nucleus disappears during cell division.

12. Nuclear membrane: semi-permeable membrane that separates nucleus from cytoplasm.

Nucleus:Made up of pairs of genetic material called Chromosomes. The chromosomes come in pairs.Each species has a certain number of pairs of Chromosomes.

Man 23 Pair or 46 chromosomes

Swine 40 pair or 80 chromosomes

Cattle 30 pair or 60 chromosomes

Sheep 32 pair or 64 chromosomes

Horse 30 pair or 60 chromosomes

Each chromosome is made of genes. The combinations of genes is what express Itself in the individual.

The genes are made up of individual DNA. When the nucleus replicates it copies The DNA. Sometimes the replication process makes mistakes. That is howMutations happen.

Cell division:

Mitosis: Normal cell division where two newCells are created with the same number ofChromosomes.

Pro Phase: two centrosomes appear and Start to form spindles which the Chromosomes will align themselves with Their sister cells.

Metaphase: The chromosomes alignThemselves on the spindles betweenThe centrosomes.

Anaphase: proteins that connect sisterCells dissolve and the spindle fibers Shorten pulling chromosomes to Opposite ends of the cell.

Telephase: the cell membrane “pinches”Off between the two ends of the cell thatThe chromosomes have segregated to.

Cytokinesis: the completion of the Splitting of the cell

Meiosis:

Cell division in which the resulting cells have onlyHalf of the genetic information (chromosomes)That the original cell had. Used for gamete orSex cell production (egg and sperm cells)

Fist a type of mitotic multiplication of chromosomesOccur, but some information is mixed between theTwo sister chromatids.

The cell divides with sister Chromatids separated forming two daughter cells.

A second division takes the two daughter cells andSplits them forming 4 cells with half of the chromosomesFrom each sister chromatids.

Fertilization:

The union of an egg cell and sperm cell formsA zygote.

The resulting cell has a complete set of chromosomesOne half from the paternal (father) side and oneHalf from the maternal (mother) side.

The zygote continues to grow geometrically 2 cells, 4 cells, 8 cells, 16 cells etc.As the cells grow it reaches a point where it is called a blastula, early in the blastula stage it can be separated (embryo splitting ). It fold inward on itself and forms what will become the gastro-intestinal tract (digestive).

At an early stage animal zygotes form the umbilical cord and attach to theUterine wall. The umbilical cord blood vessels pass very close the blood vessels of the uteri an wall and food and waste is passed through a semi-permeable membrane to support the fetus.

Formation of twins

If the blastula separates on its own it forms 2 individual blastulas with theSame genetic information. The type of twins arising from a single eggAre called Identical twins. These twins will be the same sex and be extremelySimilar in their traits (color patterns, etc.). Embryo splitting tries to imitate this type of twin.

If more than one egg is shed off the ovary at ovulation each eggCan be fertilized independently of the other. The type of twins produceBy this process are called fraternal twins. They do not have to be theSame sex, or have very many genetic traits in common.

Producers are now selecting superior females and through the use ofDrugs causing them to super-ovulate, produce many eggs at ovulation.They may then AI the individual or fertilize the eggs in vitro (outside the body).The fertilized eggs can then be transplanted in donor individuals at the same Stage of gestation and the donor will raise the young. This process is calledEmbryo transfer

Traits

The traits an individual has and the traits we see they have are two differentThings.

Genotype: is the actual genetic make up of the individual. It is the Combination of genes that formed the individual from fertilization. Think of it as the potential that the individual has according to genetics.

Phenotype: is what we physically see. Phenotype is influenced by Environment. If an individual has a genotype to gain 3 pound a dayAnd you don’t feed them enough food it will not produce 3 pounds aDay gain. The environment limited the individuals performance.

Classification of traits

The most expressive traits or genes are called dominate genes and areDenoted by a capital letter. Being polled in the beef species is dominate.

Less expressive traits or genes are called recessive genes and are denotedBy a small letter. A red hair coat in most beef breeds is recessive to darkOr black hair coats.

Homozygote individuals have either both dominate or recessive genes for aParticular trait (BB, bb) while heterozygotes have one of each (Bb)

Chi square crosses:

A Chi square is a simple method to determine the expected outcomesOf crossing animals with different traits.

The F1 (family 1) is the cross between two individuals that have a knownTrait make up. If only one individual appears to be dominate and you Cross them with an individual that is recessive for the same trait you Should be able to determine if the dominate appearing animal is homo, orHeterozygote for the trait. How?

The F2 (family 2) is a cross between animals of the F1 generation. Using Our knowledge of trait expression we would expect to see a certain ratioOf offspring if the F2 individuals were homozygotes or heterozygotes.

By working the square we can predict or compare what really happenedTo what to what we predicted to determine the genetic makeup of Individuals.

Simple crosses using a square are those that compare one or twoTraits. Predicting multiple trait outcomes requires the use of Probability.

Other trait combinations.

Incomplete Dominance:

Where the dominant gene cannot completely overcome the lessExpressive gene. If the dominate gene for hair coat is Red R andThe recessive hair coat is White r and individual with a genotypeOf Rr appears a roan color.

Sex linked:

Some traits are expressed only in the males or females of aSpecies. These traits are connected to a gene on the sex Determining chromosome.

Lethal genes:

These genes are lethal in the homozygous state. They usually causeDeath before the zygote is born. Abortions may happen for noApparent reason.

Sex determination:

In the mammal world males have the sex genes XY, while females are XX.This is true in 95-99% or males and females…..there are exceptions.If this is true then during meiosis the sex cells developed by the male areEither X or Y, and the sex cells of females will produce cells that onlyHave an X. The egg produced by the female has only the X to offer in The sex determination department. It depends on the sperm cell thatFertilizes the egg what sex it will develop into. If a sperm cell with anX fertilizes the egg a female zygote will result. If a sperm cell with a Y fertilizes the egg a male zygote will result. The sex cells of the maleDetermines the sex of the zygote.