Genetics: The Basics of Heredity and Traits

Chromosomes and DNA

Genes are contained within chromosomes, which are made of DNA and located in the cell nucleus. A chromosome contains thousands of genes. Every normal human contains 23 pairs of chromosomes, a total of 46 chromosomes.

Traits and Alleles

A trait is any gene-determined characteristic, often determined by more than one gene. Gene: A segment of DNA that controls a hereditary trait. Alleles are different versions of a gene that produce distinguishable traits in offspring. Two alleles must be present in order for a trait to appear in the offspring. One allele is provided by each parent to the offspring. When fertilization of sperm and eggs occurs, the new offspring will have 2 alleles for each gene.

Gregor Mendel's Contributions

Gregor Mendel was an Austrian monk who was born in 1822 and is known as the Father of Genetics. He discovered that some traits are caused by mutated genes that are inherited or that are the result of a new gene mutation.

Proteins

Proteins are important and are not just the building blocks for muscles, connective tissues, skin, etc. They are needed to make enzymes (complex proteins that control and carry out nearly all chemical processes and reactions within the body). The body produces thousands of different enzymes. Protein synthesis is controlled by genes.

Genotype and Phenotype

Genotype/genome: a combination of genes/a complete set of instructions on how that person's body synthesizes proteins. Phenotype: the actual structure/function of body/how the genotype manifests in a person, not all the instructions in the genotype may be carried out/expressed.

Karyotype

Karyotype: a picture of the full set of chromosomes in a person's cells.

DNA (Deoxyribonucleic Acid)

DNA is found in all living cells. DNA must be able to store information about building proteins that make the organism/must be able to copy information & information has to be easily"rea" +"replace"/made of nucleotides joined into a long strand. DNA molecule is a long double helix that allows for DNA replication + protein synthesis to occur.

Nitrogenous Bases in DNA

4 nitrogenous bases in DNA: Adenine, Thymine, Guanine, Cytosine. Each extremely long DNA molecule is coiled up inside 1 of the chromosomes.

- Two pyrimidines: C & T. - Two purines: A & G. - C is heterocyclic (being a ring composed of atoms of more than 1 kind). In both DNA & RNA & pairs with another base G (complementary base pairing). - T is a pyrimidine structure found ONLY in DNA. In RNA, a nucleobase (uracil) replaces T. T is a nucleoside molecule of T. - C - guanine is the complementary base pair of C - T - adenine is the complementary base pair of thymine. - C - has an amine group & a keto group, T - has 2 keto groups & a methyl group. groups & a methyl group.