genetics grade 11 biology

• Genetics is the study of heredity and variation of living organisms and how genetic information is passed from one generation to the next.
• Heredity is the passing on of physical or mental characteristics genetically from one generation to another.
• Nucleotide is the individual units of each strand of DNA - Phosphate group, sugar group, and a base.
• Genome is the complete DNA sequence in every cell of an organism is called the genome.
• Somatic Cell is all cells in the body which are not reproductive cells
• Traits must be passed from one cell, the parent cell, to the new cells, the daughter cells. 
• DNA stands for deoxyribonucleic acid and is the genetic material of all living things.
• We get our DNA from our parents in the form of chromosomes, long pieces of coiled DNA and proteins, but throughout most of the cell cycle it exists as strands of loosely arranged chromatin. 
• The names of the four bases found in DNA are called Adenine, Cytosine, Guanine and Thymine.
• The complimentary bases pairs are Adenine with Thymine and Cytosine with Guanine
• Human somatic cells have 46 chromosomes. 23 from the mother and 23 from the father.
• Alleles are different versions of the same gene, such as, brown hair versus blonde hair.
• Three examples of traits are eye colour, hair colour, and height
• The X and Y chromosomes are to determine the sex of an individual.
• The representation of chromosomes is called a karyotype.
• Diploid is two copies from each chromosome (2n)
• Haploid is one copy of each chromosome (n)
• Homologous chromosomes are pairs of chromosomes that appear similar in terms of: 

  • Length
  • Centromere location
  • Banding pattern when stained with certain dyes. 
• Daughter cells produced from meiosis contain half the number of chromosomes than that of the parent cell
• Gametes (AKA sperm cells and egg cells) are produced:

  • In the testes in males (Spermatogenesis)
  • In the ovaries in females (Oogenesis)
• Replication is the process of duplicating a chromosome
• Replicated copies are called sister chromatids
• Homologous chromosomes contain the same genes, but may have different versions, called ALLELES
• Sister chromatids identical copies of the SAME genes - therefore have the same alleles
• Prophase 1, homologous pair, and crossing over occurs.
• Late prophase - Chromosomes condense, spindle forms, and nuclear membrane fragments.
• In prophase 1, homologous chromosomes join to form a tedtrad. This is called a sysnapsis.
• During crossover, homologous chromosomes in a tetrad cross over each other. Pieces of chromosomes or genes are exchanged. Produces Genetic recombination in the offspring.
• Crossing-over “mixes up” the information that you receive from 2 parents, so that a different mixture is passed on to the child
• Metaphase 1 - Homologous pairs of chromosomes (as tetrads) line up on the equator of the cell.
• Anaphase 1 - Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres.
• Telophase - Nuclear envelopes reassemble. The spindle disappears. Cytokinesis divides the cell into two.
• Prophase 2 - Nuclear envelope breaks down. Spindle forms.
• Metaphase 2 - Chromosomes align along the  equator of each cell.
• Anaphase 2 - Sister chromatids separate and move to opposite poles.
• Telophase 2 - Nuclear envelope reassembles. Chromosomes unravel into chromatin. Spindle disappears. Cytokinesis divides cell into two.
• Results of Meiosis - Gametes (egg & sperm) form. Four haploid cells each with one copy of each chromosome. One allele of each gene. Different combinations of alleles for different genes along the chromosome due to crossing over.
• • Spermatogenesis - Occurs in the testes. Meiosis produces 4 spermatids. Spermatids mature into sperm. Men produce about 250,000,000 sperm per day.
• Oogenesis - Occurs in the ovaries. Meiosis produces 3 polar bodies that die and 1 egg that survives. Polar bodies die because of the unequal division of cytoplasm. Immature egg called the oocyte. Starting at puberty, one oocyte matures into an ovum (egg) every 28 days
• Genetic variation is the difference in the DNA among individuals.