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Genetics Mrs. Hoyle Chromosome: a very long DNA molecule and associated proteins, that carry portions of the hereditary information of an organism. Each chromosome has a constriction point called the Chromosomes centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes. A karyotype is an organized Karyotype - profile of a person's chromosomes. In a karyotype, chromosomes Male are arranged and numbered by size, from largest to smallest. This arrangement helps scientists quickly identify chromosomal alterations that may result in a genetic disorder. To make a karyotype, scientists take a picture of someone's chromosomes, cut them out and match them up using size, banding pattern and centromere Since its discovery back in the position as guides. 1960s, karyotyping has been used as both a `screening tool' as well as a method to determine potential genetic errors. Autosome refers to those chromosomes that are not involved in sex determination. Human diploid cells have 22 pairs of autosomes and 1 pair of sex chromosomes. Male xy Sex chromosomes are Female xx chromosomes involved in a major way in sex determination. Gregor Mendel He made two very important generalizations from his pea experiments, know today as the Laws of Heredity. Mendel coined the present day terms in genetics: recessiveness and dominance. In 1866 he published his work but it didn't take affect in the science field until 1900, years after his death. As the theory of evolution spread so did his findings and laws. Mendel and Pea Plants P – pure for trait F1- first generation F2- second generation Ever wonder how your sister Monohybrid came out with blue eyes, when both of your parents have brown eyes? All traits have two genes Some Ideas Refreshed: that represent them. Genotype: combination of Traits come in pairs. alleles in your DNA (i.e. GG) They can be all Phenotype: the trait that dominant (TT) shows up based upon the genotype (i.e. green peas) mixed (Tt) For each trait you have 2 or all recessive (tt) alleles, one comes from each parent: This is the basis for Homozygous: two of the same figuring out a Punnett alleles. square. When two genes Heterozygous: two different are paired, the dominant alleles. one will take effect. The dominant allele BLOCKS Monohybrid (One-Gene) the recessive allele (for ALL cases, unless labeled "mixed dominance") Symbol for male and female Male is on top of this punnett square Female is on the side of the punnett square Product Rule A-heads a- tails Chance of two independent events occcuring AA Aa simultaneously is = to the product of the separate A probabilities. What would be the chance of having a AA? One in 4 Aa aa Ex ½ x ½ = ¼ chance Ex. If you flip two coins at the a same time what would the odds be? Would it be possible for Aa parents to have 4 children with aa? YES! Just not as likely. Ex Aa x Aa Aa xAa ¼ x ¼ x ¼ x ¼ = 1/250 Blood Type Each of us has two ABO blood type alleles, because we each inherit Phenotype Genotype one blood type allele Type A AA , Ao from our biological Type B BB, Bo mother and one from Type AB AB our biological father. A description of the pair of alleles in our DNA is called the genotype. Since there are three different alleles, there are a total of six different genotypes Incomplete Dominance Complete the following Punnett squares using the In some instances, a cross information. Since dominance between two individuals, each is not operating, a slight differently homozygous for a modification of gene symbols particular characteristic, results is used. in partial expression of both We will use the letter C to traits in the F1 phenotype. One represent color in gene incompletely masks the snapdragons. other in the heterozygote. CR will represent the allele for red color and CW will represent the allele for white color. The hybrid of a red and a white snapdragon is pink, so would be represented as CR CW. Incomplete Dominance & Codominance There is no dominant or recessive, the heterozygous condition results in a "blending" of the two traits. Example: Snapdragons can be red, white, or pink (heterozygous) Sex Determination Female = XX Male = XY Male Determines the sex Sex Linked Traits The genes for these traits are on the X chromosome, because boys only receive one X chromosome they are more likely to inherit disorders passed to them from their mother who would be a carrier. Hemophilia and Colorblindness are sex linked traits, the punnet square below shows how a woman who is a carrier passes the trait to her son, but not her daughters.
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