Bio - Unit 8

• Heredity


  the passage of traits from parent to offspring.
• DNA in its condensed form

  chromosomes
• What do chromosomes contain?

  the genetic information stored in DNA that is passed from parent to offspring.
• Diploid


  Chromosomes in pairs
• Homologous pairs


  a set of matching but non-identical chromosomes that code for the same types of traits
• 2 sets, therefore 46 chromosomes

  How many sets of 23 chromosomes are in a human?
• a picture of an individual's chromosomes

  Karyotype
• How can karyotype analysis be used?

  By extracting an individual's DNA, we can make a karyotype and analyse the chromosomes for certain disorders
• 23rd pair of chromosomes


  Sex Chromosomes
• Female


  XX
• Male


  XY
• Who determines the childs sex

  The male can give an X or a Y
• nondisjunction


  When chromosomes are not separated properly during the formation of sex cells
• What does nondisjunction result in?

  an abnormal number of chromosomes
• Abnormal chromosome number


  is damaging to the offspring
• A monosomy results


  when an individual has only one chromosome when it should have a pair
• A monosomy disorder would have

  45 total chromosomes
• A trisomy results


  when an individual has an extra chromosome in a pair.
• Down's Syndrome


  Trisomy 21
• Where do the two parts of a homologous pair come from?


  One chromosome in a homologous pair comes from the male parent, the other comes from the female parent.
• trait


  any characteristic that can be passed from parent to offspring.
• Heredity


  the passing of traits from parent to offspring.
• Genetics


  scientific study of heredity
• "Father of Genetics"


  Gregor Mendel, an Austrian monk
• gene


  DNA sequence that determines a particular trait for an organism.
• locus


  the position of a gene on a chromosome.
• allele


  An allele is a possible form of a gene. An allele can be dominant, recessive, incompletely dominant, or codominant.
• Dominant allele


  the stronger variant of a gene, it is usually expressed more often. Represented by a capital letter
• Recessive allele


  the gene that is displayed less often in a cross. Represented by a lowercase letter
• genotype


  the allele combination for a trait, or the organism's actual genetic makeup.
• Homozygous genotype


  gene combination of 2 dominant or recessive alleles
• Heterozygous genotype


  gene combination of one dominant and one recessive allele.
• phenotype


  the physical trait resulting from a genotype
• monohybrid cross


  the study of a single trait in a genetic cross.
• two hybrids that cross (Tt)

  will always create 3 dominant : 1 recessive ratio
• Punnett Square


  The probability that an offspring will inherit a specific combination of alleles using a chart
• Non-Mendelian traits


  Traits that do not follow Mendel's patterns of heredity.
• Multiple Alleles (blood type)


  in which three alleles (two codominant and one recessive) determine human blood type
• incomplete dominance


  neither allele is completely dominant over the other and a blend of the two homozygous phenotypes is observed in the heterozygous phenotype.
• example of incomplete dominance


  In snapdragons, red flower color (RR) is incompletely dominant to white (R'R') flower color. A heterozygous snapdragon is pink (RR'). Cross a pink snapdragon with a pink snapdragon.