1 / 11

Chromosomes

Chromosomes. Humans have 23 pairs of chromosomes. The autosomes refer to pairs 1 - 22. They are identical in both males and females. Pair #23 is the sex chromosomes . A female has XX. A male has XY. Thus, it is the father that determines the sex of the offspring. Chromosome Disorders.

hestia
Download Presentation

Chromosomes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chromosomes • Humans have 23 pairs of chromosomes. • The autosomes refer to pairs 1 - 22. They are identical in both males and females. • Pair #23 is the sex chromosomes. • A female has XX. • A male has XY. • Thus, it is the father that determines the sex of the offspring.

  2. Chromosome Disorders • Nondisjunction: homologous chromosomes fail to segregate or move to opposite poles during meiosis. • Trisomy: condition of having 3 chromosomes instead of a normal pair. Examples include: Down’s Syndrome-extra #21. Klinefelters- XXY

  3. Monosomy: condition of having 1 chromosome instead of the normal pair. Example: Turner’s Syndrome- The 23rd chromosome has no pair . Only one X is present.

  4. Genetics: Study of Heredity • Gregor Mendel: “Father” of Genetics • Mendel’s Conclusions: 1856-1865 • 1) Inherited characteristics are controlled by genes (factors) that occur in pairs. • 2) Principle of Dominance and Recessiveness: One gene in a pair may mask the other, preventing the other from having an effect.

  5. 3) Law of segregation: A pair of genes is segregated or separated during the formation of gametes. (Anaphase I of meiosis) • 4) Law of independent Assortment: genes separate and distribute to gametes in a way that is independent of other gene pairs.

  6. Symbols used in genetics: Letters are used to represent the genes. • A capital letter is use to indicate a dominate trait. • A lower case letter is used to indicate a recessive trait. • The letter is chosen by the dominant trait.

  7. Genotype: indicates the actual genes, represented by letters. • For example: BB or Bb or bb. • Phenotype: indicates what you can actually “see”. For example Brown hair. • Homozygous: paired genes that are the same. For example: BB or bb.

  8. Heterozygous: paired genes that are not the same. For example Bb. • Alleles: Alternative forms of a gene. For example: B and b. • Multiple alleles: traits with more than two alleles. For example Blood type, A, B and O.

  9. Punnett Square: used to determine various combinations of genes that can result from a particular cross. • Monohybrid cross: when only one pair of contrasting traits is considered in a cross. For example, TT x tt • Dihybrid cross: two pairs of traits are considered. For example: RRYY x rryy.

  10. Traits that Mendel observed in peas: • seed texture: round - R wrinkled - r • color: yellow- Y green - y • height: tall - T short - t

  11. Incomplete Dominance: neither gene is dominant or recessive, they blend. For example: If a red flower is crossed with a white flower, the result would be pink. • Capital letters are used for both genes. • Co-Dominance: both genes dominate, or show. For example: Blood type AB

More Related