1 / 36

PATTERNS OF INHERITANCE

PATTERNS OF INHERITANCE. CAPTER 10. Pre-Mendel’s Theories. Blending Hypothesis : when parents with different traits have offspring, this will always show a blending of the traits Spontaneous generation : Non-living matter giving rise to living matter

yakov
Download Presentation

PATTERNS OF INHERITANCE

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. PATTERNS OF INHERITANCE CAPTER 10

  2. Pre-Mendel’s Theories • Blending Hypothesis: when parents with different traits have offspring, this will always show a blending of the traits • Spontaneous generation: Non-living matter giving rise to living matter • Homunculus: The little man inside the sperm

  3. Mendel’s experiments with pea plants • Trait: a variation of a particular character • Particulate hypothesis: Parents pass on to their offspring separate and distinct factors (genes) that are responsible for inherited traits • Genetics: the study of heredity

  4. Mendel’s experiments started with • True-breeding plants: when self-fertilized, a true-breeding plant produces offspring identical in appearance to itself generation after generation

  5. Cross-fertilization, sperm from the pollen of one flower fertilizes the eggs in the flower of a different plant

  6. the offspring of two different true-breeding varieties are calledhybrids.

  7. Monohybrid cross: pairing in which the parent plants differ in only one (mono) character.

  8. Mendel’s principle of segregation • There are alternative forms of factors (genes) called alleles. • For each character, an organism has two alleles for the gene controlling that character, one from each parent. Homozygous= same alleles Heterozygous= different alleles

  9. Principle of segregation (cont.) • When only one of the two different alleles in an heterozygous individual appears to affect the trait, that allele is called the dominantallele. The allele that does not appear to affect the trait is called the recessive allele • The two alleles for a character segregate (separate) during the formation of gametes (sex cells). Each gamete carries only one allele of each character (Principle of segregation)

  10. Phenotype refers to the observable trait (purple flowers) • Genotype refers to the combination of alleles (PP) Phenotypic ratio: ratio of plants with purple flowers to those with white flowers (3 purple : 1 white) Genotypic ratio: ratio of possible combinations of alleles (1 PP : 2 Pp : 1 pp)

  11. Probability and Punnett Squares Punnett Square: Diagram used to show the probability of a genetic cross Probability: Chance of Something happening

  12. Phenotype refers to the observable trait (purple flowers) • Genotyperefers to the combination of alleles (Pp)

  13. Phenotypic ratio: ratio of plants with purple flowers to those with white flowers (3 purple : 1 white) • Genotypic ratio:ratio of possible combinations of alleles (1 PP : 2 Pp : 1 pp)

  14. How can you find out the genotype of an individual showing the dominant trait?

  15. TESTCROSS • In a testcross, an individual of unknown genotype, but dominant phenotype is crossed with a homozygous recessive individual

  16. DIHYBRID CROSS • crossing of organisms differing in two characters

  17. Principle of Independent Assortment • During gamete formation in an F2 cross, a particular allele for one character can be paired with either allele of another character • The alleles for different genes are sorted into the gametes independently of one another.

  18. Not all traits are inherited following the patterns found by Mendel in pea plants • Intermediate or incomplete inheritance • Multiple alleles – codominance • Polygenic inheritance • Environment - epigenetics

  19. Intermediate or incomplete inheritance The heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes

  20. Multiple alleles - codominance For many genes several alleles exist in the population. Multiple alleles control the character of blood type in humans. There are six possible genotypes. The alleles IA and IB exhibit codominance, meaning that a heterozygote expresses both traits.

  21. http://www.youtube.com/watch?v=oz4Ctau8mC8

  22. Polygenic inheritance • When two or more genes affect a single character • In humans, height and skin color have polygenic inheritance

  23. Chromosome Theory of Inheritance • Genes are located on chromosomes • Behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns – (chromosomes undergo segregation and independent assortment during meiosis)

  24. Gene locus: location at which alleles of a gene reside on homologous chromosomes • Linked genes: genes that are located in the same region of a chromosome • Genetic linkage: tendency for the alleles on one chromosome to be inherited together. The closer two genes are on a chromosome, the greater the genetic linkage

  25. Sex-Linked Genes (any gene located on sex chromosomes) • http://www.youtube.com/watch?v=vP_h08cT5jw

  26. Morgan's monohybrid cross for fly eye color produced a 3 : 1 phenotypic ratio of red to white eyes in the F2 generation. However, none of the flies with white eyes were female.

More Related