Today s objectives
Download
1 / 17

Today - PowerPoint PPT Presentation


  • 211 Views
  • Uploaded on

Today’s Objectives. TSW employ the four primary rules for solving genetics problems. TSW successfully solve genetics crosses involving one and two alleles. TSW successfully solve monohybrid and dihybrid crosses using the Punnett Square. Solving Crosses. Steps for Solving a Genetics Problem:.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Today' - LionelDale


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Today s objectives l.jpg
Today’s Objectives

  • TSW employ the four primary rules for solving genetics problems.

  • TSW successfully solve genetics crosses involving one and two alleles.

  • TSW successfully solve monohybrid and dihybrid crosses using the Punnett Square.



Steps for solving a genetics problem l.jpg
Steps for Solving a Genetics Problem:

  • Trait – dominant = A (AA or Aa) Trait – recessive = a (aa)

  • ___________ x ___________

  • Punnett Square

  • Answer questions based on results from Punnett Square


Monohybrid crosses l.jpg
Monohybrid Crosses

  • Cross that involves one pair of contrasting traits

  • Solve using Punnett Square

  • Sample problems:

    • Rr x rr

    • RR x rr

    • Rr x Rr

    • Rr x RR


Let s solve together l.jpg
Let’s Solve Together

  • Short hair (L) is dominant to long hair (l) in mice. What is the genotype and phenotype ratio of a heterozygous short-haired mouse crossed with a long-haired mouse?


Example 1 monohybrid l.jpg
Example 1: Monohybrid

  • Short hair = dominant = L (LL or Ll) long hair = recssive = l

  • Ll x ll (heterozygote parent = Ll)

  • Punnett Square:

  • Genotype ratio: ½ Ll: ½ ll

  • Phenotype ratio: ½ short hair: ½ long hair


Dihybrid crosses l.jpg
Dihybrid Crosses

  • Involves two pairs of contrasting traits

    • Pea shape and pea color

    • Coat length and coat color in rodents

    • Plant height and flower color


Let s solve together8 l.jpg
Let’s Solve Together

  • In guinea pigs, the allele for short hair (S) is dominant to long hair (s), and the allele for black hair (B) is dominant over the allele for brown hair (b). What is the probable offspring phenotype ratio for a cross involving two parents that are heterozygotes for both traits?


Example 2 dihybrid l.jpg
Example 2: Dihybrid

  • Short hair = dominant = SS or Ss Long Hair = recessive = ss Black coat = dominant = BB or Bb Brown coat = recessive = bb

  • SsBb x SsBb (gametes done by the FOIL method)

    • SB, Sb, sB, sb and SB, Sb, sB, sb



Example 2 answer the question l.jpg
Example 2: Answer the Question

  • What is the probable offspring phenotype ratio for a cross involving two parents that are heterozygotes for both traits?

    • 9/16 Black, short coats

    • 3/16 Black, long coats

    • 3/16 Brown, short coats

    • 1/16 Brown, long coats


Other types of heredity patterns l.jpg
Other Types of Heredity Patterns

  • Incomplete Dominance – blending of traits in heterozygote.

    • Pink flowers

      • RR = red

      • Rr = pink

      • rr = white


Other types of heredity patterns13 l.jpg
Other Types of Heredity Patterns

  • Codominance – can see both alleles at the same time.

    • Roan coats in horses

      • Some white hairs, some red hairs


Multiple alleles l.jpg
Multiple Alleles

  • Blood Types in Humans

    • Single gene, but four phenotypes

      • Type A  can be AA or Ao

      • Type B  can be BB or Bo

      • Type AB  only AB (codominant pattern here)

      • Type O  only oo (both recessive)

    • All 3 blood types are dominant to O


Continuous variation l.jpg
Continuous Variation

  • Multiple genes are involved

  • Examples

    • Eye color

    • Skin color

    • Hair color


Sex linked genes l.jpg
Sex-linked Genes

  • Present on the X chromosome

  • More common in males

  • When would a female have this phenotype?

  • Examples:

    • Baldness

    • Hemophilia


Some human genetic disorders of interest l.jpg
Some Human Genetic Disorders Of Interest

  • Cystic Fibrosis

  • Sickle-cell Anemia

  • Tay-Sachs Disease

  • Phenylketonuria (PKU)

  • Hemophilia

  • Huntington’s Disease

  • Muscular Dystrophy


ad