genetics crosses

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By: mansal (8 month(s) ago)

Hi May I have a copy of this presentation please, my email address is: m_salehi@med.mui.ac.ir Thanks

By: andkid (30 month(s) ago)

Nice.

By: nysciguy (42 month(s) ago)

Am interested in expanding your presetation by including visuals for the students (roan coloring) especially for the chromosomal anomilies. Would appreciate a copy of your PPT and send you back the revised one. fmizzo@esboces.org

By: hbello (45 month(s) ago)

Raulo, I am interested in your ppt explaining the genetics crosses, I was wondering if you could please email me a copy of it. Thanks. Favoredhally@gmail.com

By: hbello (45 month(s) ago)

Hello Raulo H

Presentation Transcript

Today’s Objectives: 

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: 

Solving Crosses

Steps for Solving a Genetics Problem:: 

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: 

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: 

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: 

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: 

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 Together: 

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: 

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: Punnett Square: 

Example 2: Punnett Square

Example 2: Answer the Question: 

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: 

Other Types of Heredity Patterns Incomplete Dominance – blending of traits in heterozygote. Pink flowers RR = red Rr = pink rr = white

Other Types of Heredity Patterns: 

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: 

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: 

Continuous Variation Multiple genes are involved Examples Eye color Skin color Hair color

Sex-linked Genes: 

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: 

Some Human Genetic Disorders Of Interest Cystic Fibrosis Sickle-cell Anemia Tay-Sachs Disease Phenylketonuria (PKU) Hemophilia Huntington’s Disease Muscular Dystrophy