Genetics unit punnett squares
This presentation is the property of its rightful owner.
Sponsored Links
1 / 39

Genetics Unit: Punnett Squares PowerPoint PPT Presentation


  • 47 Views
  • Uploaded on
  • Presentation posted in: General

Genetics Unit: Punnett Squares. Genetics = the field of biology devoted to understanding how characteristics are transmitted from parents to offspring Heredity = the transmission of characteristics from parents to offspring. Mendel. “father” of modern genetics = laid the groundwork

Download Presentation

Genetics Unit: Punnett Squares

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


Genetics unit punnett squares

Genetics Unit: Punnett Squares


Genetics unit punnett squares

Genetics = the field of biology devoted to understanding how characteristics are transmitted from parents to offspring

Heredity = the transmission of characteristics from parents to offspring


Mendel

Mendel

  • “father” of modern genetics = laid the groundwork

  • experimented with

    garden peas

    - looked for traits = specific characteristics


Mendel cont

Mendel (cont)

- P1 generation = parental generation

- F1 generation = offspring of the parental generation

- F2 generation = offspring of the F1 generation


Mendel cont1

Mendel (cont)

Mendel’s 1st Law = Law of Segregation

  • Organisms inherit two copies of each gene, one from each parent

    2) Organisms donate one copy of each gene in their gametes.


Mendel cont2

Mendel (cont)

Mendel’s 2nd Law = Law of Independent Assortment

1) The presence of one trait does not affect the appearance of another trait


Basics of genetics

Basics of Genetics

- Gene = a segment of DNA on a chromosome that controls a specific trait

- because chromosomes come in pairs, genes come in pairs


Basics of genetics cont

Basics of Genetics (cont)

- Allele = each of several forms of a gene

- aka: letters

- each allele has a specific location on a chromosome (= locus)

- capital letters = dominant alleles - lowercase letters = recessive alleles


Basics of genetics cont1

Basics of Genetics (cont)

- homozygous = both alleles are alike

  • homozygous dominant = both capital letters = BB

    - homozygous recessive = both lowercase letters = bb

    heterozygous = alleles are different = Bb


Polydactyly

Polydactyly

Polydactyly is the condition of having more than the typical number of fingers or toes. The allele for polydactyly is dominant.


Basics of genetics cont2

Basics of Genetics (cont)

- Genotype = genetic makeup of an organism

- consists of alleles (letters)

- Phenotype = the appearance of an organism as a result of its genotype

- aka: what does it look like

- human phenotype can be altered by behavior

BB

Green Eyes


Monohybrid crosses

Monohybrid Crosses

= a cross between individuals that involves one pair of traits

- Example: Black hair (B) in guinea pigs is dominant to brown hair (b)


Example 1 homozygous dominant x homozygous dominant

Example 1:Homozygous Dominant X Homozygous Dominant

B

B

Genotypic Ratio

Phenotypic Ratio

4 BB :

0 Bb :

0 bb

BB

B

BB

BB

BB

B

4 Black :

0 Brown


Example 2 homozygous recessive x homozygous recessive

Example 2:Homozygous Recessive X Homozygous Recessive

b

b

Genotypic Ratio

Phenotypic Ratio

0 BB :

0 Bb :

4 bb

bb

b

bb

bb

bb

b

0 Black :

4 Brown


Example 3 homozygous dominant x heterozygous

Example 3:Homozygous Dominant X Heterozygous

B

B

Genotypic Ratio

Phenotypic Ratio

2 BB :

2 Bb :

0 bb

BB

B

BB

Bb

Bb

b

4 Black :

0 Brown


Example 4 homozygous recessive x heterozygous

Example 4:Homozygous Recessive X Heterozygous

b

b

Genotypic Ratio

Phenotypic Ratio

0 BB :

2 Bb :

2 bb

Bb

B

Bb

bb

bb

b

2 Black :

2 Brown


Example 5 heterozygous x heterozygous

Example 5:Heterozygous X Heterozygous

B

b

Genotypic Ratio

Phenotypic Ratio

1 BB :

2 Bb :

1 bb

BB

B

Bb

Bb

bb

b

3 Black :

1 Brown


Testcross

Testcross

= an individual of unknown genotype is crossed with a homozygous recessive individual

- can be used to determine the genotype of any phenotype that is dominant


Example 6 testcross

Example 6: Testcross

b

b

Genotypic Ratio

Phenotypic Ratio

0 BB :

2 Bb :

2 bb

Bb

B

Bb

bb

bb

b

2 Black :

2 Brown


Example 6 testcross1

Example 6: Testcross

b

b

Genotypic Ratio

Phenotypic Ratio

0 BB :

4 Bb :

0 bb

Bb

B

Bb

Bb

Bb

B

4 Black :

0 Brown


Example 6 testcross2

Example 6: Testcross

b

b

Genotypic Ratio

Phenotypic Ratio

0 BB :

0 Bb :

4 bb

b

bb

bb

bb

bb

b

0 Black :

4 Brown


Dihybrid cross

Dihybrid Cross

= a cross between individuals that involves two pairs of traits

- Example: Black hair (B) in guinea pigs is dominant to brown hair (b) and rough coat (R) is dominant to smooth coat (r)


Example 1

Example 1:

Homozygous Dominant X

Homozygous Recessive

BBRR

bbrr


Example 1 homozygous dominant x homozygous recessive

Example 1: Homozygous Dominant X Homozygous Recessive

BR

BR

BR

BR

BbRr

BbRr

BbRr

BbRr

br

br

BbRr

BbRr

BbRr

BbRr

br

BbRr

BbRr

BbRr

BbRr

BbRr

BbRr

BbRr

BbRr

br


Example 2

Example 2:

Heterozygous X

Heterozygous

BbRr

BbRr


Example 2 heterozygous x heterozygous

Example 2: Heterozygous X Heterozygous

BR

Br

bR

br

BBRR

BBRr

BbRR

BbRr

BR

Br

BBRr

BBrr

BbRr

Bbrr

bR

BbRR

BbRr

bbRR

bbRr

Bbrr

bbRr

bbrr

BbRr

br


Incomplete dominance

Incomplete Dominance

= the F1 Generation will have a phenotype in between that of the parents

- Example: Red flowers (R) and White flowers (r) can make Pink flowers (Rr)


Example 7 incomplete dominance pink flower x pink flower

Example 7: Incomplete Dominance Pink Flower X Pink Flower

R

Genotypic Ratio

Phenotypic Ratio

r

1 RR :

2 Rr :

1 rr

RR

R

Rr

Rr

rr

1 Red:

2 Pink :

1 White

r


Example 7 incomplete dominance pink flower x red flower

Example 7: Incomplete Dominance Pink Flower X Red Flower

R

r

Genotypic Ratio

Phenotypic Ratio

2 RR :

2 Rr :

0 rr

RR

R

Rr

RR

Rr

R

2 Red:

2 Pink :

0 White


Example 7 incomplete dominance white flower x red flower

Example 7: Incomplete Dominance White Flower X Red Flower

Genotypic Ratio

Phenotypic Ratio

r

r

0 RR :

4 Rr :

0 rr

Rr

R

Rr

Rr

Rr

R

0 Red:

4 Pink :

0 White


Example 7 incomplete dominance pink flower x white flower

Example 7: Incomplete Dominance Pink Flower X White Flower

R

r

Genotypic Ratio

Phenotypic Ratio

0 RR :

2 Rr :

2 rr

Rr

r

rr

Rr

rr

0 Red:

2 Pink :

2 White

r


Codominance

Codominance

= when both alleles for a gene are expressed in a heterozygous offspring

- Example: Red coat color (R) in horses is codominant with white coat color (R’) to make a horse with a mix of red and white coat color (RR’)


Example 8 codominance red coat x white coat

Example 8: Codominance Red Coat X White Coat

R

R

Genotypic Ratio

Phenotypic Ratio

0 RR :

0 R'R' :

4 RR'

RR'

RR'

R'

RR'

RR'

R'

0 Red Coat :

0 White Coat :

4 Red/White Coat


Example 8 codominance red white coat x white coat

Example 8: Codominance Red/White Coat X White Coat

R

R'

Genotypic Ratio

Phenotypic Ratio

0 RR :

2 R'R' :

2 RR'

RR'

R'R'

R'

RR'

R'R'

R'

0 Red Coat :

2 White Coat :

2 Red/White Coat


Example 8 codominance red white coat x red coat

Example 8: Codominance Red/White Coat X Red Coat

R

R'

Genotypic Ratio

Phenotypic Ratio

2 RR :

0 R'R' :

2 RR'

RR

RR'

R

RR

RR'

R

2 Red Coat :

0 White Coat :

2 Red/White Coat


Genetics unit punnett squares

25 min. Review:

https://www.khanacademy.org/science/biology/heredity-and-genetics/v/punnett-square-fun


  • Login