Genetics and Inheritance

1
Genetics and Inheritance
2

• Genetics the scientific study of heredity
• People in the 1770s believed that traits blended
• Most of the leading scientists in the 19th
  century accepted this "blending theory." 

3
Lemarks Idea

• The inheritance of acquired characteristics.
  Until the late nineteenth century, people
  believed that acquired traits were passed down.
• Tattoos, body building, accidents.
• The giraffes long neck is NOT an acquired trait.

4
(No Transcript)
5
(No Transcript)
6
Gregor Mendel

• Studied to be a monk in Austria in mid 19th
  century.
• Influenced by society to become a noble person
  a person of God.
• Mendel loved science, and to pass time he took
  care of the garden. Fell in love with it.
• Began to notice certain similar characteristics.

7
More Mendel

• He observed multiple generations of pea plants,
  and noticed subtle changes and wondered why
  they occurred.
• He collected data for years and began to
  formulate hypotheses.

8
(No Transcript)
9

• Mendel picked common garden pea plants for the
  focus of his research because they
• can be grown easily in large numbers
• reproduction can be manipulated. 
• Pea plants have both male and female reproductive
  organs.  As a result, they can either
  self-pollinate themselves or cross-pollinate with
  another plant. 

10
(No Transcript)
11
(No Transcript)
12

• Mendel observed seven traits that are easily
  recognized and apparently only occur in one of
  two forms
• 1.   flower color is purple or white
• 2.   seed color is yellow or green
• 3.flower position is axil or terminal       
• 4.pod shape is inflated or constricted
• 5.stem length is long or short
• 6.pod color is yellow or green
• 7.seed shape is round or wrinkled

13
Mendels Experiment

• The key to his experiment was that he started
  with pure breed plants.
• Pure breed means that they contain only one type
  of gene YY
• Allele different versions of the same gene.

14

• Mendels Experiment Continued.
• In cross-pollinating he crossed yellow and
  green seeds
• Mendel found that the first offspring generation
  (F1) produced ALL yellow peas.

15
(No Transcript)
16
Results of F2

• After he obtained the F1 offspring, he self
  pollinated a yellow seeded plant with itself.
• The results (F2 generation) had a 31 ratio 3
  yellow and 1 green.

17
(No Transcript)
18

• Mendel continued this practice 28,000 times over
  about 20-30 years with different traits.
• Mendel came up with 2 fundamental laws.

19
Mendels Laws

• Law of Independent Assortment each trait is
  found on separate genes and each gene comes in
  pairs that will separate on their own.
• Law of Segregation - TBTAALD

20
(No Transcript)
21
Mendel's Theory

• Mendel's Theory
• Each individual has two factors (we now call
  these genes) for each trait.
• When both genes are the same, the individual is
  said to be homozygous for that trait. If the two
  genes are different, the individual is
  heterozygous for that trait.
• Alternate types of genes for each trait are
  alleles.
• The actual genetic makeup of an individual is the
  genotype.Phenotype refers to the outward
  expression of the genes.

22

• What Did Mendell gather from his Data
• 2 big Laws
• Mendel's First Law Law of Segregation, says that
  only one allele is passed to a gamete, and
  gametes join randomly when uniting to form
  offspring.

23

• Mendel's Second Law Law of Independent Assortment

24
Analyzing Mendel's Results

• Punnett Squares - an easy way to express the
  probabilies of genotypes

25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29

• A dihybrid cross involves a study of inheritance
  patterns for organisms differing in two traits.
• Mendel invented the dihybrid cross to determine
  if different traits of pea plants, such as flower
  color and seed shape, were inherited
  independently.
• in a dihybrid cross that led Mendel to propose
  that alleles of different genes are assorted
  independently of one another during the formation
  of gametes.

30

• Punnet Square for Dihybrid Cross
• Ssmooth seed
• sdented seed
• Yyellow
• Ygreen

31

• Heterozygous smooth seed plant that is also
  heterozygous yellow seeded plant
• Heterozygous smooth seed plant that is also
  heterozygous yellow seeded plant is mated with

32
(No Transcript)
33
(No Transcript)
34

• Smooth, yellow phenotype

35
(No Transcript)
36

• Smooth, green phenotype

37
(No Transcript)
38

• Dented, yellow phenotype

39
(No Transcript)
40

• Dented, green phenotype

41
(No Transcript)
42
(No Transcript)
43
(No Transcript)