slide1
Download
Skip this Video
Download Presentation
Mendelian Genetics

Loading in 2 Seconds...

play fullscreen
1 / 51

Mendelian Genetics - PowerPoint PPT Presentation


  • 223 Views
  • Uploaded on

Mendelian Genetics. Vocabulary. dominant gene: F 1 generation: F 2 generation: gene: genetic trait: genotype: monohybrid cross:. Hybrid: phenotype: principle of independent assortment: principle of segregation: Punnett square: Recessive gene:. Study Questions.

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 'Mendelian Genetics' - mike_john


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
vocabulary
Vocabulary
  • dominant gene:
  • F1 generation:
  • F2 generation:
  • gene:
  • genetic trait:
  • genotype:
  • monohybrid cross:

KMarsh

slide3
Hybrid:
  • phenotype:
  • principle of independent assortment:
  • principle of segregation:
  • Punnett square:
  • Recessive gene:

KMarsh

study questions
Study Questions
  • 1. List and explain the four principles of genetics established by Mendel.
  • 2. Complete a monohybrid cross between a pure breeding tall plant (TT) and a pure breeding dwarf plant (tt). Carry the cross through to the second generation (F2 generation) by letting the plants of the first cross (Tt) self-fertilize. Describe the phenotypes and genotypes of both generations.

KMarsh

slide5
3. Show how your knowledge of meiosis provides tangible evidence concerning Mendel’s Principles of Segregation and Independent Assortment.
  • 4. Complete a monohybrid cross between (Tt X tt). List all the potential types of gametes produced by each parent and then combine them into all possible combinations in the offspring. List the various phenotypes and ratios from this cross.
  • 5. List and discuss several of the approaches which made Mendel’s work successful.

KMarsh

slide7
Mendel’s Work with Pea Plants
  • First Steps to Genetics

KMarsh

mendel s studies of the pea plant
Mendel’s Studies of the Pea Plant
  • A. Characteristics studied by Mendel (7 traits)

KMarsh

dominant vs recessive
Dominant vs Recessive
  • 1.Form of ripe seed 2.Color of seed coat

Smooth Yellow

Wrinkled Green

  • 3.Flower Color 4.Form of ripe pods
  • Purple Inflated
  • White Constricted
  • 5.Color of unripe pods 6.Position of flowers
  • Green Axial
  • Yellow Terminal
  • 7.Length of stem Tall & Dwarf

KMarsh

why pea plants
Why Pea Plants?
  • 1- Many true breeding varieties available
  • 2- The flower is self-fertile
  • 3- Generation time is very short

KMarsh

mendel sproblems
Mendel’sProblems
  • 1- No concept of DNA or chromosomes
  • 2- No concept of meiosis

KMarsh

some wise educated guesses decisions made by mendel
Some wise (educated guesses) decisions made by Mendel
  • 1- Selection of well-defined, contrasting traits
  • 2- Extensive groundwork completed prior to establishment of final experimental design
  • 3- Extensive replication of crosses

KMarsh

mendel s test evaluating the inheritance of seed shape in pea plants
Mendel’s Test Evaluating the Inheritance of Seed Shape in Pea Plants
  • Recognized two different traits for the seed shape character in pea plants: round versus wrinkled seeds.

KMarsh

testing continued
Established true-breeding varieties for each of these traits.

RR and rr

Offspring (F1 generation) are called “hybrids”.

Rr

Testing continued

KMarsh

the next step
Crossed these F1 generation hybrids among each other (individual crosses being selected at random).

Rr X Rr

Results for their offspring (F2 generation):

5474 (74.7%) were plants that produced round seeds.1850 (25.3%) were plants that produced wrinkled seeds.Ratio of round:wrinkled = approx. 3:1

The Next Step

KMarsh

the explaination
The Explaination
  • For every character (e.g., seed shape) an individual possess two instruction sets (alleles).
  • One of these alleles was originally derived from the individual’s mother, the other allele being originally derived from the individual’s father.

KMarsh

true vs hybrid
In true-breeding individuals, both alleles are the same.

Homozygous

RR or rr

Hybrids, on the other hand, one of each kind of allele.

Heterozygous

Rr

True vs Hybrid

KMarsh

mendel s further explanation
Mendel’s Further Explanation
  • Mendel believed that only two alleles were possible for a given genetic character, and that one of the alleles (the dominant one) masked the expression of the other (the recessive one) in the hybrid.
  • When the hybrid formed gametes, only one of the two possible alleles would end up in a gamete.

KMarsh

law of segregation
When the hybrid formed gametes, only one of the two possible alleles would end up in a gamete.

However, both alleles possessed an equal chance of appearing in a gamete.

Law of Segregation

KMarsh

law of segregation con t
Law of Segregation con’t
  • In the formation of gametes, two members of a gene pair (alleles) segregate into different haploid gametes with equal probability.

KMarsh

dominant and recessive
Dominant and Recessive
  • Defining alleles:
  • R = the round allele (dominant).
  • r = the wrinkled allele (recessive).

KMarsh

phenotype genotype
Phenotype & Genotype
  • Defining genotypes and their respective phenotypes:
  • RR genotype (homozygous dominant) = round phenotype.
  • rr genotype (homozygous recessive) = wrinkled phenotype.
  • Rr genotype (heterozygous) = round phenotype

KMarsh

slide29
Round Round

RR

Rr

rr

KMarsh

p generation and f 1 generation
P Generation and F1 Generation

Parental (P) Cross

  • Round X Wrinkled

RR rr

  • Gametes:

R r

F1 (first felial) Generation Hybrids

100% Round phenotype

100% Rr genotype

KMarsh

f 1 and f 2 generations
F1 and F2 Generations
  • Mendel’s Explanation for his Results
  • F1 Generation Cross Round X Round Rr RrGametes: R r R rF2 Generation OutcomeRound WrinkledRR Rr Rr rrNote: 3:1 ratio of round:wrinkled

KMarsh

test crosses

Test Crosses

When you cross an individual whose genetics you are not sure about with an individual who is homozygous recessive for the trait(s) in question.

test crosses37
Test Crosses
  • F1 Hybrids (Rr) xF2 Recessives (rr)

KMarsh

mendel s law of independent assortment
Mendel’s Law of Independent Assortment
  • Whenever two or more pairs of contrasting characters are brought together in a hybrid, the alleles of the different pairs segregate independently of one another during gamete formation.

KMarsh

dihybrid crosses
Dihybrid Crosses
  • Define Alleles and Associated Traits:Seed Shape CharacterR = round seed trait (dominant)r = wrinkle seed trait (recessive)Seed Color CharacterY = yellow seed trait (dominant)y = green seed trait (recessive

KMarsh

first cross dihybrid
First Cross (Dihybrid)
  • Parental (P) cross: crossed true-breeding plants that produce round-yellow (RRYY) seeds with true-breeding plants that produce wrinkled-green seeds (rryy).
  • F1 Genereation: hybrids for both characters (Rr & Yy; or RrYy) were100% round-yellow.

KMarsh

results
Results
  • F1 Generation Individuals (RrYy) crossed among each other.F2 Generation Results:315 (56.7%) round-yellow108 (19.4%) round-green101 (18.2%) wrinkled-yellow32 (5.8%) wrinkled-green

KMarsh

calculating expected frequencies round yellow
Calculating Expected FrequenciesRound-Yellow
  • Expect 9/16 of the F2 generation offspring to be round-yellow.Therefore, of a total of 556 offspring the expected number (frequency) of round-yellow offspring may be calculated as follows:Frequency = (9/16)*556 = 312.75

KMarsh

slide46
Calculating Expected Frequencies

Round-Green

  • Expect 3/16 of the F2 generation offspring to be round-green.Therefore, of a total of 556 offspring the expected number (frequency) of round-yellow offspring may be calculated as follows:Frequency = (3/16)*556 = 104.25

KMarsh

calculating expected frequencies wrinkled yellow
Calculating Expected FrequenciesWrinkled- Yellow
  • Expect 3/16 of the F2 generation offspring to be wrinkled-yellow.Therefore, of a total of 556 offspring the expected number (frequency) of round-yellow offspring may be calculated as follows:Frequency = (3/16)*556 = 104.25

KMarsh

calculating expected frequencies wrinkled green
Calculating Expected FrequenciesWrinkled- Green
  • Expect 1/16 of the F2 generation offspring to be wrinkled-yellow.Therefore, of a total of 556 offspring the expected number (frequency) of round-yellow offspring may be calculated as follows:Frequency = (1/16)*556 = 34.75

KMarsh

comparing observed to expected results
ObservedRound-Yellow315Round-Green108Wrinkled-Yellow101Wrinkled-Green32

Expected

Round- Yellow312.75Round-Green104.25Wrinkled-Yellow104.25Wrinkled-Green34.75

Comparing Observed to Expected Results

KMarsh

results of mendel s work
Results of Mendel’s Work
  • A. The principle of unit characters (elementum or genes)
  • B. The phenomenon of dominant and recessive genes
  • C.The principle of segregation: alleles separate from one another during
  • D. The principle of independent assortment

KMarsh

ad