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Introduction to Genetics

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Introduction to Genetics – PowerPoint PPT presentation

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Date added: 6 May 2019
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Title: Introduction to Genetics


1
Introduction to Genetics
2
Learning Targets
  • I can define and provide an example of the
    following genotype, phenotype, dominant allele,
    codominant alleles, incompletely dominant
    alleles, homozygous, heterozygous, and carrier.

3
Genetics Terms
  • Heredity is the passing of traits from parents to
    offspring
  • Traits are inherited characteristics such as eye
    color, height, hair color
  • Fertilization is the uniting of male and female
    gametes
  • Pollination is plant fertilization

4
More Terms
  • Gametes-specialized cells involved in sexual
    reproduction sperm or egg pollen or ovum
  • Gene-sequence of DNA that codes for a protein and
    thus determines a trait
  • Probability-likelihood that a particular event
    will occur

5
More terms
  • Alleles are the various genes for the same trait
  • Dominant traits are those that are always
    expressed when present (brown eyes)
  • Recessive traits are only expressed if the
    dominant trait is absent (blue eyes)

6
More terms
  • Homozygous means possessing a pair of identical
    alleles for a trait can be dominant or
    recessive. Shown by AA or aa
  • Heterozygous means possessing a pair of unlike
    alleles dominant trait is expressed recessive
    trait is carried Aa

7
More Terms
  • Phenotype is the physical appearance of a trait
  • Genotype is the actual genetic makeup XX for
    females XY for males

8
Even more terms
  • True breeders -organisms that produce offspring
    identical to themselves if allowed to
    self-pollinate
  • Hybrids offspring of crosses between parents
    with different traits

9
Learning Targets
  • I can define and provide an example of the
    following genotype, phenotype, dominant allele,
    codominant alleles, incompletely dominant
    alleles, homozygous, heterozygous, and carrier.

10
Gregor Mendel
  • http//science.discovery.com/tv-shows/greatest-dis
    coveries/videos/100-greatest-discoveries-shorts-ge
    netics.htm

11
Gregor Mendel
  • Father of genetics
  • Born 1822 on farm
  • in Austria (now Czech
  • Republic)
  • Entered monastery
  • in 1843

12
Mendel
  • Sent to University of Vienna studied botany and
    other subjects
  • Became chief gardener at the monastery
  • Monks helped feed not only themselves but their
    community

13
Mendel
  • Mendel sought to increase production and yield of
    their crops
  • Mendel started breeding peas in 1857 to study
    inheritance
  • His study took 10 years to complete
  • His methods are still used today because he kept
    meticulous records

14
Why Peas?
  • Many varieties have two clearly different traits
  • Flower color
  • Seed color
  • Seed shape
  • Plants are easy to control
  • Male and female parts on same flower (dioecious)
  • Pollen is male ovule is female

15
Learning Targets
  • I can describe the basic mechanisms of plant
    processes, especially movement of materials and
    plant reproduction.
  • I can explain the functions of unique plant
    structures.

16
(No Transcript)
17
Flowers
  • http//www.youtube.com/watch?vOpzvKdmAoI0

18
Parts of a Flower
  • Sepals-outermost circle
  • of floral parts usually green
  • and look like leaves
  • Petals-often brightly colored
  • found just inside the sepals
  • Leaf-photosynthetic organ
  • that contains on or more
  • Bundles of vascular tissue

19
Parts of a Flower Terms
  • Stamen-male part of the
  • flower made of filament
  • and anther
  • Filament-a long thin structure
  • that supports the anther
  • Anther-flower structure in
  • which haploid male gametes
  • are produced

20
Parts of a Flower Terms
  • Pistils (Carpels)-innermost
  • part of a flower that produces
  • the female gametes
  • Stigma- sticky portion at the
  • top of the style where pollen
  • grains land
  • Style-narrow stalk of the
  • carpel in a flower
  • Ovary-a flower structure that
  • contains one or more ovules
  • from which the female
  • gametes are made
  • Ovule-female gamete

21
Vascular Tissue in Plants
  • Xylem-vascular tissue that carries water from the
    roots to the rest of the plant
  • Phloem-vascular tissue that transports nutrients
    and carbohydrates made by photosynthesis
  • Vascular Bundles-a plant stem structure that
    contains xylem and phloem tissue

22
Plant Life Cycle
23
Plant Fertilization
  • http//www.youtube.com/watch?vLdlxUJhoyx4

24
Plant Fertilization
25
Learning Targets
  • I can describe the basic mechanisms of plant
    processes, especially movement of materials and
    plant reproduction.
  • I can explain the functions of unique plant
    structures.

26
Learning Targets
  • I can identify and explain Mendels laws of
    segregation and independent assortment
  • I can construct and interpret Punnett squares
    (calculating and predicting phenotypic and
    genotypic ratios of offspring)

27
Mendels Procedure
  1. Remove immature stamen from plant
  2. Took brush and removed pollen from one plant
  3. Then brushed pollen onto ova of another plant
  4. Allowed plant to seed and then planted the seeds

28
Mendels Peas
  • Studied over 30,000 plants in 10 years
  • Usually followed his plants for 3 generations
  • Studied flower color, seed color, seed shape,
    height
  • Always started with true breeders
  • Covered plants to keep pollinators away

29
Mendels Peas
  • Began by crossing tall short plants
  • Expected an intermediate height plant
  • Instead all plants were tall
  • Let these plants self pollinate and got 31 ratio
  • Three tall plants to every short plant
  • He decided that each trait had at least two
    factors for each trait called these alleles

30
Probability and Punnett Squares
  • The principles of probability can be used to
    predict the outcomes of genetic crosses.
  • Flipping a coin
  • 50/50 chance of getting a head every time

31
Punnett Squares
  • A diagram used to predict genetic probabilities
  • Can compare genetic variations that will result
    from a specific cross

32
Monohybrid Crosses
  • A monohybrid cross occurs between two parents
    that breed true for different versions of a
    single trait
  • Allows tracking of one trait only

33
Monohybrid Cross
P Generation T T
Tt Tt
Tt Tt
t t
All were tall
34
Monohybrid Cross
F1 Cross T t
TT Tt
Tt tt
T t
Phenotype 31 Genotype 121
35
Rule of Dominance
  • To be dominant, an organism must possess either
    two dominant alleles or at least one dominant
    allele
  • To be recessive, the organism must receive two
    recessive alleles one from each parent

36
Principle of Segregation
  • Pairs of alleles separate during gamete formation
    in meiosis.
  • The fusion of gametes pairs the alleles again at
    fertilization

37
Principle of Independent Assortment
  • Each pair of alleles separates independently of
    each other during gamete formation

38
Incomplete Dominance
R R
Snap Dragons Red crossed with White Expected
31 ratio Red to White
Rr Rr
Rr Rr
r r
Got all PINK!
39
Codominance
  • The expression of two different alleles in a
    heterozygote
  • Many genes have different alleles but usually
    only two or less are expressed in the individual
  • Blood is expressed in different alleles A, B, AB
    or O
  • A and B are dominant O recessive
  • AB is codominant

40
Dihybrid Crosses
  • A cross where two traits are examined
  • Predicts two different traits
  • Parents will have four possible gametes
    displaying the various combinations of the two
    traits
  • Mendel used seed shape and seed color for one of
    his dihybrid crosses

41
Dihybrid Cross
  • RRYY x rryy
  • R round
  • Y Yellow
  • r wrinkled
  • ygreen

42
Dihybrid Parent Cross
RY RY RY RY
ry RrYy RrYy RrYy RrYy
ry RrYy RrYy RrYy RrYy
ry RrYy RrYy RrYy RrYy
ry RrYy RrYy RrYy RrYy
43
Dihybrid Cross
  • Crossing pure breeding homozygous dominant with
    pure breeding homozygous recessive
  • RRYY X rryy
  • All offspring are heterozygous for the trait
  • RrYy

44
Dihybrid F1 Cross
RY rY Ry ry
RY RRYY RrYY RRYy RrYy
rY RrYY rrYY RrYy rrYy
Ry RRYy RrYy Rryy Rryy
ry RrYy rrYy Rryy rryy
45
F1 Generation Dihybrid Cross
  • Allowing F1 to cross pollinate results in a
    9331 ratio
  • 9 will be round, yellow
  • 3 will be round, green
  • 3 will be wrinkled, yellow
  • 1 will be wrinkled, green

46
Learning Targets
  • I can identify and explain Mendels laws of
    segregation and independent assortment
  • I can construct and interpret Punnett squares
    (calculating and predicting phenotypic and
    genotypic ratios of offspring)
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