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Genetics is a very young branch of biology' It started with Mendel's experiments'

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311243 Principles of Genetics/??.??.????? ? ??? ??????????????? ?????????????? ... for the first mutation discovered in the fruit fly, Drosophila, white eye. ... – PowerPoint PPT presentation

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Title: Genetics is a very young branch of biology' It started with Mendel's experiments'


1
?????????????????? History of Genetics Timeline
  • Genetics is a very young branch of biology. It
    started with Mendel's experiments.

2
??????????????????
  • In genetics special attention is focused on the
    cell nucleus.  The cell nucleus is the control
    center of the cell.  It contains the cell's
    genetic information and controls the cell's
    actions. Many experiments have been done
    affecting the cell nucleus.

3
??????????????????
  • Importance of Cell Nucleus
  • More complex cells called eukaryotes made
    their earthly debut.  Everything alive on Earth,
    except prokaryotes, is made up of one or more
    eukaryotic cells - plants, animals and even you.

4
(No Transcript)
5
??????????????????
1858 Charles Darwin Alfred Russel Wallace
???????????????????????? (theory of natural
selection)
6
??????????????????
  • 1859 Charles Darwin ??????? The Origin of
    Species.
  • 1866 Gregor Mendel ??????????????????????????????
    ????????? pea plants "factors"
  • 1900 Carl Correns Hugo de Vries Erich von
    Tschermak ????????????????????????? modern
    genetics

7
??????????????????
  • Traits are carried by discrete units, or
    genes the results are not appreciated until 1900 

8
??????????????????
  • 1902 Walter Sutton ????????????
    ???????????????????
  • 1905 Nettie Stevens Edmund Wilson Independently
    described the behavior of sex chromosomes-XX
    determines female XY determines male.

9
??????????????????
  • 1908 Archibald Garrod Proposed that some human
    diseases are due to "inborn errors of metabolism"
    that result from the lack of a specific enzyme.
  • 1909 - William Louis Johannsen.
  • The introduction of basic genetic theories
    gene, genotype, phenotype.

10
??????????????????
  • 1910 Thomas Hunt Morgan Proposed a theory of
    sex-linked inheritance for the first mutation
    discovered in the fruit fly, Drosophila, white
    eye. This was followed by the gene theory,
    including the principle of linkage.

11
??????????????????
  • 1927 Hermann J. Muller Used x-rays to cause
    artificial gene mutations in Drosophila.
  • 1928 Fred Griffith Proposed that some unknown
    "principle" had transformed the harmless R strain
    of Diplococcus to the virulent S strain.

12
??????????????????
  • 1931 Harriet B. Creighton Barbara McClintock
    Demonstrated the cytological proof for
    crossing-over in maize.
  • late 1940 Barbara McClintock Developed the
    hypothesis of transposable elements to explain
    color variations in corn.

13
??????????????????
  • 1980 McClintock discovered transposable strands
    of genes in maize already in the 1940s, but her
    work was not fully recognized for a generation.
    ?The genome may be controlling aspects of its own
    mutation

14
??????????????????
  • In her 1983 Nobel lecture, McClintock said the
    genome is "a highly sensitive organ of the cell,
    that in times of stress could initiate its own
    restructuring and renovation."

15
??????????????????
  • 1941 George Beadle Edward Tatum Irradiated the
    red bread mold, Neurospora, and proved that the
    gene produces its effect by regulating particular
    enzymes.
  • 1944 Oswald Avery Colin MacLeod Maclyn McCarty
    Reported that they had purified the transforming
    principle in Griffith's experiment and that it
    was DNA.

16
??????????????????
  • 1950 Erwin Chargaff Discovered a one-to-one
    ratio of adenine to thymine and guanine to
    cytosine in DNA samples from a variety of
    organisms.
  • 1951 Rosalind Franklin Obtained sharp X-ray
    diffraction photographs of DNA.

17
??????????????????
  • 1953 Francis Crick James Watson Solved the
    three-dimensional structure of the DNA molecule.
  • 1958 Arthur Kornberg Purified DNA polymerase I
    from E. coli, the first enzyme that made DNA in a
    test tube.

18
??????????????????
  • 1953 Watson and Crick deoxyribonucleic acid
    (DNA) is a double-strand helix of nucleotides.
    Each nucleotide consists of a deoxyribose sugar
    molecule to which is attached a phosphate group
    and one of four nitrogenous bases two purines
    (adenine and guanine) and two pyrimidines
    (cytosine and thymine). The nucleotides are
    joined together by covalent bonds between the
    phosphate of one nucleotide and the sugar of the
    next, forming a phosphate-sugar backbone from
    which the nitrogenous bases protrude. The two
    strands are linked by selective hydrogen bonds
    the purine adenine bonds only with the pyrimidine
    thymine, and the purine cytosine only with the
    pyrimidine guanine.

19
??????????????????
  • 1966 Marshall Nirenberg H. Gobind Khorana Led
    teams that cracked the genetic code- that triplet
    mRNA codons specify each of the twenty amino
    acids.

20
??????????????????
  • DNA replication is possible through the
    complementary nature of the two strands. The
    chemical complexity of the molecule is thought to
    be sufficient to store the requisite information.
    What is firmly demonstrated is that so-called
    structural genes manufacture the proteins for
    living tissues.

21
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  • 1983 James Gusella Used blood samples collected
    by Nancy Wexler and her co-workers to demonstrate
    that the Huntington's disease gene is on
    chromosome 4.

22
??????????????????
  • 1985 Kary B. Mullis Published a paper describing
    the polymerase chain reaction (PCR), the most
    sensitive assay for DNA yet devised.
  • 1988  The Human Genome Project began with the
    goal of determining the entire sequence of DNA
    composing human chromosomes.

23
??????????????????
  • 1989 Alec Jeffreys Coined the term DNA
    fingerprinting and was the first to use DNA
    polymorphisms in paternity, immigration, and
    murder cases.
  • 1989 Francis Collins Lap-Chee Tsui Identified
    (CFTR) gene on chromosome 7 that, when mutant,
    causes cystic fibrosis.

24
??????????????????
  • 1990  First gene replacement therapy-T cells of
    a four-year old girl were exposed outside of her
    body to retroviruses containing an RNA copy of a
    normal ADA gene. gtimmune system functioning.
  • 1993  Flavr Savr tomatoes, genetically
    engineered for longer shelf life, were marketed.

25
??????????????????
  • 2000 The Human Genome Project presents its
    preliminary results each of the body's 100
    trillion cells contains some 3.1 billion
    nucleotide units. Only 1 of these are thought to
    be transcriptional, clustered in possibly as few
    as 30,000 genes.
  • An accurate chemical map of the genome tells us
    surprisingly little about how it functions.
    Targeted experimentation is now possible.

26
??????????????????
  • Gregor Johan Mendel is considered as the creator
    of genetics. He discovered the basic laws of
    heredity. He hypothesized the existence of
    factors that determinate the inheritance of
    traits.

27
  • Gregor Mendel (1822-84) was an Austrian monk. His
    experiments are the basis for inheritance.  In
    his experiments he used garden pea plants (Piscum
    Sativum).

1. Why Pea Plants?
2. Steps of Mendel's Experiment 3. Mendel's
Observations
28
Why pea plant?
  • Self-pollination?????????????????????
  • Short-life harvest?????????????????????
  • Dominant characteristics????????????????????
    ??????????

???????????????????? ?????????????????????
29
??????????????????
30
Steps of Mendel's Experiment
  • ????????????? 34 ???????????? 2 ?? ?22 ??????
  • ??????????????????????????? (pure breeding)
  • ?????????? (cross pollination) ???????????????????
    ????? (monohybrid cr.)
  • ???????????????? (dihybrid cr.)
  • 7 ?????? ????????????? ??? ???-?????, ?????
    ????-???, ??????????-???????, ??????????-???,
    ?????????????-?????, ??????-???,
    ??????????-??????

31
7 pea characteristics
32
Mendel's ObservationsMonohybrid cross
33
Monohybrid explanation
34
Mendels hypothesisprobability
35
Dihybrid hypothesis
36
??????????????????
  • Mendel's Conclusions are Known as Mendel's Laws
  • 1    Mendel's first law of genetics -  the law
    of segregation
  • 2    Mendel's second law of genetics - the law
    of independent assortment

37
Mendels first law
  • ????????????????? (law of segregation)
  • ???????????????????????????????????????????
    ????????????? (2 alleles) ????????????????????????
    ???????????????????

??????????????????????????? 1 ?????? (monohybrid
cross)
38
Mendels second law
  • ??????????????????????????? (law of independent
    assortment)

?????????????????????????????????????????????????
(2 alleles) ??????????? ??????????????????????????
??????????????????????????
39
Test cross (?????????????????)
????????????????????????? (phenotype)
?????????????????????? ????????? (homozygous
genotype) ???? ?????? (heterozygote genotype)
40
Test cross (?????????????????) ???????
  • Pgt Known Homozygote Unknown genotype
  • recessive
  • ???????????????(F1) ?????????????????????????????

All dominant ?homozygote
F1gt
(?????????)
Dominant Recessive11 ?heterozygote (??????)
F1gt
41
Test cross (?????????????????)
42
?????????????
  • 1. ???????????????????????????????
    ???????????????????????? ?????????? dependent
    assortment ?????????????????????????????????
  • 2. Flavr Savr tomatoes, genetically engineered
    for longer shelf life, were marketed.
    ??????????????????????????? ??????????????????????
    ?????????????
  • ??????????????????
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