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.
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- 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.
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- 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.
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1858 Charles Darwin Alfred Russel Wallace
???????????????????????? (theory of natural
selection)
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- 1859 Charles Darwin ??????? The Origin of
Species. - 1866 Gregor Mendel ??????????????????????????????
????????? pea plants "factors" - 1900 Carl Correns Hugo de Vries Erich von
Tschermak ????????????????????????? modern
genetics
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- Traits are carried by discrete units, or
genes the results are not appreciated until 1900
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- 1902 Walter Sutton ????????????
??????????????????? - 1905 Nettie Stevens Edmund Wilson Independently
described the behavior of sex chromosomes-XX
determines female XY determines male.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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
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- 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."
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- 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.
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- 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.
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- 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.
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- 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.
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- 1966 Marshall Nirenberg H. Gobind Khorana Led
teams that cracked the genetic code- that triplet
mRNA codons specify each of the twenty amino
acids.
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- 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.
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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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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
28Why pea plant?
- Self-pollination?????????????????????
- Short-life harvest?????????????????????
- Dominant characteristics????????????????????
??????????
???????????????????? ?????????????????????
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30Steps of Mendel's Experiment
- ????????????? 34 ???????????? 2 ?? ?22 ??????
- ??????????????????????????? (pure breeding)
- ?????????? (cross pollination) ???????????????????
????? (monohybrid cr.) - ???????????????? (dihybrid cr.)
- 7 ?????? ????????????? ??? ???-?????, ?????
????-???, ??????????-???????, ??????????-???,
?????????????-?????, ??????-???,
??????????-??????
317 pea characteristics
32Mendel's ObservationsMonohybrid cross
33Monohybrid explanation
34Mendels hypothesisprobability
35Dihybrid hypothesis
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- 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) ??????????? ??????????????????????????
??????????????????????????
39Test cross (?????????????????)
????????????????????????? (phenotype)
?????????????????????? ????????? (homozygous
genotype) ???? ?????? (heterozygote genotype)
40Test cross (?????????????????) ???????
- Pgt Known Homozygote Unknown genotype
- recessive
- ???????????????(F1) ?????????????????????????????
All dominant ?homozygote
F1gt
(?????????)
Dominant Recessive11 ?heterozygote (??????)
F1gt
41Test cross (?????????????????)
42?????????????
- 1. ???????????????????????????????
???????????????????????? ?????????? dependent
assortment ????????????????????????????????? - 2. Flavr Savr tomatoes, genetically engineered
for longer shelf life, were marketed.
??????????????????????????? ??????????????????????
????????????? - ??????????????????