NAME ____________________________
Period___________
Modern Genetics Outline
Chemical Basis for Genetics
 In the 1940’s and 1950’s experiments showed that ______ are made up of
the chemical compound ______, or ________________________.
 ______ is a large complex molecule found in the __________ of the cell.
 ______ is responsible for passing __________ information from
generation to generation.
 ______ also controls the manufacture of _____________.
 __________ control cellular _________.
Nucleotides
 The ______ molecule is made up of a long chain of repeating
____________ units.
 Nucleotides contain __________ bases, a ______, and a ________ group.
 The four different bases in DNA nucleotides are




Nitrogenous Bases of DNA
DNA Structure
 The structure of _______ was discovered in the 1950’s
by James _______ and Francis Crick.
 According to ________ and _______, _____ molecules
are shaped like a twisted _______.
 The twisted ladder structure is called a ____________.
 The _____ double helix has _____ strands
or sides.
 The strands are connected at the rungs.
 The sides of the ladder consist of alternating
_______ and ___________ molecules.
 The rungs are pairs of ____________ bases.
 The nitrogen bases are attached to each
other by _____ _____________ bonds.
 The four nitrogenous bases in DNA ______
(join) together in a certain way known as
_________ pairing.
 __________ (A) and _________ (T) bond together.
 __________ (G) and _________ (C) bond together.
 No other combinations are __________.
DNA Replication
 During reproduction, _____ makes exact
_______ of itself (__________).
 The process begins with an ___________
of the _______ helix.
 The two strands “_______” leaving two
strands of ___________.
 Each strand is a _________ for the new
nucleotide strand.
 Free nucleotides present in the cytoplasm
pair with the free nitrogenous bases of
both strands.
 Two identical _____ molecules that are
identical to the original are __________.
RNA - Ribonucleic Acid
 RNA also controls cellular ___________.
 RNA contains the sugar “_______.”
 RNA is _________ stranded.
 RNA also has ___ nitrogen bases:



 ___________ instead of Thymine.
 RNA has different functions than DNA:
 ____________ RNA - mRNA – is a single, uncoiled strand that
carries the genetic code information of DNA from the _________ to
the _______________ in the _____________.
 ____________ RNA - tRNA – is a single folded strand that ______
the message for protein formation carried by mRNA. tRNA then
transfers amino acids to form amino acids.
 ____________RNA - rRNA – is a form of RNA that makes up most
of the _______________ in a cell.
Mutations
 A mutation is any _________ or _________ in the ________ or
____________ of an organism that can be inherited.
 These changes usually produce _______ characteristics.
 To be _________, these changes must occur in the ______ or ____ cell.
 As a result of ___________, the changed gene or chromosome in the sex
cell is _________ on to the new organism.
 If they occur in other cells, they can be passed on only to other ____ cells.
 Mutations occur as ______ chance events and may occur _______ within
the cell or be caused by forces outside the cell called ________________.
 X rays, ultraviolet light, radioactive substances, cosmic rays, and
chemicals such as formaldehyde and benzene, are ________ agents.
 Asbestos fibers and drugs, such as LSD, marijuana, cigarettes and
alcohol, are also known to cause changes in ____ and ___________.
 Unborn children can be injured when their pregnant mothers are exposed
to ____________ agents.
Human Genetic Diseases
 Most genetic diseases in humans are __________ as __________ genes
and involve __________ in enzyme formation.
 When there is a mistake in __________ formation, the person’s
metabolism is ___________.
 The presence of many genetic disorders can be detected either before or
after birth.
 ____________ (chemical analysis of body ________),
 ____________ (detecting chromosome abnormalities by matching
homologous chromosomes) and
 ____________ (removing a small amount of amniotic fluid from
around the fetus) are tests used to detect (identify) genetic diseases.
Genetic Engineering
 Today, scientist can deliberately remove _________ from one organism
and add them to the _________ material of another organism.
 Genetic Engineering will ______ (change) the _____ of a cell.
 The changed _______ is called _____________.
 The _____ that received the recombinant _____ receives new ______,
such as, the ability to prevent a certain disease.
How to Clone a Sheep
Modern Genetics Outline - Teacher Guide (Key)
© Lisa Michalek
Chemical Basis for Genetics
 In the 1940’s and 1950’s experiments showed that genes are made up of the chemical compound
DNA, or deoxyribonucleic acid.
 DNA is a large complex molecule found in the nucleus of the cell.
 DNA is responsible for passing genetic information from generation to generation.
 DNA also controls the manufacture of enzymes.
o Enzymes control cellular activity.
Nucleotides
 The DNA molecule is made up of a long chain of repeating nucleotide units.
 Nucleotides contain nitrogenous bases, a sugar, and a phosphate group.
 The four different bases in DNA nucleotides are
o Adenine
o Guanine
o Cytosine
o Thymine
DNA Structure
 The structure of DNA was discovered in the 1950’s by James Watson and Francis Crick.
 According to Watson and Crick, DNA molecules are shaped like a twisted ladder.
 The twisted ladder structure is called a double helix.
 The DNA double helix has two strands or sides.
 The strands are connected at the rungs.
 The sides of the ladder consist of alternating sugar and phosphate molecules.
 The rungs are pairs of nitrogenous bases.
o The nitrogen bases are attached to each other by weak hydrogen bonds.
 The four nitrogenous bases in DNA bond (join) together in a certain way known as base pairing.
 Adenine (A) and Thymine (T) bond together.
 Guanine (G) and Cytosine (C) bond together.
 No other combinations are possible.
DNA Replication
 During reproduction, DNA makes exact copies of itself (replicates).
 The process begins with an untwisting of the DNA helix.
 The two strands “unzip” leaving two strands of nucleotides.
 Each strand is a pattern for the new nucleotide strand.
 Free nucleotides present in the cytoplasm pair with the free nitrogenous bases of both strands.
 Two identical DNA molecules that are identical to the original are produced.
RNA - Ribonucleic Acid
 RNA also controls cellular activities.
 RNA contains the sugar “ribose.”
 RNA is single stranded.
 RNA also has 4 nitrogen bases:

o Adenine
o Guanine
o Cytosine
o Uracil instead of Thymine.
RNA has different functions than DNA:
o Messenger RNA - mRNA – is a single, uncoiled strand that carries the genetic code
information of DNA from the nucleus to the ribosomes in the cytoplasm.
o Transfer RNA - tRNA – is a single folded strand that reads the message for protein
formation carried by mRNA. tRNA then transfers amino acids to form amino acids.
o Ribosomal RNA - rRNA – is a form of RNA that makes up most of the ribosomes in a cell.
Mutations
 A mutation is any change or mistake in the genes or chromosomes of an organism that can be
inherited.
 These changes usually produce new characteristics.
 To be inherited, these changes must occur in the gamete or sex cell.
 As a result of fertilization, the changed gene or chromosome in the sex cell is passed on to the new
organism.
 If they occur in other cells, they can be passed on only to other body cells.
 Mutations occur as random chance events and may occur naturally within the cell or be caused by
forces outside the cell called mutagenic agents.
o X rays, ultraviolet light, radioactive substances, cosmic rays, and chemicals such as
formaldehyde and benzene, are mutagenic agents.
o Asbestos fibers and drugs, such as LSD, marijuana, cigarettes and alcohol, are also known
to cause changes in genes and chromosomes.
 Unborn children can be injured when their pregnant mothers are exposed to mutagenic agents.
Human Genetic Diseases
 Most genetic diseases in humans are inherited as recessive genes and involve mistakes in enzyme
formation.
 When there is a mistake in enzyme formation, the person’s metabolism is incorrect.
 The presence of many genetic disorders can be detected either before or after birth.
o Screening (chemical analysis of body fluids)
o karyotyping (detecting chromosome abnormalities by matching homologous
chromosomes)
o amniocentesis (removing a small amount of amniotic fluid from around the fetus) are tests
used to detect (identify) genetic diseases
Genetic Engineering
 Today, scientist can deliberately remove genes from one organism and add them to the genetic
material of another organism.
 Genetic Engineering will alter (change) the DNA of a cell.
 The changed DNA is called recombinant DNA.
 The cell that received the recombinant DNA receives new traits, such as, ability to prevent a
certain disease.