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Chapter 11 DNA and Genes
11.1 DNA: The Heredity Molecule
A. What is DNA? – DNA is the information for life
– the complete instructions for manufacturing all the proteins
for an organism (ex: skin, muscle, bone). DNA stands for
____________________________ _____________
1. The structure of DNA – DNA forms a “double
helix” and looks like a twisted ladder. It is composed of
nucleotides which have 3 parts: a simple sugar
(Deoxyribose), a phosphate group, and a nitrogen base
a. ______________ _______– a carbon ring
structure that contains one or more atoms of
Nitrogen. DNA contains four different bases.
C
G
A
T
2. There are 4 different nitrogen bases that make up DNA. The bases pair together as
follows:
___________ and
_____
3. In 1953, James Watson and Francis Crick proposed
that DNA consists of 4 nucleotides found inside the nucleus in
the form of a ____________________________
B. Replication of DNA
a. ____________________________ ______
– the copying of DNA chromosomes. Occurs in interphase
1. DNA Synthesis (replication)
a. _______________(DNA Polymerase) unzip the DNA strand
b. Free ____________________________ bond w/ open bases
c. New strands of ________ are produced
11.2 From DNA to Protein
A. Genes and Proteins – the sequences of nucleotides in DNA contain information to code
for essential proteins such as enzymes and filaments that compose body tissue. Proteins are strands
of ______________ ____________ coded for by DNA.
B. RNA (ribonucleic acid)– differs from DNA in 3 ways.
a. RNA is ____________________________ ____________________________
b. RNA has the sugar ____________________________
c. RNA uses _________ (uracil) instead of T (thymine). The bases pair together as
follows:
______
and
______
C. Transcription – Protein synthesis begins in the nucleus. DNA unzips due to the enzyme
____________________________ ______and mRNA makes a copy of the DNA code for the
desired protein sequence.
1. ____________________________ – process in the cell nucleus where enzymes
make an RNA copy of a DNA strand
2. ____________________________ ____________________________________
– transports information from DNA in the nucleus to the cell’s cytoplasm.
D. The Genetic Code – the order of nitrogen bases in mRNA determines the type and order
of amino acids in a protein. There are 20 amino acids used to build proteins
1. _____________________– set of 3 nitrogen bases that represents an amino acid
E. Translation: From mRNA to Protein – translation takes place in the ribosome.
Transfer RNA (tRNA) bring amino acids to the ribosomal RNA for protein synthesis.
1. ____________________________ – process of converting information in
mRNA into a sequences of amino acids in a protein
2. ______________________________ ____– RNA that makes up the ribosomes;
3. ____________________________ _______________– RNA that transports
amino acids to the ribosomes to be assembled into proteins
Messenger
RNA
(mRNA)
Genetic
code
11.3 Genetic Changes
A. Mutation: A Change in DNA
a. ________________ _ – any change or random error in a DNA sequence
1. ______________________________________ – changes in the nucleotide
sequence of an organism’s gametes could affect the genotype of the offspring.
2. _______________________________________________– powerful radiation that
affect non-reproductive cells may only hurt the individual and not their offspring.
Ex: UV waves which cause skin cancer
Drugs
In the 1950’s and 1960’s,
thalidomide (a sedative) was
prescribed to pregnant females.
Phocomelia is characterized by
short arms linked to this drug
3. ________________ _ _______________ – DNA mutation that occurs from a
change in a single base pair
Ex: a single letter change may change the entire expression of a protein
THE DOG BIT THE CAT
THE DOG BIT THE CAR
4. ________________ _ _______________ – mutation that occurs when a single
base is added or deleted from DNA; causes a shift in the reading of codons by one base
Ex: Deleting a G would shift all the sequence
THE DOG BIT THE CAT
THE DOB ITT HEC AT
B. Chromosomal Mutations - occurs at the chromosome level resulting in changes in the
gene distribution to gametes during meiosis
a. ________________ _ _______________ – caused when parts of chromosomes
break off or rejoin incorrectly
C. Causes of Mutations – some mutations seem to just happen spontaneously by mistakes in
base pairing during DNA replication. Others includes high-energy radiation, chemicals, or high
temperatures
a. ________________ – any agent that can cause a change in DNA
Chromosomal Mutations