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TAKS Review
DNA, Cell Growth and Genetics
Structure of DNA
• The structure of DNA is
called a double helix, it
looks like a twisted
ladder
• DNA is made of
repeating pieces called
nucleotides
• Nucleotides are made
of a 5-carbon sugar, a
phosphate group, and a
nitrogenous base
Structure of DNA
There are four different nitrogenous bases in DNA.
Only certain bases can bond. They pair to form the
rungs of the ladder.
Adenine bonds to Thymine
Cytosine bonds to Guanine.
sugar
phosphate
sugar
phosphate
sugar
phosphate
sugar
T
A
C
G
¦
¦
¦
¦
A
T
G
C
sugar
phosphate
sugar
phosphate
sugar
phosphate
The sides of the twisted ladder are made of
alternating sugar and phosphates
sugar
...
...
DNA Replication
DNA makes an exact
copy of itself using
old strands as a
template to make new
strands.
Getting information from DNA
DNA CONTAINS THE CODE TO
MAKE PROTEINS
• DNA cannot leave the nucleus
• messenger RNA (mRNA) is a copy of the code that is
used to make proteins on the ribosomes
• If even one nucleotide is missing or changed, the
resulting mutation can alter the protein being produced
 Transcription uses
DNA to make mRNA
in the nucleus; mRNA
leaves nucleus
 Translation uses the
mRNA, tRNA, rRNA
and ribosomes to
create a chain of
amino acids that will
become proteins.
What are some differences between
DNA and RNA?
Practice Question
If the template of a strand of DNA is
5’AGATGCATC 3’ , the complementary strand
will beA. 3’ TCTACGTAG 5’
B. 5’ CTACGTAGA 3’
C. 3’ AGATGCATC 5’
D. 5’ AGACGTCTA 3’
A
Practice Question
In DNA, which of the following determines
the traits of an organism?
A. Amount of adenine
B. Number of sugars
C. Sequence of nitrogen bases
D. Strength of hydrogen bonds
C
Practice Question
Which of the following is a change that could be
passed on to an organism’s offspring?
A
F Damage to the DNA of gamete cells
G Damage to skin cells from exposure to sunlight
H Damage to DNA in the cytoplasm of cheek cells
J Damage to hair pigment cells with permanent dyes
Practice Question
A biologist collects DNA samples from 2 sisters. The
younger sister has blond hair. The older sister has
red hair. The sisters have different traits because
their DNA contains different
A. orders of nucleotides
B. types of sugar molecules
C. sized phosphate groups
D. types of nitrogenous bases
A
Practice Question
“Thymine—guanine—thymine—
cytosine” describes —
F nucleotides within an RNA strand
G a sequence of bases within a DNA section
H points of DNA separation during protein
synthesis
J tRNA codons for specific amino acids
G
Practice Question
What process is occurring
in the figure on the right?
F RNA synthesis
G Protein synthesis
H Transcription
J DNA Replication
J
Practice Question
If one nucleotide is omitted or
accidentally repeated in the
process of DNA replication,
which of the following is
most likely to occur?
F Gene deletion
G Gene mutation
H Gene insertion
J Gene segregation
G
Practice Question
Which of the following must occur before
DNA replication can take place?
A Translation of DNA into amino acids
B Separation of the DNA molecule into codons
C Transformation of DNA into RNA
D Separation of the DNA double helix
D
Practice Question
3' CGGUAU 5'
This is a short section of mRNA. Which
DNA code probably produced this
section of mRNA?
A 3' GCCTUT 5'
B 5' GCCAUT 3'
C 3' ATTGCC 5'
D 5' GCCATA 3'
D
Practice Question
This illustration is an example of a normal DNA
sequence. Which of the following represents
a single base change in the sequence?
D
Cell Growth
• As an organism grows their cells do not get
bigger, they increase in number.
• Mitosis is the formation of two new
daughter cells that are identical to each
other and the original parent cell
• If mitosis is not controlled, cells multiply
too quickly---this forms a tumor.
• Cancer is uncontrolled cell growth
How cells divide
Interphase (longest phase)
Two new cells
IDENTICAL to
the parent cell
Prophase
Cytokinesis
Prometaphase
Metaphase
Telophase
Anaphase
Meiosis
• Type of cell division by which germ
cells (eggs and sperm) are produced.
• Involves a reduction in the amount of
genetic material.
Genetics and Punnett Squares
• Genotypes are the genetic make up of
organisms
Genotype: TT, Tt, or tt
• Phenotypes are the physical characteristics
Phenotype: tall or short
• Homozygous would be TT or tt
• Heterozygous would be Tt
Try this: RrYy x RrYY
RY
RY
RY
These are all the
possible allelic
combinations of
RrYY
rY
rY
Ry
rY
ry
Check this: RrYy x RrYY
Remember capital
letters are dominant,
so lower case letters
are… recessive
RY
Ry
rY
ry
RY
RRYY RRYy RrYY
RrYy
RY
RRYY RRYy RrYY
RrYy
rY
RrYy
RrYy
rrYY
rrYy
rY
RrYY
RrYy
rrYY
rrYy
Practice Question
If a cat has 38 chromosomes in each of its
body cells, how many chromosomes will be
in each daughter cell after mitosis?
A. 11
B. 19
C. 38
D. 76
C
Practice Question
If an organism has the genotype RrSsTtUu,
what proportion of its gametes will be
RSTU?
A. 1/2
B. 1/4
D
C. 1/8
D. 1/16
Practice Question
Two pea plants produce round seeds. Which
of the following should you conclude about
the genetic material in these two plants?
A. They have identical DNA.
B. They have the same parents.
C. They grew from a single seed.
D. They share a gene in common.
D
Practice Question
In guinea pigs, the allele for a rough coat (R) is
dominant to the allele for a smooth coat (r). A
heterozygous guinea pig is mated with a
homozygous recessive guinea pig. Which of the
following lists the genotypes that are likely for the
offspring from this cross?
A. 100% Rr
B
B. 50% Rr and 50% rr
C. 75% Rr and 25% rr
D. 25% RR, 50% Rr, and 25% rr
Practice Question
If a plant that is homozygous tall
and wrinkled is crossed with a
short, wrinkled plant, which
percentage of genotypes would
most likely be found in the firstgeneration offspring?
F 50% TTss, 50% ttSS
G 100% TtSs
H 100% Ttss
J 50% TtSS, 50% ttSS
H
Practice Question
The information in the box identifies some of the
organs of the kitten. Which of the following is
identical for every cell in each of the four
organs?
A Amount of ATP
B Function of cell
C Size of cells
D Genes in DNA
C
Practice Question
A deletion of a DNA base from a gene
affects an organism by —
F causing future gametes to have additional
chromosomes
G changing the sequence of amino acids in a protein
H causing chromosome fragments to form long chains
J changing the structure of ribose sugar in nucleic acids
G