1. DNA, Cell Growth and Genetics
TAKS Review
DNA, Cell Growth and Genetics

2. 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

3. Adenine bonds to Thymine
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.
The sides of the twisted ladder are made of alternating sugar and phosphates
sugar
phosphate
... T A C G

4. DNA Replication
DNA makes an exact copy of itself using old strands as a template to make new strands.

5. 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
Emphasis: DNA contains the code to make the proteins; like the blueprint for your body
Emphasis: Mutations are CHANGE in genetic material (can be good, bad, or neutral)

6. 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.
Have S copy process map on top
Point out that transcription takes place in nucleus because DNA is involved and DNA can’t leave nucleus
Translation takes place in cytoplasm on ribosome

7. What are some differences between DNA and RNA?
Press play; ask S to make T-chart to remember differences between RNA and DNA;
Press next when blinking or after students have shared some differences; add name of sugar to chart
Press next; add different base to chart
Press next; add number of strands to chart

8. Practice Question A If the template of a strand of DNA is
5’AGATGCATC 3’ , the complementary strand
will be-
A. 3’ TCTACGTAG 5’
B. 5’ CTACGTAGA 3’
C. 3’ AGATGCATC 5’
D. 5’ AGACGTCTA 3’ A
Remind students of bonding pairs: A=T and G=C

9. 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
Remind students the structure of everyone’s DNA is the same is the order of the As, Ts, Gs, and Cs.

10. Practice Question
Which of the following is a change that could be passed on to an organism’s offspring?
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 A
Remind students that the only information that a new organism starts with is the DNA found in the parents’ gametes or sex cells.
Vocabulary review: gamete is sex cell

11. 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

12. Practice Question G “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
Have students use T-chart for DNA and RNA to assist with this question G

13. Practice Question
What process is occurring in the figure on the right?
F RNA synthesis
G Protein synthesis
H Transcription
J DNA Replication J

14. 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

15. 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

16. 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
Remind S of:
Differences between DNA and RNA
Base pairing A-T and C-G

17. 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

18. 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

19. How cells divide Interphase (longest phase)
Two new cells IDENTICAL to the parent cell
Prophase
Cytokinesis
Prometaphase
Students do NOT need to rememorize each stage for TAKS, but briefly summarize the process with them.
Interphase: DNA replicates and cell grows
Prophase: DNA condenses into chromosomes and pairs up with copy
Metaphase: Chromosomes line up in middle
Anaphase: They split
Telophase/Cytokinesis: nucleus forms, cytoplasm splits and cell membrane pinches
Product is two new identical cells
Metaphase
Telophase
Anaphase

20. Meiosis
Type of cell division by which germ cells (eggs and sperm) are produced.
Involves a reduction in the amount of genetic material.
Quick Vocabulary Review
Eggs and sperm are called sex cells, germ cells or gametes

21. Have S make T-chart
Mitosis: Meiosis:
2 cells 4 cells
Identical to original Half as many chromosomes
DNA replicates once DNA replicates once
Cells divide once Cells divide twice

22. 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
Remind S of roots homo- means same and hetero- means different

23. Try this: RrYy x RrYY RY Ry rY ryRY Ry rY ry
These are all the possible allelic combinations of RrYY
Remind students how to fill in the square.
If they remember, save time and flip to next slide

24. Check this: RrYy x RrYY RY Ry rY ry RRYY RRYy RrYY RrYy RRYY RrYy rrYY
Remember capital letters are dominant, so lower case letters are… RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
 RRYY
 RrYy
rrYY
rrYy
recessive
Review dominant and recessive and how to write each

25. 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
Mitosis creates two new daughter cells that are identical to the original. So if the original started off with 38 then the new cells must as well.

26. Practice Question
If an organism has the genotype RrSsTtUu, what proportion of its gametes will be RSTU?
1/2
1/4
1/8
1/16 D
Remember ½ of chromosomes of parent are in gametes. Each copy of gene has equal chance of being there so for Rr, R and r each have a 50% (1/2) shot of being in a gamete.
All genes are assumed independent of one another so ½ * ½ * ½ * ½ = 1/16

27. 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
Can’t be A because we don’t know about all the other traits.
B could be true, but based on the information given we can’t tell.
For C gCan’t be A because we don’t know about all the other traits.
For C generally only one plant comes from one seed.
The two plants do indeed share the copy of the gene that codes for round seeds.

28. 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. 50% Rr and 50% rr
C. 75% Rr and 25% rr
D. 25% RR, 50% Rr, and 25% rr B
Parent #1 Heterozygous means Rr
Parent #2 Homozygous recessive means rr.
All offspring will have at least one r from parents number two. Each offspring has a ½ chance of getting R and ½ change of getting r.

29. 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 first-generation offspring?
F 50% TTss, 50% ttSS
G 100% TtSs
H 100% Ttss
J 50% TtSS, 50% ttSS
Parent #1: TTss
Parent #2: ttss
All offspring get T and s from parent #1
All offspring get t and s from parent #2
All offspring get Tt and ss H

30. 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

31. 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
Remind S that DNA codes for proteins! G