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 DNAThere are four different nitrogenous bases in DNA.

Only certain bases can bond. They pair to form the rungs of the ladder.

AdenineAdenine bonds to ThymineCytosine bonds to Guanine.

The sides of the twisted ladder are made of alternating sugar and phosphates

sugar phosphate sugar phosphate sugar phosphate sugar ...

T A C G¦ ¦ ¦ ¦

A T G C

sugar phosphate sugar phosphate sugar phosphate 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 be-A. 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 bondsC

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

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 differentA. 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

synthesisJ tRNA codons for specific amino acids

G

Practice Question

What process is occurring in the figure on the right?

F RNA synthesisG Protein synthesisH TranscriptionJ 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 deletionG Gene mutationH Gene insertionJ Gene segregation G

Practice Question

Which of the following must occur before DNA replication can take place?

A Translation of DNA into amino acidsB Separation of the DNA molecule into

codonsC Transformation of DNA into RNAD Separation of the DNA double helix

D

Practice Question

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

3' CGGUAU 5'

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 divideInterphase (longest phase)

Metaphase

Anaphase

Telophase

Cytokinesis

Prophase

Prometaphase

Two new cells IDENTICAL to the parent cell

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

Genetics and Punnett Squares

• Genotypes are the genetic make up of organisms

Genotype: TT, Tt, or tttt

• Phenotypes are the physical characteristics

Phenotype: tall or shortshort

• Homozygous would be TT or tt

• Heterozygous would be Tt

Try this: RrYy x RrYY

  RY Ry rY ry

RY      

RY      

rY        

rY        

These are all the possible allelic combinations of RrYY

Check this: RrYy x RrYY

  RY Ry rY ry

RY RRYY RRYy RrYY RrYy

RY  RRYY RRYy RrYY RrYy

rY  RrYy RrYy rrYY rrYy

rY RrYY RrYy rrYY rrYy

Remember capital letters are dominant, so lower case letters are… recessive

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

C. 1/8

D. 1/16

D

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 QuestionIn 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% RrB. 50% Rr and 50% rrC. 75% Rr and 25% rrD. 25% RR, 50% Rr, and 25% rr

B

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% ttSSG 100% TtSsH 100% TtssJ 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 ATPB Function of cellC Size of cellsD 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