UNIT 4 DNA, RNA, and Gene Expression

DNA STRUCTURE

DNA is the primary material that causes

recognizable, inheritable characteristics in

related groups of organisms.

DNA is the GENETIC MATERIAL

Contain genes which are segments of DNA which

code for specific traits.

DNA is a relatively simple molecule

Composed of only four different subunits:

adenine, guanine, thymine, and cytosine (we will

talk more about these later)

DNA STRUCTURE CONT.

James Watson and Francis Crick discovered the

structure of DNA.

A winding Staircase: A DNA molecule is shaped

like a spiral staircase and is composed of two

parallel strands of linked subunits.

Known as a double helix

Each subunit is called a nucleotide.

Each nucleotide is made up of three parts: a

phosphate group, a five-carbon sugar, and a nitrogen

base.

The phosphate group and the five-carbon sugar link

together to form the “backbone” of the DNA

A NUCLEOTIDE

Deoxyribose

Can be Adenine,

Thymine, Guanine,

Cytosine

THE STRUCTURE OF DNA

The structure of DNA is very important

The information in DNA is contained in the order

of the bases (adenine, thymine, guanine,

cytosine)

BASE-PAIRING RULES

Adenine always pairs with thymine, and guanine

always pairs with cytosine to connect each side of

the helix.

These bases are held together by weak hydrogen

bonds.

THE CELL CYCLE: DNA REPLICATION

DNA REPLICATION

When cells divide , each new cell contains an

exact copy of the original cell’s DNA.

What is the name of this process?

Remember DNA is always made of two strands of

complementary base pairs.

The process of making a copy of DNA is called

DNA Replication

DNA molecule unwinds, two sides split apart

(splitting hydrogen bonds), new nucleotides are

added to each side until two identical sequences

result.

DNA REPLICATION CONT.

The location where the DNA separates is called

the replication fork.

At the replication fork, new nucleotide bases are

added.

REPLICATION PROTEINS

During the replication of DNA, many proteins

form a machinelike complex of moving parts

LIKE A FACTORY!!!!!!

DNA Helicase Protein that unwinds the DNA

double helix during replication.

DNA Polymerase Aids in the formation of the

new DNA sequences.

At the replication fork, DNA Polymerase moves along

the strands adding nucleotides to produce the new

double helix.

What if DNA polymerase messes up???

Oops mutations Cancer

THE BACKBONE OF DNA CONSISTS OF:

A. Deoxyribose Sugar only

B. Phosphate only

C. Deoxyribose Sugar and Phosphate

D. Adenine, Thymine, Cytosine, and Guanine

WHICH OF THE FOLLOWING LISTS BOTH

PURINES:

A. Guanine and Cytosine

B. Adenine and Thymine

C. Thymine and Guanine

D. Adenine and Guanine

THE REPLICATION PROTEIN INVOLVED IN

REASSEMBLY OF TWO NEW DNA STRANDS:

A. DNA Helicase

B. DNA Polymerase

C. DNA Ribase

D. DNA Phosphase

THE REPLICATION PROTEIN INVOLVED IN

UNZIPPING AND UNWINDING PARENT DNA

A. DNA Helicase

B. DNA Polymerase

C. DNA Ribase

D. DNA Phosphase

NITROGEN BASES ARE HELD TOGETHER BY

WHICH BOND TYPE

A. Covalent

B. Ionic

C. Sulfuric

D. Hydrogen

EOC: A NUCLEOTIDE IS COMPOSED OF SUGAR,

A PHOSPHATE GROUP, AND WHICH OF THE

FOLLOWING?

A. Amino Acid

B. Fatty acids

C. Glycerol

D. Nitrogenous Base

EOC: CHARGAFF’S RULE STATES THAT IN A GIVEN STRAND OF

DNA, THE PERCENTAGE OF ADENINE WILL EQUAL THE

PERCENTAGE OF THYMINE. IF A SEGMENT OF DNA WAS

COMPOSED OF 23% A, WHAT PERCENT OF T WILL THE SEGMENT

CONTAIN? A. 77%

B. 26%

C. 23%

D. 99%

GENE EXPRESSION

DNA does not directly make proteins.

RNA is essential in taking the genetic

information from DNA and building proteins!

Genes from DNA produce proteins at the

RIBOSOME, but this cannot be completed without

RNA!

TRANSCRIPTION: DNA TO RNA

The first stage– making RNA from the

information in DNA

Called TRANSCRIPTION

You can think of transcription as copying notes from the

board (DNA) to a notebook (RNA)

DNA vs. RNA

DNA RNA

Deoxyribose sugar, phosphate group,

nucleotide

Ribose sugar, phosphate group,

nucleotide

Double stranded Single stranded

Adenine (A), Cytosine (C), Guanine (G) ,

Thymine (T)

Adenine (A), Cytosine (C), Guanine (G) ,

Uracil (U)

MESSENGER RNA (MRNA)

Messenger RNA (mRNA)

When DNA is transcribed into RNA, mRNA is the

type of RNA that is produced. The mRNA carries

instructions for making a protein from a gene and

delivers them to ribosomes.

READING THE GENE

Transcription begins with a molecule called RNA

polymerase that unwinds and locates a “start”

codon.

mRNA molecule comes in at that locations and

starts producing the complementary RNA

molecule.

RNA polymerase eventually reaches a “stop”

codon where the mRNA stops getting longer.

INSTEAD OF CONTAINING THE BASE

THYMINE, RNA CONTAINS THE BASE:

A. Uracil

B. Catalase

C. Pepsin

D. Helicase

E. Polymerase

WHICH OF THE FOLLOWING WOULD DESCRIBE

A SIMILARITY BETWEEN DNA AND RNA?

A. Made of a single strand of nucleotides

B. Contain the base Uracil

C. Leaves the nucleus through nuclear pores

D. Contains phosphate in its “backbone”

E. Contain the base Thymine

TRANSLATION: RNA TO PROTEINS

Uses information in RNA to make a specific

protein.

mRNA codes for specific amino acids, that, when

linked together, form proteins.

TRANSFER RNA (TRNA)

During translation, tRNA reads the mRNA

sequence.

tRNA has amino acids connected to them

Attach these amino acids to a growing protein

chain

BASED ON THE DNA SEQUENCE :

ATCTGA , WHAT IS THE CORRECT

COMPLIMENTARY MRNA SEQUENCE?

A. TAGACT

B. CGCGCT

C. UAGACU

D. UAGACT

THE PROTEIN THAT UNWINDS DNA TO

ALLOW FOR TRANSCRIPTION IS CALLED:

A. DNA Helicase

B. DNA Polymerase

C. RNA Polymerase

D. RNA Helicase

THE PROCESS OF TRANSCRIPTION

PRODUCES:

A. tRNA

B. DNA

C. mRNA

D. Amino Acids

THE PROCESS OF TRANSLATION PRODUCES:

A. Amino Acid Chain

B. tRNA

C. mRNA

D. DNA

BASED ON THE MRNA SEQUENCE UCG,

WHAT IS THE CORRECT ANTICODON?

A. AGC

B. ACG

C. TGC

D. TCG

BASED ON THE DNA SEQUENCE AAG,

WHAT IS THE CORRECT ANTICODON?

A. TTC

B. UUC

C. AAG

D. UUA

NAME THE AMINO ACID CODED FOR BY

THE FOLLOWING CODON: GUC

A. Phenylalanine

B. Valine

C. Serine

D. Leucine

NAME THE AMINO ACID CODED FOR BY

THE FOLLOWING CODON: ACA

A. Valine

B. Tyrosine

C. Serine

D. Threonine

EOC: WHICH OF THE FOLLOWING MRNA

SEQUENCES CODES FOR VAL-GLU-SER,

RESPECTIVELY

A. UGG AGG CUA

B. GUA GGG AGC

C. GUC GAA ACU

D. GUG GAG AGC

JOINING AMINO ACIDS TOGETHER AT THE

RIBOSOME PRODUCES:

A. Carbohydrates

B. Proteins

C. Lipids

D. Nucleic Acids

EOC: WHICH MUTATION IS SHOWN

DNA-> ACC GTC ATT CGG

MUTATED DNA-> ACC GTC ATT CAG G

A. Frameshift Deletion

B. Frameshift Insertion

C. Point Mutation

D. Polymerase Mutation

REGULATING GENE EXPRESSION

How do butterflies develop from caterpillars?

We know that every cell in an individual starts with the same genes.

So, during a butterfly’s lifetime, not every gene is always at work.

Some genes are ON, while others are OFF. (Genetic Switch)

GENE EXPRESSION

Cells have complex systems that regulate

whether or not specific genes are expressed.

Expression depends on the cell’s needs and

environment. This is called gene regulation.

Accounts for changes during development.

OPERONS

The major form of gene regulation in

prokaryotes depends upon operons that

respond to environmental factors.

An operon is a gene regulation system in

which DNA segments control the

expression of a gene.

Operons are common in bacteria, but

uncommon in eukaryotes.

SO HOW DOES A EUKARYOTE (YOU)

REGULATE GENES?

Like prokaryotic cells, eukaryotic cells have

proteins that regulate transcription.

Transcription factors interact with RNA

polymerase to promote transcription.

Some transcription factors act as activators, and

some act as repressors.

Activators can bind at enhancer DNA segments

and when they interact with promotor region

(where RNA polymerase attaches), transcription

begins.