Guided Notes: Molecular Genetics

The Structure of DNA

DNA is ___________________________________________________________________

Stands for:

Made up of repeating _____________________________________________

“Unit of Heredity”

-Where is it found?

DNA is in the _______________ of

prokaryotes and the

__________________ of eukaryotes

The nucleus of a human cell contains

30,000 or more __________ in the form

of DNA, called a __________________.

-Function of DNA

Purpose: ___________________________________________________________________

This is essential to life! DNA RNA Proteins

-Structure of DNA

These proteins play a key role in how we look and grow-“It’s in your genes!”

Specialization:

o In embryo, all genes on the DNA are “______”. These _____________ cells

(_____________________) can develop into any type of cell

o Specialization occurs when certain genes are turned “______” and other genes remain

“______”-making that a particular type of cell.

Example: _______________________________________________________

DNA is packaged tightly into

pieces called

_____________________

that are visible during cell

division

Each chromosome includes

several thousand

________________

Each gene contains the

directions to make one or

more __________________

-Proteins are made up of

______________________

Structure of DNA

DNA is comprised of two strands that twist around each other, called a ___________________

______________________

o Discovered by ____________________________

o “Twisted Ladder Structure”

DNA is made of building blocks called

_____________________

A nucleotide is made up of:

o One _________________

o One ___________________ (called

_____________)

o One __________________ (adenine,

thymine, cytosine, guanine)

Nucleotides put together make up the DNA strand!

“Backbone of DNA” is composed of ____________________________________________

“Rungs of the ladder” make up ________________________________________________

o The four bases are: A (____________), T (_____________), G (____________), and C

(_______________)

o A pairs with T (____ H Bonds)

o G pairs with C (____ H Bonds)

In the diagram of DNA on the right, do the following:

1. Label a phosphate of the backbone

2. Label a sugar (deoxyribose) of the backbone

3. Identify and pair the bases 4. Place a square around 1

nucleotide

DNA Replication DNA Replication is the process of producing 2 __________ replicas from one

___________ DNA molecule

1. To replicate means “______________”

During replication, the DNA molecule separates into __________ strands, and builds two

new ____________________ strands using the base pairing rule! (A::T; C:::G)

The molecule is ___________ and ____________ with the help of ____________, an

enzyme!

-Steps in DNA replication:

1. DNA

____________ and then _____________, exposing the _______________

2. New DNA N-Bases are added to each side of the molecule, making separate

____________

If the unzipped side read ATCG, then _________ would be added to that

side. Now it is an _______________ strand!

Each new DNA strand (__________________) is made up of 1 strand from the

___________ DNA, and one __________ strand

Think about it: Use the strand below to fill in what the complementary DNA strand would be.

Old Strand: A G G T C A C T A C C T

New Strand:

The Cell Cycle

The ______________ describes the life of a cell from

birth to death

There are three main parts of the cycle:

______________ : Normal cell activities; broken

up into 3 parts

______________ : The process of cell division (1

cell becomes 2)

______________ : The division of the organelles

and cytoplasm following mitosis

Interphase ______________ : Period of cell growth

Cells can remain in the G1 phase indefinitely, called ______________ ______________ : Period when DNA replication occurs

Once a cell copies its DNA, it ______________ divide ______________ : Cell growth and preparation for Mitosis

Mitosis Mitosis is a form of ______________ reproduction

Means only _____ organism required Occurs in response to the body’s need for growth and repair _____ stages of mitosis: Prophase, Metaphase, Anaphase, Telophase

Cytokinesis The cell cycle ends with ______________ : the division of the _____________

Accompanies mitosis This means one cell has divided into two cells, and those two cells can continue with their own

independent cell cycles!

-Regulation of the Cell Cycle ______________ : Proteins that regulate the rate of the cycle

______________ regulation: cell cycle can’t proceed until certain levels of these proteins are reached

▪ ex. Poor nutrition cell stays in G1 ______________ regulation: cycle can speed up or slow down

Think about it: Do you think a paper cut on your finger would cause the cell cycle to speed up or slow down?

Cell Cycle Checkpoints

Cancer

Sometimes errors in the cell cycle can lead to ________: uncontrolled cell growth Errors can be ______________ or due to an ______________ toxin

Internal regulation error followed by external; cells cannot “feel” their neighbors, and thus begin uncontrolled division

Lack ______________ dependence (tumor) and ______________ dependence (metastasized cancer cells)

Mitosis

______________ refers to the division of the cell Asexual reproduction for ______________ ______________ Occurs in response for the body’s need for ____________ and ____________

-More about Mitosis Occurs in ______________ ______ cell divides to produce ______ daughter cells These cells are ______________ to the original cell

o Same number of ______________

Stage 1: ______________ ______________ ______________ dissolves ______________ condenses into ______________

o ______________: uncondensed DNA (looks like spaghetti)

o ______________: condensed DNA (looks like X’s)

______________ move to opposite ends of the cell ______________ forms and fibers extend from one side to the other

Stage 2: ______________ ______________ (middle of chromosome) attach

to spindle fibers Chromosomes are ______________ to the

middle of the cell

Stage 3: ______________

Spindle fibers pull ______________ apart Each sister ______________ moves toward

______________ end of the cell

Stage 4: ______________ ______________ ______________ reforms Spindle fibers disappear Animal Cells:

o Cell membrane ______________ Plant Cells:

New ______________ begins to form

Cytokinesis

Division of ______________ and ______________ _____ cell is now _____ identical cells

RNA and Protein Synthesis

_________ is responsible for controlling the production of ___________ in the cell, which is essential to life!

o DNARNAProteins _____________ contain several thousand _________, each with directions to make one

_____________

Where are Proteins Produced?

Proteins are produced on _________________! Found in two places:

o Free floating in _______________o Attached to _______________________

How does information needed to build a protein gets delivered from the DNA to the ribosomes?

o With the help of ___________ in a process called ______________________

What is RNA?

RNA stands for _______________________ One subunit is called a _________________

o 1 5-carbon ________ (ribose)o 1 _____________ groupo 1 nitrogenous __________

Three types of RNA: ____________________

A Closer Look at mRNA

How is mRNA different from DNA?o ____________ strandedo ____________ and able to leave the ____________o The sugar is ____________ o There is a different base

______________ (U) takes the place of ___________ (T)

The job of mRNA is to take directions for one gene and transport it to a ____________ in the ________________.

o This is so a cell can begin assembling _________________, the building blocks of ________________!

o It’s sending a _______________ on how to do the job!

Think about it: What is happening in each photo below during transcription?

Protein Synthesis

Protein synthesis is a two stage process: ______________________________________o A _________________ molecule (mRNA) carries instructions from DNA to ribosomes

DNA __________ leave the nucleus; ___________ can! ____________ makes it possible for ____________ to be assembled by

_____________ outside the nucleus

Protein Synthesis: Transcription

Transcription is when _________ is turned to _________ Happens when ___________ need to be made in the ____________ Since DNA CANNOT leave the ___________, it is ___________ into RNA (DNARNA)

o Transcribe: _____________ (copy in the same nucleic acid language, but only what is needed!)

How does it happen?1) After an ___________ targets the portion of the DNA that should be copied

(_________), the sections of DNA (_________) will temporarily _________ to allow mRNA to _________ (copy). This will continue until an enzyme signals “the end”

2) mRNA leaves the __________, travels into the _________ and attaches to a ________3) The “message” from DNA can now be translated to make a ___________

Transcribing DNA to mRNA is very easy if you remember these complementary pairs!o _______ (in RNA) will attach to a ______ (in DNA)o _______ (in RNA) will attach to a ______ (in DNA)o _______ (in RNA) will attach to a ______ (in DNA)o _______ (in RNA) will attach to a ______ (in DNA)

Try it!o A piece of DNA reads: T A G C A T T C C G A U

Transcribe to mRNA: _____________________________________ o 1 side of DNA reads: A A G C G T A T C C C G

Transcribe to mRNA: _____________________________________

Protein Synthesis: Translation

Translation The process in which ________ is used as a ___________ to form chains of _______________ (RNAProtein)

o Amino acids linked together form a ______________o Translate: To change a sentence from one language (_____________) to another

(________________) Every 3 letters on an mRNA chain = _________________ Each codon (3 DNA letters) = 1 _____________________

Given the ________, we can read a __________ chart to translate it into amino the amino acid it codes for!

o Remember, 1 word in nucleic acid language is a __________ (three nucleotides)

Translation occurs in a ____________ in ALL cells Uses all three forms of RNA (_______________________________) DNA is not directly used!

Steps of Translation

1) The mRNA leaves the _____________ and lands on a ____________ (rRNA)

2) ________ (with correct anticodon) lands on the ribosome opposite a ________ on the mRNA

3) The tRNA leaves the ribosome, but the ___________ that it coded for stays on the ribosome to wait for next codon to be read

4) The _____________ moves to the next __________ bringing in another __________ to the growing protein chain

Think about it: What amino acid is coded for?

1) AUG ____________________

2) GUC ____________________

3) GCC ____________________

4) CGA ____________________

5) UAA ____________________

tRNA: A Closer Look

Notice the tRNA is carrying the amino acid leucine, coded for by the sequence “CUA”

The tRNA knows how to match using bases! So…mRNA codon reads “CUA,” so the tRNA

anticodon will be “GAU”

Think about it: Label the diagram of translation to the right with the following terms!

a) ribosomeb) mRNAc) tRNAd) codone) anticodonf) amino acid chain

The amino acid chain will ALWAYS begin with the “_______________”- AUG The tRNA will continue to add amino acids until it reaches a “_______________” (UAA, UAG,

UGA) When it reaches a stop codon, then a complete ______________has been built! The protein

_______________ from the ribosome.

Let’s Practice!

Given the strand of DNA ATCo What would it’s complementary DNA strand read? ________

o Now, transcribe the DNA to mRNA __________

o What amino acid does the codon code for? (use chart) _________

o What would the anticodon on tRNA read? __________

Given the strand of DNA TGAo What would it’s complementary DNA strand read? ________

o Now, transcribe the DNA to mRNA __________

o What amino acid does the codon code for? (use chart) _________

o What would the anticodon on tRNA read? __________

Mutations

Changes to DNA are called _____________o These mutations change the _______ code that determines proteinso May result in ______________, may change the ___________, or may change the

whole _____________!o They can be ___________ or caused from exposure to _____________

Types of Mutations

Changes to the letters (ATGC bases) in DNA! Substitution change to _________ letter in the DNA!

o May (or may not) cause a change to proteino No change is called a silent mutation

Deletion or Addition a letter is ____________ or ___________o Changes how the mRNA codons are reado Big changes to protein