1. what is dna? 2. list anything you know about dna (from readings, class… · 2018-09-10 · list...
TRANSCRIPT
1. What is DNA?2. List anything you know about DNA
(from readings, class, TV…?)
Before we begin, let’s investigate the way DNA molecules are set up!
http://learn.genetics.utah.edu/content/molecules/builddna/
What is DNA?
DNA is the genetic material found in cells Stands for: “Deoxyribonucleic Acid” Is made up of repeating nucleic acids It’s the “Unit of Heredity”
DNA is found in the cytoplasm of prokaryotes and the nucleus of eukaryotes
The nucleus of a human cell contains 30,000 or more genes in the form of DNA called a genome
Purpose: DNA controls the production of proteins in the cell
▪ This is essential to life!
▪ DNA RNA Proteins
DNA is packaged tightly into pieces called chromosomes that are visible during cell division
Each chromosome includes several thousand genes
Each gene contains the directions to make one or more proteins
▪ Proteins are made of amino acids
These proteins play a key role in the way we look and grow…ever hear someone say “it’s in your genes?”
One Chromosome
Contains many genes
Each gene codes for a proteinEx. Keratin protein
Specialization▪ In embryo, all genes on the
DNA is “on”. This undifferentiated cell (stem cell) can develop into any type of cell.
▪ Specialization occurs when certain genes are turned “off” and other genes remain “on” – making a particular type of cell▪ Ex. Muscle cells and Nerve
cells in your body have the same DNA, but they have different genes activated.
DNA is comprised of two strands that twist around each other, called a double helix
▪ Discovered by Watson and Crick in 1953
“Twisted ladder structure”
Think of DNA as a spiral staircase!
DNA is a made of building blocks called nucleotides
A nucleotide is made of:▪ one phosphate
▪ one 5-carbon sugar (called deoxyribose)
▪ one nitrogen base▪ Adenine
▪ Thymine
▪ Guanine
▪ Cytosine
Nucleotides put together make up the DNA strand!
The sides, or “backbone” of the DNA are composed of alternating phosphate-sugar groups
Each “rung of the ladder” is made up of complementarynitrogenous base pairs
The four bases are A (adenine), T (thymine), G (guanine), and C (cytosine)
▪ A pairs with T (2 H Bonds)
▪ G pairs with C (3 H Bonds)
They form weak hydrogen bonds that hold the DNA strand together and are the reason DNA can be replicated
▪ A::T forms 2 H-bonds, and C:::G forms 3 H-Bonds
Phosphate-purple Sugar- blue Adenine-red Thymine-green Guanine-yellow Cytosine-orange
Go to: Socrative.com Click on: Student login Type room XX7CWRJG
Labe the diagram with the following terms: Nucleotide, Sugar, Phosphate, Base, Hydrogen Bonds
A B C
D
E
1. DNA is packaged into pieces. What are these pieces called?
2. There are thousands of genes on a chromosome. A single gene contains the directions to make what?
3. The base adenine (A) always pairs with ____________, while the base guanine (G) always pairs with _________________.
Locate your DNA paper model sheet. You will be completing this with your partners. When finished:
▪ Anaerobic graphing lab
▪ Post Assessments
▪ Extra Credit Assignment
Making a new strand
DNA replication is the process of producing 2 identical replicas from one original DNA molecule▪ Replicate means “to copy”
During replication, the DNA molecule separates into two strands, and builds two new complimentary strands using the base pairing rules (A::T, C:::G)
The molecule is unwound and “unzipped” with the help of helicase, an enzyme!
Step 1: DNA unwinds, then “unzips,” exposing the N-bases (remember, the bases are ATCG)
Step 2: New DNA N-bases are added to each side of the molecule, making two separate strands▪ If the unzipped side read ATCG,
then TAGC would be added to that side. Now it is an independent strand!
http://www.youtube.com/watch?v=hfZ8o9D1tus
Each new DNA strand (daughter chromosome) is made up of 1 strand from the original DNA (blue) and one new strand (red)
Given one strand, you can always find the other strand using base pairing rules!
Let’s practice! If the DNA sequence of bases on one strand was
G C T A C A T, what would the complementary side be during replication?
C G A T G T A
https://www.youtube.com/watch?v=z685FFqmrpo
Go to: Socrative.com Click on: Student login Type room XX7CWRJG
1. What is the result of DNA replication?
2. For each strand below, determine its complementary strand.
1. A A T C G G A T
2. T C G G T A A C
1. What are the steps in DNA replication?
1. What is the outcome of DNA replication?
1. Given the following strand of DNA, what would the complementary side read?
C T G A A T C G A
How does a cell grow and divide?
The Cell Cycle describes the life of a cell from birth to death
There are three main parts of the cycle:
▪ Interphase-Normal cell activities; broken up into 3 parts
▪ Mitosis-The process of cell division (1 cell becomes 2!)
▪ Cytokinesis-The division of the organelles and cytoplasm following mitosis
Interphase is indicated in grey-it is the longest phase of the cycle, broken into 3 parts
Mitosis is indicated in pink-we will discuss the stages of mitosis later!
G1 phase (Gap/Growth 1)-Period of cell growth▪ Cells can remain in the G1 phase
indefinitely▪ Called G0
S phase (Synthesis)-Period when DNA replication occurs▪ Once a cell copies its DNA, it must
divide▪ S phase allows daughter cells to have
exact copy of parent DNA after division!
G2 phase (Gap/Growth 2)-Cell growth and preparation for Mitosis
Mitosis is a form of asexual reproduction-means only 1 organism required
Occurs in response to the body’s need for growth and repair
4 stages of mitosis: Prophase, Metaphase, Anaphase, Telophase
▪ We’ll talk more about this in a bit!
The cell cycle ends with cytokinesis the division of the cytoplasm
▪ Accompanies mitosis
This means one cell has divided into two cells, and those two cells can continue with their own independent cell cycles!
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html
Cyclins-Proteins that regulate the rate of the cycle
▪ Internal regulation-cell cycle can’t proceed until certain levels of these proteins are reached (ex. Poor nutrition cell stays in G1)
▪ External regulation-cycle can speed up or slow down
▪ Do you think a paper cut on your finger would cause the cell cycle to speed up or slow down?
Sometimes errors in the cell cycle can lead to cancer-▪ Errors can be genetic or due
to an environmental toxin Internal regulation error
followed by external; cells cannot “feel” their neighbors, and thus begin uncontrolled division ▪ Lack density dependence
(tumor) and anchorage dependence (metastasized cancer cells)
From 1: 15 https://www.youtube.com/watch?v=IeUANxFVXKc
1. Draw a simple diagram of the cell cycle, breaking it into the 4 main phases discussed today.
2. What is the purpose of cyclins within the cell cycle?
3. Explain why regulation of the cell cycle is so important to organisms.
1. Label the diagram on the right with the appropriate stage of the cell cycle.
2. At one point within the cell cycle, it divides. Why would cell division be necessary?
3. Explain how cancer is related to regulation of the cell cycle.
Cell Growth: Cell may stay indefinitely if it does not meet checkpoints
DNA is replicated.
Growth and preparation for division
Cell divides
Cytoplasm divides: 1 cell is now 2
Stages of Asexual Cell Division
Recall that the cell cycle is made up of three main parts
▪ Interphase (G1, S, and G2)
▪ Mitosis
▪ Cytokinesis
Mitosis refers to the division of the cell
▪ Asexual reproduction for unicellular eukaryotes
▪ Occurs in response to the bodies need for growth and repair
Occurs in eukaryotes 1 cell divides to produce 2 daughter cells These cells are identical to the original cell
same number of chromosomes!
What happens when the cell leaves interphase and is ready to begin division…?
What Happens?▪ Nuclear membrane dissolves
▪ Chromatin condenses into chromosomes▪ Chromatin: uncondensed DNA
(looks like spaghetti)
▪ Chromosome: condensed DNA (looks like X’s)
▪ Centrioles move to opposite ends of the cell
▪ Spindle forms and spindle fibers extend from one side to the other
What Happens?
▪ Centromeres (middle of chromosome) attach to spindle fibers
▪ Chromosomes are pulled to the middle of the cell
What Happens?
▪ Spindle fibers pull chromosomes apart
▪ Each sister chromatidmoves toward opposite end of the cell
What Happens?▪ Nuclear membrane
reforms
▪ Spindle fibers disappear
▪ Animal Cells: ▪ Cell membrane pinches
▪ Plant Cells: ▪ New cell wall begins to
form
What happens?
▪ Division of the cytoplasm and organelles
▪ 1 cell is now 2 identical cells!
INTERPHASE PROPHASE METAPHASE
ANAPHASE TELOPHASE
CYTOKINESIS
1. Draw and label the stages of mitosis. You should provide a brief explanation of what is happening beneath each stage.
Bellringer Day 06
1. Where is DNA located in Eukaryotic
organisms?
2. What is the purpose of DNA in organisms?
3. DNA is a nucleic acid. What is the other
nucleic acid?
4. Nucleotides are the building blocks of
nucleic acids. Draw and label a nucleotide.
DNA/RNATranscription and Translation
Review…
• DNA is responsible for controlling the production of proteins in the cell, which is essential to life–DNARNAProteins
• Chromosomes contain several thousand genes, each with the directions to make one protein
• Do you remember the organelle where proteins are produced?
Where are Proteins
Produced?
• Ribosomes!
• Ribosomes are where proteins are made
• Ribosomes are found in two places:
– Free floating in the cytoplasm
– Attached to Endoplasmic Reticulum (Rough ER)
• So…how does information needed to build the
protein get delivered from the DNA to the
ribosomes???
-With the help of RNA in a process called protein
synthesis!
What is RNA?
• RNA stands for ribonucleic acid
• One subunit of RNA is a nucleotide
(just like DNA!)
– 1 - 5 carbon sugar (it’s ribose in
RNA)
– 1 - phosphate group
– 1 – nitrogenous (N) base
• Three types of RNA
– mRNA, rRNA, tRNA
– First, we will look at mRNA!
A Closer Look: mRNA
• Looking at the mRNA to the right,
how is it different visually from DNA?
– It is single stranded
– It is shorter and able to leave the
nucleus
– The sugar is ribose
– There is a different base
• Uracil (U) takes the place of
Thymine (T)
About mRNA
• The job of mRNA is to take the
directions for one gene and
transport it to a ribosome in the
cytoplasm where it is translated.
– This is so the cell can begin
assembling amino acids, the
building blocks of proteins
– Like it’s name, it is sending a
message on how to do the job
– This is part of a process called
protein synthesis
A ribosome up close!!
Bellringer Day 07
1. List 3 differences you see between DNA and
RNA molecules.
2. Which organelle in cells is responsible for the
production of proteins?
3. In eukaryotes, DNA exists in the nucleus.
Hypothesize why RNA is necessary to carry
out the protein making process?
Protein Synthesis
• Protein synthesis is a two stages process
– Transcription and Translation
• In this process, a messenger molecule (mRNA)
carries instructions from DNA to ribosomes
– DNA cannot leave the nucleus!
– mRNA can!
• mRNA makes it possible for proteins to be
assembled by ribosomes outside of the nucleus
Protein SynthesisTranscription
Protein Synthesis:
Transcription
• Transcription happens when DNA is
turned into mRNA
• This happens when proteins need to be
made in the cytoplasm!
• Since DNA cannot leave the nucleus, it is
transcribed into RNA (DNARNA)
– Transcribe: to copy (copy in the same
nucleic acid language, but only copy what is
needed)
Protein Synthesis:
Transcription
• How does it happen?
– After an enzyme targets the portion of the DNA that
should be copied (initiation), the sections of DNA
(genes) will temporarily unwind to allow mRNA to
transcribe (copy). This will continue until an enzyme
signals “the end”
– mRNA leaves the nucleus, travels into the cytoplasm
and attaches to a ribosome
– The “message” from DNA can now be translated to
make a protein
Transcription
Practicing Transcription
• Transcribing DNA to mRNA is very easy if you
remember these complementary pairs!
– C (in RNA) will attach to a G (in DNA)
– G (in RNA) will attach to a C (in DNA)
– A (in RNA) will attach to a T (in DNA)
– U (in RNA) will attach to a A (in DNA)
• Try it!
A piece of DNA reads: T A G C A T T C C G A U
transcribe to mRNA:___________________________
Practicing Transcription
•If 1 side of DNA reads:
A A G C G T A T C C C G
•Then mRNA reads:
____________________________
Bellringer Day 08
1. Describe the steps taken during
transcription.
2. Transcribe the following to mRNA:
– AAT CGA TAG CCG ATA
3. What does it mean to translate something?
Protein SynthesisTranslation
TRANSLATION
• Translation: the process in which mRNA is
used as a blueprint to form chains of amino
acids (RNAProtein)
– Amino acids linked together form a protein
– Translate: To change a sentence from one
language (nucleic acid) to another (amino acid)
• Every 3 letters on an mRNA chain = codon
– Each codon (3 DNA letters) = 1 amino acid
Reading a Codon Chart
• Given the mRNA, we
can read a codon chart
to translated into the
amino acid it codes for
• Remember, 1 word in
nucleic acid language
is a codon (three
nucleotides)
Practice: Reading a Codon
Chart
• What amino
acid is coded
for?
– A U G
– G U C
– G C C
– C G A
– U A A
Protein Synthesis:
Translation
• Occurs in a ribosome
in ALL cells
• This process uses all
three forms of RNA
(mRNA, rRNA, and
tRNA)
• DNA is not directly
used!
mRNA
rRNA
tRNA
anticodon
AA (amino acid)
Steps of Translation
1.The mRNA leaves the nucleus and
lands on a ribosome (rRNA)
Steps of Translation
2. tRNA (with the correct anticodon)
lands on the ribosome opposite a
codon on the mRNA
tRNA: A Closer Look
Notice the tRNA is
carrying the amino acid
leucine, coded for by the
sequence “CUA” (check
your codon chart”)
The tRNA knows how to
match using bases! In RNA,
GC and AU:
So…mRNA codon reads
“CUA,” so the tRNA
anticodon will be “GAU”
tRNA: A Closer Look
anticodon
Amino acid
Steps of Translation
3. The tRNA leaves the ribosome, but
the amino acid that it coded for stays
on the ribosome to wait for next
codon to be read
Steps of Translation
4. The ribosome moves to the next codon
bringing in another amino acid to the
growing protein chain.
An Amino Acid Chain
• The amino acid chain will ALWAYS
begin with the “START codon”- AUG
• The tRNA will continue to add amino
acids until it reaches a “STOP codon”
(UAA, UAG, UGA)
• When it reaches a stop codon, then a
complete protein has been built! The
protein unattaches from the
ribosome.
DNA
molecule
DNA strand
(template)
3
TRANSCRIPTION
Codon
mRNA
TRANSLATION
Protein
Amino acid
35
5
Let’s practice…….
• Given the strand of DNA below, what would it’s
complementary DNA strand read?
ATC
• Now, transcribe the DNA to mRNA
• What amino acid does the codon code for? (use
codon chart)
• What would the anticodon on the tRNA read?
Try Again!
• Given the strand of DNA below, what would it’s
complementary DNA strand read?
TGA
• Now, transcribe the DNA to mRNA
• What amino acid does the codon code for? (use
codon chart)
• What would the anticodon on the tRNA read?
Day 04 – 2/3/17
• Given the strand of DNA below, complete the
following:
ATT GCT AGG TAA
• Transcribe the DNA to mRNA
• What amino acid are the codons coding for
during translation? (use codon chart)
• What would the anticodons on the tRNA read?
Protein Synthesis Activity
Bellringer Day 09
• Label the following: amino acid, mRNA, tRNA,
amino acid chain, ribosome, codon, anticodon
• Determine if this illustrates transcription or
translation.
6
7
Review: Protein Synthesis
• https://www.youtube.com/watch?v=2
zAGAmTkZNY
Protein Synthesis Review
• Use your whiteboards to answer the questions.
• Remember, you will have a quiz tomorrow on RNA
and protein synthesis!
1. DNA and RNA are both made up of subunits
(monomers) called what?
2. Draw and label a nucleotide.
3. There are numerous differences between DNA
and RNA. List 3 differences.
4. What are the two steps of protein synthesis
called?
5. True or false: DNA can leave the nucleus.
6. Transcription is the process of turning DNA into
________.
7. Transcribe the following DNA to mRNA:
ATC GGC AGC TTC AAG
8. What are the 3 types of RNA involved in
translation? Include what they stand for.
9. mRNA carries the directions for an amino acid.
Every 3 letters on the code is called a _______.
10. When mRNA leaves the nucleus, it lands on a
_________, which is responsible for making
proteins.
11. All strands of mRNA begin with AUG, which
means ______. The protein will continue to be built
until a ______ codon is reached.
12. Use your codon chart to translate the following
mRNA into amino acids:
AUG CCG AGG UGA UUG
Bellringer
Day 10
1. Label the
diagram of
protein
synthesis.
Quiz: Protein Synthesis
2009-2010
Mutations
Changes to DNA
Mutations
• Changes to DNA are called mutations
– These mutations change the mRNA code that
determines proteins
– This may result in no change, may change the
amino acid, or may change the whole protein!
• Mutations may be random, or they may be
caused by exposure to radiation/chemicals
Types of Mutations
• Substitutions:
– Change to one letter (base) in the DNA!
– Ex. A instead of T
– This may result in a different amino acid,
or it may be a silent mutation: no
change to the strand
Example: Sickle Cell Anemia
A substitution causes misshapen red blood cells.
Notice the change in the amino acid sequence?
Types of Mutations
• Deletion or Addition:
– A letter is added or removed
– Example: AACG instead of AAG
– This shifts the way the entire sequence
is read, resulting in an entirely new
strand of amino acids! This is a major
change to the protein, meaning it may
change the trait!
Heredity of Mutations
• Only mutations located in sex cells
(sperm and egg) can be passed on!
– For example, you could not inherit skin
cancer from a family member who
developed it after extensive UV
exposure.
Bellringer Day 11
1. Name and describe the main
types of mutations we talked
about yesterday.
2.Do mutations always cause a
change in amino acid? Why or
why not?
Bellringer Day 12
1.Explain the steps of protein
synthesis. You may write this in your
own words, but you should create at
least 5 steps to describe the process.
You may include as many steps as
you need. Be as detailed as possible.
Test: Day 13
• We will also be doing binder checks. Make sure
materials are in your binder in the correct order.