Week 7 DNA Fingerprinting Discussion I attached my assignment below.*Please send it by TODAY (July 16) at 4pm (Eastern Time Zone – USA) *Please send it by

Week 7 DNA Fingerprinting Discussion I attached my assignment below.*Please send it by TODAY (July 16) at 4pm (Eastern Time Zone – USA) *Please send it by TODAY (July 16) at 4pm (Eastern Time Zone – USA)
*The assignment should be over 12 sentences
Week 7: Biotechnology
This week, you are learning about DNA. In this week’s discussion forum, I wanted to talk about
some of the applications of DNA in society today, including the pros and cons.
Reading Chapter 10: Biotechnology is a good place to start with this discussion, although all of
these topics are not covered in great detail.
Discussion Leaders: Choose one of the following topics (please take a quick look at the forum
before you post to make sure someone else hasn’t already chosen your topic): (McCauley, Munoz,
Pavoncello
Kelley,
Pinto,
Rodriguez)
•
•
•
•
•
•
•
genetically modified organisms
stem cells
DNA fingerprinting
gene therapy
cloning
genetic counseling
gene patenting
For your chosen topic, please find at least one website to share with your classmates on the topic
– it can be a news article, a website with general information, etc. – and link it to your forum post
using the hyperlink tool (Type the title, select the text, and click on the chain link symbol in the
editor – make sure the new link opens in a new window). For your response, please describe your
topic and why it is important to society today. Include in your response the pros and cons to your
topics, as all of these topics are controversial in some nature.
Reading:
Chapter 10 Biotechnology: https://openstax.org/books/concepts-biology/pages/10-introduction
Example (An example of a student who chose the Genetic counseling)
https://www.cdc.gov/genomics/gtesting/genetic_counseling.htm
Genetic counseling gives information about how genetic conditions such as disorders, may affect
an individual or their family. In counseling, health care professionals also give medical advice
based on the risk for specific diseases. This information is based on personal and family health
history. It is important to society because it informs people of any potential health risks they may
have inherited or are common in their family, and this allows them to know how they can focus
on best taking care of their health or how to prepare for treatments in the future upon diagnosis.
People can be informed of genetic conditions such as family history of infertility or multiple
miscarriages, birth defects, cancer, Huntington’s disease, sickle cell disease, muscular dystrophy,
and more.
The pros include being informed of possible genetic conditions when for planning for pregnancy,
or having tests for the baby done during pregnancy, and beginning early learning how to care for
a child born with a disorder. Also, pros include helping individuals tend to specific areas of their
health which may be affected with a genetic condition or develop into a serious health disease.
There are no direct cons associated with genetic counseling. The only disadvantages related to
learning health risks is that it could affect people’s stress and anxiety levels worrying about if they
will be diagnosed, and that counseling does not eliminate risk for diseases.
DNA Structure and Function
Eukaryotic Chromosomes
• All organisms pass DNA to offspring when they
reproduce
• In cells, each DNA molecule is organized as a
chromosome
• chromosome
• Structure consisting of DNA and associated proteins
• Carries part or all of a cell’s genetic information
• Eukaryotic cells have a number of chromosomes
Chromosome Duplication
• During most of a cell’s life, each of its
chromosomes consists of one DNA molecule
• As it prepares to divide, the cell duplicates its
chromosomes, so both offspring get a full set
• After chromosomes are duplicated, each consists
of two DNA molecules (sister chromatids)
attached to each other at a centromere
Chromosome Duplication
A duplicated chromosome consists of
two long, tangled filaments (sister
chromatids) bunched into an X shape
1 The DNA inside the nucleus of
a eukaryotic cell is typically
divided up into a number of
chromosomes.
Chromosome Structure
2 At its most condensed, a
duplicated chromosome
is packed tightly into an X
shape.
3 A chromosome unravels
as a single fiber, a hollow
cylinder formed by coiled
coils.
4 The coiled coils consist of a
long molecule of DNA (blue)
and the proteins that are
associated with it (purple).
5 At regular intervals, the DNA
molecule is wrapped twice
around a core of histone
proteins. In this “beads-on-astring” structure, the “string” is
the DNA, and each “bead” is
called a nucleosome.
6 The DNA molecule itself has
two strands that are twisted into
a double helix.
Fig 8.2a, p. 124
Chromosome Number
• Eukaryotic DNA is divided among a number of
chromosomes that differ in length and shape
• The sum of all chromosomes in a cell of a given type is
the chromosome number
• Diploid cells have two of each type of chromosome
• Each species has a characteristic chromosome number
▫ Gorilla – 48
▫ Pea plant – 14
▫ Shrimp – 254
▫ Earthworm – 6
Human Chromosome Number
• Human body cells have 46 chromosomes
(chromosome number 46)
• Human body cells have two of each type of
chromosome (23 pairs) so the chromosome
number is diploid (2n)
• Each pair of chromosomes has two versions, one
maternal and one paternal
Types of Chromsomes
• Members of a pair of sex chromosomes differ
among males and females – the differences
determine an individual’s sex
• All others chromosomes are autosomes, which
are the same in both females and males
• Autosomes of a pair have the same length,
shape, and centromere location, and carry the
same genes
Karyotype
Sex Determination
• Body cells of human females contain two X
chromosomes (XX); those of males contain one X
and one Y (XY)
DNA Structure
• A DNA nucleotide has a five-carbon sugar, three
phosphate groups, and one of four nitrogencontaining bases
• How the four nucleotides — adenine (A),
guanine (G), thymine (T), and cytosine (C) — are
arranged in DNA was a puzzle that took over 50
years to solve
Chargraff’s Rules
• 1950s: Erwin Chargaff made two discoveries:
• Chargaff’s first rule: A = T and G = C (amounts of
thymine and adenine in all DNA are the same, as
are amounts of cytosine and guanine)
• Chargaff’s second rule: Proportions of adenine
and guanine differ among the DNA of different
species
DNA Structure – The Scientists
Watson and Crick
Rosalind Franklin
Determined DNA to be a helix – used
Franklin’s images to determine bases
were rungs on a ladder
Used x-ray crystallography to
determine the size, shape , and
distance between DNA’s subunits
DNA Structure
• 3’ carbon of a sugar is joined
by a phosphate group to 5’
carbon of next sugar, forming
2 sugar-phosphate backbones
running in opposite directions
• Inside are paired bases: A to T,
and G to C
Base-Pair Sequences
• The order in which one base pair follows the
next varies tremendously among species
(Chargaff’s second rule)
• Variations in base sequence are the source of
life’s diversity
DNA Replication and Repair
• The order of nucleotide bases in a strand of DNA
– the DNA sequence – is genetic information
• Descendant cells must get an exact copy of DNA
• When the cell reproduces, it must contain two
sets of chromosomes: one for each of its future
offspring
• DNA duplicates itself by DNA replication
Key Enzymes
• DNA helicase
• Unwinds the DNA, breaking the hydrogen bonds
• DNA polymerase
• DNA replication enzyme
• Uses a DNA template to assemble a complementary
strand of DNA
• DNA ligase
• Enzyme that seals gaps in double-stranded DNA
DNA Replication
Semiconservative Replication
• A parental DNA strand serves as a template for
assembly of a new strand of DNA
• The two parental DNA strands stay intact, and a
new strand is assembled on each of the parental
(old) strands
• Each new DNA molecule that forms consists of
one old strand and one new strand
DNA Synthesis
• Each DNA strand has an unbonded 5’ carbon at
one end and an unbonded 3’ carbon at the other:
• DNA synthesis occurs in the 5’ to 3’ direction
DNA Synthesis
• Only one of the new
DNA strands can be
assembled in a single
piece – the other
forms in short
segments called
Okazaki fragments
Proofreading
• A DNA molecule is not always replicated correctly –
luckily, DNA polymerases proofread their own work
• DNA repair mechanisms correct mismatches by
reversing the synthesis reaction to remove a
mismatched nucleotide, then resuming synthesis in
the forward direction
• When proofreading and repair mechanisms fail, an
error becomes a mutation
From DNA to Protein
Nature of Genetic Information
• DNA contains all of the instructions for building a
new individual
• The linear order or sequence of the four bases (A, T,
G, C) in the DNA strand is the genetic information,
which occurs in subsets called genes
• gene
• Part of a DNA base sequence
• Specifies an RNA or protein product
DNA to Protein
1. Transcription
▫ Enzymes use the base sequence of a gene as a
template to make a strand of RNA
2. Translation
▫ Information in the RNA strand is decoded
(translated) into a sequence of amino acids
Converting a gene to RNA
• Transcription converts information in a gene to
RNA
• Enzymes use the nucleotide sequence of a gene as a
template to synthesize a strand of RNA (ribonucleic
acid)
• transcription
• Process by which an RNA is assembled from
nucleotides using the base sequence of a gene as a
template
Three Types of RNA
• Three types of RNA have roles in protein
synthesis:
• Ribosomal RNA (rRNA) is the main
component of ribosomes, the structures upon
which polypeptide chains are built
• Transfer RNA (tRNA) delivers amino acids to
ribosomes in the order specified by a
messenger RNA (mRNA)
RNA Structure
• RNA is a single-stranded chain
of four kinds of nucleotides
• Like DNA, a RNA nucleotide
has three phosphate groups, a
sugar, and one of four bases,
but RNA is slightly different:
• The sugar in RNA is ribose,
not deoxyribose
• RNA uses the base uracil
instead of thymine
DNA and RNA Compared
Converting mRNA to protein
• Translation converts information in an mRNA to
protein
• mRNA carries a protein-building message encoded
in the sequence of sets of three nucleotide bases
• mRNA is decoded (translated) into a sequence of
amino acids, resulting in a polypeptide chain that
folds into a protein
• translation
• Process by which a polypeptide chain is assembled
from amino acids in the order specified by an mRNA
Transcription
• During transcription, DNA acts as a template
upon which a strand of RNA (transcript) is
assembled from RNA nucleotides
• Each new RNA is complementary in sequence to
the DNA template: G pairs with C; A pairs with
U (uracil)
• RNA polymerase adds nucleotides to the end
of a growing transcript
3 Steps in Transcription
• Transcription begins with a gene on a chromosome: RNA
polymerase and several regulatory proteins attach to a specific
binding site (promoter) in the DNA
3 Steps in Transcription
• 2. RNA polymerase starts moving along the DNA, in the 3′ to
5’ direction over the gene, unwinding the double helix to
“read” the base sequence of the DNA strand
3 Steps in Transcription
•
RNA polymerase bonds free RNA nucleotides into a chain, in
the order dictated by that DNA sequence, making an RNA
copy of the gene
Finishing Transcription
• When the polymerase reaches the end of the gene,
the DNA and the new RNA strand are released
• Typically, many polymerases transcribe a particular
gene region at the same time, so many new RNA
strands can be produced very quickly
Post-transcriptional Modifications
• Eukaryotes modify their RNA inside the nucleus,
then ship it to the cytoplasm
• Introns are nucleotide sequences that are removed
from a new RNA, and exons are sequences that stay
in the RNA
• Sometimes, some exons are removed and the
remaining exons are spliced together (alternative
splicing) which enables one gene to encode
different proteins
Post-transcriptional Modifications
• New transcripts that will become mRNAs are
further modified after splicing
• A modified guanine “cap” is added to the 5’ end,
which will help the mRNA bind to a ribosome
• A tail of 50-300 adenines (poly-A tail) is added
to the 3’ end
Genetic Code
• The protein-building information in mRNA consists
of a sequence of three mRNA bases (codon); each
is a code for a particular amino acid
• The four bases A, C, G, and U can be combined into
64 different codons, which constitute the genetic
code
• Example: AUG codes for the amino acid methionine
(met), and UGG codes for tryptophan (trp)
Codons and Amino Acids
• There are only twenty kinds of amino acids found in
proteins, so some amino acids are specified by more
than one codon
• Some codons signal the beginning and end of a
protein-coding sequence:
• AUG (methionine) start translation
• UAA, UAG, and UGA are stop codons
• The order of mRNA codons determines the order of
amino acids in the polypeptide that will be
translated from it
The Genetic Code
DNA, mRNA, and Proteins
rRNA and tRNA: the Translators
• Ribosomes (containing rRNA and structural
proteins) and tRNAs interact to translate an mRNA
into a polypeptide
• One large and one small ribosomal subunit join with
mRNA, and rRNA enzymatically catalyzes the
formation of a peptide bond between amino acids
• Transfer RNAs deliver amino acids to ribosomes in
the order specified by mRNA
Ribosome Strucutre
tRNA Structure
Translation
• Translation converts the information carried by
an mRNA into a polypeptide
• Translation occurs in the cytoplasm
• Translation proceeds in three stages: initiation,
elongation, and termination
6 Steps in Translation
(1) Translation
initiates when
ribosome subunits
and an initiator
tRNA converge on
an mRNA
• A second tRNA
binds to the second
codon
6 Steps in Translation
(2) The ribosome
catalyzes
formation of a
peptide bond
between the first
two amino acids
6 Steps in Translation
(3) The first tRNA
is released and the
ribosome moves to
the next codon.
• A third tRNA
binds to the third
codon
6 Steps in Translation
(4) A peptide
bond forms
between the
second and third
amino acids
6 Steps in Translation
(5) The second
tRNA is released
and the
ribosome moves
to the next codon
• A fourth tRNA
binds the fourth
codon
6 Steps in Translation
(6) A peptide bond
forms between the
third and fourth
amino acids
• Process repeats
until the ribosome
encounters a stop
codon
Overview
Mutated genes and Protein Products
• If a mutation changes the genetic instructions
encoded in the DNA, an altered gene product
may result
• Example: Hemoglobin consists of four
polypeptides (globins) folded around a heme
(iron-containing cofactor)
• Various defects in the polypeptides can cause
anemia
Hemoglobin
• Hemoglobin consists of
4 polypeptides: 2 alpha
globins (blue) and 2
beta globins (green)
• Oxygen molecules bind
to the iron atom at the
center of each heme
Defects in Hemoglobin
• Frameshift mutations:
• A deletion from DNA of the beta globin gene causes a
type of anemia called beta thalassemia
• An insertion mutation can also alter polypeptides
• deletion
• Mutation in which one or more base pairs are lost
• insertion
• Mutation in which one or more base pairs are added
Frameshift Mutations
• A frameshift garbles the genetic message like adding or
deleting a letter garbles the meaning of a sentence:
The cat ate the rat
T hec ata tet her at
Th eca tat eth era t
Base-Pair Deletion
Defects in Hemoglobin (cont.)
• Other types of mutations do not cause frameshifts:
• In base-pair-substitution, a nucleotide and its partner
are replaced by a different base pair
• Sickle-cell anemia results from a substitution of valine for
glutamic acid
• base-pair substitution
• Type of mutation in which a single base-pair changes
Base-Pair Substitution
Sickle-Cell Anemia
• Substitution of valine
for glutamic acid causes
HbS protein to clump
• Normally round red
blood cells are distorted
into sickle shapes
What Causes Mutations?
• There are many causes of mutations:
• Transposable elements can cause insertion mutations
• Mistakes occur during DNA replication
• Environmental agents can damage DNA
• Natural or synthetic chemicals can cause mutations
• transposable element
• Segment of DNA that can spontaneously move to a new
location in a chromosome
Environmental Factors in Mutation
• Ionizing radiation (such as x-rays) breaks chromosomes into
pieces that get lost during DNA replication, or forms
destructive free radicals
• Nonionizing radiation (such as UV light) can form thymine
dimers (two adjacent thymine bases covalently bonded to one
another) that kink DNA
• Chemicals in cigarette smoke can cause mispairing during
replication, or stop replication entirely

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