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Standard 4 - Genetics
Unit 10 – DNA, RNA, & Protein
Synthesis
Objectives
• B4.2C: Describe the structure and function of DNA.
• B4.2D: Predict the consequences that changes in the
DNA composition of particular genes may have on an
organism (e.g., sickle cell anemia, other).
• B4.2f: Demonstrate how the genetic information in DNA
molecules provides instructions for assembling protein
molecules and that this is virtually the same mechanism
for all life forms.
• B4.2g: Describe the processes of replication,
transcription, and translation and how they relate to each
other in molecular biology.
Mitosis
The Big Picture
somatic (body) cells
Meiosis
sex cells (sperm or egg)
2N
2N
2N = Diploid
1N = Haploid
2N
2N
2N
2N
1N
1N
1N
2N
Diploid
1N
GENETICS
• PAIRS OF CHROMOSOMES IN LIVESTOCK & HUMANS:
• Species
# of Chromosomes
Turkeys
41
Chickens
39
Horses
32
Cattle
30
Goats
30
Sheep
27
Humans
23
Swine
19
GENETICS
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Homo sapiens (human)46
Mus musculus (house mouse)40
Drosophila melanogaster (fruit fly)8
Caenorhabditis elegans (microscopic roundworm)12
Saccharomyces cerevisiae (budding yeast)32
Arabidopsis thaliana (plant in the mustard family)10
Xenopus laevis (South African clawed frog)36
Canis familiaris (domestic dog)78
Gallus gallus (chicken)78
Zea mays (corn or maize)20
Muntiacus reevesi (the Chinese muntjac, a deer)23
Muntiacus muntjac (its Indian cousin)6
Myrmecia pilosula (an ant)2
Parascaris equorum var. univalens (parasitic roundworm)2
Cambarus clarkii (a crayfish)200
Equisetum arvense (field horsetail, a plant)216
GENETICS
• Chromosomes = Part of a cell that contains genetic information.
• Genes = small bits of heredity information; genes are composed of DNA and
are carried on the chromosomes.
• DNA = deoxyribonucleic acid, the molecule that holds genetic information. It
is the biochemical molecule that makes chromosomes and genes.
• Relationship between DNA – chromosomes – genes?
– DNA is the concrete, Chromosomes are the wall, Genes are individual blocks.
DNA Molecule: DNA Unzip 1:16
GENETICS
• DNA = deoxyribonucleic acid
• Found in the nuclei of cells – there is 46
chromosomes in each human cell nuclei
• If the DNA in all 46 human chromosomes
in 1 cell were uncoiled it would stretch out
to be more than 6 feet in length
• Crick and Watson worked out the
structure of DNA = double helix
• Contains all your traits (genes) and
makes up chromosomes
• Thousands of genes are contained on
each DNA molecule
DNA: Deoxyribonucleic Acid (02:02)
GENETICS
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DNA = deoxyribonucleic acid
The vertical sides of DNA are made up of sugar and phosphate
Cross pieces are nucleotide bases: A-T C-G
Genetic traits are determined by the order of the DNA nucleotide
bases A T C G
• DNA makes a copy of itself = replication
GENETICS
• Two different kinds of genetic material exist: deoxyribonucleic
acid (DNA) and ribonucleic acid (RNA).
• Most organisms are made of DNA, but a few viruses have RNA
as their genetic material. The biological information contained in
an organism is encoded in its DNA or RNA sequence.
• Interestingly, as much as 98% of human DNA does not code for
a specific product.
• Prokaryotic genetic material is organized in a simple circular
structure that rests in the cytoplasm.
• Eukaryotic genetic material is more complex and is divided into
discrete units called genes.
Genes (02:17)
GENETICS
• The information passed from parents to offspring is transmitted by
means of genes that are coded in DNA molecules. These genes
contain the information for the production of proteins.
• Genes express their functional effect through the production of
proteins, which are complex molecules responsible for most functions
in the cell. Proteins are chains of amino acids, and the DNA
sequence of a gene (through an RNA intermediate) is used to
produce a specific protein sequence.
• Each group of three nucleotides in the sequence, called a codon,
corresponds to one of the twenty possibly amino acids in protein —
this correspondence is called the genetic code. The specific
sequence of amino acids results in a unique three-dimensional
structure for that protein, thereby determining its behavior and
function.
GENETICS
• The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is
composed of a chain of nucleotides, of which there are four types: adenine
(A), cytosine (C), guanine (G), and thymine (T). Genetic information exists
in the sequence of these nucleotides, and genes exist as stretches of
sequence along the DNA chain.
The genetic code: DNA, through a messenger RNA intermediate, codes for
protein with a triplet code.
GENETICS
• Nucleotide = Basic building block of DNA and RNA. A nucleotide is
made of a ribose sugar, nitrogenous base, and phosphate group.
• 4 Bases: Adenene, Guanine, Cytosine, Thyamine
→
A-T
C-G
• The nucleotides join together to form a chain. The phosphate end of the
chain is referred to as the 5’ end. The opposite end is the 3' end.
GENETICS
• Replication = The process of
making an identical copy of a
section of duplex (double-stranded)
DNA, using existing DNA as a
template for the synthesis of new
DNA strands
• Transcription = Transcription is
the process through which a DNA
sequence is enzymatically copied
by an RNA polymerase to produce
a complementary RNA. In the case
of protein-encoding DNA,
transcription is the beginning of the
process that ultimately leads to the
translation of the genetic code (via
the mRNA intermediate) into a
functional peptide or protein.
• Translation = The process of
turning instructions from mRNA,
base by base, into chains of amino
acids that then fold into proteins.
Introduction:
Transcription of DNA
to Messenger RNA
(02:24)
GENETICS
Identical Genes: The Science
of Identical Twins (02:13)
• TWINS:
• Identical Twins = (monozygotic) result when a single
fertilized egg splits after conception. The resulting twins are
the same sex and genetically alike, with similar foot and
hand prints, but different fingerprints and teeth marks. The
egg then splits into two genetically identical halves. They
share 100% of their genes.
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1 egg and 1 sperm
• Fraternal Twins = (dizygotic) result when two eggs are
released by the mother at the same time and each egg is
fertilized by a different sperm. Fraternal twins can be of the
same or opposite sex. They share up to 50% of their genes,
and are no more alike or different than any two siblings
would be, but their bond is just as special.
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2 eggs and 2 sperm
GENETICS
• Sex-linked = If a gene is found only on the X chromosome and not
the Y chromosome, it is said to be a sex-linked trait. Because the
gene controlling the trait is located on the sex chromosome, sex
linkage is linked to the gender of the individual. Usually such genes
are found on the X chromosome. The Y chromosome is thus missing
such genes (See Diagram above.). The result is that females will
have two copies of the sex-linked gene while males will only have
one copy of this gene. If the gene is recessive, then males only need
one such recessive gene to have a sex-linked trait rather than the
customary two recessive genes for traits that are not sex-linked. This
is why males exhibit some traits more frequently than females.
Examples of Sex-linked Traits:
Red-green colorblindness
Male Pattern Baldness
Hemophilia
Duchenne Muscular Dystrophy
Genetic Variation
• Mendelian Genetics can only account for a majority of the genetic
variations in species seen on earth. Other sources of Genetic
Variation include Chromosomes Crossing over, Mutations, and
Genetic Drift.
• Crossing Over
• How do you get a chromosome that is totally different from the
original chromosomes of both parents? Crossing-Over takes place
during Meiosis. During the process, DNA lengths are shared between
chromosomes. In the illustration at left, two chromosomes intertwine,
and exchange one end of the chromosome with the other. The end
Chromosome has a completely different chemical composition from
the starting two chromosomes.
Genetic Variation
• Mutations
• Mutation takes place when an organism undergoes a
spontaneous genetic change during replication. During the
process of replication, the nucleotides of a chromosome are
altered, so rather than creating an identical copy of DNA
strands, there are chemical variations in the replicated strands.
The alteration on the chemical composition of DNA triggers a
chain reaction in the genetic information of an individual. The
mutation can be passed to offspring. For example, the mutation
toward sickle cell anemia is based upon the production of one
different amino acid, which in turn affects the polypeptide
strands produced, etc. Mutations are usually non-beneficial to
an organism, however, they are almost always recessive and
unless two mutations are coupled together the mutation will not
be expressed.
• * Predict how mutations may be transferred to progeny
(offspring)
Genetic Variation
Mutations (02:03)
• Mutations …
• Gene mutation in a cell
can result in uncontrolled
cell division called
cancer.
• Also, exposure of cells to
certain chemicals and
radiation increases
mutations and thus
increases the chance of
cancer.
Basal Cell Carcinoma of the Nose
Genetic Variation
• Genetic Drift
• Gene flow refers to the passage of traits or genes between
populations. The passage of genes from one population to another
prevents high occurrences of mutation, and genetic drift. In genetic
drift, random variation occurs because the genetic population is
small, leading to the proliferation of specific traits within a population.
For example, the population in the colonial history of Martha's
Vineyard, settled in Massachusetts in 1642, had an unusually high
occurrence of deafness among it's inhabitants. The high occurrence
of deafness was a result of genetic drift, in that the population was so
small that differing traits from outside populations could not enter in.
To prevent genetic drift, genetic material must be shared between
differing populations, even so, variations can occur. For example, the
trait for sickle cell anemia is beneficial in some climates where there
is a high rate of malaria. An individual with a heterozygous genotype
for sickle cell anemia is more resistant to malaria. The concept of
gene flow consequently ties directly into the concept of adaptation
and natural selection.
Mutations
• A mutation is a permanent change in the DNA sequence of a gene.
Mutations in a gene's DNA sequence can alter the amino acid sequence
of the protein encoded by the gene. How does this happen? Like words
in a sentence, the DNA sequence of each gene determines the amino
acid sequence for the protein it encodes. The DNA sequence is
interpreted in groups of three nucleotide bases, called codons. Each
codon specifies a single amino acid in a protein.
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Types of mutations:
Original:
The fat cat ate the wee rat.
Point Mutation: The fat hat ate the wee rat.
Frame Shift:
The fat caa tet hew eer at.
Deletion:
The fat ate the wee rat.
Insertion:
The fat cat xlw ate the wee rat.
Inversion:
The fat tar eew eht eta tac.
Mutations
• Mutate a sentence!
• We can think about the DNA sequence of a gene as a sentence made up
entirely of three-letter words. In the sequence, each three-letter word is a
codon, specifying a single amino acid in a protein. Have a look at this
sentence:
• Thesunwashotbuttheoldmandidnotgethishat.
• If you were to split this sentence into individual three-letter words, you would
probably read it like this:
• The sun was hot but the old man did not get his hat.
• This sentence represents a gene. Each letter corresponds to a nucleotide
base, and each word represents a codon. What if you shifted the three-letter
"reading frame?" You would end up with this:
• T hes unw ash otb utt heo ldm and idn otg eth ish at.
• Or
• Th esu nwa sho tbu tth eol dma ndi dno tge thi sha t.
Mutations
• As you can see, only one of these three "reading frames"
translates into an understandable sentence. In the same
way, only one three-letter reading frame within a gene
codes for the correct protein.
• Now, going back to the original sentence:
• Thesunwashotbuttheoldmandidnotgethishat.
• See how you can mutate the reading frame of this
sentence by inserting or deleting letters within the
sentence.
• It's easy to make mutations that create "nonsense"
sentences. Can you make mutations that maintain or
change the meaning of the sentence without creating
such nonsense?
Mutations
Mutations
I have been told that due to pestacide use that some tree frogs in the
southern US have been having pigment mutation and turning blue.
Mutations
Mutations
Natural Selection and Mutation The Case of the Peppered Moth
This poor little rascal knows what it's
like to have part of his genome deleted
Mutations
Six Legged Calf
Walking Two Legged Dog
Two Headed Turtle
Mutations
Frog and a Half
Eight Legged Cat
Genetic Variation
• Jumping Genes = Transposons are sequences of DNA that can
move around to different positions within the genome of a single cell,
a process called Transposition. In the process, they can cause
mutations and change the amount of DNA in the genome.
Transposons are also called "jumping genes" or "mobile genetic
elements". There are a variety of mobile genetic elements, they can
be grouped based on their mechanism of transposition.
• Deletion = when a part of a chromosome is missing, or part of the
DNA code is missing, in the process of DNA replication, a deletion
occurs if a nucleotide or series of nucleotides is not copied. Such
deletions may be harmless, may result in disease, or may in rare
cases be beneficial.
• Duplication = A double copy of part of a chromosome resulting in an
extra (abnormal) dose of the duplicated material, or when a part of a
chromosome is present in two copies.
Genetic Variation
• It may be possible to identify genetic defects from a karyotype of a few cells.
• Karyotype = A picture of the chromosomes in a cell that is used to check for
abnormalities. A karyotype is created by staining the chromosomes with dye
and photographing them through a microscope. The photograph is then cut
up and rearranged so that the chromosomes are lined up into corresponding
pairs.
This is an example of trisomy 21 (47,
XY, +21) also known as Down
syndrome. Additions or deletions of
genetic material are generally lethal in
utero, but Trisomy 21 is an example of
one form of addition in which the fetus
may occasionally survive to term and
beyond. The overall incidence is 1 in
1000 livebirths, but the nondysjunctional event in meiosis that
produces this anomaly increases in
incidence with increasing maternal
age, particularly over age 40.
Genetic Engineering
-Genetic engineering techniques provide great potential and
responsibilities.
-Genetic engineering, recombinant DNA technology, genetic
modification/manipulation (GM) and gene splicing are terms that are applied
to the manipulation of genes, implying that the process is outside the
organism's natural reproductive process. It involves the isolation, manipulation
and reintroduction of DNA into cells or model organisms, to express a protein.
-The aim is to introduce new characteristics or attributes physiologically or
physically, such as making a crop resistant to herbicide, introducing a novel trait
or enhancing existing ones, or producing a new protein or enzyme.
-Successful endeavors include the manufacture of human insulin by bacteria,
the manufacture of erythropoietin in Chinese hamster ovary cells, the
production of new types of experimental mice such as the OncoMouse (cancer
mouse) for research, and round up ready crops.
Genetic Engineering
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Roundup Ready Corn and Soybeans - All plants make proteins.
Roundup Ready plants produce the same natural proteins as any
other plant with one notable exception. These plants make an
additional protein which allows them to grow in the presence of
Glyphosate, known commercially as “Roundup,” one of the most
widely-used herbicides employed by back-yard gardeners,
homeowners, golf courses and commercial farms for the past 25
years. The protein is not a toxin to plants, animals, insects, humans
or bacteria.
Transgenics: Splicing Genes
Across Species (03:19)
Cloning Debate (37-3 / Debate)
Pros of Cloning: + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
• If the vital organs of the human body can be cloned, they can serve as
backup systems for human beings. Cloning body parts can serve as a
lifesaver. When a body organ such as a kidney or heart fails to function, it
may be possible to replace it with the cloned body organ.
• Cloning in human beings can prove to be a solution to infertility. Cloning
has the potential of serving as an option for producing children. Cloning may
make it possible to reproduce a certain trait in human beings. We will be
able to produce people with certain qualities, human beings with particular
desirable traits, thus making human beings a man-made being!
• Cloning technologies can prove helpful for the researchers in genetics.
They might be able to understand the composition of genes and the effects
of genetic constituents on human traits, in a better manner. They will be able
to alter genetic constituents in cloned human beings, thus simplifying their
analysis of genes. Cloning may also help us combat a wide range of
genetic diseases.
• Cloning can make it possible for us to obtain customized organisms and
harness them for health benefits of society. Cloning can serve as the best
means to replicate animals that can be used for research purposes.
• Cloning can enable the genetic alteration of plants and animals. If
positive changes can be brought about in living beings with the help of
cloning, it will indeed be a boon to mankind.
Cloning Debate (37-3 / Debate)
Cons of Cloning: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - • Cloning created identical genes. It is a process of replicating a genetic
constitution, thus hampering the diversity in genes. While lessening the
diversity in genes, we weaken our ability of adaptation. Cloning is also
detrimental to the beauty that lies in diversity.
• While cloning allows man to tamper with genetics in human beings, it also
makes deliberate reproduction of undesirable traits, a probability. Cloning
of body organs might invite malpractices in society.
• In cloning human organs and using them for transplant, or in cloning human
beings themselves, technical and economic barriers will have to be
considered. Will cloned organs be cost-effective? Will cloning techniques
really reach the common man?
• Moreover, cloning will put human and animal rights at stake. Will cloning
fit into our ethical and moral principles? Cloning will leave man just another
man-made being. Won't it devalue mankind? Won't it undermine the value of
human life?
• Cloning is equal to emulating God. Is that easy? Is that risk-free? Many are
afraid it is not!
Genetic Engineering
• What are the advantages and disadvantages of
human manipulation of DNA? …
• Debate
Video Quiz: Genetics: The Molecular Basis of Heredity (01:14)