Unit 8 Lesson 3: Genetic Variation from Errors Flashcards
Cell theory
Cell theory states that all organisms are made of cells and that cells reproduce from pre-existing cells
Genetic variation can occur from
chromosomal changes that happen during meiosis.
Any changes made to the DNA sequence is called a
mutation
Chromosomal changes could be in the form of..
Chromosomal changes could be in the form of numeric mutations affecting the number of chromosomes, or structural mutations that alters the way the chromosome is coded.
Exmaple of a strucutal mutation
For example, a structural mutation can be an insertion or deletion of a portion of the chromosome. This is why the process of meiosis is important in sexual reproduction.
What happenes during Meiosis
Meiosis creates new sex cells, that is, sperm and egg cells. These cells are known as haploid cells because they contain half the chromosomes that normal body cells do. The changes that occur mostly happen during the early stages of development.
genetic information is found in the double-stranded structures of
deoxyribonucleic acid, or DNA, in the chromosomes of cells.
The strands of DNA contain nucleotide bases that code for
triplet codons.
What does each condon of DNA code for
Each codon codes for a particular amino acid. The amino acid patterns become the building blocks for proteins.
What must take place before mitosis or meiosis can begin
Before mitosis or meiosis can begin, cells must copy, or replicate, the strands of DNA so they are available for new cells
In order for replication to occur, the strands of DNA must
separate
How does DNA repliacte
This occurs when an enzyme “unzips” the strand of DNA. Complementary strands are created for each separated strand. This results in two matching chromosomes that are identical to the original chromosome.
DNA polymerase
an enzyme that plays a critical role in placing nucleotides in the correct order
Role of DNA polymerase
Another enzyme, DNA polymerase, plays an important role during replication by placing the copied nucleotide bases in the correct order.
What does DNA polymerase do
DNA polymerase double-checks, or proofreads, the bases as they are added.
What does DNA polymerase do if theres a mistake
If there is a mistake, DNA polymerase will “cut out” and release the incorrect nucleotide.
What will DNA polymerase do if there a correct base
The correct base will then be added into the sequence.
How does a substitution mutation happen
Nucleotide bases are represented by the letters A, T, C, and G, with A and T pairing up and C and G pairing up. If any of the bases are mistakenly exchanged for another, the mutation is called a substitution mutation.
Substitution mutation
a nucleotide base is replaced with the wrong corresponding pair
Substitution Mutations: if G is added instead of A, the G will pair up with T. What effect could this have
if G is added instead of A, the G will pair up with T. This could create a codon that changes the amino acid being produced. This, in turn, could cause a small change in the protein that is created. Sickle cell anemia could happen
Substitution Mutations: What is Sickle cell anemia
Sickle cell anemia is a disorder caused by a substitution mutation, in which a single amino acid is altered in the beta-hemoglobin gene located in red blood cells.
Substitution Mutations: What are Silent mutations
Silent mutations are mostly harmless because the substitution creates a codon that still produces the same proteins. This does not result in any change in gene expression, hence it is “silent.”
Substitution Mutations: What happens if a substitution creates a “stop” codon
If a substitution creates a “stop” codon, the copied strand will produce an incomplete protein. This type of protein will not be able to function properly. Sometimes this is called a nonsense mutation.
Insertion mutations
add extra base pairs to the DNA sequence making it longer than it should be to code specific proteins
What do the effects of insertion mutations rely on
Remember that nucleotide codons are found in groups of three, so the effects of this type of mutation depends on the number of bases inserted.
(insertion mutations) If the inserted number of bases is not in a multiple of three, what kind of mutation occurs?
If the inserted number of bases is not in a multiple of three, a frameshift mutation occurs, shifting the reading frame for all the codons that follow.
What impact can a frameshift mutation have
This mutation can change the entire protein that is made and can lead to serious problems, such as birth defects or no development at all.
Frameshift mutation
adding or removing base pairs so that the DNA sequence can no longer be put into exact triplets
. A frameshift mutation means that the nucleotides in the DNA sequence can no longer be put into
exact triplets
(insertion mutations) In a frameshif mutation what could lead to an essential protein not be coded
There might be one or two bases left which could potentially lead to an essential protein not being coded.
If the frameshift mutation occurs towards the beginning of the sequence, what could happen?
If the frameshift mutation occurs towards the beginning of the sequence, then it could potentially result in a completely different translation than the original strand.
(insertion mutations) If there is an insertion of a three-base group, what happens
If there is an insertion of a three-base group, then there is no frameshift mutation, and the insertion will potentially have less harmful effects.
When do Deletion mutations occur
Deletion mutations occur where sections of DNA are not copied during replication.
What impact do Deletion mutations have
This means some parts of a codon may be read incorrectly and the length of the copied gene might change.
What is a Point deletion
when one base is deleted in the DNA sequence which can lead to incorrect protein synthesis
Cystic fibrosis is an example of a disease that is a result of a
a point deletion on the CFTR gene
How does Cystic fibrosis affect somebody
a point deletion on the CFTR gene that affects the proteins that move salt and water in and out of cells, creating mucus buildup in different areas of the body.
What impact can the deletion of 1 or 2 bases have
A deletion of one or two bases may also cause a frameshift mutation that can result in changes in the rest of the DNA depending on where in the sequence it occurs.
(Deletion mutations) What impact could three or more bases are lost in a gene have
If three or more bases are lost in a gene, entire amino acids can be missing from proteins, which can lead to even more serious functional effects.
Many replication errors can contribute to inheritable genetic variations, what are those
changes in genetic material that can be passed to offspring
viable errors
changes that can be passed to living offspring
viable errors are those that can be passed to the next generation because they allow the offspring to develop and survive. However what downside may viable errors have
However, the inherited genetic variations may result in severe health disorders, a shortened life span, or sterile offspring.
Impact od serve replication errors
Most replication errors are so severe they prevent an offspring from developing at all, which means the error is not viable. The offspring will not develop or survive, and thus no inheritable genes are passed on.
Look at the following segments of DNA, and describe the types of mutation that occurred.
a) Original: ACT CAT
Mutation: ACT GCAT
b) Original: ATT TGA GCC
Mutation: ATT GAG CC
c) Original: ATT GAC CCT
Mutation: CTT GAC CCT
Reveal Answer
a) insertion mutation and frameshift mutation
b) deletion mutation and frameshift mutation
c) substitution mutation
Which of the following will cause frameshift mutations?
insertions only
deletions only
insertions and deletions
substitutions only
insertions and deletions
Describe how genetic variation occurs through meiosis.
Genetic variation through meiosis can lead to chromosomal abnormalities in the form of numeric mutations affecting the number of chromosomes, or structural mutations that alters the way the chromosome is coded. For example, a structural mutation can be an insertion or deletion of a portion of the chromosome. As genetic material copies before meiosis, other mutations can occur such as insertion, deletion, substitution, and frameshift mutations.
Sometimes mistakes are made when copying DNA. Explain the results of this mistake.
When mistakes are made when copying DNA, mutations can occur. These mutations help contribute to genetic variation in the offspring.
Explain the process of replication during cell division.
In replication, the genetic material is copied. The length of DNA that makes up a chromosome is copied to make an identical sister chromatid.
Which of the following is the enzyme that assists in placing nucleotides in the correct order?
amylase
DNA polymerase
helicase
primase
DNA polymerase
Explain what is meant by a viable error.
A viable error is an error in genetic material. The error can be passed to future generations.
Scientists have learned that any fault in the replication of DNA can cause something known as epigenetic changes. What is Epigenome
made of compounds and proteins that attach to DNA and can affect which genes are turned “on” or “off” in the production of certain proteins
Epigenetic changes
DNA modifications that do not affect the sequence but the expression of certain genes
what can impact epigenome
. Research shows that factors such as a person’s diet, exposure to pollutants, and stress can also impact the epigenome and that these changes are viable errors that may be inherited through the generations.
An example of epigenetics is methylation whats what
the attaching of methyl groups (made of one carbon and three hydrogen) to DNA to regulate gene expression
What does methylation do
With these groups added to a gene, the gene is turned off, and the protein production from that gene stops.
What impact does methylation have on peope
This action can lead to abnormal gene activity, or inactivity, and cause genetic disorders for people with a high risk of some diseases.
Under-methylation
Under-methylation – having too few methyl groups to help regulate gene expression that can lead to neurological symptoms and disorders
What impact does Under-methylation have on the body
Having too few methyl groups can cause symptoms such as obsessive-compulsive disorder, increased fear, frequent headaches, or poor concentration.
What studies have been amd eon Under-methylation
Studies are being conducted to understand the connection between under-methylation and several neurological disorders such as depression, anxiety, autism, schizophrenia, and Alzheimer’s disease.
Over-methylation
having too many methyl groups trying to regulate gene expression that can lead to neurological symptoms and disorders
What are the symptoms of people who have Over-methylation
Symptoms of people who are have over-methylation include panic attacks, sleep disorders, body aches, food or chemical sensitivities, and paranoia.
In similar studies of under-methylation, over-methylation has been linked to neurological disorders such as
depression, anxiety, and schizophrenia.
Over-methylation realsionship with sxhizopheria
Roughly 45% of schizophrenic diagnoses show that the patient also has an excess of methyl groups.
impactof studying epigenetics
Studying epigenetics can help scientists learn what effects these modifications have on gene function, the production of protein, and human health.
Describe how epigenetics can affect the characteristics of organisms.
Epigenetics affects the characteristics of organisms by changing how genes are expressed. Genes may be turned off or on when they do not need to be, and this can affect the health of some individuals.
Jose states that he is experiencing body pain, a sensitivity to certain foods, and having trouble sleeping. If tested, which would you most likely see affecting the gene expression in Jose: over-methylation or under-methylation? Explain your reasoning.
Jose seems to be producing too many methyl groups that is affecting his gene expression. The symptoms of over-methylation include body pain, sensitivity to foods, and trouble sleeping.
