8.7 Mutation

What are the differences between gene mutation and chromosomal mutation?

Gene mutation affects only one gene while chromosomal mutations affect multiple genes. Gene mutation happens during Replication and chromosomal mutation happend during Meiosis.

What are the two differences between gene mutation and chromosomal mutation.

Gene mutation effects a single gene , but chromosomal mutation effects many genes . Gene mutation happens during replication but chromosomal mutaion happens during meiosis 1 in prophase1 .

On the inside of a protein, a mutation causes the swap of one amino acid with another. This change does not affect the internal structure of the protein, and both proteins act similarly in their roles. Which of the following represents this situation?

Missense mutation

Describe three ways in which mutations can occur.

Mutations can occur from mutagens, replication errors, or errors in the exchange of chromosome segments during meiosis.

Mutations happen both in body cells and in germ cells. What is the difference?

Mutations in body cells affect only the organism in which they occur. In contrast, mutations in germ cells may be passed to offspring. They are the underlying source of genetic variation, which is the basis of natural selection.

If GUA is changed to GUU, will the resulting protein be affected? Explain.

No, because it still codes for valine in this case

Can DNA polymerase catch and correct every replication error? Yes or No? and Why?

No. Because the DNA replication process is very fast and big errors are not corrected.

Generally, mutations that affect a single gene occur during ____________________

Replication

Gene mutations

Mutations that produce changes in a single gene Point shift mutation Frameshift mutation(deletion, insertion)

A mutation is a change in an organism's _________________

DNA

If a nucleotide is deleted from a strand of DNA, what type of mutation has occurred?

frameshift mutation

Cystic fibrosis is an example of a genetic disease caused by the deletion of a nucleotide. What is the term for this type of mutation?

frameshift mutation

From the following list, select the two types that are chromosomal mutations. gene duplication frameshift mutation translocation point mutation (substitution)

gene duplication translocation

Generally, mutations that affect a single gene occur during __________________

replication

Mutations that affect a single gene happen during .............................., whereas mutations that affect a group of genes or an entire chromosome happen during ..................................

replication, meiosis

How many bases are effected in a point mutation?

One

Explain why mutagens can damage DNA in spite of repair enzymes.

Mutagens may produce so much damage that the repair enzymes can't keep up

Agent that can induce or increase the frequency of mutation in organisms.

Mutagen

A mutation can affect an organism to different degrees. The effect depends on factors such as:

the number of genes involved and the location of the mutation.

Gene mutations, though smaller in scale, can also have a big effect on an organism. Suppose a substitution occurs in a coding region of DNA that changes an AAG codon to CAG. The resulting protein will have a glutamine in place of a lysine. What happens if this change happens in the active site of an enzyme?

1. the enzyme may not be able to bind to its substrate. 2. If the substituted amino acid differs from the original one in size or polarity, the mutation could affect protein folding and thus possibly destroy the protein's function. 3. A substitution could also result in a premature stop codon.

Silent mutation

A mutation that does not affect the resulting protein

Why aren't mutations in body cells passed on to offspring?

Because body cells do not give rise to gametes

True or False A duplication happens when a piece of one chromosome attaches to a nonhomologous chromosome.

False

True or False if the error occurred in a body cell, the offspring could be affected.

False

Mutation that involves the insertion or deletion of a nucleotide in the DNA sequence.

Frame-shift mutation

For a mutation to be passed to offspring, it must occur in the autosomal / germ cells.

Germ cells

One of the following examples includes a silent mutation. Which one? -A sunbather forgets to put sunscreen on. The DNA within many skin cells is damaged, and several mutations happen when it is repaired. -In the third spot of the codon, a C mutates to a G. Both codons call for threonine amino acid -Due to a mutation, a changed amino acid within an enzyme cause it to slow down.

In the third spot of the codon, a C mutates to a G. Both codons call for threonine amino acid

An agent in the environment that can change DNA is called a______________

Mutagen

change in the DNA sequences of nucleotides.

Mutation

Mutation that involves a substitution of only one nucleotide.

Point mutation

Explain why frameshift mutations have a greater effect than do point mutations.

Point mutation can just change a single codon where frameshift can shift the whole sequence

True or False A mutation that will not affect phenotype is one that does not change the amino acid sequence, or one that does not affect protein function.

True

True or False UV light damages a DNA strand by causing neighboring thymine nucleotides to break their hydrogen bonds to adenine and bond with each other instead.

True

Mutagens

agents in the environment that can change DNA. They speed up the rate of replication errors and, in some cases, even break DNA strands. Some mutagens occur naturally, such as ultraviolet (UV) rays in sunshine. Many others are industrial chemicals.

Mutations are not uncommon, and organisms have many tools to repair them. However, events and substances can make mutations happen faster than the body's repair system can handle. DNA polymerase has a built-in proofreading function. Nevertheless, a small number of replication errors are not fixed. They build up over time, and eventually affect how the cell works. For example, many studies suggest that mutations are a significant cause of ...............................

aging

If a nucleotide was added, or inserted, and all the letters shifted to the right. In the same way, a nucleotide sequence loses its meaning when an insertion or deletion shifts all the codons by one nucleotide. This change throws off the reading frame, which results in codons that code for different ....................................

amino acids.

A translocation happens when a piece of one chromosome attaches to / detaches from a nonhomologous chromosome.

attaches to

The human body has DNA repair enzymes that help find and fix mutations. For instance, UV light can cause neighboring thymine nucleotides to break their hydrogen bonds to adenine and bond with each other instead. Typically, one enzyme removes the bonded thymines, another replaces the damaged section, and a third bonds the new segment in place. Sometimes, these enzymes do not work. If these mistakes interfere with regulatory sites and control mechanisms, they may result in .....................

cancer.

Cystic fibrosis (CF) is a genetic disease that is most commonly caused by a specific ............................... It causes the overproduction of thick, sticky mucus. Although CF cannot be cured, it is treated in a number of ways, including oxygen therapy

deletion

What type of mutation is a translocation?

chromosomal mutation

Which type of mutation affects more genes, a gene mutation or a chromosomal mutation? ___________________

chromosomal mutation

Frameshift mutation

involves the insertion or deletion of a nucleotide in the DNA sequence. It usually affects a polypeptide much more than does a substitution.

Point mutation

is a mutation in which one nucleotide is substituted for another. Very often, such a mistake is caught and fixed by DNA polymerase. If it is not, the substitution may permanently change an organism's DNA.

Translocation

is another type of chromosomal mutation. When a piece of one chromosome moves to a nonhomologous chromosome. Translocations are often reciprocal, which means that the two nonhomologous chromosomes exchange segments with each other.

Chromosomal Mutations

mutations that affect the number or structure of chromosomes, gene duplication and gene translocation. Chromosomal mutations affect a lot of genes and tend to have a big effect on an organism.

Frameshift mutations are so named because:

they shift the entire sequence following them by one or more nucleotides.

Mutations in the germ line affect the .................................... of offspring. Often, this effect is so harmful that offspring do not develop properly or die before they can reproduce. Other mutations, though less severe, still result in less adaptive phenotypes. In such cases, natural selection removes these mutant alleles from the population. More rarely, a mutation results in a more beneficial phenotype. These mutations are favored by natural selection and increase in a population.

phenotype

From the following list, select the two types of mutations that are gene mutations. gene duplication point mutation (substitution) translocation frameshift mutation

point mutation (substitution) frameshift mutation

Which type of mutation has no effect on phenotype?

silent mutation

A _____________________ happens when a piece of one chromosome attaches to a nonhomologous chromosome.

translocation

When point mutations occur in non-coding regions they may result in:

1. No change 2. Lack of regulation 3. Altered splice site

When point mutations occur in coding regions they may result in:

1. Nonfunctional protein 2. Premature stop code 3. No change

Even a gene mutation that occurs in a noncoding region can cause problems. For example, such a mutation could:

1. disrupt an mRNA splice site and prevent an intron from being removed. 2. Could interfere with the regulation of gene expression, keeping a protein from being produced or causing it to be produced all the time.

What is the difference between a nonsense mutation and a silent mutation?

A silent mutation does nothing, while a nonsense mutation can be significantly disruptive

In the nucleotide chains below is a string of nucleotides. a. Indicate the reading frame of the nucleotide sequence of codons. ATGCGTCCATGA b. Make a point mutation. Circle the mutation. ATGCGTCCATGA c. Make a frameshift mutation. Use brackets to indicate how the reading frame would be altered by the mutation. ATGCGTCCATGA (SOLVE ON PAPER)

A) Sequence of Codons: UAC GCA GGU ACU. (Which is mRNA codons) B) AT(G)CGTCCATGA--> AT(C)CGTCCATGA. From the first codon G replaced with C (during DNA replication C) ATGCGTCCATGA----> AT(A)GCGTCCATGA. A is inserted so instead of being ATG triplet that is converted into ATA triplet due to insertion of A (during DNA replication)

True or False Point mutation would probably have a lesser effect on the organism than a frameshift mutation, because an incorrect amino acid might have little effect on a protein if it has about the same size and the same polarity as the original amino acid or if it is far from an active site.

True

Which of the following is an example of a mutagen? repair enzyme triglyceride thymine UV sunlight

UV sunlight

Gene duplication happens when there is equal / unequal cross-over event.

Unequal

Gene duplication

When homolohous chromosomes do not align with each other, the segments exchanged during crossing over may be different in size. As a result, one chromosome may have two copies of a gene or genes.

Mutation

a change in an organism's DNA.

During meiosis, homologous chromosomes exchange DNA segments through crossing over. If the chromosomes do not align with each other, these segments may be different in size. As a result, one chromosome may have two copies of a gene or genes, which is called .................................. The other chromosome may have no copy of the gene or genes. Gene duplication has happened again and again throughout eukaryotic evolution.

gene duplication.

Mutations that can affect the offspring of an organism occur in what cell type?

germ cells

Many gene mutations, however, do not affect an organism's phenotype. Remember that many codons code for the same amino acid. Therefore, some substitutions have no effect, especially those occurring in the third nucleotide of a codon. If AAG changes to AAA, the resulting protein still has the correct amino acid, lysine. A mutation that does not affect the resulting protein is called ........................................

silent

An incorrect amino acid might have little effect on a protein if it has about the same ................................. as the original amino acid or if it is far from an active site. If a mutation occurs in a noncoding region, such as an intron, it may not affect the encoded protein at all.

size or polarity

In rare cases, people inherit mutations that make their DNA repair systems less active, which makes these people very vulnerable to the damaging effects of .................................. Some cancer drugs take advantage of mutagenic properties by causing similar damage to cancer cells. One type of drug wedges its way between nucleotides, causing so many mutations that cancer cells can no longer function.

sunlight