Unit 4 - Topic 1 (Mutations)

Question 1

What are mutations?

Answer 1

A mutation is a permanent alteration in the genetic material (DNA or RNA) that can affect a single gene, a segment of a chromosome, or an entire chromosome, potentially leading to changes in an organism’s traits.

Question 2

What are causes of mutations?

Answer 2

• spontaneous: naturally occurring during DNA replication or meiosis
• induced: caused by exposure to a mutagen

Question 3

What are spontaneous point mutations?

Answer 3

A spontaneous point mutation is a naturally occurring change in a single nucleotide of DNA, caused by random errors during replication or normal cellular processes.

Question 4

What are spontaneous frameshift mutations?

Answer 4

A spontaneous frameshift mutation is a random naturally occurring insertion or deletion of nucleotides in DNA that alters the reading frame, changing the sequence of amino acids produced.

Question 5

What is spontaneous non-disjunction?

Answer 5

Spontaneous non-disjunction is a random error in cell division where chromosomes fail to separate correctly, leading to cells with abnormal chromosome numbers.

Question 6

What is aneuploidy?

Answer 6

Aneuploidy is the presence of an abnormal number of chromosomes in a cell due to errors in chromosome separation during cell division

Examples:
- trisomy 21 (down syndrome): an extra chromosome 21
- monosomy X (turner syndrome): one X chromosome missing

Question 7

What are induced mutations?

Answer 7

An induced mutation is a change in the DNA sequence caused by exposure to external agents (mutagens) such as radiation, chemicals, or viruses.

Question 8

How are mutations inherited?

Answer 8

Mutations are inherited only if they occur in the gametes (the sperm or egg cells) because these cells pass genetic information to offspring during reproduction.

Germline mutations occur in reproductive cells and can be passed on to the next generation. Every cell in the offspring will carry the mutation.
- example: a mutation in a sperm cell that leads to a genetic disorder in a child.

Somatic mutations occur in body (non-reproductive) cells. These cannot be inherited, as they aren’t part of the gametes. They can cause diseases like cancer but only affect the individual.

Question 9

How do mutations affect genotype and phenotype?

Answer 9

Mutations alter the genotype by changing the DNA sequence, which can in turn affect the phenotype by changing the structure or function of the proteins the genes produce.

Question 10

How do mutations lead to genetic variation?

Answer 10

Mutations can introduce new alleles into a population of organisms and increase the population’s genetic variation

Question 11

What are block mutations?

Answer 11

Block mutations are structural changes in a chromosome that affect a large segment of DNA, potentially altering multiple genes and their functions.

Types:
- deletion: a section of the chromosome is lost
- duplication: a section of the chromosome is repeated
- inversion: a section of the chromosome is reversed end to end
- translocation: a section of the chromosome moves to a different location

Question 12

What are chromosome mutations?

Answer 12

Chromosome mutations are alterations in the structure or number of chromosomes, which can lead to changes in gene arrangement or dosage and may affect an organism’s traits.

Types of chromosome mutations:
- Structural mutations (block mutations): deletions, duplications, inversions, translocations.
- Numerical mutations (aneuploidy or polyploidy): changes in the number of chromosomes, such as trisomy 21 (Down syndrome).

Question 13

What is spontaneous mutation?

Answer 13

A spontaneous mutation is a random alteration in DNA caused by natural errors during DNA replication, cell division, or normal chemical changes in the DNA.

Question 14

What is congenital?

Answer 14

Congenital describes a condition or trait that is present at birth, which may result from genetic factors, environmental influences during development, or a combination of both.

Question 15

What is a mutagen?

Answer 15

A mutagen is a physical, chemical, or biological agent that causes changes (mutations) in DNA, potentially altering gene function, leading to genetic disorders, cancer, or evolutionary variation.

Question 16

What is a double-strand break?

Answer 16

A double-strand break (DSB) is a type of DNA damage where both strands of the DNA helix are broken, potentially causing mutations, chromosomal rearrangements, or cell death if unrepaired.

Question 17

What is an indel?

Answer 17

An indel is a small insertion or deletion of nucleotides in a DNA sequence, which can disrupt gene function, alter protein coding, or affect regulatory regions.

Question 18

What is intraspecific variation?

Answer 18

Intraspecific variation is the variation in traits (genetic or phenotypic) that occurs within a single species, caused by genetic differences, mutations, or environmental influences.

Question 19

What is an autosomal chromosome?

Answer 19

An autosomal chromosome is any chromosome that is not a sex chromosome, present in pairs in both males and females, and carries genes determining most body traits and functions.

Question 20

What is a sex chromosome?

Answer 20

A sex chromosome is a chromosome that determines an organism’s biological sex (e.g., X or Y in humans) and carries genes related to sexual development and some other traits.

Question 21

Describe how an inherited mutation can alter the variations in the genotype of offspring?

Answer 21

An inherited mutation is passed from parent to offspring via gametes, introducing new alleles that alter the offspring’s genotype, potentially creating novel traits or increasing genetic variation within a population.

Question 22

List four effects as a result of a chemical mutagen in DNA?

Answer 22

• point mutations
• base substitutions
• frameshift mutations
• chromosomal rearrangements

Question 23

What is a point mutation?

Answer 23

A point mutation is any mutation that changes a single nucleotide in the DNA. It can be spontaneous or induced.

Question 24

What is a frameshift mutation?

Answer 24

A frameshift mutation is a mutation caused by insertion or deletion of nucleotides that shifts the reading frame of a gene. It can be spontaneous or induced.

Question 25

What is trisomy?

Answer 25

Trisomy is a chromosomal abnormality in which a cell has three copies of a particular chromosome instead of the normal two, often causing developmental disorders

Question 26

What is monosomy?

Answer 26

Monosomy is a chromosomal abnormality in which a cell has only one copy of a particular chromosome instead of the normal two, often leading to developmental disorders or lethality.