Mutations Flashcards
4.1.13 Identify how mutations in genes and chromosomes can result from errors in DNA replucation (point and frameshift mutations).
What is a gene mutation?
A gene mutation is a change in the nucleotide sequence of a section of DNA that codes for a specific trait. This is because a change in the nucleotide may change the resulting protein that is produced.
There are two types of mutations:
1) point mutations
2) frameshift mutations
4.1.13 Identify how mutations in genes and chromosomes can result from errors in DNA replucation (point and frameshift mutations).
What is a point mutation?
Point mutations occur within a codon where there is a substitution of one nucleotide for another. A point mutation occurs in a genome when a single base pair is added, deleted or changed. While most point mutations are benign, they can also have various functional consequences, including changes in gene expression or alterations in encoded proteins. A point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism’s genome.
4.1.13 Identify how mutations in genes and chromosomes can result from errors in DNA replucation (point and frameshift mutations).
What do frameshift mutations involve?
Frameshift mutations involve the insertion or deletion of nucleotides from the DNA sequence, that changes the reading frame when the ribosome is decoding the message from the mRNA. A frameshift mutation in a gene refers to the insertion or deletion of nucleotide bases in numbers that are not multiples of three. This is important because a cell reads a gene’s code in groups of three bases when making a protein. Each of these “triplet codons” corresponds to one of 20 different amino acids used to build a protein. If a mutation disrupts this normal reading frame, then the entire gene sequence following the mutation will be incorrectly read. This can result in the addition of the wrong amino acids to the protein and/or the creation of a codon that stops the protein from growing longer.
- 1.13 Identify how mutations in genes and chromosomes can result from errors in
- Cell division (non-disjunction)
4.1.14 Explain how non-disjunction leads to aneuploidy
Explain how mutations in genes and chromsomes lead to non disjunction mutations to aneuploidy?
Non-disjunction mutations occur when homologous chromosomes or sister chromatids are not equally divided between daughter cells during either phase of meiosis. It can happen during meiosis I if homologous chromosomes fail to seperate, or during meiosis II if sister chromatids fail to seperate. This results in gametes with either too many or too little chromosomes. This is termed aneuploidy (an abnormal number of chromosomes in a cell. This can involve the sex chromosomes (sexual aneuploidy) or autosomes (autosomal aneuploidy).
4.1.13 Identify how mutations in genes and chromosomes can result from errors from damage by mutagens
Identify the causes of DNA damage by defining mutagens.
A mutagen is an agent, chemical or high energy radiation that changes genetic material by directly interacting with the DNA. Types of damages include double strand break, chemical bond between neighbouring nucleotides, chemical modification of a nucleotide. When the cell’s machinery tries to repair the DNA, mutations can be introduced which may or may not be harmful. Examples of chemical mutagens include radiation from UV light and x-rays, chemicals such as carcinogens, processed foods, cosmetics and infectious agents (i.e. viruses and bacterias).
4.1.13 Identify how mutations in genes and chromosomes can result from errors from damage by mutagens
What are the two was that mutations are classfied.
Hereditary- inherited from a parent, present through life and found in virtually every cell
Acquired- may occur at some point in a person’s life in a non-reproductive cells (so cannot be passed to the next generatio). Can be a result of environmental factors or man-made agents.
4.1.13 Identify how mutations in genes and chromosomes can result from errors from damage by mutagens
Describe how UV radiation causes mutations.
UV radiation changes the DNA structure causing the DNA to be read incorrectly and leading to mutations. UV radiation breaks the DNA molecule potentially causing a mutation such as cancer if DNA repair doesn’t occur.
4.1.15 Use a human karyotype of identity ploidy changes and predict a genetic disorder from given data
Define karyotype and their relation to non-disjunction mutations.
Karyotype is a display of all the chromosomes from an organism, using the condensed chromosomes from mitosis. Karyotypes are used to study chromosomal abnormalities. Non-disjunction can produce individuals with unusual combinations of chromosomes. These are called aneuplodies. Having missing or extra chromosomes is a condition called aneuploidy. The presence of an extra chromosomes 21, for example, in the karyotype is associated with Down Syndrome in humans (also known as Trisomy 21).
Describe how inherited mutations can alter the variations in the genotypes of offspring.
An inherited mutation is a permament variation in the DNA sequence and is present in virtually every cell. Variations can cause no change, a small change or a large change in phenotypes depending where in the genome the mutation occurs. Changes in genes can however cause major changes in body morphology or the functioning of cells. There are three main mechanisms by which genetic variation between individuals in a species may occur: Mutations – Changing the genetic composition of gametes (germline mutation) leads to changed characteristics in offspring. Mutations can introduce new alleles into a population of organisms and increase the population’s genetic variation.
