Variation and Mutations Flashcards
What is an aneuploidy mutation?
Aneuploidy is the presence of a chromosome number that is different from the simple multiple of the basic chromosome number.
How do aneuploidy mutations occur?
Loss or addition of one or more chromosomes.
What is a monoploidy mutation?
Monoploidy involves a haploid number of chromosomes that act as a complete set, instead of diploid.
What is a polyploidy mutation?
Polyploidy occurs when an organism acquires one or more complete extra sets of chromosomes.
What is nondisjunction?
When some chromosomes/chromatids fail to separate during the first or second cell division.
What does nondisjunction lead to? Give an example.
This leads to the production of diploid gametes which when fertilised produce a trisomy of chromosomes. E.g. trisomy 21 (Down syndrome).
What are some environmental factors that can influence phenotypes?
- Temperature
- pH
- Wind exposure
- Light exposure
- Availability of food
What is recombination?
The process in which homologous chromosomes (maternal and paternal pair) ‘cross over’.
When does recombination occur?
Occurs in Prophase I
What does recombination lead to?
As a result of ‘crossing over’ maternal and paternal genes are exchanged. This creates gametes with entirely different genomes, thus increasing genetic diversity.
What is independent assortment?
The process in which maternal and paternal homologous chromosomes align independently of one another.
When does independent assortment occur?
Occurs in Metaphase I
What does independent assortment lead to?
Different gametes will have different arrangements of maternal and parental chromosomes.
What is random fertilisation?
The random union of gametes to form a zygote is known as random fertilisation.
Why is random fertilisation important for variation?
- Random mates increase variation as there is mixing of genetic information.
- It creates new combinations of alleles in the offspring.
What is genetic variation?
The variety of phenotypes in an organism, population or ecosystem.
What is a mutation?
A permanent change to an organism’s DNA sequence of nucleotides.
How do mutations occur?
Can arise spontaneously during DNA replication/cell division, induced by mutagens or through the action of biological agents.
What cells can mutations occur in?
Somatic and gametes.
What are the types of DNA mutations?
Point and frameshift mutations.
What are mutagens?
Physical or chemical environmental factors that can cause mutations.
What are the types of point mutations?
- silent
- missense
- nonsense
What are the types of frameshift mutations?
- insertion
- deletion
What is the difference between point and frameshift mutations?
A point mutation is where one base/nucleotide is replaced with another. A frameshift mutation is where one nucleotide/base is added/removed, this causes a change in the following genetic sequence too.
What is a silent mutation?
substitution that doesn’t affect corresponding amino acid.
What is a missense mutation?
substitution that does affect the corresponding amino acid.
What is a nonsense mutation?
Substitution that causes a stop codon when it shouldn’t.
What is an insertion mutation?
When an extra nucleotide is added.
What is a deletion mutation?
When a nucleotide is removed.
What are some examples of mutagens?
- UV light
- X rays
- Mustard gas
- Nitric acid
- Agrobacterium bacteria
