Mutation Flashcards
What is a diploid cell when are they produced
Contains 2 of each type of chromosome
One inherited from the father and one from the mother = homologous pair
Produced when a diploid cell divides by mitosis
What is a haploid cell and when is it produced
Contains only one of each type of chromosome
They are produced when a diploid cell divides by meiosis
Describe sexual reproduction lifecycle
Adult cell (diploid) divided by meiosis to produce a gamete (haploid). Two gametes fuse to form a zygote (diploid)
What is the purpose of meiosis
To produce gametes that contain a haploid number of chromosomes and a different combination of alleles
Which steps create haploid and diploid cells in meiosis
Diploid cell —meiosis 1——> diploid cell ——-meiosis 2——> haploid cell
What is synapsis
When homologous chromosomes condense and pair up to form bivalents
What is crossing over and what does it introduce
Happens in prophase I
Chiasmata = when sister chromatids form each chromosome attach to each other
Crossing over occurs at each chiasma:
- the chromatids break and the detached parts swap over and recombine
Introduces genetic variation as it produces 4 sister chromatids that each carry a different combination of alleles
What is independent segregation and what does it introduce
The bivalents line up on the spindle in a random orientation at metaphase 1
Introduces genetic variation as it produces 4 gamers that each carry a different combination of maternal + paternal chromosomes
Define gene mutation
A change to one or more nucleotide bases in DNA of a gene resulting in the formation of a new allele
What is substitution
Replacement of one nucleotide with a different nucleotide
(Due to dna degeneracy could cause a silent mutation)
What is insertion and the effect
Addition of one or more nucleotide
If only one or two bases are inserted it leads to frame shift( all the following codons are affected amd the protein will be non functional)
What is deletion amd the effect
Loss of one or more nucleotide
Could cause frame shift causing protein to be non functional
What is inversion and the effect
DNA of a single gene cut in 2 places, the cut portion is inverted 180 degrees amd rejoined in the same place in the gene
Frequently results in a non functional protein usually occurs during crossing over in meiosis
What is duplication and the effect
A whole gene or section of a gene is duplicated so that 2 copies of the gene/section appear on the same chromosome
The original version of the gene remains intact and therefore the mutation is not harmful
Is an important source of evolutionary change
What is translocation and its effect
Gene is cut in 2 places and the section that is cut off attaches to a seperate gene
The cut gene is now non functional due to having a section missing and the gene that has gained the translocated section is likely to also be non functional
What is a chromosome mutation
A change in the structure of number of whole chromosomes
What is polyploidy
When organisms have 3 or more sets of chromosomes rather than the usual two
Mostly occurs in plants
What is a hybrid
Can be formed by combining sets of chromosomes from 2 different species by cross pollinating 2 closely related species
A new species may arise if the chromosome number of the hybrid is a multiple of the original chromosome number as meiosis can occur
What is non disjunction
During meiosis homologous pairs of chromosomes fail to seperate during meiosis. A gamete will either have one more or one fewer chromosome
How do mutations occur in dna replication
Spontaneously
What are examples of 2 mutagenic agents
High energy ionising radiation
Chemicals like nitrogen dioxide and benzopyrene
What is the effect of high energy ionising radiation on dna
Can disrupt the structure of DNA- found in alpha and beta particles as well as short wavelength radiation such as x rays and uv light
What is the effect of nitrogen dioxide
Disrupts the structure of dna or interferes with transcription
From combustion of fossil fuels
What is the effect of benzopyrene
Inactivates tumour suppressor gene TP53 leading to a cancer
Found in tobacco smoke
Define mutagenic agent
An outside factor that increases the basic mutation rate
Explain the outcome of a mutation if it is silent or have no effect
New allele formed but degeneracy means that amino acid may not change
If a new allele is formed in an intron there will be no effect due to the splicing of mRNA
New allele doesn’t affect tertiary protein structure as it is a recessive allele
Survival and reproduction not affected
Explain the outcome of a harmful mutation
New allele is formed and results in a change in polypeptide that negatively changes the tertiary properties of the protein and thus the phenotype
May result in decreased survival and reproduction
Explain the outcome if the mutation is beneficial
New Allele is formed and results in a change in polypeptide that positively changes the tertiary structure and thus the phenotype
May result in increased survival and reproduction
