Mutations & Meiosis Flashcards
Mutations
Changes in DNA sequence
Additon mutations
Where one or more bases are added to the DNA sequence.
E.g. ATCGTT → ATCCGTT
Deletion mutations
Where one or more bases are removed from the DNA sequence.
E.g. ATCGTT → ATCTT
Substitution mutations
Where one or more bases are changed in the DNA sequence.
Mutation agents
ncrease the rate at which mutations occur.
Mutagenic agents include:
Chemicals (e.g. bromine and benzene).
Exposure to ionising radiation and ultraviolet radiation.
Non-Disjunction Mutations
mutations in the number of chromosomes in the cells.
Meiosis
A type of cell division that produces four genetically different daughter cells (gametes) with a haploid number of chromosomes. It involves two divisions.
Haploid
Have half the number of chromosomes as diploid cells).
Diploid
An organism with two copies of every chromosome
What is the term to describe an organism that has two copies of every chromosome?
A diploid organism
Steps of meisosis include:
- Chromosomes replicate to produce sister chromatids
- Chromosomes condense to form a double-armed chromosome
- Chromosomes are arranged in the center of the cell
- Chromosomes in a homologous pair are separated
- The cell divides and one chromosome from each pair is in each daughter cell
- The sister chromatids are separated
Homologous pairs
chromosomes with identical genes but different alleles
What does meisosis II produce?
Four genetically different haploid cells
What is the process of separating chromosomes into random combinations?
Independent segregation
Explain how the orientation of homologous chromosomes during metaphase I of meiosis contributes to greater variation in gametes.
The random alignment of homologous chromosomes at the metaphase plate ensures the random destination of the chromosomes in the daughter cells
Which three processes lead to variation among offspring that have the same two parents?
Fertilization, crossing over, random chromosome assortment
Reproductive cells in most species are different from the cells that make up the rest of the organism.
What are the “body” cells called and how are they different from the reproductive cells?
Somatic cells and have double the number of chromosomes found in reproductive cells
In prophase I, the homologous chromosomes are paired up and linked together. What binds the chromosomes together and maintains their alignment?
Tertrads
What causes mutations?
Additon of bases
Deletion of bases
Subsitiution of bases
What type of substances can increase the rate at which mutations occur?
Mutagenic agents
How many chromosomes are found in cells produced during human meiosis?
23
What is the percentage difference in the amino acid sequence between mammals and insects?
33%
What statistical measures should be used to ensure accurate results when investigating variation?
Standard devation
Calculating the mean
Random sampling
What statistical measure shows how far away the measured values are from the mean average?
The standard devation
When does crossing over occur?
Prophase I
