4B: Natural Selection Flashcards
Describe the steps involved in Meiosis
After interphase, a reproductive cell undergoes meiosis’s. In humans, this results in 4 haploid cells, each with half the number of chromosomes as the parent cell.
Meiosis 1: chromosomes carrying the same genes pair up and then are separated into 2 daughter cells
Meiosis 2: Sister chromosomes move apart to form a new pair of daughter cells
Main differences between Mitosis and Meiosis?
Mitosis involves 1 division whilst meiosis involves 2
Mitosis produces 2 genetically identical daughter cells whilst meiosis produces 4 genetically different cells
Mitosis produces Diploid cells, meiosis produces haploid cells
What is independent segregation?
In meiosis, homologous pairs of chromosomes line up opposite each other at the equator of the cell. It’s random which side of the equator the maternal and paternal chromosomes line up. The pairs are separated so one of each homologous chromosomes end up in the daughter cell
What is crossing over?
Chromatids can become twisted around each other. Tension on the chromatid causes some of it to snap and fall off. Where they break off, they can recombine on the opposite chromatid creating a new combination of alleles.
Explain how a mutation can result in new alleles of a gene
Many mutations are harmful but in certain environments the new allele might benefit its processor leading to reproductive success. Advantageous alleles are inherited by members of the next generation. Over many generations new alleles are increased in the population frequency
what are the three causes of mutations?
Deletion, addition and substitution of bases
What type of substance can increase the rate at which mutations occur
Mutagenic agents
What is the percentage difference in the amino acid sequence between mammals and insects?
33%
How are gene technologies used to study genetic diversity
Allow the alleles in an individual to be directly measured
Allow genetic diversity to be directly measured for example the number of different alleles for a gene and the number of individuals with each allele directly shows the genetic diversity
What statistical measures should be used to ensure accurate results when investigating variation?
Random sampling
Calculating the mean
Standard deviation
When does crossing over occur?
Prophase I
What is genetic diversity?
The degree of variation in the genes that exist in a certain population
What are genes?
Multiple versions of genes
2 ways in which genetic diversity is increased
Mutations
Gene flow ( introduction of new alleles by migration)
What is evolution
A change in the allle frequency over time