Genetic Variation Flashcards
what are linked genes
Linked genes are on the same chromosome and are therefore inherited together. This means one phenotype would almost always be inherited from another. Therefore linked genes would reduce genetic diversity and produces less-diverse phenotypes than unlinked genes
why do linked genes reduce genetic/genotype diversity
Because linked genes cannot independently assort and segregate. Which will produce less genetic variety in gametes. For example, a heterozygous BbLl with unlinked genes could produce four gametes, BL, Bl, bL and bl. With fewer types of gametes, there would be less diversity in the offspring, unless crossing over occured, for example, BBLL, BbLl and bbll are the only possible genotypes,no BBll or bbLL
Independent assortment
it is when the homologous pairs RANDOMLY line up along the equator of the cell during meiosis. alleles are reshuffled and new combination chromosomes are made, producing new allele combinations and therefore variation
crossing over
is the exchange of alleles segments of a chromosome segments of DNA between homologous pairs chromosome
( diagram)
crossing over can separate linked genes on the same chromosome, therefore new combinations of alleles resulting in new combination chromosomes
what is a mutation
A mutation is a random and permanent change in the( base sequence ) DNA/RNA/gene
Gametic vs somatic mutation
Gametic mutations forms new alleles in sperm/eggs/ovum/pollen that can be inherited, whereas, somatic mutations form a new allele in a body cell, which may effect the individual but cannot be inherited
Somatic mutation
Affects the individual but not the gene pool. in some cases, skin cells give individuals cancer. Because cancer is a random mutation in body cells the gene pool remains the same
Gametic mutation with example
affect both the individual and gene pool. This is because they are inherited and passed to the next generation. for example, an allele for giant roosters affects the individual/changes it’s phenotype. The allele for giant roosters also increases genetic variation in the gene pool as a new allele has been created
Meiosis
Meiosis is a type of cell division/ reduction division that produces sex cells/gametes/sperm and eggs with half the number of chromosome/haploid(as the body/parent/somatic cells). Produces genetically unique daughter cells
Segregation
is where homologous chromosomes separate/pull apart and migrate to the poles of the cell. During segregation, only one chromosome( gene/allele) from each homologous pair is placed into the new cell/gametes made. During gametic formation, alleles for each gene pull apart/separate so that each gamete carries one allele per gene. Therefore genetic variation increases because each new cell has a different combination of alleles from each other, and or only half of the chromosomes as the parent
Founder effect
Is when a small group of individuals from an existing population moves to another area and establishes a new population/ are reproductively isolated from the original population
Bottleneck
a sudden/rapid/drastic reduction in population that results in an under-representation of alleles in the gene pool(compared to the original gene pool)
genetic diversity high and low
high genetic diversity is lots of Variations in the genetic makeup/genotype/total number of genetic characteristics in a species/ population/genome/ gene pool:
low genetic diversity = low number of differing alleles in a population/ fixed alleles
expected genetic diversity in small populations
Small populations likely have low genetic diversity because there are fewer individuals (alleles) in a population and most likely have an allele frequency, not representative of the original population/ increased chance of inbreeding. Small populations are likely to have fixed alleles
Genetic drift
Chance/random change ( removal or addition) of alleles in a population that result in a loss, gain or fixed alleles
