Chapter 9: Genetic diversity Flashcards
What are gametes?
Gamete are the sex cells in organisms. Sperm cells in males and egg cells in females
What happens at fertilisation?
Gametes (eggs and sperm) join together at fertilisation to form a zygote. A haploid sperm fuses with a haploid egg to make a cell with the normal diploid number of chromosomes
What is the diploid number (2n) of chromosomes i humans?
The diploid number of chromosomes in humans is 46
Why do gametes have a haploid number of chromosomes?
The number of chromosomes would double to when the gametes fuse and the zygote would have too
Gametes have a haploid (n) number of chromosomes. What does haploid mean?
Hint: H-aploid H-alf
It means that the gametes only have one copy of each chromosome
Meiosis is a type of cell division that takes place where?
Meiosis is a type of cell division that takes place in the reproductive organs
Why is variation between the members of a population is important?
Variation between the members of a population is essential to enable the population to withstand the pressures of natural selection to evolve
What are the 3 ways in which meiosis produces variation?
random segregatiom/assortment of homologous chromosomes
random segregatiom/assortment of chromatids
crossing over or chiasmata
When gametes fuse in fertilisation, new combinations of _____ are formed
alleles
What is a mutation?
A mutation is a change in the sequence of bases in a nucleotide chain
What is deletion in gene mutation?
One or more bases are removed during replication
What is insertion in gene mutation?
One or more bases are added to the sequence
What is substitution in gene mutation?
One or more bases are replaced
What is inversion in gene mutation?
Two or more bases are reversed in sequence
What is translocation in gene mutation?
One or more bases are transferred from the end of one gene onto the end of another gene
What are mutagens?
Mutagens are environmental factors that increase the frequency of mutations
How do mutagens increase the frequency
High energy mutagens can damage the genetic meterial directly by breaking it up or
They can alter the reactivity of other chemicals in the body (e.g. water) which the damade the DNA
How does independent segregation lead to genetic
During meiosis I, homologous pairs are separated. Whcih chromosmes of a pair
The four dughter cells prduced by meiosis have different combination fo maternal and paternal chromosomes
How does independent segregation lead to genetic variation?
During meiosis I, the homologous pairs of chromosmes line up together and are separated. The way they line up is completely random so that
The four dughter cells prduced by meiosis have different combination fo maternal and paternal chromosomes
What is genetic diversity?
Genetic diversity is described as the total number of different alleles in a species or a population
Give 2 ways in which genetic diversity within a population can be increased
mutations
in DNA forms new alleles
gene flow
when different alleles are introduced into a population such as when individuals from another population migrate into them and reproduce
Explain how genetic bottlenecks reduce genetic diversity?
A genetic bottleneck causes a great reduction in a population and thus a reduction in the number of different alleles in the gene pool because for example lots of organisms die before reproducing. The survivors reproduce and a larger population is created from a few individuals and thus a few different alleles
What is a genetic bottleneck?
A genetic bottleneck is an event that reduces the genetic diversity of a population by reducing the number of individuals in the population
gene pool
o
founder effect
The founder effect is a type of genetic bottleneck
a few organisms start a new colony
there are only a small number of different alleles in the initial gene pool
alleles present in the initial gene pool are more likely to get passed on
Why is greater genetic diversity better than lower genetic diversity?
Greater genetic diversity means there is a larger number of different alleles and thus characteristics. Likelihood that
Give an example of a behavioural adaptation.
behaviour
possums play dead to escape attach from a predator
Give an example of a physiological adaptation.
internal processes
hibernation - brown bears lower their metabolic rate to conserve energy during winter months when food is scarce
Give an example of an anatomical adaptation.
structural features
whales have a thick layer of blubber to act as insulation in cold seas
Natural selection increases advantageous alleles in a population…
random mutations new allele harmful dies out quickly beneficial increases their chances of survival certain environment more likely to survive reproduce pass on genes + advantageous allele larger portion of next generation inherits advantageous allele next generation also more likely to survive so frequency increases from gen to gen over many many gens evolution more common
