inheritance 3.27 - 3.39 Flashcards
main types of variation within a species (3)
- genetic variation
- environmental variation
- combination of both
genetic variation is caused by
differences in genes and inheritance
environmental variation is caused by
differences in the environment like diet and climate
combination of both is caused by
combination of genetic and environmental factors
can mutation affect an organisms phenotype
yes but that’s rare
what is mutation
a random and rare change in an organisms DNA which can be inherited
How does a change in DNA affect the phenotype of an organism?
it can alter the sequence of amino acids in a protein, which may result in a change in the protein’s structure and function, ultimately affecting the organism’s phenotype.
What are the effects of most mutations on an organism’s phenotype?
Most mutations have no effect on the phenotype. Some may have a small effect, but rarely do they cause a significant change in the phenotype.
what can increase the incidence of mutations
- ionising radiation (gamma, X, and ultraviolet rays)
- chemical mutagens (chemicals in tobacco)
explain Darwin’s theory of evolution by natural selection
Organisms produce more offspring than can survive.
There is variation between individuals in a population.
Some variations are advantageous for survival and reproduction.
Individuals with advantageous traits are more likely to survive, reproduce, and pass on their traits.
Over time, these traits become more common in the population, leading to evolution.
How can resistance to antibiotics increase in bacterial populations?
Random mutations in bacteria can make some resistant to antibiotics.
Natural selection favors the resistant bacteria, allowing them to survive and reproduce.
Over time, the population of resistant bacteria increases, making the infection harder to treat.
why is an increase in antibiotic resistance a concern (3)
Increased antibiotic resistance makes infections difficult to control.
It leads to treatment failure because bacteria that are resistant to antibiotics cannot be easily killed by them.
Antibiotic-resistant bacteria can spread, posing a serious public health risk.
How do most mutations affect an organism’s phenotype?
Most mutations have no effect on the phenotype. Some mutations may have a small effect, but rarely do they cause a significant change to the organism’s phenotype.
What is the role of mutation in evolution?
Mutations introduce genetic variation in populations. If a mutation is advantageous (e.g., resistance to disease), it may be passed on to future generations, contributing to the process of evolution by natural selection.
What is genetic variation and how does it occur?
Genetic variation refers to the differences in DNA sequences among individuals in a population. It occurs due to mutations, genetic recombination during meiosis, and sexual reproduction.
What is polygenic inheritance?
Polygenic inheritance is when a trait is controlled by multiple genes. This often results in a continuous variation (e.g., human height, skin colour).
What is the relationship between mutation and evolution?
Mutations are the source of genetic variation, and when these mutations give an advantage in survival or reproduction, they can spread through a population, leading to evolution by natural selection.
How can mutations be inherited?
mutations can be inherited if they occur in germ cells (sperm or egg), allowing the altered genetic material to be passed on to the next generation.
How does resistance to antibiotics increase over time in bacterial populations?
Mutations occur randomly in bacteria, and some may make the bacteria resistant to antibiotics.
Natural selection favors the resistant bacteria, allowing them to survive and reproduce.
Over time, the proportion of resistant bacteria in the population increases.
How is the sex of offspring determined at fertilisation?
The mother’s egg always carries an X chromosome.
The father’s sperm carries either an X or a Y.
If a sperm with an X fertilises the egg → the child is female (XX).
If a sperm with a Y fertilises the egg → the child is male (XY).
➡ Sex is determined by the sperm.
What happens when a diploid cell divides by mitosis?
The cell divides once to form two identical daughter cells.
Each has the same number of chromosomes as the original (diploid).
The daughter cells are genetically identical.
key functions of mitosis (4)
Growth
Repair of damaged tissues
Asexual reproduction
Cloning (in biotechnology or natural cases like plant runners)
What happens when a diploid cell divides by meiosis?
The cell divides twice to form four daughter cells.
Each daughter cell is haploid (has half the number of chromosomes).
The four cells are genetically different.
➡ Meiosis produces gametes (sperm and egg).
Why are the gametes produced by meiosis genetically different?
Because chromosomes are shuffled and separated randomly during meiosis.
This leads to variation in the combination of alleles each gamete receives.
