Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
36 Cards in this Set
- Front
- Back
|
What does diversity indicate? |
How much variation exists |
|
|
How does Genetic Variation occur? |
Because of differences in what genes are present and due to the presence of different alleles |
|
|
How has variation arisen? |
1) Mutation 2) Random assortment 3) Crossing over 4) Random fusion of gametes |
|
|
What is a gene mutation? |
A change in the sequences of bases in a gene |
|
|
What could a mutation in DNA result in? |
A change in amino acids in the polypeptide chain and may alter the function of the protein |
|
|
What is a substitution mutation? |
A substitution in a base |
|
|
What is a silent mutation? |
The mutation does not alter the amino acid coded for. The third base is the most degenerate. |
|
|
What will a substitution at the first base result in? |
1) Change the amino acid sequence 2) May alter the shape and function of the polypeptide |
|
|
What happens if a mutation codes for a stop codon? |
This will cause the growing polypeptide chain to terminate prematurely |
|
|
What is a deletion mutation? |
The complete loss of a base in a region of DNA coding for a gene. |
|
|
What does a deletion mutation result in? |
The reading frame of a codon to shift to the left by one letter (frame shift). |
|
|
What happens if a deletion mutation happens at the beginning of sequence coding? |
All the triplet codes will be altered and as a result so will the amino acids |
|
|
What is a chromosome mutation? |
A mutation in the chromosome number can arise by chromosome non-disjunction during meiosis |
|
|
When do mutations occur? |
Spontaneously during DNA replication |
|
|
What are mutagenic agents? |
They increase the rate of mutation and include high energy radiation |
|
|
How do mutagenic agents cause a mutation? |
High radiation damages the DNA molecule and chemicals that alter the DNA structure or interfere with DNA replication |
|
|
What is selection? |
A process by which organisms that are better adapted to their environment survive and reproduce in greater numbers. |
|
|
What does selection result in? |
An increase in the frequency of the advantageous allele within the population |
|
|
Give an example of a mutagenic agent. |
1) X-rays 2) Gamma rays |
|
|
Describe natural selection. |
1) Environmental change 2) Mutation creates new alleles 3) Better adapted individuals more likely to survive and reproduce 4) Organisms are more likely to pass on their allele 5) The advantageous allele frequency increases over time |
|
|
What determines the spread of an allele within the gene pool? |
Selection pressure |
|
|
What is genetic diversity? |
the number of different alleles of genes in a species or population |
|
|
What is a genetic bottleneck? |
an event that causes a big reduction in a population eg. when a large number of organisms within a population die beforereproducing |
|
|
What effect does a genetic bottleneck have? |
Reduces the different alleles in the gene pool and so reduces genetic diversity |
|
|
What does a genetic bottleneck result in? |
The survivors reproduce and a larger populations created from a few individuals |
|
|
What is the founder effect? |
Describes what happens when just a few organisms from a population start a new colony and there are only a small amount of different alleles |
|
|
What adaptations do mutations cause? |
1) Behavioral- ways an organism acts that increase its chance of survival + reproduction 2) Physiological- processes inside the body that increase the chance of survival 3) Anatomical- structural features |
|
|
What is directional selection? |
Where individuals with alleles for characteristics of an extreme type are more likely to survive |
|
|
What could directional selection be a result of? |
In response to an environmental change |
|
|
Give an example of directional change. |
Bacteria evolving antibiotic resistance |
|
|
Describe the process of directional change. |
1) Some individuals have alleles that are resistant to antibiotics 2) Bacteria not resistant are killed in an exposure to the antibiotic 3) Resistant bacteria survive and reproduce 4) Over time, most organisms will carry the antibiotic resistant allele |
|
|
What is stabilising selection? |
where individuals with alleles for characteristics towards the middle or the range are more likely to survive. |
|
|
When does stabilising selection occur? |
When the environment isn't changing and it reduces the range of possible characteristics |
|
|
Give an example of stabilising selection. |
Human birth weight |
|
|
Describe the process of stabilising selection? |
1) Very small babies are less likely to survive 2) Very large babies can be difficult when giving birth and so are less likely to survive 3) Conditions are more favorable to medium-sized babies, so the weight of human babies tends to shift towards the middle range |
|
|
How do you interpret data on the effects of selection? |
1) Describe what the data shows 2) Suggest a possible cause |
