Genetic diversity

Question 1

What is a mutation

Answer 1

any change in the quantity or base sequence of the DNA

Question 2

What is a substitution mutation

Answer 2

when one of the bases is exchanged for another which could result in a change in the codon which could encode for a different amino acid

Question 3

What is a deletion mutation

Answer 3

when a base is removed from the base sequence resulting in a frame shift

Question 4

Explain how a deletion mutation could effect protein structure

Answer 4

it could change every codon in a specific sequence resulting in a completely different protein being produced

Question 5

Explain the term non-disjunction

Answer 5

the failure of homologous chromosomes to separate properly during cell devision resulting in the gamete having one more or less chromosomes
e.g. an extra chromosome results in downs syndrome

Question 6

Explain the term polyploidy

Answer 6

containing more than two homologous sets of chromosomes

Question 7

What is the importance of meiosis

Answer 7

to produce 4 gametes with a haploid number of chromosomes for the offspring

Question 8

How does meiosis lead to variation

Answer 8

• independent segregation of homologous chromosomes where one pair can pass into a daughter cell is a matter of chance
• crossing over
• recombination of chromosomes produces 4 different types of cell are produced

Question 9

What is crossing over

Answer 9

where new combinations of maternal and paternal alleles are produced when:

• homologous chromosome pairs become twisted around each other
• portions of chromatids break off and rejoin with the homologous partner and alleles are axchanged
• producing new combinations of alleles

Question 10

How is meiosis 1 different from meiosis 2

Answer 10

meiosis 1 - homologous chromosomes are separated

meiosis 2 - chromatids are separated by further devision leaving 4 cells each with a single chromatid

Question 11

What is a gene pool

Answer 11

the total number of genes of every individual in a population

Question 12

What is genetic diversity

Answer 12

the total number of of different alleles in a population

-the greater the genetic diversity within a species, the greater that species’ chances of long-term survival

Question 13

What is directional selection

a shift

Answer 13

selection that favours individuals in one direction away from mean which have the phenotypes suited to new changes in the environment due to a mutation

Question 14

What is stabilising selection

peak is taller and less spread

Answer 14

when the environmental conditions are stable the individuals with the phenotypes closest to the mean are favoured and are more likely to pass on there alleles to the next generation

Question 15

How is antibiotic resistance an example of directional selection

Answer 15

• when the antibiotics develop resistance to the antibiotics e.g. penicillin the death of bacteria decreased
• the resistance to the antibiotics was due to a mutation which occurred in the allele of a gene which enabled the bacterium to make an enzyme that breaks down the penicillin
• the bacterium that survived where able to divide by binary fission to produce a new population of resistant bacteria

Question 16

What is the process of meiosis

Answer 16

meiosis 1 - first devision where homologous chromosomes pair up and the chromatids wrap around each other, where crossing over may take place, and the result of this devision is the homologous pairs separate to form 2 daughter cell

meiosis 2 - chromatids move apart and at the end of the devision 4 cells will be formed with each containing 23 chromosomes

Question 17

How does reproductive success affect allele frequency

natural selection

Answer 17

• within a population there will be a gene pool
• random mutations of alleles within a gene pool result in the possessor having an advantage over others in the population and be better adapted to the environment
• as a result these parents have an advantage in the competition for survival and are more likely to survive, eat and reproduce to pass on the allele
• over time the frequency of the advantageous allele will increase and the non-advantageous allele will decrease