Genetic Diversity

Question 1

What is a genetic mutation?

Answer 1

Any change to the quality or sequence of DNA

Question 2

What is a germline mutation?

Answer 2

Change in the DNA base sequence of gametes

Question 3

Who is affected by a germline mutation?

Answer 3

The offspring only

Question 4

What is a somatic mutation?

Answer 4

Change in the DNA sequence in cell other than gametes

Question 5

When do gene mutation occur?

Answer 5

During DNA replication randomly and spontaneously

Question 6

Why do gene mutations occur during DNA replication?

Answer 6

Vulnerable to damage as DNA helicase has broken hydrogen bonds between the strands

Question 7

What are the 2 types of gene mutation?

Answer 7

Base substitution and base deletion

Question 8

What is base substitution?

Answer 8

DNA molecule is replaced by a different DNA molecule with a different base

Question 9

What is the significance of base substitution?

Answer 9

• depends on role of amino acid
• can alter tertiary structure of a protein or could be part of an intron

Question 10

How can base substitution lead to a non-functional protein/enzyme?

Answer 10

• base in DNA molecule has been replaced with a different base
• sequence of amino acids altered
• alters tertiary shape of protein/enzyme as different hydrogen bonds form
• active sit is no longer complementary to the substrate so no E- complex formed

Question 11

What is base deletion?

Answer 11

A nucleotide is lost from the sequence so all bases shift to left so triplets are read wrong (frameshift)

Question 12

How does a base deletion result in a non-functional protein/enzyme?

Answer 12

• DNA base has been lost from the sequence so all
• all bases shift left (frameshift)
• DNA bases read wrong
• change in amino acids altered sequence
• alters bonds in tertiary structure which alters shape
• enzyme no longer complementary to the substrate so no E-S complexes formed

Question 13

What are the 2 types of chromosome mutations?

Answer 13

• changes to whole sets of chromosomes
• changes to individual chromosomes

Question 14

How does a change to a whole sets of chromosomes occur and what is it called?

Answer 14

3 or more sets of chromosomes rather than the normal 2 (polyploidy)

Question 15

How does changes to individual chromosomes occur?

Answer 15

• non-disjunction in meiosis as the individual chromosomes have failed to split
• gametes have either one more to one fewer chromosome

Question 16

What does meiosis produce?

Answer 16

4 genetically different daughter cells each with half the number of chromosomes than the parent cell

Question 17

What is a chromosome?

Answer 17

Thread like structure made up of protein and DNA that passes on hereditary material

Question 18

What is a chromatid?

Answer 18

One of the 2 strands of a chromosome that are joined by a centromere

Question 19

What is a centromere?

Answer 19

Joins pair of sister chromatids together

Question 20

What is a diploid cell and how may copies of each chromosome does it have?

Answer 20

• normal body cell
• 2 copies

Question 21

What is a haploid cell and how many copies of the chromosomes does it have?

Answer 21

• gamete
• 1 copy

Question 22

What happens before meiosis 1?

Answer 22

• chromosomes replicate (2 copies of the chromatids)
• DNA condenses to form double armed chromosomes (2 sister chromatids joined by centromeres)

Question 23

What happens in meiosis 1?

Answer 23

• chromosomes arrange into homologous pairs and wrap around eachother crossing over
• homologous pairs are separated into different daughter cells (half the number of chromosomes)

Question 24

What happens in meiosis 2?

Answer 24

• 2nd division and chromosomes are separated with each sister chromatids going into different directions
• creating 4 haploid cells

Question 25

What are the 2 ways meiosis creates genetic variation?

Answer 25

- independent segregation of homologous chromosomes - genetic recombination by crossing over

Question 26

What is independent segregation of homologous chromosomes?

Answer 26

- maternal and paternal chromosomes are randomly mixed - as the homologous pairs that line up in meiosis 1 are split into different daughter cells with any possible combination of other homologous pairs are

Question 27

How does genetic recombination by crossing over cause genetic diversity?

Answer 27

- in meiosis 1 chromatids twist around eachother creating tension breaking off portions of chromatids - the broken off chromatids can join of its homologous pair - giving the chromatids the same genes but different combinations of maternal and paternal alleles

Question 28

What is an allele?

Answer 28

A version of a gene

Question 29

What causes new alleles to arise?

Answer 29

Genetic mutations

Question 30

What is the gene pool?

Answer 30

The total number of alleles in a particular population at a particular time

Question 31

What is genetic diversity?

Answer 31

- the number of different alleles of a gene in a population - the greater the number of different alleles the greater the genetic diversity

Question 32

Why is a large genetic diversity good?

Answer 32

More likely individuals can survive an environmental change

Question 33

What are the 2 factors that can cause variation in a species?

Answer 33

Genes and the environment

Question 34

What does genetic diversity enable and why?

Answer 34

Natural selection because some alleles will be more advantageous than others so they are more likely to survive and reproduce

Question 35

How dos natural selection occur?

Answer 35

- there is a gene pool with a variety of alleles in a population at - random mutation of alleles result in a new allele - the new allele is advantageous other alleles in the population - individual with the new allele has a higher chance of surviving and reproducing - the new allele is passed to the next generation - increasing frequency of the new allele in the population

Question 36

What are the 2 types of selection?

Answer 36

Directional and stabilising

Question 37

What is directional selection?

Answer 37

When selection favours individuals that vary in one direction from the mean population changing the phenotype of the population

Question 38

How does directional selection occur?

Answer 38

- environmental change occurs - a phenotype that varies from the mean is best suited to the environment - those individuals are more likely to survive and reproduce - pass the advantageous allele to next generation - mean moves in direction of these individuals as the alleles become more frequent in the population

Question 39

How did directional selection lead to penicillin resistant bacteria?

Answer 39

- random mutation occurred in allele of a gene of a bacterium - that allele produced an enzyme called penicillinase that broke down penicillin - the bacteria was able to break down penicillin when exposed to it by penicillinase so it survived - it reproduced by binary fission passing the allele onto the next generation - population of penicillin-resistant bacteria increase increasing the frequency of the allele - populations normal distribution curve shifted in direction of resistance

Question 40

What happens to the characteristics n a population in directional selection?

Answer 40

Changes characteristics of the population

Question 41

What phenotype is favoured in directional selection?

Answer 41

Phenotypes away from the mean

Question 42

What environmental conditions causes directional selection?

Answer 42

Changing environmental conditions

Question 43

What happens to normal distribution curve in directional selection?

Answer 43

Curve remains same shape but shifts to left or right

Question 44

What is stabilising selection?

Answer 44

Selection that favours average individuals and preserves characteristics of a population

Question 45

How does stabilising selection occur?

Answer 45

- environmental conditions remain stable - individuals with phenotypes closest to mean are favoured - more likely to survive and reproduce - pass on allele to next generation - eliminating extreme phenotypes

Question 46

What are the 3 different adaptations that are caused by natural selection?

Answer 46

- anatomical (e.g. thick fur) - physiological (e.g. oxidising fat for additional after in dry environment) - behavioural (e.g. bird migration)