Genetic variation

Question 1

What is a gene?

Answer 1

A section of DNA that contains the coded information for making polypeptides and functional RNA

Question 2

What does a universal code mean?

Answer 2

Every sequence of the bases codes for the same amino acids

Question 3

What does a degenerate code mean?

Answer 3

More than one different triplet can code for the same amino acid

Question 4

What is an intron?

Answer 4

Non-coding DNA

Question 5

What is an exon?

Answer 5

Coding DNA

Question 6

Describe tRNA

Answer 6

a small single stranded molecule folded into a clover leaf shape, with one end of the chain extending beyond the other.

Question 7

Describe mRNA

Answer 7

Single stranded molecule small enough to pass through nuclear pores to enter the cytoplasm where the codons are translated to synthesise a protein.

Question 8

Describe the process of protein synthesis

Answer 8

Transcription- production of mRNA by using DNA as a template. A length of DNA is transcribed into a mRNA molecule
DNA helicase acts on a specific region of the dna causing 2 strands.
Translation- after DNA is transcribed to mRNA, the codons then must be translated into a sequence of amino acids to make a polypeptide using tRNA
Once mRNA is outside the nuclear pore and tRNA is now bound to amino acids, must associate with a ribosome on the RER.

Question 9

What is a mutation?

Answer 9

A change to the dna base sequence causing a change to the phenotype of an organism

Question 11

Define a gene mutation by deletion

Answer 11

Arises when a nucleotide is lost from the normal dna sequence- the removal of a single base will cause a frame shift resulting in an entirely different polypeptide

Question 12

Define a gene mutation by base substitution

Answer 12

The polypeptide will differ in a single amino acid, the significance of this depends upon the precise role of the amino acid

Question 13

What is a chromosome mutation?

Answer 13

Changes in the structure or number of whole chromosomes

Question 14

Define polypoidy

Answer 14

Changes in whole sets of chromosomes occur when organisms have three or more sets of chromosomes

Question 15

Define non-disjunction

Answer 15

The failure of homologous chromosomes to separate properly during cell division

Question 16

What is the purpose of mitosis

Answer 16

To produce 2 genetically identical diploid daughter cells

Question 17

What is the purpose of meiosis

Answer 17

To produce 4 genetically different haploid daughter cells

Question 18

What happens in prophase 1

Answer 18

The chromosomes condense and the nuclear envelope breaks down. Crossing-over occurs.

Question 19

What happens in metaphase 1

Answer 19

Pairs of homologous chromosomes move to the equator of the cell

Question 20

What happens in anaphase 1

Answer 20

Homologous chromosomes move to the opposite poles of the cell

Question 21

What happens in telophase 1 and cytokinesis

Answer 21

Chromosomes gather at the poles of the cells and the cytoplasm divides

Question 22

What happens in prophase 2

Answer 22

A new spindle forms around the chromosomes

Question 23

What happens in metaphase 2

Answer 23

Chromosomes line up at the equator

Question 24

What happens in anaphase 2

Answer 24

Centromeres divide. Chromatically move to the opposite poles of the cells.

Question 25

What happens in telophase 2 and cytokinesis

Answer 25

A nuclear envelope forms around each set of chromosomes. The cytoplasm divides.

Question 26

When does independent segregation occur

Answer 26

Metaphase 1 and metaphase 2

Question 27

What happens during independent segregation

Answer 27

Each chromosome lines up alongside its homologous partner

Question 28

Describe the process of crossing over

Answer 28

During prophase 1, chromatids of each pair become twisted around one another, during this twisting process tensions are created and portions of chromatids breaks off and rejoin

Question 29

Define genetic diversity

Answer 29

Variety of different alleles within a population

Question 30

Define gene pool

Answer 30

Total collection of genes and their alleles present in a population of a particular species

Question 31

Define genotype

Answer 31

All of the alleles that an organism carries on its chromosomes

Question 32

Define Phenotype

Answer 32

Physical and behavioural traits of an organism

Question 33

What is natural selection

Answer 33

The process where advantageous traits increase in frequency within a population over time e

Question 34

What are the three types of natural selection?

Answer 34

-directional selection -stabilising selection -disruptive selection

Question 35

What is directional selection

Answer 35

Favours one extreme phenotype, causing a shift in the populations traits

Question 36

Define stabilising selection

Answer 36

Favours intermediate phenotypes and selects against extreme traits

Question 37

What is disruptive selection?

Answer 37

Favours extreme phenotypes at both ends of the spectrum and selects against intermediate phenotypes

Question 38

Define genetic diversity

Answer 38

Variety of different alleles in a population

Question 39

Define population

Answer 39

A group of organisms of the same species, living in the same area at the same time

Question 40

Define community

Answer 40

A group of populations living and interacting with each other in an area

Question 41

Define habitat

Answer 41

The environment in which a species normally lives

Question 42

Define ecosystem

Answer 42

A community and its abiotic environment

Question 43

What are the different groups in classification

Answer 43

Domain, kingdom, phylum, class, order, family, genus, species

Question 44

What are the different forms of classification?

Answer 44

Artificial classification, natural classification and phylogenetic classification

Question 45

What are the different domains?

Answer 45

Bacteria, archaea, eukarya

Question 46

What are the 4 kingdoms?

Answer 46

Protocista, fungi, plantae, animalia

Question 47

Define phylogeny

Answer 47

Evolutionary relationship between organisms

Question 48

What are the 3 components of biodiversity

Answer 48

-genetic diversity -species diversity -community/ecosystem diversity

Question 49

Define species diversity

Answer 49

Refers to the number of different species and the number of individuals of each species within any on community

Question 50

Define genetic diversity

Answer 50

Refers to the variety of genes possessed by the individuals that make up a population of a species

Question 51

Define Ecosystem diversity

Answer 51

Refers to the range of different habitats from a small local habitat to the whole of the earth

Question 52

What are the 8 habitats

Answer 52

- temperate forest - tropical rainforest - deserts - grasslands - the taiga - the tundra - the chaparral - the ocean

Question 53

Define species richness

Answer 53

The number of different species in a particular area at a given time

Question 54

What are the solutions to maintain biodiversity

Answer 54

- use hedges rather than fences - maintain hedgerows - introduce conservation headlands - leave the cutting of verges until after seed dispersal - maintain ponds and create new ones - plant native trees on land with low species diversity - reduce the use of pesticides - use organic fertilisers - use crop rotation with nitrogen fixing crops

Question 55

What data would students need to collect to calculate the index of diversity in each habitat?

Answer 55

- how many species there are - numbed of each individual species (abundance)

Question 56

Give 2 ways the students would have ensured their index of diversity was representative of each habitat

Answer 56

- they used a large sample size - data should be collected randomly

Question 57

Suggest and explain one advantage and one disadvantage to a farmer of replanting hedges on her farmland

Answer 57

Advantage: it promotes biodiversity by providing habitats for wildlife enhancing crop health Disadvantage: reduces the amount of land available for planing this means less profits for the farmer

Question 58

What are the two forms of variation

Answer 58

- intraspecific - interspecific

Question 59

Define standard deviation

Answer 59

A measure of the spread of values about the mean

Question 60

What does a low standard deviation mean

Answer 60

Narrow range, most of the data is grouped around the mean, data is very precise

Question 61

What does a high standard deviation mean

Answer 61

Wide range, data is spread out, data is less precise