Topic 4 Booklet

Question 1

What does degenerate mean?

Answer 1

More than one triplet for each amino acid

Question 2

Define non-overlapping

Answer 2

Each base is part of only one triplet

Question 3

What are some aseptic techniques?

Answer 3

1. Keep lid on Petri dish/ open lid as little as possible
   - to prevent unwanted bacteria contaminating the dish
2. Wear gloves/mask / wash hands
   - to prevent contamination from bacteria on hands/mouth
3. Use sterile pipette/ flame the loop
   - to maintain a pure culture of bacteria

Question 4

Give the two types of molecule form which a ribosome is made

Answer 4

Ribosomal RNA and amino acids

Question 5

Describe the role of a ribosome in the production of a polypeptide.

Answer 5

1. mRNA binds to the ribosome
2. Two codons/ binding sites
3. Allows tRNA with anticodons to bind
4. Catalyses formation of peptide bond between amino acids
5. Moves along (mRNA to the next codon)

Question 6

Define species

Answer 6

A group of organisms that are able to produce fertile offspring

Question 7

Define species richness

Answer 7

The number of different species in a community

Question 8

Explain how the chromosome number is halved during meiosis

Answer 8

1. Homologous chromosomes
2. One of each pair goes to each daughter cell

Question 9

Describe the process of crossing over and explain how it increases genetic diversity

Answer 9

1. Homologous pairs of chromosomes form a bivalent
2. Chiasmata form
3. Alleles are exchanged
4. Producing new combinations of alleles

Question 10

Explain how differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic relationships between species

Answer 10

1. Mutations change base/ nucleotide sequence
2. Causing change in amino acid sequence
3. Mutations build up over time
4. More mutations between distantly related species

Question 11

Describe and explain the appearance of one chromosome during meiosis (before division)

Answer 11

1. Chromosome is formed of two chromatids
2. Because DNA replication
3. Sister chromatids held together by centromere

Question 12

Describe what happens in meiosis I

Answer 12

1. Chromosome in homologous pair
2. One of each into daughter cells

Question 13

Identify one event that occurs in meiosis II but not meiosis I

Answer 13

Separation of chromatids

Question 14

Name two ways in which meiosis produces genetic variation

Answer 14

1. Crossing over
   Independent segregation

Question 15

Explain the importance of meiosis in the life cycles of organisms which reproduce sexually

Answer 15

1. Meiosis produces haploid cells
2. When gametes fuse, the diploid number is restored
3. This keeps the chromosome number constant
4. Introduces GENETIC variation

Question 16

Suggest one source of DNA from deceased organisms

Answer 16

Preserved remains, skin, bones

Question 17

Suggest reasons why populations might show very low levels of genetic diversity

Answer 17

1. Inbreeding
2. Population might have been very small

Question 18

What is genetic diversity

Answer 18

The number of different alleles of a gene in a population

Question 19

Describe the process of natural selection

Answer 19

1. New alleles for a gene are created by random mutations
2. If the new alleles increases the chances of the individual to survive in that environment, they are more likely to survive and reproduce
3. Reproduction passes on the advantageous allele to the next generation
4. Over many generations the allele increases in frequency in the population

Question 20

What is directional selection

Answer 20

1. One of the extremes has the selective advantage
2. Occurs when there is a change in the environment
3. The model trait changes

Question 21

What is stabilising selection

Answer 21

1. The modal trait has the selective advantage
2. Occurs when there is no change in the environment
3. Standard deviation decreases, as individuals with the extreme trait decrease

Question 22

Why do different species look similar?

Answer 22

1. Live in a similar environment
2. Have similar selection pressures
3. Similar alleles will have the selective advantage
4. Produces similar/same proteins and therefore have similar characteristics

Question 23

What is as hierarchy?

Answer 23

1. Smaller groups arranged within larger groups
2. No overlap between groups

Question 24

What are the modern and accurate classification methods?

Answer 24

1. DNA sequence
2. mRNA sequence
3. Amino acids sequence
4. Immunological - comparing similarity in self-antibody shape

Question 25

What are the farming techniques that reduce biodiversity?

Answer 25

1. Destruction of hedgerows 2. Selective breeding 3. Monocultures 4. Over-grazing 5. Filling in ponds and draining wetlands

Question 26

What is the index of diversity

Answer 26

1. A measure of species diversity 2. A calculation to measure the relationship between the number of species in community and the number of individuals in each species

Question 27

What does ‘N’ represent in the index of diversity

Answer 27

Total number of organisms of all species

Question 28

What does the ‘n’ represent in the index of diversity

Answer 28

Total number of organisms of a particular species

Question 29

What does the ‘D’ represent in the index of diversity

Answer 29

Simpson’s diversity index