Topic 4

Question 1

What is a gene

Answer 1

Base sequence of DNA that codes for a polypeptide

Question 2

How is mRNA in eukaryotic cell different to mRNA in prokaryotic cell

Answer 2

Eukaryotes - mRNA must be spliced to remove introns

Prokaryotes - splicing not needed as they have no introns

Question 3

Role of ATP in process of translation in protein synthesis

Answer 3

Releases energy

Forms peptide bonds

Question 4

What is genetic diversity

Answer 4

Number of different alleles in a population

Question 5

What factors can cause variation in a species

Answer 5

Genetic factors

Environmental factors

Question 6

What is a species

Answer 6

Group of similar organsims that are fertile

Question 7

Describe how mRNA is formed by transcription in eukaryotes

Answer 7

Hydrogen bonds between bases break

Only one strand acts as a template

Free RNA nucleotides align opposite the exposed complementary bases

In RNA uracil base pairs with adenine

RNA polymerase joins the adjacent RNA nucleotides

By forming phosphodiester bonds

This forms pre mRNA

premRNA undergoes splicing to remove the introns and form mRNA

Question 8

Describe how a polypeptide is formed by a translation of mRNA

Answer 8

Ribosome attaches to mRNA

tRNA anticodons bind to complementary mRNA codons

tRNA brings a specific amino acid

Amino acids join by peptide bonds

With the use of ATP

tRNA released

Ribosome moves along mRNA to form the polypeptide

Question 9

Define gene mutation

Answer 9

Change in base sequence of DNA which results in the formation of a new allele

Question 10

How can a gene mutation have a positive effect on an individual

Answer 10

Improves chances of survival

May mutate into advantageous gene

Question 11

How can a gene mutation have no effect on an individual

Answer 11

Genetic code is degenerate

Mutated triplet may still code for same amino acid

Changed amino acid may have no effect on tertiary structure

Question 12

Name the fixed position occupied by a gene on a DNA molecule

Answer 12

Locus

Question 13

How do genes code for production of polypeptide

Answer 13

Base sequence

In triplets

Determines sequence of amino acids

Question 14

Exon

Answer 14

Base sequence coding for polypeptide

Question 15

DNA in eukaryote compared to prokaryote

Answer 15

Eukaryote - Linear DNA
Prokaryote - Circular DNA

Eukaryote - Associated with histones
Prokaryote - No histones

Eukaryote - Introns
Prokaryote - No introns

Eukaryote - No plasminds
Prokaryote - Plasmids

Eukaryote - Longer
Prokaryote - Shorter

Question 16

Why don’t all mutations in the nucleotide sequence of a gene cause a change in polypeptide structure

Answer 16

Triplets code for same amino acid

Occurs in introns

Question 17

Similarities between DNA in eukaryotes and prokaryotes

Answer 17

Nucleotide structure is identical

Nucleotides joined by phosphodiester bond

Question 18

Differences in tRNA and mRNA structure

Answer 18

tRNA is clover leaf shape
mRNA is linear

tRNA has hydrogen bonds
mRNA does not

tRNA has amino acid binding site
mRNA does not

tRNA has anticodon
mRNA has codon

Question 19

Difference between mRNA and pre-mRNA

Answer 19

mRNA has no introns

Due to splicing

Question 20

How is ONE amino acid added to a polypeptide that is being formed during translation

Answer 20

tRNA brings specific amino acid

Anticodon binds to codon

Amino acids join to form a peptide bond using ATP

Question 21

How is mRNA produced from an exposed template strand of DNA

Answer 21

Free RNA nucleotides form complementary base pairs

Phosphodiester bonds form

By RNA polymerase

Question 22

Proteome

Answer 22

Full range of different proteins a cell is able to produce at a given time

Question 23

Role of ribosome in polypeptide creation

Answer 23

mRNA binds to ribosome

Allows tRNA with anticodons to bind

Moves along mRNA to next codon

Question 24

Mutagenic agent

Answer 24

Factor that increases the rate of mutations

Question 25

How can genetic variation within a species increase

Answer 25

Mutation Random fertilisation Produces new allele combinations

Question 26

Differences between mitosis and meiosis

Answer 26

Mitosis - One division Meoisis - Two divisions Mitosis - Daughter cells genetically identical Meiosis - Daughter cells genetically different Mitosis - 2 cells produced Meiosis - 4 cells produced Independant segregation only in meoisis Crossing over only in meiosis

Question 27

Why can a change in one amino acid have no effect but a change in another amino acid will reduce rate of reaction

Answer 27

Change at first amino acid does not change shape of active site Second amino acid may have been involved in (ionic, disulfide or hydrogen) bond and so the tertiary structure may have changed

Question 28

How is chromosome number halved during meiosis

Answer 28

Homologous chromosomes pair One of each pair goes to each daughter cell

Question 29

Process of crossing over

Answer 29

Homologous pairs of chromosomes associate Chiasmata form Equal lengths of chromatids are exchanged

Question 30

Why might there be change in chromosome number after meoisis

Answer 30

In meiosis Homologous chromosomes do not seperate

Question 31

Binomial system

Answer 31

Identifying organisms by referring to species name and genus name

Question 32

Why is it more useful to calculate index of diversity to record species richness

Answer 32

Index of diversity also measures abundance of each species So useful because may be many of some species

Question 33

What data is needed to calculate index of diversity

Answer 33

Number of species Number of individuals in each species

Question 34

Ways which students can ensure their index of diversity was representative of each habitat

Answer 34

Random samples Large number of samples

Question 35

Advantages to a farmer replanting hedges on their farmland

Answer 35

Greater biodiversity SO increase in predator of pests Increase in pollinators SO more yield May attarct more tourists SO more income

Question 36

Disadvantages to a farmer replanting hedges on their farmland

Answer 36

Reduced land area FOR crop growth Greater biodiversity SO increase pest population Increase pest population SO less yield

Question 37

Species richness

Answer 37

Number of different species in a community

Question 38

Species

Answer 38

Group of organisms that are able to produce fertile offspring

Question 39

Difference between species richness and index of diversity

Answer 39

Species richness doesnt measure number of individuals

Question 40

Ways which genetic diversity between species is measured

Answer 40

Comparing differences in base sequence of DNA Comparing observable characteristics Comparing amino acid sequences

Question 41

Students t test

Answer 41

Method used to determine whether there is a significant difference between mean of 2 groups

Question 42

Order of taxons

Answer 42

Dear - Domain King - Kingdom Philip - Phylum Came - Class Over - Order For - Family Great - Genus Soup - Species

Question 43

Why might populations show very low levels of genetic diversity

Answer 43

Hunting Population might have been very small Inbreeding Population might have been started with small number of individuals