topic 4

Question 1

chromosome

Answer 1

long linear dna associated with histones
in the nucleus of euk

Question 2

genes

Answer 2

sequences of dna bases that code fro an amino acid
or functional RNA

Question 3

universal

Answer 3

the same triplet of bases codes for the same amino acid in all organism

Question 4

non coding base sequences

Answer 4

dna that doesn’t code for an amino acid
between genes and in genes

Question 5

tRNA

Answer 5

clover leaf shape
hydrogen bonds between bases
short fixed length
anticodon and amino acid. binding site

Question 6

mRNA

Answer 6

linear
long variable length
codons

Question 7

transcription

Answer 7

hydrogen bonds between comp base pairs break
1 strand acts as template
free RNA nucleotides align next to comp base pairs on the template strand
in rna uracil replaces thymine
rna polymerase joins adjacent RNA nucleotides
forming phosphodiester bonds via condensation
pre MRNA formed spliced to remove introns

Question 8

translation

Answer 8

mana attaches to ribosome and ribosome moves to start codon
tRNA brings specific amino acid
tRNA anticodon binds to comp mRNA codon
ribosome moves to next codon and another tRNA binds so two amino acids joined by condensation to form peptide bonds
using energy from hydrolysis of ATP
tRNA released after amino acid joined polypeptide
Ribosome moves along mRNA to form the polypeptide, until a stop codon is reached

Question 9

meiosis

Answer 9

meiosis 1 separates homologous chromosomes
chromosomes arrange in homologous pairs
crossing over and independent segregation
meiosis II separates chromatids

Question 10

crossing over

Answer 10

Homologous pairs of chromosomes form a bivalent
Chiasmata form
Alleles exchanged between chromosomes
Creating new combinations of (maternal & paternal) alleles on chromosomes

Question 11

independant segregation

Answer 11

Homologous pairs randomly align at equator
so random which chromosome from each pair goes into daughter cell
= Dif combo of paternal and maternal chromosmes

Question 12

importance of meiosis

Answer 12

two divisions creates haploid cells
diploid number resorted at fertilisation
Independent segregation and crossing over create genetic variation

Question 13

genetic diversity

Answer 13

number of different alleles of genes in a population

Question 14

importance of genetic diversity

Answer 14

allow natural selection to occur
new allele may benefit possesor
giving selective advantage and leading to reproduce

Question 15

how do alleles arise

Answer 15

variations of gene on same locus df base sequence arise by mutation

Question 16

evolution

Answer 16

change in allele frequency over many generations
occurring through the process of natural selection

Question 17

anatomical adaptations

Answer 17

structural and physical features that increase the chance of survival

Question 18

phyological

Answer 18

chemical processes that increase the change of survival

Question 19

behavioural

Answer 19

ways in which an organism act that increase the chance of survival

Question 20

why cant two different organisms breed

Answer 20

different chromosome numbers so offspring will have odd chromosomes
homologous pairs cant form and meiosis cant happen

Question 21

necessity of courtship behaviour

Answer 21

● Allows recognition of members of same species so fertile offspring produced
● Allows recognition of opposite sex
● synchronises mating
● Indicates sexual maturity
● Establishes a pair bond

Question 22

two advances that have helped identify evolutionary relationships

Answer 22

Advances in genome sequencing allowing comparison of DNA base sequences More differences in DNA base sequences more distantly related build up over time
2. Advances in immunology allowing comparison of protein tertiary structure higher amount of protein from one species binds to antibody against the same protein from
another species → more closely related
As indicates a similar amino acid sequence and tertiary structure So less time for mutations to build up

Question 23

how do farming techniques reduce biodiversity

Answer 23

removing woodland and hedgegrows
monoculture and herbicides to remove weeds Leeds to less variety of plants fewer habitats and niches and less variety of food sources

Use of pesticides to kill pests Predator population of pest decreases

Question 24

how to measure genetic diversity between species

Answer 24

● Comparing frequency of measurable or observable characteristics
● Comparing base sequence of DNA
● Comparing base sequence of mRNA
● Comparing amino acid sequence of a specific protein encoded by DNA and mRNA

Question 25

how does measuring DNA AA MRNA indicate relationships between organisms

Answer 25

More differences in sequences → more distantly related
● As mutations build up over time More mutations cause more changes in amino acid sequences

Question 26

quantitative investigations of variation
within a species

Answer 26

Collect data from random samples (use a random number generator) → removes bias
● Use large sample size representative of whole population
● Ethical sampling
● Calculate a mean value of collected data and standard deviation of that mean
● Interpret mean values and their standard deviations
○ If standard deviations overlap, any difference
between the two may be due to chance
● Use statistical test → analyse whether there is a significant difference between populations

Question 27

semi conservative dna replication

Answer 27

DNA helicase breaks hydrogen bonds between complementary bases, unwinding the double helix
2. Both strands act as templates
3. Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
4. Hydrogen bonds form between adenine-thymine and guanine-cytosine
5. DNA polymerase joins adjacent nucleotides on new strand by condensation reactions
6. Forming phosphodiester bonds

Question 28

how are genes a code for the production of a polypeptide

Answer 28

nucleotide sequence in triplet determine the order of amino acid sequence

Question 29

how does the structure of a chromosome differ along its length

Answer 29

difference in base sequence
difference in histone interactions
difference in condensation