topic 4

Question 1

eukaryotes vs prokaryotes

Answer 1

longer vs shorter
histone proteins vs no histone proteins
linear vs circular

Question 2

mitochondri and chloroplasts DNA

Answer 2

similar to prokaryotes as shorter, circular and not bound by histone protein

Question 3

gene

Answer 3

base sequence of DNA that codes for

amino acid sequence of a polypeptide
functional RNA

Question 4

locus

Answer 4

fixed position of gene on the chromosome

Question 5

the features of the genetic code

Answer 5

degenerate
universal
non overlapping

degenerate- more than one codon codes for the same amino acids so mutations may result in no effect as even though the codon has changed, it still produces the same amino acid

universal- the same codons code for the same amino acieds in most organisms on earth

non overlapping- each codon is read as a discrete unit
adfvantage as if mutation occurs, it will only affect one codon and one amino acid.

Question 6

introns and exons

Answer 6

introns- sections of DNA that do not code for polypeptides
introns are only in eukaryotic not prokaryotic DNA

Exons are sequences of DNA that do not code for amino acids
in eukaryotes a lot of the nuclear DNA is made up of introns

Question 7

codon

Answer 7

3 bases on mRNA that code for specific amino acid

Question 8

start codon

Answer 8

3 bases at the start of the gene which intiiate translation

Question 9

stop codon

Answer 9

3 bases at the end of the gene which cause the ribosome to detach and translation stops.

Question 10

genome and proteome

Answer 10

genome- organisms’s entire srt

Question 11

mRNA

Answer 11

has a codon
complimentary to tRNA anticodon
short
length of one gene
found in the cytooplasm and nucleus

Question 12

tRNA

Answer 12

has a sequencee of three basees/anticodon, which is complimentaaary to mRNA codon
single stranded
clover leaf shape
held in place by hydrogen bonds between complimentary bases
brings specific amino acids to the cytoplasm
each tRNA is specific to one amino acid

Question 13

transcription

Answer 13

occurs in the nucleus
DNA helicase enzyme breaks hydrogen bonds between cmomplimentary bases, separating the two polynucleotide strands
free mRNA nucleotides align opposite complimentary exposed DNA bases
enzyme RNA polymerase joinss adjacent nucleotides by fforming phosphodieesster bonds.
formation of pre mRNA
introns removoed from premRNA through splicing to form mRNA
only one strand of DNA acts as a template

Question 14

translation

Answer 14

mRNA attaches to ribosome at start codon
tRNA anticodon aligns opposite mRNA codon
tRNA brings specific amino acids to the cytoplasm
two amino acids are joined via a peptide bond- requires an enzyme and ATP
ribosome moves along codon on mRNA
continues until ribosome reaches stop codon- ribosome dettaches and polypeptide chain released
polypeptide chain is now formed and enters golgi apparatus for folding and modification

Question 15

chromsome mutations- non disjunction

Answer 15

chromsomes/chromatids do not separate equally during anaphase of meiosis

Question 16

changes to whole sets of chromosomes

Answer 16

polyploidy
often occurs in plants
organisms have 3 or more sets of chromosomes when they should only have 2

Question 17

changes to individual numbers of chromosomes

Answer 17

after fertilisation,hte zygote will have one more or one fewer chromosomes in each of its body cells e.g. down syndrome is 3 copes of chromosome 21

Question 18

meosis

Answer 18

to produce gametes
4 haploid cells produced from one diploid cell
genetic variation among offspring due to crossing over and independent segregation

Question 19

genetic diversity and why it is important

Answer 19

totaal number of alleles of a gene within a population
for natural selection to occur, there must be variation within the population.

allows population to become better adapted to their environment.

Question 20

types of selectioni

Answer 20

disruptive
directional
stabilising

Question 21

what produces genetic variation in meisois?

Answer 21

crossing over- prophase
independnent segregation- metaphase
random fusion of gametes

Question 22

natural selection

Answer 22

mutations produce new allele
in certain environmental conditions, organisms with these alleles have a selsective advantage/more likely to survive and reproduce.
alleles inherited by offspring
alleles increase in frequency in the population over many generations.

Question 23

directional selection

Answer 23

organisms with extreme phenotypes have selective advantage
modal trait changes as more organisms with extreme phenotypes
e.g. antibotic resistance in bacteria

Question 24

stabilising selection

Answer 24

occurs when there is no environmental change
organisms with most common allele have selective adfvantage
decrease in standard deviation/mean as fewer organisms with extreme phenotype e.g. birth weight of babies.

Question 25

what is a species?

Answer 25

organisms that can interbreed to produce fertile offspring

Question 26

why is courtship behaviour important?

Answer 26

successful mating
species recognition- recognise members of the same species and opposite sex
form a bond pair
ensure sexual maturity- in season

Question 27

courtship behaviour

Answer 27

sequence of actions unique to each species.
-feathers, antlers, fighting,pheromones.

Question 28

phylogenetic classification

Answer 28

organises species into groups based on evolutionary relationships and common anscetors.

can work out most recent common ancestor and how closely related they are.

Question 29

features of a hierarchy

Answer 29

smaller groups within larger groups
no overlap of groups

Question 30

binomial system

Answer 30

genus
species

each species is universally identified using binomial system.

Question 31

genetic diversity
ecosystem diversity
species diversity
species richness

Answer 31

genetic diversity- total number of different allele within a gene in a population.
ecosystem diversity- range of different habitats.

species diversity- no of different species and number of individuals within each species.

species richness- total number of different species in a community.

Question 32

farming techniques

Answer 32

farming reduces biodiversity so there needs to be a balnce between farming and biodiversity,

monculturs
selective breeding
overgrazing
filling in ponds and draining wetlands.

Question 33

how genetic diversity can be compared

Answer 33

DNA base sequence
mRNA sequence
amino acid sequence of proteins
frequency of observable characteristics.