Genetic information, variation & relationships

Question 1

gene

Answer 1

a DNA base sequence that codes for the amino acid sequence of a polypeptide or a functional RNA like tRNA

Question 2

locus

Answer 2

the location of a particular gene on a chromosome

Question 3

allele

Answer 3

a version of a gene

Question 4

chromosome

Answer 4

a long, coiled molecule of DNA

Question 5

homologous chromosomes

Answer 5

pairs of matching chromosomes
they are the same size and have the same genes, but may have different alleles

Question 6

the genetic code as degenerate

Answer 6

each amino acid can be coded fro y more than one triplet of bases

Question 7

why is it a benefit for the genetic code to be degenerate

Answer 7

if a point mutation occurs, even though the triplet of bases will be different, it may still code for the same amino acid

Question 8

the genetic code as universal

Answer 8

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

Question 9

why is the genetic code being universal an advantage

Answer 9

it means genetic engineering is possible
making recombinant DNA e.g. inserting a human gene into bacteria

Question 10

the genetic code as non-overlapping

Answer 10

each base in a gene is only part of one triplet of bases that codes for one amino acid
each codon is read as a discrete unit

Question 11

why is the genetic code being non-overlapping an advantage

Answer 11

if a point mutation occurs, it will only affect one codon, therefore one amino acid

Question 12

introns

Answer 12

sections of DNA that do not code for amino acids
they are found in eukaryotic DNA but not prokaryotic DNA
they are spliced from mRNA molecules

Question 13

genome

Answer 13

the complete set of genes in a cell

Question 14

proteome

Answer 14

full range of proteins a cell/organism is able to produce

Question 15

transcription

Answer 15

DNA helicase breaks the hydrogen bonds between complementary base pairs, causing the DNA helix to unwind to expose the bases to act as a template
free RNA nucleotides in the nucleus align opposite to their complementary base pair
RNA polymerase bonds together the RNA nucleotides by forming phosphodiester bonds

Question 16

translation

Answer 16

pre-mRNA is modified - spliced to remove introns
the mRNA eaves the nucleus and attaches to a ribosome in the cytoplasm
the ribosome attaches at the start codon
the tRNA molecule with the complementary anticodon to the start codon aligns opposite the mRNA
the ribosome moves along the mRNA molecule, allowing another complementary tRNA molecule to attach to the next codon
the two amino acids are joined by a peptide bond, requiring an enzyme and ATP
the ribosome has two binding points
this continues until the ribosome reaches the stop codon, where it detaches
the polypeptide chain enters the Golgi body for post-translational modifications

Question 17

how can genetic variation be introduced

Answer 17

meiosis, mutation, and random fertilisation of gametes

Question 18

crossing over

Answer 18

crossing over occurs in meiosis I
homologous pairs line up opposite each other at the equator and equal lengths of the non-sister chromatids twist around each other
this puts tension on the chromatids so they break at the chiasmata
the broken parts recombine with the other chromatid
this results in new combinations of alleles in the gametes

Question 19

independent segregation

Answer 19

in meiosis I homologous pairs of chromosomes line up opposite each other at the equator of the cell
it is random which side of the equator the paternal and maternal chromosomes from each homologous pair lie
these pairs are separated, so one of each homologous pair ends up in the daughter cell
this creates a large number of possible combinations of chromosomes in the daughter cells produced

Question 20

how is the total no. possible combinations of chromosomes calculated

Answer 20

2n
n = number of homologous pairs

Question 21

silent mutation

Answer 21

the new codon still codes for the same amino acid as the genetic code is degenerate

Question 22

chromosomal non-disjunction

Answer 22

the chromosomes or chromatids do not split equally during anaphase

Question 23

polyploidy

Answer 23

changes in whole sets of chromosomes

Question 24

aneuploidy

Answer 24

changes in the number of individual chromosomes

Question 25

genetic diversity

Answer 25

the number of different alleles in a population

Question 26

types of adaptation

Answer 26

anatomical - e.g. spikes on a hedgehog physiological - e.g. hedgehogs hibernating and slowing their metabolic reactions in winter behavioural - e.g. hedgehogs curl up when in danger

Question 27

generic process of natural selection

Answer 27

random mutations occur within the populationthis introduces genetic variation to the populationwhilst some mutations are harmful, mutations can sometimes give rise to new alleles that provide an organism with an advantage to survive in its environmentthe new allele provides a reproductive selective advantage - it is more likely to reproduce and pass on the advantageous alleleover many generations, there will be an increase in the frequency of the allele within the population

Question 28

courtship behaviour

Answer 28

different behaviours animals demonstrate to attract a mate each species has its own unique behaviour and this is essential for successful acting

Question 29

species

Answer 29

group of similar organisms that can breed to make fertile offspring

Question 30

when do animals display courtship behaviours and why are they important

Answer 30

only when they are sexually mature and fertile this synchronises mating behaviour so that animals are more likely to mate when the female is releasing eggs it increases the likelihood of successful mating as it enables individuals to recognise members of the same species and opposite sex

Question 31

how can courtship behaviour lead to increased survival of offspring

Answer 31

the ritual helps form a pair bond between parents so they are more likely to stay together and raise the offspring as a team it allows females to select a strong and healthy mate to reproduce with and ensures more successful alleles are passed on

Question 32

types of courtship behaviours

Answer 32

sequence of dances/movements certain sounds release of pheromones displays of feathers

Question 33

binomial naming system

Answer 33

universal - international and avoids confusion two name system where individuals are named after there genus and species Homo sapiens in italics (or underlined if handwritten) with the genus first and capitalised

Question 34

phylogenetic classification

Answer 34

arranges species into groups according to their evolutionary origins and relationships it also shows common ancestors

Question 35

how is the accuracy of classification and phylogeny improving

Answer 35

advices in immunology and genome sequences the DNA base sequence of organisms for common genes can be compared the sequence of amino acids in proteins can also be compared as this is determine by DNA

Question 36

taxa classification hierarchy

Answer 36

domain kingdom phylum class order family genus species

Question 37

species diversity

Answer 37

the number of different species and individuals within each species in a community

Question 38

species richness

Answer 38

the number of different specie in a particular area at the same time

Question 39

biodiversity

Answer 39

the range of habitats - the range of physical, biological, and environmental factors in which a species can live in

Question 40

community

Answer 40

all the organisms living in a particular area at a particular time

Question 41

which farming practices increase the efficiency and quality of food production but reduce biodiversity

Answer 41

destruction of hedgerowsselective breedingmonoculturesover-grazingfilling in ponds and draining wetlands

Question 42

index of diversity

Answer 42

measures the relationship between the number of species in a community and number of individuals in each species

Question 43

diversity index equation

Answer 43

D = N(N-1)/∑n(n-1) N = the total number of organisms of all the species n = the population size of one species 1 is the lowest value for D (it is typically between 1-10)

Question 44

how can genetic diversity of a population/community be measured

Answer 44

comparing observable characteristics or looking at the base sequence of DNA, mRNA, and the amino acid sequence of proteins