section 4: genetic information, variation and relationships between organisms

Question 1

gene

Answer 1

a section of DNA that contains coded information for making polypeptides and functional RNA

Question 2

allele

Answer 2

a version of a gene

Question 3

genetic code

Answer 3

a series of triplet codes that each code for an amino acid or a stop/start codon,
4 different bases that when together in 3s code for each of the 20 different amino acids in proteins.

Question 4

features of genetic code

Answer 4

• degenerate - because some amino acids are coded for by more than one triplet.
• non-overlapping - the three bases are totally separate from the next 3, each base is only read once.
• universal- each triplet always comes for the same amino acid.

Question 5

homologous chromosomes

Answer 5

one of the pair is derived from the maternal chromosomes, the other is derived from the paternal chromosomes a homologous pair is always two chromosomes that carry the same genes but not always the same alleles of the genes

Question 6

genome

Answer 6

the complete set of genes in a cell,

including those in mitochondria and chloroplasts

Question 7

proteome

Answer 7

the full range of proteins produced by the genome,

(sometimes cakes complete proteome, in which case the term proteome refers to the proteins produced by a given type of cell under a certain set of conditions)

Question 8

gene mutation

Answer 8

any change to one or more nucleotide bases, or change in the sequence of bases, in DNA

Question 9

explain homologous chromosomes, chromosomes and sister chromatids

Answer 9

homologous chromosomes - made up of 2 chromosomes, one maternal and one paternal

chromosomes - made up of 2 chromatids, joined by a centromere

sister chromatids - (phrase only used during parts of cell revision) made up of 2 chromatids, joined by a centromere

Question 10

genetic diversity

Answer 10

number of different alleles of genes in a population

Question 11

population

Answer 11

a group of individuals of the same species that live in the same place at the same time and can interbreed

Question 12

locus

Answer 12

the position of a gene on a chromosome or DNA molecule

Question 13

gene pool

Answer 13

the total number of alleles in a particular population at a specific time

Question 14

phenotype

Answer 14

observable characteristics that an organism has

Question 15

genotype

Answer 15

genetic make up of an organism

Question 16

allele frequency

Answer 16

the number of times an allele occurs within the gene pool

Question 17

selection

Answer 17

the process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted

Question 18

species

Answer 18

a group of similar organisms that can breed together to produce fertile offspring

Question 19

purposes of courtship behaviour

Answer 19

• recognise members of their own species
• identify a mate that is capable of breeding
• form a pair bond
• synchronise mating
• become able to breed

Question 20

identification

Answer 20

the organisation of living organisms into groups

Question 21

taxonomy

Answer 21

the theory and practice of biological classification

Question 22

phylogeny

Answer 22

the evolutionary relationships between organisms

Question 23

biodiversity

Answer 23

the range and variety of genes, species and habitats in a particular region

Question 24

species diversity

Answer 24

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

Question 25

genetic diversity

Answer 25

the variety of genes possessed by the individuals that make up a population of a species

Question 26

ecosystem diversity

Answer 26

the range of different habitats, from a small local habitat to the whole of the earth

Question 27

process of transcription

Answer 27

1. DNA helicase (enzyme) acts on a region of DNA, separating the two strands and exposing the nucleotide bases in that region
2. free-floating RNA nucleotides match up to their complementary base on the DNA
3. RNA polymerase joins the nucleotides together to form pre-mRNA, forms strong chemical bond between sugar and phosphate group
4. when the RNA polymerase reaches a stop codon, the chain is terminated and the pre-mRNA detaches
5. the DNA behind the RNA polymerase rejoins to form the double helix

Question 28

introns

Answer 28

don’t code for anything, useless

Question 29

exons

Answer 29

functional, code for things

Question 30

process of translation

Answer 30

1. mRNA attaches to a ribosome at a start codon (AUG)
2. the tRNA molecule with the complimentary anticodon moves to the ribosome and pairs up with the codon on the mRNA
3. that tRNA molecule brings an amino acid with it
4. the ribosome moves along the mRNA, bringing in two tRNA molecules at any one time, each pairing up with their complimentary codons
5. an enzyme and ATP join the amino acids with a peptide bond
6. the first tRNA molecule is released and can go and collect another amino acid from the cell
7. the process is repeated until the stop codon is reached, then the ribosome, mRNA and last tRNA all separate

Question 31

mutagenic agents

Answer 31

increase the rate and likelihood of gene mutation

Question 32

phylogenetic naming

Answer 32

DOMAIN 
KINGDOM 
PHYLUM 
CLASS 
ORDER 
FAMILY 
GENUS
SPECIES