Unit 4

Question 1

describe the similarities between DNA and RNA


Answer 1

• nucleotides
• four nitrogenous bases (adenine, cytosine, guanine)
• phosphate group
• have hydrogen and phosphodiester bonds

Question 2

describe differences between DNA and RNA


Answer 2

• DNA has deoxyribose and thymine, RNA has ribose and uracil
• DNA is a double helix and RNA is a single helix
• DNA is longer

Question 3

define codon


Answer 3

three bases (triplet) that code for an amino acid

Question 4

name for a location of a gene

Answer 4

locus

Question 5

are introns or exons removed


Answer 5

introns are removed in splicing to form mRNA from pre-mRNA

Question 6

how many amino acids do we have


Answer 6

20 - 64 possible triplets

Question 7

features of the genetic code


Answer 7

• non-overlapping - triplets only read once
• degenerate - more than one triplet codes for the same protein
• universal - same codon always codes for the same amino acid
• start/stop codons - initiates and terminates the translation process

Question 8

differences between DNA in prokaryotic and eukaryotic cells


Answer 8

• prokaryotic; nucleoid free in cytoplasm, short, circular and not associated with proteins, no introns.
• eukaryotic; chromosome membrane bound in nucleus, long, linear and associated with proteins (histones), introns (longer)

Question 9

does translation or transcription come first


Answer 9

transcription

Question 10

describe the structure of mRNA


Answer 10

• single stranded helix
• complementary to dna
• pre-mrna contains introns, removed in spicing (shorter than DNA)

Question 11

describe the structure of tRNA


Answer 11

single polypeptide in a clover shape, smaller then mRNA

Question 12

describe transcription - breaks H bonds between between A-T and C-G bases…


Answer 12

• RNA polymerase attach complementary nucleotides to the DNA template strand A-U, T-A, C-G in a condensation reaction forming phosphodiester bonds
• splicing - removing introns from mRNA to become mRNA that diffuses through nuclear pores

Question 13

describe translocation - mRNA associates with ribosomes, tRNA collects amino acids and takes them to the ribosome…


Answer 13

• tRNA attaches to the mRNA by complementary base pairing
• amino acids by peptide bonds in a condensation reaction, ATP used
• this repeats until a stop-codon is reached, tRNA dissociates as ribosomes moves along mRNA

Question 14

define mutation


Answer 14

change in the base sequence

Question 15

define genome


Answer 15

all the genes in an organism

Question 16

define proteome


Answer 16

all of the proteins that an organism can produce

Question 17

describe substitution

Answer 17

one nucleotide is replaced by another

Question 18

describe deletion

Answer 18

nucleotide is removed causing a frame shift meaning multiple different amino acids

Question 19

variation - describe independent assortment

Answer 19

chromosomes line up in pairs at random

Question 20

variation - describe crossing over

Answer 20

when homogenous chromosomes become bivalent they swap genes

Question 21

describe meiosis I

Answer 21

• nuclear membrane breakdown. synapsis
• chromosomes move together and touch so their bivalent
• crossing over - swapping genes

Question 22

describe meiosis II

Answer 22

• chromatids move apart and the cell divides into four then divides again by mitosis

Question 23

finish the order - Kingdom, Phylum, class…


Answer 23

…order, family, genus, species

Question 24

describe natural selection

Answer 24

• environmental change occurs causing selection pressure
• individuals with advantageous alleles survive and reproduce
• advantageous alleles are passed onto the offspring
• increased frequency of allele in population

Question 25

define selection

Answer 25

process in which individuals are better suited to their environment

Question 26

define gene pool


Answer 26

the total number of different allele in the population

Question 27

when naming animals the genus is always written...


Answer 27

...with a capital letter

Question 28

define niche

Answer 28

species with a specific role in an environment

Question 29

describe directional selection

Answer 29

environmental condition change the favourable allele best suited to the new conditions. those with the allele are more likely to survive and reproduce

Question 30

describe stabilising selection

Answer 30

environment stays the same as one characteristic is favoured genes are lost

Question 31

name ways to increase biodiversity


Answer 31

hedgerows, intercropping, reduce pesticides and herbicides, preserving wetlands

Question 32

limitation to not using amino acid sequence to compare species


Answer 32

- could be degenerate - characteristics could be influenced by environment

Question 33

how does agriculture effect biodiversity

Answer 33

only one species grown, reduces biodiversity - less habitats and food sources for other species

Question 34

index of diversity=...

Answer 34

...N(N-1) of the total organisms/the sum of n(n-1) of the separate species