Protein synthesis and selection

Question 1

What bonds are nucleotides joined by

Answer 1

phosphodiester bonds

Question 2

Structures in DNA nucleotide

Answer 2

phosphate group
deoxyribose sugar
base

Question 3

purine bases

Answer 3

adenine
guanine

Question 4

pyrimidine bases

Answer 4

thymine
cytosine

Question 5

what is adenine matched with

Answer 5

thymine

Question 6

what is cytosine matched with

Answer 6

guanine

Question 7

difference between eukaryotic DNA and prokaryotic DNA

Answer 7

linear vs circular
histones vs no histons
introns vs no introns

Question 8

RNA nucleotide contents

Answer 8

phosphate groups
ribose sugar
base

Question 9

how is mRNA different to DNA

Answer 9

double stranded vs single stranded
longer vs shorter
GC + AT vs GC + AU
hydrogen bonds vs no hydrogen bonds
introns vs no introns

Question 10

mRNA characteristics

Answer 10

single stranded
shorter than DNA
GC + AU

Question 11

tRNA characteristics

Answer 11

1 polynucleotide chain
75 nucleotides
single stranded
hydrogen bonds
amino acid attachment site
anticodon

Question 12

name the 2 protein synthesis processes

Answer 12

transcription
translation

Question 13

Transcription steps

Answer 13

-DNA helicase breaks H bonds between two strands and unwinds DNA double helix
-DNA strands separate
-only 1 strand used as a template
-free nucleotides bind to exposed DNA bases via complementary base pair rules on template strand
-U to A + C to G
-RNA polymerase joins RNA nucleotides together by forming phosphodiester bonds
-introns are removed via splicing to produce mature mRNA
mRNA passes out of nucleus via nuclear pore to ribosome

Question 14

translation steps

Answer 14

-mRNA binds to ribosome
-mRNA has two binding sites
-allows tRNA with anticodons to bind
-catalyses formation of peptide bond between two amino acids
-moves along to next codon

Question 15

3 ways to describe genetic code

Answer 15

-universal
-non overlapping
-degenerate

Question 16

what does universal genetic code mean

Answer 16

the same 3 bases on DNA code for the same amino acid in all organisms

Question 17

what does non-overlapping genetic code mean

Answer 17

each base is only 1 triplet code

Question 18

what does degenerate genetic code mean

Answer 18

more than 1 triplet DNA codes for an amino acid

Question 19

mutation definition

Answer 19

change to a single base in DNA base sequence of a gene
mutations occur randomly and could happen spontaneously

Question 20

result of mutation

Answer 20

-may result in a change in the PRIMARY STRUCTURE OF POLYPEPTIDES sequence of amino acids in the polypeptide chain
-may alter the SECONDARY STRUCTURE by changing the position of the weak hydrogen bonds affecting the alpha helices and beta-pleated sheets
-may alter the TERTIARY STRUCTURE by changing the position of the weak Hydrogen, Ionic bonds between the R groups of amino acids and the Disulphide bonds
-and may alter the ACTIVE site of enzymes and make the protein non-functional.

Question 21

silent mutation

Answer 21

-mutation does not change the amino acid coded
-so will have no effect on the polypeptide chain
-as DNA code is degenerate

Question 22

substitution mutation

Answer 22

a substitution of a base with another base

Question 23

what happens if there is a mutation for the STOP codon

Answer 23

-cause the growing polypeptide chain to terminate prematurely
-may not be able to perform its intended function

Question 24

addition/deletion mutations

Answer 24

-nucleotide added or deleted
-alteration of base triplet from the mutation onward
-reading frame has been shifted and is known as a frameshift
-addition/deletion that occurs towards the end of a sequence of bases would have a lesser effect but still alter some amino acids at the end of a gene

Question 25

mutagenic agents

Answer 25

1. high energy ionising radiation x-ray and gamma ray 2. DNA reactive chemicals such as benzene or bromine 3. biological agents such as virus and bacteria

Question 26

chromosomal mutations

Answer 26

-chromosome nondisjunction -too many chromosomes produced

Question 27

inversion mutation

Answer 27

-when a segment of bases is reversed end to end

Question 28

duplication mutation

Answer 28

-doubling of a part of a chromosome OR of an entire chromosome OR even the whole genome

Question 29

translocation mutations

Answer 29

when a group of base pairs relocate from one area of the genome to another usually between non-homologous chromosomes

Question 30

allele definition

Answer 30

different versions of the same gene

Question 31

genetic diversity definition

Answer 31

number of different alleles of genes in a population

Question 32

natural selection definition

Answer 32

-organisms that are better adapted to their environment survive and reproduce -in greater numbers -resulting in the increase of the frequency of the advantageous allele within the population

Question 33

stabilising selection and example

Answer 33

-occurs in all populations where environment is stable. -selection pressure at both ends of distribution. -favours the average. -tends to eliminate extremes. -reduces variability and the size of the range within population. -reduces opportunity for evolutionary change -birth mass

Question 34

directional selection and example

Answer 34

-mean in population represents optimum phenotype for existing conditions -environmental change produces new selection pressure that favours an extreme phenotype -changed conditions, favour allele combination necessary for survival -some organisms will possess the new optimum phenotype (allele combination) -over time, selection means this allele combination will predominate -the mean phenotype will shift -eg. thicker fur for mice

Question 35

disruptive selection

Answer 35

-is the opposite of stabilising selection -environmental has selection pressures that favour 2 extreme phenotypes -when conditions change the optimum phenotypes necessary for survival will also change -some organisms will possess the new extreme optimum phenotypes -over time selection means these 2 extremes will dominate and the mean will shift in both directions of extremes -it is the least common type of selection but it is the most important in evolution

Question 36

what are viable counts of bacteria

Answer 36

counts living cells only