genetic diversity

Question 1

why genetic code in degenerate

Answer 1

most amino acids coded for by more than 1 triplet

Question 2

non overlapping

Answer 2

each base is only needed once

Question 3

universal

Answer 3

each triplet codes for the same amino in all organisms on earth

Question 4

transciption makes

Answer 4

mrna

Question 5

translation makes

Answer 5

polypeptide

Question 6

primary strcutre

Answer 6

the sequence of amino acids

Question 7

tertiary structure

Answer 7

3d strucutre determines by hyrodgen ionic and disulphide bonds

Question 8

mutations

Answer 8

a change in the dna base sequence or quantity

Question 9

causes of mutation

Answer 9

-spontaneous during dna replication
-due to mutagens which acceleates the rate of spontaneous mutations
-eg.high energu/ioinising radiation , some chemicals
-increases genetic diveristy which is important in natural selection and speciation

Question 10

types of gene mutation

Answer 10

substitiution
addition
deletion
duplication
inversion
transloaction

Question 11

substiituion
addition
duplication
deletion

Answer 11

one base replaced by another
extra base added to sewuence
a base repeated
base is deleted

Question 12

nonsense

Answer 12

a stop codon -shortened polypeptide

Question 13

mis sence

Answer 13

a diff amino aicd - affects fiuncitoning of polypeptide

Question 14

silent

Answer 14

same amino acid

Question 15

insertion mutation

Answer 15

a mutation that occurs when a nucleotide with a new base is randomly inserted into the dna sequence

Question 16

what does insertion mutation change

Answer 16

changes the amino acid that wouldhave been coded for by the original base triplet as it creates a new different triplet of bases this is because every group of three bases in a dna sequence codes for an amino acid

Question 17

what is a frameshift mutation

Answer 17

changes the triplets further on in the dna sequence
this may dramatically change the amino acid sequence produced from this gene and therefore the ability of the polypeptide to function

Question 18

haploid cells

Answer 18

have a single copy of each chromosomes

Question 18

homologous pair

Answer 18

pair of chromosomes
one maternal and one paternal - same gene loci

Question 18

diploid

Answer 18

nucleus has 2 sets of chromosomes

Question 18

gametes formation

Answer 18

human cells 46 chromosomes
diploid 2n=46
gametes-23 chromseomes one of each homologus pair and 1 sex chromoskmes
haploid = n=23

Question 20

independent assortmrnt

Answer 20

one chromodome
2 vhromatids from each homologus pair ends up in each gamete
each homologus pair lines up independent of any others
this depends on their random alignment during meiosis

Question 21

crossing over

Answer 21

homologus region of line up chromatids may be exchanged by bresking and rejoining at regiond vslled chiasma
joining with another set of chromosomes at fertillisation ensures variation

Question 22

key points about meoisis

Answer 22

-there are two didiviosns meiosis 1 and 2
-four non identical daughter cells
-variation in the offspring is increased in two main ways

Question 23

what is genetic divedrity

Answer 23

total number of different alleles in a pop

Question 24

population

Answer 24

group of individuals of same species that in the same pplaxce and can interbreed

Question 25

species

Answer 25

group of similar organisms that can breed together to produce fertile ofsping

Question 26

steps of natural seledction

Answer 26

1)variation as a result of mutation
2)indifvuals with advantageous alleles more likely to survive and reporidyce
3)pass on alleles to nexr generation
4)continues over manty generatiosn

Question 27

environmental factors

Answer 27

affect the chance or survival of an organisms are selection pressures for example there could be high competition for food between lions if there is not plentiful prey available
this envionmental factor selects for faster more poweerful lions that are better hunters
these selection pressures can have a different efects on thr allele frequencies of a populationthrough natural seelction
there are different types of selection -stabilising
directional

Question 28

stabilising selection

Answer 28

-envionemnt is stable
-eg.short plants compete with tall for sunlight
-tall- wind will kill it
-medium - in between - no of them increase
-when selctive pressures select against 2 extreemes of a trait - population experiences stabilising selection

Question 29

directional selection

Answer 29

environmental conditions change and indiviudals on one side of the mean are favoured to survivr and reporudcde

one extreme is selected for one extreme selected against

populations trait distribution therfrore shifts towards one extreme

selection pressure against short necked giraffe
distribution shifts towards those with long neckss

Question 30

polymphorism

Answer 30

-directional selection of peppered moth
-due to selective predation of moths

Question 32

example of directional selection -

Answer 32

-the presence of antibiotics is selection pressure
-mjutations are ocurring in bacteria populations randomly
-a mutation arises that confers antibiotic resistance it is a beneficial allele
-bacteria with mutation are more likely to survive and reporduce
-most bacteria without the resistance mutations die
-over generatiions this leads to an increase in the the frequency of benefical allele produces antibiotic resistance