3.4 Genetic info, variation + relationships

Question 1

how is DNA stored in euk

Answer 1

euk-long, linear, associated with histone proteins

tightly coiled into chromosomes

Question 2

how is DNA stored in prok

Answer 2

short
circular
not associated with proteins
free floating in cytoplasm

Question 3

define gene

Answer 3

sequence of DNA bases
that code for 
-amino acid sequence of polypeptide 
-functional RNA
occupies fixed position, called a locus

Question 4

nature of genetic code

Answer 4

universal
-same DNA triplet codes for same amino acids in all organisms
non-overlapping
-each base read only once in one triplet
degenerate
-same amino acid can be coded for by more than one base triplet q

Question 5

define genome

Answer 5

complete set of genes in a cell

Question 6

define proteome

Answer 6

full range of proteins cell is able to produce

Question 7

define allele

Answer 7

different version of same gene

Question 8

similiarities + differences of mRNA and tRNA

Answer 8

similarities
-both single polynucleotide strand

differences

• mRNA single helix/tRNA folded into clover shape
• mRNA longer/tRNA shorter
• mRNA no paired bases/H bonds / tRNA has some paired bases + H bonds

Question 9

describe transcription

Answer 9

in nucleus
DNA double helix unzipped by DNA helicase
H bonds broken
free floating RNA nucleotides allign to complementary base on template strand
forming H bonds
RNA polymerase joins adjacent nucleotides-condensation reaction
forms phosphodiester bonds
RNA polymerase reaches STOP codon, detaches from DNA
-splicing
mRN leaves nucleus via nuclear pores

Question 10

describe translation

Answer 10

sequence of mRNA codons determines sequence of amino acids
tRNA carry specific amino acids in relation to their amino acids
at ribosome tRNA codon binds to complementary mRNA codon
H bonds form
two amino acids join via condensation reaction
tRNA detaches, ribosome moves along mRNA
till stop codon

Question 11

role of ATP in translation

Answer 11

hydrolysis of ATP releases energy
to form bond between amino acid + tRNA molecule
to form peptide bond between two amino acids

Question 12

define gene mutation

Answer 12

change in base sequence of chromosomes
arise spontaneously during DNA replication
involve base deletion/substitution

Question 13

how can a mutation lead to a non-functional protein

Answer 13

• change in base sequence of DNA
• changes sequence of mRNA
• changes sequence of amino acids
• changes position of bonds
• changes tertiary structure
• substrate cant bind

Question 14

define mutagenic agent

Answer 14

increase rate of gene mutation

Question 15

describe the process of meiosis

Answer 15

Meiosis I - seperates homologous pairs

• chromosomes arrange into homologous pairs
• cross over
• independent segregation

Meiosis II -seperates chromatids

• creates 4 haploid cells
• genetically varied

Question 16

how does meiosis create genetic variation

Answer 16

crossing over between homologous chromsomes

• alleles exchanged between chromosomes
• creates new combination

independent segregation of homologous chromosomes
-random allignment of homologous pairs at equator
creates different combinations

random fertilisation

Question 17

importance of meisosis

Answer 17

• two divisions- creates haploid gametes
• diploid no restored at fertilisation
• maintains chromsomes from one gen to the next
• genetic variation

Question 18

describe chromsome non-disjuncyion

Answer 18

• homologous chromosomes/sister chromatids fail to seperate
• during anaphase
• both chromosomes/chromatids go to one pole of spindle

Question 19

formula to calulcate no of different combinations of chromosomes

Answer 19

2^n

Question 20

no of different combinations of chromsomes following random fertilisation of two gametes
(

Answer 20

(2^n)^n

Question 21

define genetic diversity

Answer 21

no. of different alleles in a population

Question 22

define population

Answer 22

group of interbreeding individuals of same species

Question 23

how does natural selection lead to evolution

Answer 23

1. variation of alleles due to random DNA mutations
2. selection pressure
3. advantageous allele–>increased chance of survival + reproduction
4. survive–>pass on advantageous allele to offspring
5. frequency of advantageous allele increases in population over time/many generations

Question 24

define evolution

Answer 24

change in allele frequency over time

Question 25

describe directional selection

Answer 25

change to environment selection pressures acts one side of mean one extreme phenotype more likely to survive + produce mean phenotype changes

Question 26

describe stabilising selection

Answer 26

stable environment selection pressure acts on either side of mean both extremes of phenotype less likely to survive + reproduce mean phenotype remains the same

Question 27

define species

Answer 27

-two organisms of same species able to produce fertile offspring

Question 28

why is courtship behaviour needed in species recognition

Answer 28

- species specificn - indication of sexual maturity - recognition of opposite sex - stimulates release of gametes - establishes pair bond - synchronised mating

Question 29

define phylogenetic classification system

Answer 29

arranges species based on evolutionary origins

Question 30

define hierarchy

Answer 30

- smaller groups placed within larger groups | - no overlaps between each group

Question 31

order of hierarchy

Answer 31

``` Domain Kingdom Phylum Class Order Family Genus Species ```

Question 32

what is genome sequencing

Answer 32

compare order of base sequence of whole genome of diff species -higher match =more closely related

Question 33

what is immunology

Answer 33

DNA->mRNA->sequence of amino acids in polypeptide | same antibody binds to specific antigen = closely related

Question 34

define biodiversity

Answer 34

variety of living organisms in an area

Question 35

define species diversity

Answer 35

no. of different species + no. of individuals of each species within a community

Question 36

define community

Answer 36

all the populations of different species | in a habitat

Question 37

define index of diversity

Answer 37

describes relationship between no. of species in a community + no of individuals in each species

Question 38

farming techniques that reduce biodiversity

Answer 38

- removal of woodland + hedgerows - monoculture - use of pesticides/herbicides/inorganic fertilisers - competition

Question 39

balance between conservation + farmin

Answer 39

- use crop rotation of nitrogen fixing crops instead of fertilisers - maintain exisiting hedgerows + plant new hedges - reduce use of pesticides

Question 40

define continuous variation

Answer 40

no distinct categories quantitative data controlled by many genes strongly influenced by height

Question 41

define discontinuous variation

Answer 41

distinct,discrete categories qualitative data controlled by a single gene unaffected/not strongly influenced by environment

Question 42

how can genetic diversity be made between or within species

Answer 42

by measuring - the frequency of measurable or observable characteristics - the base sequence of DNA - the base sequence of mRNA - the amino acid sequence of the proteins encoded by DNA and mRNA.

Question 43

what is limited by looking at frequency of measurable characteristics

Answer 43

- many observable characteristics coded for by more than one gene->vary continnously->difficult to distinguish from each other - characterisitcs could be modified by environment

Question 44

how to take a representative sample

Answer 44

random sample-eliminates bias large sample -minimises effect of chance -anomalies have less influence + can be identified