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AQA A level biology <33 > November mock prep- topic 4 > Flashcards

November mock prep- topic 4 Flashcards

1
Q

gene

A

section of DNA that codes for a specific sequence of amino acids, making a polypeptide

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2
Q

locus

A

specific location of a gene on a chromosome

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3
Q

what are the 3 characteristics of the genetic code?

A

universal-
same for multiple organisms

non-overlapping-
each base sequence only read once

degenerate-
amino acids coded for by multiple triplets

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4
Q

what is the same at the start of every DNA sequence?

A

the start codon

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5
Q

what marks the end of the DNA sequence?

A

the stop codon

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6
Q

what are introns?

A

non-coding sequences found in a gene

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7
Q

what are exons?

A

coding sequences within a gene

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8
Q

when are chromosomes visible?

A

when a cell is dividing

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9
Q

what are chromatids?

A

one of the two strands that make up a chromosome joined at the centromere

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10
Q

how are chromosomes formed?

A

DNA combines with histone forming a DNA-histone complex

coils then folds to form loops

loops coil and pack together to form the chromosome

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11
Q

what is a homologous pair?

A

one chromosome from maternal chromosomes and one chromosome from paternal chromosomes

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12
Q

what is an allele?

A

alternative form of a gene

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13
Q

what happens when the base sequence of a gene changes?

A

a new allele is produced due to the mutation

this codes for a different amino acid creating a different polypeptide

this therefore creates a different protein

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14
Q

what is a codon?

A

sequence of 3 bases on mRNA

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15
Q

what is the genome?

A

complete set of genes in a cell

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16
Q

what is the proteome?

A

full range of proteins produced by the genome

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17
Q

what is the structure of RNA?

A

ribose sugar
phosphate group
bases- A-U/ C-G

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18
Q

mRNA

A

single helix
long strand
transcription
leaves through nuclear pores
acts as template for protein synthesis
information in form of codon

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19
Q

tRNA

A

small
around 80 nucleotides
anticodon on opposite end- specific to the amino acid
clover leaf shape with one end extended past the other where the amino acid attaches

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20
Q

describe transcription

A

process of making pre-mRNA

DNA helicase breaks hydrogen bonds exposing the nucleotides in that area, creating a template strand

bases on template strand pair with complementary RNA nucleotides using RNA polymerase

RNA polymerase reaches stop codon and detaches

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21
Q

describe splicing

A

process of making mRNA

introns removed as they are non coding and would prevent protein synthesis

functional exons are joined

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22
Q

describe translation

A

1) mRNA leaves through nuclear pore into cytoplasm
2) ribosome attaches to start codon
3) tRNA with complementary anticodon pairs up with codon, carrying a specific amino acid
4) tRNA binds with next codon carrying a different amino acid
5) ribosome moves along mRNA bringing two tRNA molecules each time with amino acids being joined by peptide bonds
6) first tRNA is released when ribosome moves to third codon so it can collect another amino acid
7) process continues until stop codon is reached

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23
Q

what is a mutation?

A

any change to the quantity or base sequence of the DNA

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24
Q

what are the 3 mutations?

A

substitutions-
nucleotide replaced by a different one
usually coding for a new amino acid
this doesn’t always happen due to the genetic code being degenerate

deletion-
nucleotide is lost causing a frame shift often completely changing the amino acid sequence

addition-
new nucleotide is added causing a frameshift

25
Q

what are the two chromosome mutations?

A

polyploidy-
change in whole set of chromosomes

non-disjunction-
changes in the number of individual chromosomes when chromosomes fail to separate
leads to gamete having one more or one less chromosome

26
Q

why is meiosis important?

A

for sexual reproduction

if each gamete was diploid, the cell would produce 92 chromosomes

to maintain a constant number they must be halved at some point

27
Q

how many daughter cells does meiosis produce?

A

4 daughter cells (haploid)

28
Q

describe meiosis

A

first division:
1) homologous chromosomes pair up and chromatids wrap around each other
2) equivalent portions can be exchanged during crossing over
3) divides with one chromosome from each pair going into one daughter cell

second division:
1) chromatids move apart
2) 2 daughter cells divide to produce 4 daughter cells

29
Q

how does meiosis produce genetic variation?

A

independent segregation of homologous chromosomes

new combinations of alleles by crossing over

30
Q

what is independent segregation?

A

one of each chromosome pair will go into one of the daughter cells

depends on how they are lined up to which daughter cell they go in

31
Q

describe crossing over

A

chromatids of each pair become twisted creating tension, breaking a portion of the chromatids

32
Q

describe recombination

A

rejoin with chromatids of its homologous partner

33
Q

what is genetic diversity?

A

total number of different alleles in a population

34
Q

what is a population?

A

group of individuals of the same species that can reproduce to make fertile offspring

35
Q

what does genetic diversity enable?

A

natural selection to occur

36
Q

when is genetic diversity greater?

A

with more different alleles
wider range of characteristics
more likely some individuals will survive environmental change

37
Q

describe natural selection

A

1) random mutation of alleles within gene pool may result in a new allele
2) this may give the possessor an advantage
3) they will have better chance of breeding successfully and producing more offspring
4) this passes the advantageous allele on to the next generation
5) over time the frequency of the allele increases

38
Q

what is selection?

A

process by which organisms better adapted to their environment tend to survive and breed

39
Q

directional selection

A

more extreme phenotypes selected for

40
Q

stabilising selection

A

favour average individuals- normal phenotype selected for

41
Q

what are the 3 adaptations?

A

anatomical
physiological
behavioural

42
Q

what is courtship behaviour?

A

individuals can identify other members of their own species by how they act

identify a mate capable of breeding

form a pair bond

synchronise mating

become able to breed

43
Q

classification

A

grouping of organisms

44
Q

taxonomy

A

theory and practice of biological classification

45
Q

artificial classification

A

divides organisms according to differences that are useful at the time

46
Q

phylogenetic classification

A

based upon evolutionary relationships

classifies species into groups using shared features

arranges groups into hierarchy

47
Q

taxon

A

each group in a phylogenetic biological classification

48
Q

what are the taxons in the phylogenetic classification?

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

mnemonic:
do keep ponds clean or frogs get sick

49
Q

what is a phylogeny?

A

evolutionary relationship between organisms represented by a phylogenetic tree

50
Q

what is biodiversity?

A

variety of different species in an ecosystem

51
Q

species diversity

A

number of different species and individuals within a community

52
Q

genetic diversity

A

variety of genes possessed by the individual

53
Q

ecosystem diversity

A

range of different habitats

54
Q

species richness

A

measure of species diversity

55
Q

index of diversity

A

sum of total no. of organisms of all species/ sum of total no. of organisms of each species

56
Q

impact of agriculture

A

agricultural ecosystems controlled by humans
genetic variety of alleles reduced as farmers select species for specific qualities

57
Q

practices removing habitats

A

removal of hedgerow/ woodland/ ponds
overgrazing
creating monocultures

58
Q

practices of farming with an indirect effect

A

use of pesticides
escape if effluent
lack of crop rotation

59
Q

conservation techniques

A

maintain hedgerows
plant hedges as field boundaries
create ponds
leave wet corners of fields
organic fertilisers

AQA A level biology <33 (12 decks)

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