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Biology > TOPIC 4 genetics, biodiversity and classification > Flashcards

TOPIC 4 genetics, biodiversity and classification Flashcards

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1
Q

what are the 3 components of nucleotides

A

pentose sugar
phosphate group
organic base

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2
Q

describe structure of DNA

A

deoxyribose sugar, a phosphate group, 1 of 4 organic bases

double stranded
hydrogen bonds between the bases from a helix shape

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3
Q

describe the role of DNA

A

carries genetic information, determines our inherited characterisitics

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4
Q

describe the structure of RNA

A

ribose sugar, phosphate group, 1 of 4 organic bases

single stranded

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5
Q

describe role of RNA

A

transfers genetic information from DNA to ribosomes for protein synthesis

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6
Q

which bases are purine and which are pyrmidine

A

purine (double ring)= adenine, guanine

pyrimidine (single ring) = cytosine , thymine, uracil

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7
Q

define genetic code

A

the order of bases on DNA

consists of codons

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8
Q

what are the features of the genetic code

A
  • non overlapping = each triplet is only read once
  • degenerate = more than 1 triplet codes for the same amino acid
  • universal = same bases and sequences used by all species
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9
Q

define a gene

A

a sequence of bases on a DNA molecules that codes for a specific sequence of amino acids to make a polypeptide

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10
Q

what is a locus

A

the fixed position on a DNA molecule occupied by a gene

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11
Q

what is an allele

A

different versions of the same gene, found at the same locus on a chromosome

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12
Q

what are exons and introns

A

exons = regions of DNA that code for amino acid sequences, separated by one or more introns

introns = regions of DNA that do not code for anything

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13
Q

where are introns found

A

between exons

within genes

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14
Q

what is the genome

A

the complete set of genetic information contained in the cells of an organism

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15
Q

what is the proteome

A

the complete set of proteins that can be produced by a cell

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16
Q

describe the structure of messenger RNA

A

a long, single strand
its base sequence is complementary to the DNA it was transcribed from

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17
Q

advantage of using mRNA rather than DNA for translation

A
  • shorter and contains uracil = breaks down quickly so no excess polypeptide forms
  • single stranded and linear = ribosome moves along strand and tRNA binds to exposed bases
  • contains no introns
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18
Q

describe the structure of tRNA (transfer rna)

A

single strnad

80 nucleotides folded over into a clover leaf shape

one end is an anti-codon, on the opposite end is an amino acid binding site

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19
Q

what is produced by transcription

A

mRNA

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20
Q

where does transcription take place

A

nucleus

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21
Q

outline process of transcription

A
  • DNA uncoils into t2 strands with exposed bases
    one used as a template
  • free nucleotides line up next to their complementary bases, and are joined together by RNA polymerase
22
Q

what happens to mRNA after transcription

A

pre-mRNA must be spliced to remove introns, leaving only the coding regions

then it moves out of the nucleus and attaches to a ribosome

23
Q

what is produced by translation

A

proteins

24
Q

where does translation take place

A

in the cytoplasm (on ribosomes)

25
Q

outline the process of translation

A
  • the anti codon of tRNA attaches to complementary bases on the mRNA
  • amino acids bonded to tRNA form peptide bonds, continuing to form a polypeptide chain until a stop codon is reached
  • requires ATP
26
Q

what is a mutation

A

an alteration to the DNA base sequence
often arise spontaneously during DNA replication

27
Q

why might a mutation not lead to change in the amino acid sequence

A
  • genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet
  • mutation may occur in intron
28
Q

what is a substitution mutation

A

when a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation, meaning no change occurs in the amino acid sequence

29
Q

what is a deletion mutation

A

when a nucleotide in the DNA sequence is lost.

this is more likely to be harmful and significant, as it leads to a frame shift, which means the entire amino acid sequence will be different

30
Q

what is a mutagenic agent, give examples

A

factors that increase the rate of gene mutation

  • X rays
  • UV light
  • gamma rays
  • chemicals such as in alcohol and tobacco
31
Q

what is a polyploidy chromosome mutation

A

where an individual has 3 or more sets of chromosomes instead of 2

32
Q

what is chromosome non disjunction

A

when chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal

33
Q

what is meiosis

A

a form of cell division that produces 4 genetically different haploid cells known as gametes

34
Q

how is meiosis different from mitosis

A
  • meiosis produces 4 genetically different cells with half the number of chromosomes as the parent cell
  • mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cells
35
Q

what happens during meiosis 1

A
  1. homologous chromosomes pair to form bivalents
  2. crossing over occurs at chiasmata
  3. cell divides into 2, homologous chromosomes separate randomly
    each cell contains either maternal or paternal copy
36
Q

what happens during meiosis 2

A
  1. independent segregation of sister chromatids
  2. each cell divides again, producing 4 haploid cells
37
Q

which 2 ways does meiosis produce genetic variation

A
  1. crossing over during meiosis1
  2. independent assortment of homologous chromosomes and sister chromatids

result in new combinations of alleles

38
Q

define population

A

all the organisms of a particular species that live in the same place

39
Q

what is an allele

A

different forms of a particular gene, found at the same locus on a chromosome

a single gene could have many alleles

40
Q

define genetic diversity

A

the total number of different alleles in a population

41
Q

what advantage does a high genetic diversity provide

A

Ability to adapt to a change in environment ; allows natural selection to occur

42
Q

explain how natural selection results in development of new characteristics

A
  • random mutations result in new alleles
  • some alleles provide an advantage, making an individual more likely to survive and reproduce
  • their offspring receive the new allele and frequency continues to increase over many generations
43
Q

what is directional selection

A

occurs when environmental conditions change

individuals with phenotypes suited to the new conditions will survive and pass on their genes

over time the mean of the population will move towards these characteristics

44
Q

example of directional selection

A

antibiotic resistance
- bacteria with a mutation allowing them to survive in the presence of antibiotics will reproduce , therefore frequency of this allele will increase and the population will shift to have greater antibiotic resistance

45
Q

what is stabilising selection

A

occurs when environmental conditions stay the same

individuals closest to the mean are favoured, and any new characteristics are selected against - results in low diversity

46
Q

example of stabilising selection

A

birth weight; babies that weigh around 3kg are more likely to survive that those at lower or higher weights

47
Q

define a niche

A

the role of a species within its environment.
species sharing the same niche will compete with each other

48
Q

3 types of adaptation and examples for each

A
  1. anatomical (changes to body structure) = oily fur
  2. physiological (changes to bodily processes) = venom production
  3. behavioural (changes to actions) = hibernation
49
Q

define species

A

a group of organisms that can interbreed to produce fertile offspring

50
Q

advantages of courtship behaviour

A

individuals can recognise sexually mature members of their own species of the opposite sex, synchronising mating, form a pair bond and successfully breed

Biology (6 decks)

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