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biology > 3.4 Genetic information, variation and relationships between organisms > Flashcards

3.4 Genetic information, variation and relationships between organisms Flashcards

1
Q

explain how DNA is in eukaryotes

A

long
linear
associated with proteins called histones

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2
Q

what protein is associated with DNA in eukaryotes

A

histones

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3
Q

exxplain how DNA is in prokaryotes

A

short
circular
not associated with proteins

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4
Q

which two organelles have their own DNA

A

mitochondria and chloroplast

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5
Q

describe the DNA found in the mitochondria or chloroplast

A

short
circular
not associated with proteins

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6
Q

what are genes

A

sequence of DNA that codes for the amino acid sequence of a polypeptide. and a functional RNA

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7
Q

what things can DNA code for

A
  • the amino acid sequence in a polypeptide
  • a functional RNA
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8
Q

what is a locus

A

a fixed position occupied by a gene on a particular DNA molecule

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9
Q

what can a DNA molecule and a histone form

A

a chromosome

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10
Q

what are three DNA bases called

A

triplet

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11
Q

why is the genetic code reffered to as universal

A

the same DNA base triplet can code for the same amino acids in all living organisms

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11
Q

what does a triplet code for

A

amino acids

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12
Q

why is the genetic code reffered to as non-overlapping

A

discretee, each base can only be used once and in only one triplet

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13
Q

why is the genetic code reffered to as degenerate

A

the same amino acids can be coded for by more than one base triplet

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14
Q

what is the area that cant code for polypeptides called between genes

A

non codding multiple repeats

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15
Q

define the term exon (1 mark)

A

nucleotides/bases/ triplet sequence that codes for an amino acid sequence

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16
Q

what are introns

A

non coding piece of DNA

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17
Q

what is a genome

A

the complete set of genes in a cell

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18
Q

what is a proteome

A

the full range of proteins a cell is able to produce

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19
Q

what are alleles

A

differrent versions of the same gene

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20
Q

what are homologus chromosomes

A

chromosomes with the same genes but different alleles

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21
Q

describe the structure of mRNA

A
  • straight chain molecule
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22
Q

what is mRNA

A

made by transcription
acts as a template forr translation in the cytoplasm

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23
Q

what is the anticodon

A

bases that are complimentary to mRNA codon

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24
Q

what is tRNA

A

carries an amino acid
and has an amino binding site

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25
Q

describe the structure of transfer RNA

A

a single polynucleotide
folded hairpin loop
held together by hydrogen bonds

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26
Q

what are the similarities between mRNA and tRNA

A

both single polynucleotide strands

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27
Q

what are the differences between mRNA and tRNA

A
  • mRNA is a single helix, whereas tRNA folded into clover shape.
  • mRNA is longer, whereas tRNA is shorter
  • mRNA contains no paired bases and hydrogen bonds, whereas tRNA has some bases and hydrogen bonds
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28
Q

where does transcription occur

A

nucleus

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29
Q

describe the role of DNA helicase in transcription

A

double stranded DNA is unzipped and hydrogen bonds are broken

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30
Q

what is the next step after the hydrogen bonds are broken

A

free RNA nucleotides bind to the exposed bases by complimentary base pairing

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31
Q

what is the role of RNA polymerase

A

joins adjacent nucleotides via a condensation reaction
forms phosphodiester bonds

32
Q

where does mRNA leave the nucleus

A

via nuclear pore

33
Q

what does transcription directly produce in prokaryotes

34
Q

what does transcription directly produce in eukaryotes

35
Q

what is splicing

A

when introns are removed

36
Q

why dont prokaryotic DNA undergo splicing

A

mRNA is produced directly from DNA
no splicing

37
Q

what bond is formed when an anti codon binds to a codon

A

hydrogen bonds

38
Q

where does translation occur

A

ribosomes in the cytoplasm

39
Q

what is translation

A

where amino acids are joined together to make a polypeptide chain

40
Q

what is the 1st stage of translation

A

mRNA attaches to ribosomes and tRNA carring an amino acid to it binds to the codon on mRNA. by complimentary base pairing

41
Q

what is the 3rd step of translation

A

the two amino acids are joined by a condensation reaction forming a peptide bond
using Atp

42
Q

what is a stop codon

A

prevents amino acids from binding together

43
Q

in RN what base is replaced

A

uracil is replaced by thymine

44
Q

what is a gene mutation

A

a change in the base sequence of DNA

45
Q

when can gene mutations occur

A

they arise spontaneously during DNA replication (interphase)

46
Q

what does gene mutation involve

A

base deletion/ substitution

47
Q

how does a mutation lead to the production of a non-functional protein/enzymes. (5 marks)

A
  • change in the base sequence of DNA
  • changes sequence of codons on mRNA
  • changes the sequence of amino acids in the primary structure of the protein
  • changes the position of hydrogen/ionic/disulphide bonds in tertiary structure of protein
    -tertiary structure of protein changes or active site of protein
  • substrate cant bind to the active site no ESCs
48
Q

what is base substitution

A

one base is subsitiuted with another

49
Q

why do some substituiton mutaions don’t change the amino acid

A

genetic code is degenerate
the same amino acids can be coded for by different DNA bases

50
Q

what is base deletion

A

one base is deleted

51
Q

why does deletion definetly change the sequence of amino acids

A

changes the numb er of bases present

52
Q

what are mutagenic agents

A

increase the rate of gene mutations

53
Q

what are some examples of mutagenic agents

A

ultraviolet radiation

54
Q

what occurs before meiosis

A

DNA replication

55
Q

what is the diploid number for humans

56
Q

what is the haploid number forr humans

57
Q

what is the haploid number in gamets

58
Q

how does random fertilisation cause genetic diveristy

A

fertilisation is random
zygotes arre produced with different combinations of chromosomes

59
Q

where does meiosis occur

A

in reproductive organs

60
Q

what occurs in meiosis 1

A

chromosomes are arranged into homologus pairs
thee homologus chromosomes are separated chromosmee number is halved

61
Q

what occurs in meiosis II

A

the sister chromatids are separated

62
Q

what is produced in meiosis

A

4 haploid cells that are gentically differnt from each other

63
Q

what creates genetic variation in gametes

A

crossing over of chromatids
independant segragation

64
Q

what is crossing over homologus chromosomes

A

when alleles are exchanged between chromosmes
they have same genes but different alleles

65
Q

what is independant segragation of homologus chromosmes

A

when homologus chromosmes are separated in meiosis I

66
Q

how many chrmosomes are at the product of meiosi

A

its halfed

67
Q

2^n

A

the number of pairs of homologus chromosmes

68
Q

what is the importance of meiosis

A

chrmosome number is maintained from 1 generation to the next
genetic variation is crreatedd

69
Q

explain the differences between mitosis and meiosis

A
  • mitosis produces diploid cells, meiosis produces haploid cells
  • daughter cells in meiosis are genetically different to each other and parent cells. mitosis daughter cells are genetically identical
  • 2 daughter cells in mitosis and 4 in meiois
  • crossing over and independant segragation and none in meiosis
  • meiosis is 2 divisions mitosis is 1 division
70
Q

describe where the non-coding multiple repeats are positioned in the genome

A

between genes

71
Q

not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide
suggest why (2 marks)

A
  • the genetic code is degenerate. triplets code for the sae amino acids
  • may occur in introns
72
Q

suggest one way in which the structure of the chromosome could differ along its length

A

different base sequences

73
Q

describe how a polypeptide is formed by the translation of mRNA

A

(mRNA attaches) to ribosomes
OR
(mRNA attaches) to rough endoplasmic reticulum;
2. (tRNA) anticodons (bind to) complementary (mRNA) codons;
3. tRNA brings a specific amino acid;
4. Amino acids join by peptide bonds;
5. (Amino acids join together) with the use of ATP;
6. tRNA released (after amino acid joined to polypeptide);
7. The ribosome moves along the mRNA to form the polypeptide;

74
Q

describe the role of ribosomes in the production of a polypeptide

A
  1. mRNA binds to ribosome;
  2. Idea of two codons / binding sites;
  3. (Allows) tRNA with anticodons to bind / associate;
  4. (Catalyses) formation of peptide bond between amino acids
    (held by tRNA molecules);
  5. Moves along (mRNA to the next codon) / translocation
    described;
75
Q

what has more nucleotides mRNA or pre mRNA

76
Q

describe the process of crossing over

A

homologous chromosomes form a bivalent
chiasmata is formed
equal lengths of alleles are exchanged

77
Q

explain how crossing over increases genetic diversity

A

produces new combinations of alleles

78
Q

describe the role of RNA polymerase

A

catalyses the condensation reaction between adjacent nucleotides and forms phosphodiester bonds.
sugar phosphate backbone is formedd

biology (10 decks)

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