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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
what is tRNA
carries an amino acid and has an amino binding site
25
describe the structure of transfer RNA
a single polynucleotide folded hairpin loop held together by hydrogen bonds
26
what are the similarities between mRNA and tRNA
both single polynucleotide strands
27
what are the differences between mRNA and tRNA
- 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
28
where does transcription occur
nucleus
29
describe the role of DNA helicase in transcription
double stranded DNA is unzipped and hydrogen bonds are broken
30
what is the next step after the hydrogen bonds are broken
free RNA nucleotides bind to the exposed bases by complimentary base pairing
31
what is the role of RNA polymerase
joins adjacent nucleotides via a condensation reaction forms phosphodiester bonds
32
where does mRNA leave the nucleus
via nuclear pore
33
what does transcription directly produce in prokaryotes
mRNA
34
what does transcription directly produce in eukaryotes
pre-mRNA
35
what is splicing
when introns are removed
36
why dont prokaryotic DNA undergo splicing
mRNA is produced directly from DNA no splicing
37
what bond is formed when an anti codon binds to a codon
hydrogen bonds
38
where does translation occur
ribosomes in the cytoplasm
39
what is translation
where amino acids are joined together to make a polypeptide chain
40
what is the 1st stage of translation
mRNA attaches to ribosomes and tRNA carring an amino acid to it binds to the codon on mRNA. by complimentary base pairing
41
what is the 3rd step of translation
the two amino acids are joined by a condensation reaction forming a peptide bond using Atp
42
what is a stop codon
prevents amino acids from binding together
43
in RN what base is replaced
uracil is replaced by thymine
44
what is a gene mutation
a change in the base sequence of DNA
45
when can gene mutations occur
they arise spontaneously during DNA replication (interphase)
46
what does gene mutation involve
base deletion/ substitution
47
how does a mutation lead to the production of a non-functional protein/enzymes. (5 marks)
- 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
what is base substitution
one base is subsitiuted with another
49
why do some substituiton mutaions don't change the amino acid
genetic code is degenerate the same amino acids can be coded for by different DNA bases
50
what is base deletion
one base is deleted
51
why does deletion definetly change the sequence of amino acids
changes the numb er of bases present
52
what are mutagenic agents
increase the rate of gene mutations
53
what are some examples of mutagenic agents
ultraviolet radiation
54
what occurs before meiosis
DNA replication
55
what is the diploid number for humans
46
56
what is the haploid number forr humans
23
57
what is the haploid number in gamets
23
58
how does random fertilisation cause genetic diveristy
fertilisation is random zygotes arre produced with different combinations of chromosomes
59
where does meiosis occur
in reproductive organs
60
what occurs in meiosis 1
chromosomes are arranged into homologus pairs thee homologus chromosomes are separated chromosmee number is halved
61
what occurs in meiosis II
the sister chromatids are separated
62
what is produced in meiosis
4 haploid cells that are gentically differnt from each other
63
what creates genetic variation in gametes
crossing over of chromatids independant segragation
64
what is crossing over homologus chromosomes
when alleles are exchanged between chromosmes they have same genes but different alleles
65
what is independant segragation of homologus chromosmes
when homologus chromosmes are separated in meiosis I
66
how many chrmosomes are at the product of meiosi
its halfed
67
2^n
the number of pairs of homologus chromosmes
68
what is the importance of meiosis
chrmosome number is maintained from 1 generation to the next genetic variation is crreatedd
69
explain the differences between mitosis and meiosis
- 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
describe where the non-coding multiple repeats are positioned in the genome
between genes
71
not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide suggest why (2 marks)
- the genetic code is degenerate. triplets code for the sae amino acids - may occur in introns
72
suggest one way in which the structure of the chromosome could differ along its length
different base sequences
73
describe how a polypeptide is formed by the translation of mRNA
(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
describe the role of ribosomes in the production of a polypeptide
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
what has more nucleotides mRNA or pre mRNA
pre mRNA
76
describe the process of crossing over
homologous chromosomes form a bivalent chiasmata is formed equal lengths of alleles are exchanged
77
explain how crossing over increases genetic diversity
produces new combinations of alleles
78
describe the role of RNA polymerase
catalyses the condensation reaction between adjacent nucleotides and forms phosphodiester bonds. sugar phosphate backbone is formedd

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