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Biology Paper 1 > DNA & Genetic Diversity > Flashcards

DNA & Genetic Diversity Flashcards

1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

What does RNA stand for?

A

Ribonucleic acid

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3
Q

What does DNA do?

A

hold genetic info

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4
Q

What does RNA do?

A

transfer genetic information from DNA to ribosomes

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5
Q

What is DNA and RNA polymers of?

A

Nucleotides

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6
Q

What is the structure of DNA?

A

two polynucleotide strands
joined by hydrogen bonding
forming a double helix

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7
Q

What is in a DNA nucleotide?

A

pentose sugar> deoxyribose
phosphate group
nitrogen containing bases

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8
Q

What are the bases in DNA?

A

Adenine
Thymine
Guanine
Cytosine

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9
Q

What bonds join nucleotide together?

A

phosphodiester bonds
formed by condensation reactions

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10
Q

What bond joines bases together?

A

hydrogen bonds
(Maintain stable structure due to its abundance)

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11
Q

Describe the process of semi-conservative DNA replication

A
  • DNA helicase breaks hydrogen bonds & separates the two polynucleotide strands
  • strands act as a template
  • free nucleotides attach to complementary bases
  • DNA polymerase join the strands of the nucleotides
  • two new identical DNA strands (new and old)
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12
Q

What are the differences between DNA and RNA

A

pentose is Ribose in RNA

Uracin instead of Thymine

mRNA and tRNS are single strands

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13
Q

What are the properties of mRNA?

A

has linear structure

codons(base triplets)

involved in protein synthesis

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14
Q

Describe the shape of tRNA

A

clover leaf shape due to hydrogen bonds between complementary bases

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15
Q

Describe the properties of tRNA

A

anticodon ( 3 unattached tRNA nucleotide bases) on one end

binding site for amino acids on the other end

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16
Q

How is a chromosome formed?

A

from DNA and its associated protein

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17
Q

What is the shape of DNA in the nucleus of eukaryotic cells?

A

long and linear

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18
Q

What is the shape of DNA in mitochondria and chloroplasts?

A

short and circular

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19
Q

What are Chromosomes?

A

2 sister chromatids joined together by a centromere
product of DNA replication
formed from histones and DNA during cellular division

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20
Q

What is a gene?

A

A section of DNA base that code for specific amino acid sequence

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21
Q

What are diploid cells?

A

Have chromosomes in pairs, one inherited from one parent and one from the other

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22
Q

what is a homologous pair of chromosome?

A

two chromosomes that carry the same genes but not the same alleles

maternal and paternal chromosome

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23
Q

What is a locus?

A

Fix position of a gene on a particular DNA molecule or chromosome

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24
Q

what is a base triplet?

A

A sequence of three nucleotide bases the code for a specific amino acid

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25
what are codons?
based triplets in mRNA that code for an amino acid
26
what is it meant by degenerate?
One amino acid can be coded for by different triplets
27
what are stop codes?
They do not code for an amino acid, but they indicate the end of a code for specific polypeptide
28
How are codes none overlapping?
each base is only read **once** as part of a specific triplet
29
How are codes universal?
The same triplets code for the same amino acid in all organisms
30
What is an Intron?
Base sequences present in genes, but don’t code for amino acids
31
what is an Exon?
base sequences in genes that code for amino acids
32
What are multiple repeats?
some of the base sequences present between genes it consists of the same sequence occurring again and again
33
What are some examples of non-coding DNA?
intron Multiple repeats
34
What is a genome?
complete set of genes in a cell
35
what is a proteome?
The full range of proteins that are cell is able to produce
36
What is transcription?
occurs in the nucleus involves rewriting part of the DNA into a strand of messenger RNA
37
Outline transcription
- The relevant DNA uncoils and strand separate - One of these strands act as a template - Individual RNA nucleotides lineup along the complementary DNA base - individual RNA is joined together by RNA polymerase - The two strands of DNA will join back together once mRNA has been produced
38
what is pre-mRNA?
mRNA formed during transcription
39
What is splicing?
removing introns from pre-mRNA and joining together exons to form mRNA
40
Why does splicing not happen in prokaryotes?
prokaryotes DNA does not contain introns
41
What happens during translation?
happenes in ribosomes sequence of codons on the mRNA strand is used to determine the sequence of amino acids in the polypeptide
42
What is genetic diversity?
The number of different alleles in a population
43
What causes genetic diversity?
- gene & chromosome mutations - meiosos - random fusion of gametes during fertilisation
44
What is gene mutation?
changes in the sequence of nucleotide bases new alleles of genes are produced
45
What are mutagenic agents?
increase the rate of mutation (x-rays, benzene)
46
What are the different types of mutations?
substitution addition Deletion Duplication Inversion Translocation
47
What is substitution?
the replacement of one or more bases by a one or more different base
48
What does substitution result in?
- a new triplet coding for a different amino acid, this may result in a **non functional protein** - one different amino acid changes but a **functional protein is still produced** - same amino acid may be coded for due to degeneracy, so **polypeptide remains unchanged**
49
What is deletion?
removal of one or more bases resulting in frame shift
50
What is a frame shift?
alteration in all triplets from the point of mutation the protein formed is nearly always non functional
51
What is addition?
addind one or more bases results in frame shift
52
What is duplication?
when one or more bases are repeated results in frame shift
53
What is inversion?
where a sequence of bases is reversed
54
What is translocation(mutation)?
where a sequence of bases is moved from one location to another
55
What is an allele?
different forms of genes that code for different types of the same characteristic arise due to mutations of a gene
56
What is mitosis?
produces cells that are genetically identical two daughter cells
57
What are the stages of mitosis?
Prophase Metaphase Anaphase Telophase
58
What happens during interphase?
cell prepares for nuclear division - DNA is doubled - Increase in protein synthesis - cell organelles are replicated
59
What happenes in prophase?
**each chromosome shortens then thickens**(condensation) **nuclear membrane breaks down**
60
What happens during metaphase?
centrioles from a spindle across the cell, this spindle consist of protein microtubules Each chromosome moves to the equator of the spindle and attaches to it by its centromere
61
What happens during anaphase?
The centromere splits and sister chromatids separate sister chromatids are pulled to opposite poles of the cell **by the spindle microtubules**
62
what happens during telophase?
chromatids are at opposite poles and begin to **uncoil** **Nuclear membrane reforms** The two cells or genetically identical to each other and the original parent cell
63
What happens during Cytokinesis?
The cytoplasm splits in two Two new cells form as the cell surface membrane (plant cell: cell wall) forms
64
What is cancer?
A group of diseases caused by uncontrolled growth and rapid cell division Results from damage to genes that regulate mitosis s and cell cycle
65
What is a tumour?
A group of abnormal cells
66
how do drugs help with cancer?
They can inhibit the enzymes, (DNA helicase or DNA polymerase) or inhibit the formation of the spindle
67
What is meiosis?
nuclear division that produces cells that are genetically different four non identical daughter cells
68
What type of gametes are produced during meiosis?
Haploid diploid number will be restored at fertilisation
69
What happenes during meiosis?
two nuclear divisions
70
What happens during late interphase in meiosis?
DNA replication Buildup of ATP Protein synthesis and replication of organelles
71
what happens in meiosis I?
The first division separates the membranes of each homologous pair
72
what happens in meiosis II?
Chromatids are separated from each chromosome
73
What is independent segregation of homologous chromosomes?
In meiosis, chromosomes pair then separate so one from each pair enters the gamete
74
how do you calculate the possible number of varied combinations?
2^n n= number of pairs
75
What is crossing over?
The two members of each homologous pair lie side-by-side forming a **bivalent** The chromatids of the homologous chromosomes then **interwine**
76
What is the name of the place where crossing over occurs?
Chiasma
77
What does does crossing over lead to?
exchange of alleles of the same gene this can produce new combinations of alleles called **recombinants**
78
Why is the number of recombinants low?
beacuse crossing over is rare
79
What is chromosome non-disjunction?
when a homologous pair of chromosomes do not separate on the first meiotic division both members of a homologous pair o to the same side during anaphase I
80
What is the result of chromosome non-disjunction?
gametes will have one extra/less chromosome than normal
81
What is genetic diversity?
the number of different alleles of genes in a population
82
How do new alleles come about?
random mutations
83
What is directional selection?
when there is a change in the environment in which the alleles of an extreme type are selected for
84
What is stabilising selection?
(nothings changing) an average phenotype is selected for and extremes of the phenotype are selected against

Biology Paper 1 (8 decks)

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