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Biology > 19 - Genetics of living systems > Flashcards

19 - Genetics of living systems Flashcards

1
Q

What is a mutation?

A

A change in the sequence of bases in DNA

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2
Q

What is a substitution mutation?

A

When a nucleotide is replaced by a different nucleotide

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3
Q

What is an insertion mutation?

A

When a nucleotide is inserted into the sequence causing a frameshift if it is not in multiple of threes

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4
Q

What is a deletion mutation?

A

When a nucleotide is removed, causing a frame shift if not removed in multiples of three

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5
Q

What is a frameshift mutation?

A

It changes the sequence of codons by shifting nucleotides

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6
Q

What is a point mutation?

A

where a single nucleotide base is substituted, inserted or deleted.

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7
Q

What is a synonymous mutation?

A

The DNA sequence is changed but is has no
affect on the amino acids coded for due to the degenerative characteristic of the genetic code

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8
Q

What are the affects of mutations? 3 types

A

Physical, chemical and biological.

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9
Q

What are mutagens?

A

agent which causes a mutation or increases the rate of mutation

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10
Q

What a physical mutagens?

A

ionizing radiations such as x-rays. They break DNA strands causing mutations

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11
Q

What are chemical mutations?

A

deaminating agents- they chemically alter bases in DNA and change the base sequence causing mutation

Base analogues - Are chemicals that take the place of DNA bases causing mutations

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12
Q

What are biological mutations?

A

methyl and ethyl groups- they can bind to
bases causing incorrect pairing

viruses - can insert their DNA into an organisms genome

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13
Q

State 4 chromosome mutations

A

deletions
duplication
translocation
inversion

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14
Q

What is deletion (chromosomal mutation)?

A

a section of chromosome breaks off and is lost within the cell

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15
Q

What is duplication (chromosomal mutation)?

A

sections get duplicated on a chromosome

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16
Q

What is translocation (chromosomal mutation)?

A

A section of one chromosome breaks off and joins another non-homologous chromosome

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17
Q

What is inversion (chromosomal mutation)?

A

A section of chromosome breaks off, is
reversed, then joins back onto the chromosome

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18
Q

What is a housekeeping gene?

A

A gene that codes for constantly required
proteins

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19
Q

What are tissue-specific genes called?

A

Proteins that are only required by certain cells at certain times

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20
Q

Why do genes have to be regulated?

A

The entire genome of an organism is within the nucleus of each cell. This includes genes not required by that cell, so the expression of that gene and the rate of synthesis of that protein has to be regulated. Genes can be turned on or off or the rate of production can be increased or decreased.

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21
Q

What are the 4 ways genes are regulated?

A

-transcriptional = genes can be turned on
or off
-Post-transcriptional = mRNA can be
modified which regulates translation and
the types of proteins produced
-Translational = translation can be stopped
or started
-Post-translational = proteins can be
modified after synthesis which changes
their functions

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22
Q

Two example of transcriptional control in
eukaryotic cells.

A

Chromatin remodelling
Histone modification

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23
Q

What is chromatin remodelling?

A

Transcription can be stopped or started
depending on what type of chromatin is
present.

Heterochromatin- It is tightly wound DNA
causing chromosomes to be visible during cell division. Transcription cant happen as RNA polymerase cant access the genes

Euchromatin- is loosely wound DNA present during interphase, that can be transcribed

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24
Q

Why is chromatin remodelling important?

A

Protein synthesis does not occur during cell
division but during interphase between cell
division. it ensures the proteins necessary for cell division are synthesised in time.
It also prevents the complex and energy-consuming process of protein synthesis during

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25
What is histone modification?
DNA coils around histones because they are positively charged. Histones can be modified to increase or decrease the degree of packaging. Acetylation- the addition of acetyl groups or phosphate groups (phosphorylation) reduces the positive charge on the histones, causing the DNA to coil less tightly allowing certain genes to be transcribed. Methylation- The addition of methyl groups makes the histones more hydrophobic so they bind more tightly to each other causing DNA to coil more tightly and preventing transcription of genes
26
What is an operon?
A group of genes that are expressed at the same time and are controlled by the sane regulatory mechanism. They are mainly found in prokaryote genomes.
27
What is Lac operon?
It is found in E.coli bacteria and is used to control the production of enzymes that are used to metabolise lactose to produce ATP. It ensures that these enzymes are only produced when they are needed
28
What are the stages of the Lac operon?
1) The regulatory gene produces a repressor protein 2) The repressor protein binds to the operator 3) RNA polymerase attempts to bind to the promoter so it can transcribe the Lac genes 4) RNA is blocked by the repressor proteins so transcription cannot occur 5) If lactose is present in the cell, some of it will bind to the repressor proteins 6) This causes the repressor protein to change shape so it can no longer bind to the operator. Any already bound to the operator 7) RNA polymerase is now free to bind to the promoter 8) RNA polymerase transcribes the gens in Lac operon 9) The mRNA is translated into enzymes by ribosomes 10) These enzymes metabolise the lactose producing ATP 11) Without the presence of lactose the repressor proteins return back to their normal shape 12) The repressor protein reattaches to the operator and prevents transcription of the Lac genes so no more enzymes are produced
29
What are transcription factors?
Are used by eukaryotes to increase, decrease, start or stop the transcription. This can alter how much of the protein is produced.
30
What is activator and a repressor? where does a transcription factor bind to?
Activator- A transcription factor that starts transcription Repressor- A transcription factor that stops transcription Transcription factors bind to the promoter
31
What is needed for transcription factors to control a gene?
All transcription factors are needed to function properly
32
How can transcription be controlled by transcription factors?
Can be controlled by the suppression of one or more transcription factor
33
What is RNA processing?
Transcription does not produce mRNA in a form that it can produce proteins, It initially produces “pre-mRNA”, this is modified to produce mature mRNA
34
How does RNA processing work?
1. A cap and a tail are added to the ends. These aid the binding of mRNA to ribosomes and slow its degradation in the cytoplasm. 2. The non-coding “Introns” are cut out and the coding “Exons” are spliced together
35
What are exons?
coding parts of the mRNA sequence
36
What are introns?
non-coding parts of the mRNA. They’re integral for the regulation of gene expression
37
What is RNA editing?
mRNA can be further modified by post-transcriptional base substitutions, deletions or insertions. This means that one gene can produce many proteins
38
2 examples of post-transcriptional regulation.
RNA processing RNA editing
39
3 examples of translational regulation
mRNA degradation Initiation factors Inhibitory proteins
40
What is mRNA degradation?
The more robust an mRNA molecule is the longer it will remain in the cytoplasm, the more proteins it will produce
41
What is an initiation factor?
Sometimes mRNA is produced before it is needed. In these cases initiation factors must be activated before the mRNA is translated. It aids the binding of mRNA to ribosome Initiation factors are proteins that facilitate the assembly of the ribosome on the mRNA and help initiate the formation of the translation initiation complex. The initiation factors participate in the recognition of the start codon on the mRNA and the recruitment of the initiator tRNA (transfer RNA) to the ribosome. This process is essential for the accurate and efficient initiation of protein synthesis.
42
What is an inhibitory protein?
these bind to mRNA preventing binding to ribosomes and prevent the synthesis of proteins -Initiation inhibitors:Some proteins inhibit the initiation of translation by preventing the formation of the translation initiation complex. proteins like 4E-BP (eukaryotic initiation factor 4E-binding protein) can bind to the eukaryotic initiation factor 4E (eIF4E), hindering its interaction with the mRNA 5' cap and suppressing translation initiation. Termination inhibitors: These proteins can affect the termination phase of translation, delaying the release of the newly synthesized protein from the ribosome. This regulation ensures that protein synthesis is tightly controlled.
43
What does post-translational regulation involve?
addition of prosthetic groups addition or removal of components which can change structure modifying amino acids and formation of bonds folding or shortening protein
44
What is protein kinase A ?
An enzyme made up of 4 subunits
45
How dos protein kinase A become active?
-Before cAMP binds to it, the four subunits are bound together and the enzyme is inactive -When cAMP binds to it, the structure of the enzyme changes and 2 of the subunits are released -These subunits now are free to catalyse reactions (specifically phosphorylation
46
What is a homeotic gene?
Homeotic genes are regulatory genes found in animals, plants and fungi.
47
What is a regulatory gene?
They control the expression of genes. They are responsible for ensuring organisms form the correct shape during development.
48
What is a homeobox gene?
Homeobox genes are a type of homeotic gene that all contain a homeobox region, which is 180 base pairs long.
49
What is a homeodomain?
The homeobox region in a homeotic gene codes for a part of the protein called a homeodomain. The homeodomain binds to DNA and switches other genes on and off
50
What are homeodomains examples of?
Transcription factors, the homeodomain increases, decreases, start or stop the transcription.
51
What is special about the homeobox gene?
it is highly conserved, they have changed little throughout evolutionary history, to the point they are almost identical across very different organisms.
52
What are homeobox genes highly conserved?
Mutation in homeobox genes usually results in a missing body part / a body part not where it should be / a non-functioning body part. There is also a knock-on effect with other genes. In the wild, this would be selected against i.e. the mutant would die and not be able to pass their genes on.
53
What are hox genes?
Hox genes are a group of homeobox genes found exclusively in animals. They work in the same way – by making a homeodomain protein to act as a transcription factor.
54
What is the purpose of hox genes?
They are responsible for the correct positioning of body parts. In animals, Hox genes are found in clusters.
55
What is special about Hox genes?
The order they appear along a chromosome is the order in which they are expressed in an organism. This top to bottom expression is known as the anterior – posterior axis.
56
Where do individual structures develop from?
Individual structures all develop from segments known as somites. These segments determine key body plan features such as the position of limbs, and other structures i.e. the location and orientation of eyes.
57
Why do vertebrates at the early embryonic stage look similar?
Hox genes, given how conserved and ultimately ancient they are, mean that most Vertebrates look very similar in the early embryonic stage. The basic body plan has remained the same for millions of years.
58
What are the three types of symmetry?
Radial- no left or right sides just top and bttom Bilateral - left and right sides, and a head and tail asymmetry - no lines of symmetry
59
When an organism is formed, what is involved?
mitosis and apoptosis (which is programmed cell death)
60
Why is apoptosis needed during embryonic development?
In the womb fingers and toes actually start out webbed – this webbing is destroyed by apoptosis.
61
What is the process of apoptosis?
1. Cell shrinks from other cells. 2. Cytoskeleton broken down. 3. Chromatin condenses and is digested by nucleases. 4. Cell forms “blebs”. 5. Blebs break away and form apoptotic bodies. These release chemicals to attract phagocytes. 6. Engulfment and digestion by phagocytes

Biology (24 decks)

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