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A-Level Bio > Topic 8 > Flashcards

Topic 8 Flashcards

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Biology 101 flashcards
1
Q

Define gene mutation

A

Change in the DNA base sequence of a gene

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2
Q

When do gene mutations occur?

A

DNA replication

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3
Q

What do mutagenic agents do?

A

Increase the rate of mutations occuring

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4
Q

What does a mutation do?

A

Different amino acid sequence in Primary structure
Causes hydrogen and ionic bonds to form in different locations
Results in different tertiary structure
And diferent 3D shape
Resulting in a different functino/non-functioning protein

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5
Q

Why might some mutations have no effect?

A

Some gene mutations change only one triplet code. Due to the degenerate nature of the genetic code, not all such mutations result in a change to the encoded amino acid.

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6
Q

What is a frame shift

A

Some gene mutations change the nature of all base triplets downstream from the mutation including how they are read

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7
Q

6 gene mutations

A

Addition
Deletion
Substitution
Inversion
Duplication
Translocation of bases

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8
Q

With which mutations does frame shift occur?

A

Addition
Deletion
Duplication

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9
Q

How does the inversion mutation work?

A

A section of bases detach from the DNA sequence, but are inverted when they rejoin
This section of code is back to front
All affected bases after are read differently
Causes different AAs to be coded for

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10
Q

What is the duplication mutation?

A

One particular base is duplicated at least once in the sequence
This causes a frame shift to the right
A different sequence of AAs are coded for

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11
Q

What happens in a translocation mutation? why is this mutation significant?

A

A section of bases on one chromosome detached and attached to a different chromosome
It can cause significant impacts on gene expression and the resulting phenotype

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12
Q

What is a stem cell?

A

An undifferentiated cell which can continually divide and become specialised

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13
Q

4 types of stem cells

A

Totipotent
Pluripotent
Multipotent
Unipotent

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14
Q

Totipotent stem cells function and time of occurrence

A

Divide to produce any type of body cells

Occur for limited time in early mammalian embryos

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15
Q

Pluripotent stem cells function, where to find and what they can be used for

A

Can divide into unlimited numbers
Used in treating human disorders
Found in embryos

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16
Q

Where are multi and unipotent stem cells found, what are unipotent ones used for and how much can they differentiate?

A

Mature mammals
Used to make cardiomyocytes
Can divide to form limited numbers of diff cell types

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17
Q

Why use induced pluripotent stem cells? (IPS cells)

A

To overcome ethical issues from using embryonic stem cells by using adult somatic cells

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18
Q

How to make IPS cells?

A

Genes that were switched off to make the cell specialised must be switched back on using transcription factors

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19
Q

How is transcription controlled?

A

Specific TFs move from the cytoplasm into the nucleus
This can turn on/off genes, so only certain proteins are produced in the cell

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20
Q

What enables cell specialisation?

A

The turning on/off of specific genes in a cell

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21
Q

Explain how TFs are used to control transcription?

A

A specific TF moves from the cytoplasm to the nucleus and binds to it’s specific gene in DNA
Once bound, transcription begins and the mRNA molecule is produced
Without the TF, the gene is inactive and the protein won’t be made

22
Q

Oestrogen’s role in transcription?

A

It’s a steroid hormone that can initiate transcription
It does this by binding to the TFs receptor
The TF changes shape slightly, which makes it complementary and able to bind to DNA to initiate transcription

23
Q

Epigenetics definition and what it’s caused by?

A

Heritable change in gene function without changing the DNA base sequence
Changes in the environment cause it

24
Q

How does increased methylation of DNA inhibit transcription?

A

Methyl groups attach to the cytosine base
This prevents TFs from binding and attracts proteins
These condense the DNA-histone complex

25
Q

How does decreased acetylation of histones inhibit transcription?

A

If acetyl groups are removed from DNA, histones become more positive and are attracted to the negative phosphate group on DNA more
This makes the DNA and histones more strongly associated so
It is harder for TFs to attach

26
Q

What is it called when the DNA is available/unavailable for transcription with TFs?

A

Euchromatin(active)
Heterochromatin(silent)

27
Q

What does RNAi interfere with?

A

Translation

28
Q

What happens when RNAi occurs?

A

An mRNA molecule that’s already been transcribed is destroyed before it is translated to create a PPT chain
This is done by small interfering RNA (siRNA)

29
Q

What does siRNA do?

A

An enzyme cuts the mRNA into siRNA
One strand of siRNA combines with another enzyme
This siRNA-enzyme complex will bind via complementary base pairing to another mRNA molecule
Once bound, the enzyme cuts up the mRNA (from transcription) so it cannot be translated

30
Q

How does cancer occur?

A

Mutations in genes that regulate mitosis
Cause production of non functioning proteins
Mitosis is not regulated
It results in uncontrollable division of cells and creation of a tumour

31
Q

Benign tumours 4 points

A

Grow large but at a slow rate
Non cancerous due to adhesive molecules sticking them together and to a particular tissue
Often surrounded by a capsule so remain compact and can be removed by surgery and rarely return
Often not life threatening

32
Q

Malignant tumours 5 points

A

Grow large and rapidly
Cell can become unspecialised again
No adhesive produced, so the cells metastasise
The thmour is not encapsulated and can grow projections into surrounding tissues to develop its own blood supply
Can be life threatening and radio/chemotherapy is needed

33
Q

Why would a tumour develop?

A

Due to a gene mutation in either the tumour suppressor gene or oncogene, abnormal methylation of tumour suppressor or oncogenes or increased oestrogen concentrations

34
Q

What is an oncogene

A

Mutated proto-oncogene
Create protein for initiation of DNA replication
Mutations can cause these genes to be permanently activated so cells divide continually

35
Q

What are tumour suppressor genes (TSG)

A

Produce proteins to slow down cell division and cause cell death if DNA copying errors are detected
If a mutation results in proteins for this function not being produced, cell division can continue and mutated cells would not be destroyed

36
Q

How does abnormal methylation cause tumour development?

A

If TSGs become hypermethylated, the gene becomes inactivated
If oncogenes become hypomethylated, the gene may become permanently switched on

37
Q

How can increased oestrogen concentration cause tumour formation

A

After menopause, oestrogen isn’t produced for the menstrual cycle
It can be produced by fat cells in breast tissues
This can cause breast cancer post menopause
The tumour causes more oestrogen production increasing its size further

38
Q

Genome definition

A

Entire genetic material of an organism in a cells nucleus

39
Q

What happens when a genome is sequenced

A

The dna base sequence for all the dna in a cell is worked out

40
Q

Sequencing methods are now…..

A

Automated

41
Q

Why can’t the genome be easily used to translate our proteome?

A

We have introns and regulatory genes in our DNA

42
Q

3 recombinant DNA technologies

A

Creating DNA fragments
Genetic fingerprinting
Genetic screening, counselling and locating genes

43
Q

What is genetic fingerprinting used for (3)

A

Forensic science
Medical diagnoses
Paternity tests

44
Q

What is genetic screening, counselling and gene location used for?

A

Screening for genes
Personalised medicine

45
Q

What do genetic fingerprinting and genetic screening, counselling and gene locating have in common?

A

Both use gel electrophoresis

46
Q

How can DNA fragments be made?

A

Gene machine
Reverse transcriptase
Restriction endonucleases

47
Q

2 ways to clone fragments and amplify the sample

A

In vivo cloning
In vitro cloning

48
Q

Creating dna fragments by reverse transcription and an advantage

A
  1. The reverse transcriptase enzyme makes DNA copies from mRNA
  2. Naturally occurs in viruses eg HIV
  3. A cell that naturally produces the protein of interest is selected
  4. Cell should have large amounts of mRNA for the protein
  5. RT enzyme joins the DNA nucleotides with complementary bases to the mRNA sequence
  6. Single stranded DNA is made (cDNA)
  7. To make this DNA fragment double stranded, DNA polymerase is used

cDNA is intron free as it is based on the mRNA template

49
Q

How can restriction endonucleases be used to cut up DNA

A

Many REs occur naturally in bacteria
They have an active site complementary in shape to a range of different DNA base sequences (recognition sequences) so each enzyme cuts at a specific locatioen

50
Q

What are sticky ends and how are they formed

A

They are exposed DNA bases at the end of a double strand
They are palindromic
They are formed when enzymes do not cut at the same location and don’t form a blunt end

51
Q

How can a gene machine create DNA fragments and an advantage

A
  1. Examine the protein to find the amino acid sequence, mRNA and DNA sequences
  2. The DNA sequence is entered into the computer generating small sections of overlapping single strands of nucleotides that make up the gene, called oligonucleotides
  3. These can be joined to create DNA for the entire gene
  4. PCR can amplify the quantity and create the double strand

Quick, accurate and makes intron free DNA (prokaryotes can use it)

A-Level Bio (9 decks)

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