Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-Level OCR Biology > Chapter 19 - Genetics of Living Systems > Flashcards

Chapter 19 - Genetics of Living Systems Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

In lac operon, what happens when there is no lactose present?

A
  • The repressor protein binds to the operator

- This means that RNA polymerase cannot bind to the promoter, so no transcription of the enzymes occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

In lac operon, what does the lac Z gene code for?

A

B-galactosidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In lac operon, what does the lac Y gene code for?

A

Lactose permease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does B-galactosidase do to lactose?

A

It breaks it down into more easily metabolisable sugars (glucose and galactose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does lactose permease do in lac operon?

A

It helps to transfer lactose into the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

In what organisms are lac operons found?

A

Prokaryotes- common example is E. coli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is an operon?

A

An operon is a group of genes under the control of the same regulatory mechanism and are expressed at the same time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

In lac operon, what is the role of allolactose?

A

Allolactose will also be present when lactose is present, and will bind to the repressor protein. This will prevent the repressor protein from binding to the operator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In lac operon, what happens when the repressor protein is no longer bound to the operator?

A

It allows RNA polymerase to bind to the promoter and so allows for the transcription of the genes which code for the enzymes necessary to metabolise lactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the role of cAMP in lac operon?

A

If cAMP is present, it will bind to the CAP. The CAP will then bind to the CAP site, which increases the rate of transcription, allowing the required quantity of enzymes needed to efficiency metabolise lactose to be produced.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the relationship between cAMP and glucose and what does this mean in a regulatory sense?

A

Glucose inhibits the creation of cAMP, therefore when glucose is present, cAMP will not be (and visa versa)
This means that when there are high levels of glucose, the rate of transcription will be much lower (even if lactose is present), as there is no need to metabolise lactose when the preferred sugar (glucose) is present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the 3 structural genes in lac operon and what is their role?

A

LacZ, lacY and lacA. They code for three different enzymes, that are involved in the metabolism of lactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the role of the regulator gene (lacI), which is found near the lac operon?

A

It codes for the repressor protein that inhibits transcription from occurring when lactose is not present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is it called when only one nucleotide is affected by mutation?

A

Point mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does insertion or deletion of a nucleotide lead to?

A

A frameshift mutation, which will shift the reading frame of the sequences of bases, hence changing every successive codon from the point of mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the effect of damaging mutations?

A

The phenotype of an organism is affected in a negative way, as proteins are no longer synthesised, or the proteins synthesised are non-functional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How are some mutations beneficial (with an example)?

A

Very rarely, a protein is synthesised that results in a new and useful characteristic in the phenotype.
For example a mutation in a protein in cell surface membranes of human cells can give HIV immunity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where do mutations often spontaneously occur?

A

During DNA replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is a mutagen?

A

An agent that increases the rate/likelihood of mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the 3 types of mutagens?

A

Physical, chemical and biological

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Give an example of a physical mutagen

A

Ionising radiation such as x-rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Give an example of a chemical mutagen

A

Deaminating agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How do deaminating agents work?

A

Chemically alter bases in DNA, changing the base sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Give an example of a biological mutagen

A

A virus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How are viruses biological mutagens?

A

Viral DNA may insert itself into a genome, changing the base sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What does it mean for a mutation to be silent?

A

The mutations do not change any proteins, or the activity of any proteins synthesised. Therefore they have no effect on the phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why are most mutations silent?

A
  • They can occur in the non-coding regions of DNA

- Due to the degenerate nature of genetic code, mutated codons can code for the same amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are nonsense mutations?

A

Nonsense mutations result in a codon becoming a stop codon instead of coding for an amino acid. This creates a shortened often non-functional protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are missense mutations?

A

Result in the incorporation of an incorrect amino acid into the primary structure during protein synthesis. The missense mutation can be conservative or non-conservative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is a conservative missense mutation?

A

When the amino acid change leads to an amino acid that has similar properties to the original being added to the primary structure, meaning the mutation is less severe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is a non-conservative missense mutation?

A

When the amino acid change leads to an amino acid that has different properties to the original being added to the primary structure, meaning the mutation is more severe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the difference between gene and chromosome mutations?

A

Gene mutations occur in single genes or sections of DNA, whereas chromosome mutations affect the whole chromosome or a number of chromosomes

33
Q

When do chromosome mutations often take place?

A

During meiosis

34
Q

What 4 ways can chromosome mutations occur?

A

Deletion
Duplication
Translocation
Inversion

35
Q

In chromosomal mutation, what is deletion?

A

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

36
Q

In chromosomal mutation, what is duplication?

A

Where sections get duplicated on a chromosome

37
Q

In chromosomal mutation, what is translocation?

A

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

38
Q

In chromosomal mutation, what is inversion?

A

Where a section of chromosome breaks off, is reversed, and then rejoin the chromosome

39
Q

What are housekeeping genes?

A

Genes that code for enzymes that are constantly required (e.g. enzymes for respiration)

40
Q

What are the 4 levels of gene regulation control?

A

Transcriptional
Post-transcriptional
Translational
Post-translational

41
Q

What is transcriptional control?

A

The control of gene expression by regulating the transcription stage (i.e. regulating the conversion of DNA to RNA)

42
Q

What is an example of transcriptional control?

A

Chromatin remodelling

43
Q

How does chromatin remodeling work to control gene expression?

A

DNA winds around proteins called histones, forming a chromatin.
The tightness of the winding of the DNA around the histone dictates whether transcription can occur

44
Q

What is it called when the DNA is tightly wound around the histone, and what is the effect on transcription?

A

Heterochromatin, which makes the transcription of genes not possible as RNA polymerase cannot access the genes

45
Q

What is it called when the DNA is loosely wound around the histone, and what is the effect on transcription?

A

Euchromatin, which allows the genes to be freely transcribed

46
Q

What is the purpose of chromatin remodeling?

A
  • Ensures proteins necessary for cell division are synthesised
  • Prevents protein synthesis from occuring when cells are actually dividing
47
Q

What is histone modification?

A

Histones can be modified to increase or decrease the degree of packing and the coiling of DNA

48
Q

What is the effect of acetylation in histone modification?

A

The addition of acetyl groups makes histones more negative, causing DNA (which is negative) to coil more loosely

49
Q

What is the effect of methylation in histone modification?

A

The addition of methyl groups makes histones less polar so they bind more tightly to one another, causing DNA to bind more tightly

50
Q

What are introns?

A

Non-coding sections of DNA

51
Q

What are exons?

A

Coding sections of DNA

52
Q

What is epigenetics?

A

A term that is used to describe the control of gene expression through the modification of DNA

53
Q

What is the product of transcription, and what does this turn into?

A

The product of transcription is the precursor molecule pre-mRNA. This is then modified to form mature mRNA

54
Q

What is a cap in post-transcriptional control?

A

A modified nucleotide

55
Q

What is a tail in post-transcriptional control?

A

A long chain of adenine nucleotides

56
Q

What is the 5’ end of DNA?

A

The 5’ end of the DNA is the one with the phosphate group on the 5’ carbon of the deoxyribose

57
Q

What is the 3’ end of DNA?

A

The 3’ end of the DNA is the end with the ending OH group on the 3’ carbon of the deoxyribose

58
Q

In what order is DNA read?

A

From 5’ to 3’

59
Q

What is splicing in post-transcriptional control?

A

Splicing is where the the RNA is cut at specific points. The introns are removed and the exons are joined together

60
Q

How is pre-mRNA turned into mature mRNA?

A

A cap is added to the 5’ end and a tail to the 3’ end of the RNA. Then splicing occurs, removing the introns and joining the exons together

61
Q

What are the effects of adding a cap and tail to pre-mRNA?

A

They both act to help stabilise and delay degradation. The cap also aids in binding of mRNA to ribosomes

62
Q

Where does the processes turning pre-mRNA into mature mRNA take place?

A

In the nucleus

63
Q

What is RNA editing?

A

In post-transcriptional control, mRNA molecules can be changed through base addition, deletion or substitution.

64
Q

What is the effect of RNA editing?

A

It increases the range of proteins that can be produced from a single mRNA molecule

65
Q

What is translational control?

A

Mechanisms that regulate the process of protein synthesis translation

66
Q

What is the effect of inhibitory proteins binding to mRNA?

A

Prevents it from binding to ribosomes and hence prevents the synthesis of proteins

67
Q

What is the effect of initiation factors on mRNA?

A

Aids the binding of mRNA to ribosomes, initiating protein synthesis

68
Q

What are inhibitory proteins binding to mRNA and initiation factors examples of?

A

Translational control

69
Q

What do protein kinases do?

A

They are enzymes that catalyse the addition of phosphate groups to proteins

70
Q

What does post-translational control involve?

A

Modifications to proteins that have been synthesised

71
Q

Give two examples of post-translational control

A
  • Addition of non-protein groups to the protein

- Folding or shortening of proteins

72
Q

Give an example of gene control in lac operon

A

In the lac operon cAMP binds to the cAMP receptor protein, increasing the rate of transcription of the genes

73
Q

What are homeobox genes?

A

Regulatory genes that control body development

74
Q

What do homeobox genes code for?

A

The homeodomain, a highly conserved part of a protein 180 base pairs long

75
Q

What does highly conserved mean?

A

Very similar in plants, animals and fungi

76
Q

What is an example of a homeobox gene and what does it control?

A

Pax6 is a homeobox gene that controls eye development

77
Q

What can homeobox genes do in response to stimuli?

A

Homeobox genes can induce mitosis or apoptosis in response to external and internal stimuli

78
Q

What are hox genes?

A

Homeobox genes found only in animals

79
Q

What can stress on an organism be defined by?

A

The condition produced when the homeostatic balance is upset

A-Level OCR Biology (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions