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OCR A Level Biology > Module 6: Cellular Control > Flashcards

Module 6: Cellular Control Flashcards

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1
Q

What are the different types of mutation

A

Point
Indel
Chromosomal

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2
Q

What are the different types of point mutations

A

Silent: which replaces letter but makes same amino acid (code is degenerate)

Nonesense: introduces a stop coding, making the protein truncated

Missense: changes the codon to a different amino acid, can be
conservative changes to a similar amino acid, or non conservative changes to a different amino acid

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3
Q

What happens during an insertion or deletion

A

A codon is inserted or deleted
This causes a frame shift
Causing the amino acid sequence to change

For example insertion, all the letters shift one down, changing all the amino acids after that point

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4
Q

What causes a chromosomal mutation

A

Caused by mutagen

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5
Q

How does the chromosomal mutation affect meiosis

A

Deletion: a section breaks off
Duplication: section of chromosome breaks of and joins another one
Inversion: section of chromosome is broken of reversed and placed onto another chromosome

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6
Q

What are the causes of mutation

A

Physical mutagens: causes break in DNA (ionisation and X-rays)
Chemical mutagens: changes base sequence
Biological agents
-alkylating agents (changes base sequence
-base analogs (incorporated into DNA)

Viruses: inserts itself into genome and changes base sequence

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7
Q

What are the benefits and disadvantages

(sort this flashcard out)

A

Benefits
-lactose one

Disadvantages
-check textbook

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8
Q

Explain the transcriptional level of control

Histone modification and chromatin remodelling)

A

DNA is tightly wrapped around histones (heterochromatin)
To make gene more accessible you can add a phosphate group or an acyl group (decreases postiive charge of histones) to turn it itno euchromatin
This allows for RNA polyermase to bind
To make it back hetrochromatin you add a methyl group ( increase hydrophobic nature of histone)

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9
Q

What are the post transcriptional factors

A

Splicing
RNA editing

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10
Q

What is an intron

A

non coding DNA

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11
Q

What is an exon

A

Coding DNA

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12
Q

How does splicing work

A

A splicosome is used
Causes a loop to form
Introns are spliced out, remaining exons fused together to make mature mRNA from pre mRNA
mRNA leaves the nucleus

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13
Q

How does mRNA editing work

A

add polyA tail and cap (this stabilises mRNA and prevents mRNA degradation, which now makes mature mRNA)
you can edit mRNA through base deletion and subsituation

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14
Q

What are the types of post-translational control

A

Protein modification

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15
Q

How do we regulate genes at a translational level (mRNA after it leaves the nucleus and wants to bind to a ribosome)

A

To decrease translation you can bind of inhibitory proteins on mRNA which prevents it from binding onto the ribsosone

To increase translation you can activate inititaion protein aids binding of mRNA to ribosome

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16
Q

How does protein modification occur in post-translation control?

A

Add non-proteins (phosphates, lipids)
Can modify amino acids by adding bonds (like disulphide bridges)
Fold or shorten proteins
Or can modify by using cAMP in the example of protein kinase where, when cAMP binds it causes a change in the 3D structure of the enzyme, making it active

17
Q

What is an operon

A

a group of genes controlled by the same regulatory mechanism and expressed at the same time

18
Q

What is a promoter

A

DNA sequenence that RNA polyermase binds to

19
Q

What is a repressor

A

transcription factor that stops transcription

20
Q

What are structural genes

A

genes that code for proteins not involved in DNA regulation

21
Q

What are regulatory genes

A

code for proteins involved in DNA regulations eg repressor protein

22
Q

what is the operator

A

DNA sequence where repressor protein binds to

23
Q

How does the lac operon work

Glucose present

A

Lac I codes for repressor protein
person protein binds to operator
so RNA polymerase cannot bind

24
Q

How does a lac operon work

Lactose present

A

Lactose binds to the repressor protein
this changes the shape of repressor protein so it can no longer bind to the operon
RNA polymerase cann bind to to promotor so structural genes can be made

25
Q

How does a lac operon work

Lactose present

A

Lactose binds to the repressor protein
this changes the shape of repressor protein so it can no longer bind to the operon
RNA polymerase can bind to promotor so structural genes can be made
CRP can bind to cAMP which can make it easier for RNA polymerase to bind

26
Q

How does the lac operon work when

Glucose and lactose is present

A

Cell prefers glucose (provides more energy)
Glucose decreases cAMP concentration, so the CRP-CAMP-RNA polymerase complex will dissociate
downregulating transcription

27
Q

What do the three structural genes (lacY, lacZ, lacA) make in a lac operon

A

Beta galactosidase
lactose permease, lactose transferacylase

28
Q

What are homebox genes

A 
regulatory genes (180 base pairs long)
-Code for homeodomain (part of protein)
29
Q

What are the functions of homeobox genes

A
  • Controls body development (poistioning of body parts)
  • Highly conserved in plants, animals, fungi
  • Regulate mitosis and apoptosis by responding to internal and external stimuli
30
Q

How do homeobox genes help with development

A

-homeodomain of the protein can act as a transcription
factors and bind to sites of DNA

  • binds to DNA at the start of developmental
  • can alter production of proteins involved in the development of the body plan
31
Q

What are hox genes

A

Homeobox genes found in animals
39 across mutiple chromosomes

32
Q

What is apoptosis

A

Programmed cell death

33
Q

Give an example of internal stimulas where apotosis may need to occur

A
  • DNA damage
  • If damage is detected during the cell cycle then apotosis may be triggered
34
Q

Give an example of external stimulas where apotosis may need to occur

A
  • lack of nutrients availability could result in apoptosis
  • or a pathogen
  • stress
35
Q

How does apoptosis happen

A
  1. DNA in the proteins and nucelus in the cytoplasm
  2. Other cell components e.g mitochondria and cytoskelton are broken down by enzymes.
  3. As cell contents are broken down it begins to shrink are also broken down
  4. Blebs develop on cell surface
  5. Blebs are engulfed by phagocytes and are digested

This is to prevent harmful products being released into the body

36
Q

What is necrosis

A
  • can happen due to trauma or infection
  • unprogrammed cell death
37
Q

What is epigenetic regulation

A

noticiable changes in gene functions without changes to the base sequence
changes are caused by the enviorment

OCR A Level Biology (24 decks)

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