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Biology A level (Edexcel SNAB) > UNIT 3 - The Voice of the Genome > Flashcards

UNIT 3 - The Voice of the Genome Flashcards

1
Q

What are the differences between eukaryotic and prokaryotic cells?

A

Eukaryotes:

  • Contain membrane-bound organelles (nucleus, mitochondrion, ER)
  • 80s ribosomes

Prokaryotes:

  • No membrane bound organelles (circular DNA instead of nucleus)
  • 70s ribosomes
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2
Q

What is A

A

Nucleolus

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3
Q

What is B

A

Smooth endoplasmic reticulum

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4
Q

What is C

A

Golgi apparatus

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5
Q

What is D

A

Lysosome

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6
Q

What is E

A

Cytoplasm

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7
Q

What is F

A

Mitochondrion

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8
Q

What is G

A

Ribosomes

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9
Q

What is H

A

Rough endoplasmic reticulum

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10
Q

What is I

A

Centriole

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11
Q

What is A

A

Nuclear envelope/membrane

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12
Q

What is B

A

Nuclear pore

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13
Q

What is C

A

Nucleolus

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14
Q

What is the function of the nucleolus?

A

Ribosome synthesis

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15
Q

What is the function of the lysosome?

A

Contains digestive enzymes to digest invading cells or break down cell components.

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16
Q

What is the function and structure of the ribosomes?

A

Protein synthesis. Made out of a small and big subunit.

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17
Q

What is the function of the rER?

A

Folds and processes proteins which were synthesised at the ribosomes on its surface.

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18
Q

What is the function of the Golgi apparatus?

A

Processes and packages lipids and proteins (thus, it also makes lysosomes)

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19
Q

What is the function of the mitochondria?

A

Site of aerobic respiration, where ATP is produced.

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20
Q

What is the funtion of the centriole?

A

Involved in separaton of chromosomes.

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21
Q

What is the function of the nucleus?

A

Controls transcription and synthesis of DNA. Stores chromatin (DNA+proteins(histones))

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22
Q

What is A

A

Cristae

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23
Q

What is B

A

Intermembrane space

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24
Q

What is C

A

Matrix

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25
Q

What is D

A

Inner membrane

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26
Q

What is E

A

Outer membrane

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27
Q

What is the structure of a centrosome?

A

It is composed of 2 centrioles arranged perpendicular to each other.

Each centriole isa hollow cylinder composed of 9 microtubule triplets.

They are found in animal cells, bu tonly in some plant cells. ​​

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28
Q

Describe the steps in protein production and transport

A
  1. Chain of A.A. is synthesised in the ribosomes. (on rER, if the protein is going to be excreted, attached to cell membrane or in vesicle. In cytoplasm if protein is going to be there)
  2. rER folds proteins into 2ary and 3ary structure.
  3. Proteins are transported in vesicles from ER to Golgi apparatus in vesicles.
  4. In the Golgi apparatus, proteins are processed i.e. adding carbohydrate groups to form glycoproteins
  5. Cells exit the Golgi in a vesicle. Extracellular enzymes are secreted by exocytosis.
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29
Q

What is A

A

70s ribosomes

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30
Q

What is B

A

Pili

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31
Q

What is C

A

Circular DNA inside nucleoid. Not attached to histoe proteins.

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32
Q

What is D

A

Slime capsule

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33
Q

What is E

A

Murein (glycoprotein) cell wall

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34
Q

What is F

A

Cytoplasm (cytosol)

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35
Q

What is G

A

Plasmid (small loop of DNA)

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36
Q

What is H

A

Flagellum

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37
Q

What is the function of pili

A

Help prokaryotes stick to other cells and can be used in the transfer of genetic material.

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38
Q

What is the function of the slime capsule

A

Protect bacteria from attacking cells (i.e. cells from immune system)

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39
Q

What are mesosomes? What is their function?

A

Mesosomes are inward folds in the plasma membrane. Scientists still aren’t sure about their role.

Some think they’re involved in cellular processes i.e. respiration.

Others think that they are produced during the preparation of the cell for viewing through an electron microscope.

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40
Q

What is the function of plasmids?

A

They store genes like antibiotic resistance.

41
Q

What is the equation for magnification

A

Magnification = image size / actual size

42
Q

What is the difference between magnification and resolution

A

Magnification is how much bigger the image is while resolution is how detailed the image is.

43
Q

What is the maximum resolution and magnification of a light microscope?

A

0.2 micrometers (resolution) and x 1500 (magnification)

44
Q

What is the maximum resolution and magnification of an electron microscope?

A

0.0002 micrometres (resolution) and x 1 500 000 (magnification)

45
Q

What are the principal differences between transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs)?

A

TEMs have high resolution and produce a 2D image where the denser parts are darker.

SEMs have lower resolution, 3D images.

46
Q

How do you calibrate an eyepiece graticule suing a stage micrometer?

A

Line up the stage micrometer and the eyepiece graticule.

Measure the length of the eyepiece graticule using the stage micrometer and divide by the number of divisions to get the length of 1 division of the eyepiece graticule.

47
Q

What is a tissue?

A

A group of similar cells that are specially adapted to work together to carry out a particular function.

i.e. cartilage

48
Q

What is an organ?

A

A group of different tissues that work together to perform a particular function.

i.e. the heart

49
Q

What is an organ system?

A

A group of different organs working together for the same function.

i.e. circulatory system

50
Q

What are the phases in the cell cycle?

A

Gap phase 1

Synthesis

Gap phase 2

Mitosis

51
Q

In the cell cycle, what happens during gap phase 1?

A

Cell grows and new organelles and proteins are made.

52
Q

In the cell cycle, what happens during the synthesis phase?

A

Cell replicates its DNA (from haploid to diploid).

53
Q

In the cell cycle, what happens during the gap phase 2?

A

Cell keeps growing and proteins needed for cell division are made.

54
Q

What stages of the cell cycle constitute the interphase?

A

Gap phase 1, synthesis and gap phase 2.

(all except mitosis)

55
Q

What are the 4 phases of mitosis?

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
56
Q

What happens during prophase?

A
  • Chromosomes condense. Getting shorter and fatter.
  • Centrioles move towards opposite ends of the cell, forming a spindle fibres network across the cell.
  • Nuclear envelope breaks down and chromosomes lie free in the cytoplasm.
57
Q

What happens during metaphase?

A
  • Chromosomes line up and become attached to the spindle fibre by their centromere (what holds the two chromatids together)
58
Q

What happens during anaphase?

A
  • The centromeres break apart, separating each pair of cromatids.
  • Spindles contract, pulling chromatids to opposite poles of the spindle - chromatids appear v-shaped with the centromere closer to the pole.
59
Q

What happens during telophase?

A
  • A nuclear envelope forms around each group of chromosomes.
  • Chromosomes uncoil and become long and thin.
  • Cytokinesis will then occur and two genetically identical cells are produced.
60
Q

What is A

A

Sister chromatids

61
Q

What is B?

A

Centromere

62
Q

How can root tips be stained and squashed to observe mitosis?

CP

(8)

A
  • Cut 1 cm from the tip of a growing root (here’s where mitosis takes place).
  • Put it in a water bath at 60C and add 1M HCl. Incubate it for 5mins.
  • Use a pipette to rinse the root tip with cold water and let it dry.
  • Place the root tip on a microscope slide and cut 2mm of the tip.
  • Use a mounted needle to spread the cells thinly.
  • Add a small drop of stain: Toluidine blue O
  • Place a cover slip and squash the tissue.
  • Now look under a light microscope.
63
Q

How can the. mitotic index be calculated?

A

number of cells with visible chromosomes / total number of cells observed

64
Q

How is an egg cell specialised to its function?

A

Much larger than sperm - big food stores.

Follicle cells with protective coating

Zona pellucida - protective glycoprotein layer.

65
Q

How are sperm cells adapted to their function?

A

Flagellum - allows sperm to swim

Lots of mitochondria - provide energy for swimming

Acrosome - contains enzymes that can break down the zona pellucida.

66
Q

Describe the process of fertilisation (5)

A
  1. Once one sperm makes contact with the zona pellucida, the acrosome reaction occurs (enzymes are released from the acrosome of the sperm)
  2. The enzymes digest the zona pellucida so that the sperm cell can move to the membrane of the egg cell.
  3. Sperm head fuses with egg membrane. Only the sperm nucleus enters.
  4. Cortical reaction - chemicals released by the cortical granules makes the zona pellucida thicken so that no other sperm can enter.
  5. The two nucleus then fuse, forming a diploid nucleus. A zygote is produced.
67
Q

Describe the process of meiosis

A
  1. DNA replicates, so there are two identical chromatids for each chromosome.
  2. DNA condenses
  3. The double armed chromosomes arrange themselves into homologous pairs (both chromosomes 1 - one from each parent)
  4. 1st division - the homologous pairs are separated.
  5. 2nd division - the pairs of sister chromatids are separated.
  6. 4 new haploid, genetically different cells are produced.
68
Q

What are the two factors that create genetic variation?

A

Crossing over and Independent assortment of chromatids.

69
Q

What is crossing over of chromatids?

A
  1. Before the 1st division, homologous pairs of chromosomes come and pair up.
  2. Two of the chromatids in each homologous pair may twist around each other.
  3. This bits break off their original chromatid and rejoin the other chromatid, recombining their genetic material.
  4. The chromatids still have the same genes, but they have changed alleles for that specific section.
70
Q

What is independent assortment of chromosomes?

A

When chromosomes are separated, they can create different combinations. (i.e. the first one from the first set, with the second one from the second set, with the first one from the first set….)

This produced different combinations of both maternal and paternal chromosomes when producing a gamete.

71
Q

Why are some genes linked?

A

If genes have their loci in different chromosomes, then independent assortment means that they will end up randomly distributed.

The closer together genes have their loci in a chromosomes, the lower the chance of crossing over separating them.

72
Q

Why are some characteristics sex linked?

A

The X chromosome is larger and has more genes than the y chromosmes.

This means that for a recessive trait with its gene in the unique part of the X chromosme, males (XY) would only have to inherit 1 recesiive allele while females (XX) would need to inherit two.

i.e. colour blindness.

73
Q

What is a totipotent cell?

A

A cell that has the ability to produce all cell types, including all the specialised cells in an organism and extraembryonic cells.

74
Q

What is a pluripotent cell?

A

A stem cell that has the ability to produce all the specialised cells in an organism but not extraembryonic because the genes for these cells have become inactivated.

75
Q

What are stem cells?

A

Unspecialised cells that can develop into other types of cells.

76
Q

How does an zygote become a developed fetus through cell differentiation?

A
  1. During the first few divisions, cells remain totipotent.
  2. Then, cells at the exterior of the blastocyst develop into extraembryonic cells, the inner part is called the inner cell mass (become pluripotent).
  3. Cells in the ICM (Inner cell mass) further specialise into cells such as muscle cells.
77
Q

Where do plants have stem cells?

A

In areas where they are growing i.e. roots and shoots

78
Q

Stem cells are also found in adult tissue where they become specialised cells that need to be replaced. Give examples of these places and compare the potency of these stem cells with those in the embryo.

A

Examples:

In insestine - replace epithelial cells.

In bone marrow - production of red blood cells.

White blood stem cells.

These are much less flexible than embryonic stem cells - they can only develop into some cell types.

79
Q

How do cells become specialised?

A

They activate certain genes.

Under the right conditions different genes are activated or inactivated.

mRNA is only transcribed from active genes, this is then translated into proteins.

The proteins modify the cell - they determine the cell structure and control cell processes.

These changes are difficult to reverse.

i.e. Stem cells in bone marrow activate the gene for haemoglobin production and the ones for the nucleus removal. (many others are activated and desactivated).

80
Q

How do transcription factors affect gene expression?

A

Transcription factors are proteins that bind to the DNA in order to alterate the rate of transcription (activators and repressors).

Activators help RNA polymerase bind to the DNA while repressors stop it from binding.

In eukaryotes, this happens near the start of the target genes while in prokaryotes, they often bind to operons.

81
Q

What is an operon?

A

A section of DNA that contains a cluster of structural genes that are transcribed together, control elements, and a regulatory gene (sometimes).

Structural genes code for proteins.

Control elements are a promoter and an operator. The promoter is a section of DNA before the structural genes and an operator is a DNA sequence where transcription factors bind to.

The regulatory gene codes for a transcription factor (activator or repressor).

82
Q

How do transcription factors in the lac operon in E. coli bacteria allows it to respire lactose when lactose is present?

A

The lac operon contains 3 structural genes that produce the enzymes needed to respire lactose - lacZ, lacY and lacA.

The regulatory gene (lacl) produces the lac repressor (transcription factors) that binds to the operator when there’s no lactose, blocking RNA from binding to the promoter.

When lactose is present, it binds to teh repressor, changing the repressor’s shape so that it no longer bind to the operator and so RNA polymerase can transcribe the structural genes.

83
Q

Give an example of a stem cell therapy that already exists.

A

Treatment for leukaemia - bone marrow transplants can be given to patients.

84
Q

Give examples of stem cell therapies scientists are researching for

A
  • Spinal cord injuries - repair damaged nerve tissue.
  • Damaged heart tissue by heart attacks may be replaced by stem cells-
85
Q

How can stem cells be obtained from the bone marrow in adults?

A

A needle is inserted into the centre of a bone (i.e. te hip) and a small quantity of bone marrow is removed from the donor.

To reduce risk of rejection, this can be done with the patients’ own healthy tissue.

86
Q

How can embryonic stem cells be obtained?

A

Embryos are created in a laboratory using IVF.

Once the embryos are 4 to 5 years old, stem cells are removed and the rest of the embryo is destroyed.

Embryonic stem cells can develop into all types of cells in our bodies.

However, it brings ethical concerns and there’s risk of rejection.

An alternative could be producing embyos by using artificially activated egg cells.

87
Q

How do regulatory authorities regulate the use of stem cells?

A
  • Look at research proposals and decide if they should be allowed due to ethical and practical reasons.
  • Licensing centres so that fully trained staff work on it.
  • Produce guidelines and codes of practice to ensure all scientists are working in a similar manner.
  • Monitoring development to make sure new changes are regulated.
  • Informing society and governments.
88
Q

What is continuous variation?

A

When a population varies within a range - there are no distinct categories. i.e. height, mass, skin colour…

89
Q

What is discontinuous variation?

A

When individuals in a population vary in 2 or more distinct categories, falling only into 1 of these.

i.e. blood group (A, B, AB or O)

90
Q

What are monogenic characteristic and what type of variation do they tend to show?

A

A characteristic controlled only by one gene. Tends to show discontinuous variation (grouped, i.e. blood groups).

91
Q

What are polygenic characteristics and what type of variation do they usually show?

A

Characteristic controlled by a number of genes at different loci.

They tend to show continuous variation (i.e. height).

This describes most characteristics.

92
Q

How does the environment affect height?

A

Nutrition is very important, because protein is needed for growth.

93
Q

How does the environment affect Monoamine Oxidase A (MAOA) levels?

A

MAOA is an enzyme that breaks down monoamines in humans low levels of it have been linked to mental health problems.

It is monogenic.

Taking anti-depressants or smoking tobacco can reduce the amount produced.

94
Q

How does the environment affect animal hair colour?

A

Animal hair colour is polygenic and it can be triggered by environmental factors such as temperature.

95
Q

How does DNA methylation repress a gene?

A

Methyl group is attached to the DNA at a CpG site (Cytosine followed by guanine).

This changes the DNA structure so that proteins and enzymes needed for transcription can’t bind to it.

96
Q

How does histone acetylation repress a gene?

A

When histones are acetylated, the chromatin is less condensed so proteins and enzymes needed for transcription can bind to it.

97
Q

Can epigenetic changes be passed on after cell division?

A

Yes.

98
Q
A

Biology A level (Edexcel SNAB) (5 decks)

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