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A Level Biology (Salters-Nuttfield SNAB) > Topic 3: Voice of the genome > Flashcards

Topic 3: Voice of the genome Flashcards

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1
Q

What is cell theory?

A

That all living things are made up of cells, sharing common features such as
-cell surface membrane
- cytoplasm
- DNA
- ribosomes

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2
Q

What is a eukaryotic cell?

A

Animals and plant cells are both eukaryotic that contains membrane bound compartments called organelles and large 80S ribosomes.

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3
Q

What is a nucleus structure and function?

A

A double membrane organelle surrounded by a nuclear envelope (containing pores). It functions is to store genetic material (chromosomes and chromatin) and the nucelus.
Also the site of protein synthesis (transcription) and DNA replication.

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4
Q

What is the nucleolus and its function?

A

Found in the nucleus and is the site of ribosome synthesis.

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5
Q

What are ribosomes and their function?

A

A complex of ribosomal RNA (rRNA) and pertains. Found as free organelles in the cytoplasm or part of the rough endoplasmic reticulum.
They are the site of translation of protein synthesis.

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6
Q

What is the stature and function of the mitochondria?

A

A double membrane organelle that contains a cytoplasm called the matrix (contains respiratory enzymes) and whose inner membrane folds to create cristae.
It is the site of aerobic respiration.

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7
Q

Structure and function of the rough endoplasmic reticulum?

A

A double membrane organelle that consists of stack of vesicles with ribsomes attached to their surface.
It’s functions is to fold and process protein as that have been synthesis on its ribosomes.

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8
Q

Structure and function of smooth endoplasmic reticulum?

A

A double membrane organelle that consists of stacks of vesicles.
It synthesis and processes lipids.

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9
Q

What is the structure and function of the Golgi apparatus?

A

Consists of flattened membrane bound sacs of different sizes.
It is involved in processing, packaging and modifying protein and lipids before packing then into the Golgi vesicles.

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10
Q

What is the structure and function of centrioles?

A

Made up of hollow fibres called microtubules.
They organise single fibres during cell divisions.

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11
Q

What is the structure and function of lysosomes?

A

Specialist forms of vesicles which contain digestive enzymes p.
There roles is to break down waste materials such as worn out organelles and can programme cell death.

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12
Q

The movement of proteins through cells (RER and Golgi)?

A
  1. Transcription of DNA into mRNA occurs in the nucleus. The mRNA strand is the transported out of the nucleus through nuclear pores onto a ribosome on RER.
  2. The mRNA is translated and a protein is synthesised, which enters the rough endoplasmic reticulum.
  3. The protein is folded and processed into its secondary/tertiary structures in RER
  4. Proteins then packaged into vesicles which travel to the Golgi apparatus and fuse with its membrane.
  5. the proteins are modified further and checked within the Golgi apparatus
  6. The Golgi apparatus then packages the proteins into vesicles which are pinched off.
  7. They then travel to where they are required. Some vesicles fuse with the cell membrane and release their contents into extracellular fluid by exocytosis.
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13
Q

What are prokaryotic cells?

A

Small cells that contain circular non-linear DNA and contain no membrane bound organelles.
Such as bacteria.

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14
Q

What is the structure and function of a capsule?

A

A layer surrounding the prokaryote cells that’s acts as a protective layer. It also helps to retain moisture and adhere to surfaces.

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15
Q

What is the structure and function of cell wall?

A

The cell was in a prokaryote is made up of peptidolgylcan. It roles is to keep the cell rigid and maintain structure.

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16
Q

What is the structure and role of a plasmid?

A

Small rings of DNA that can be exchanged between cells. It allows genes to be passed between cells.
Flagellum
Pili
Ribsomes
Mesosmes
Circulated dna

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17
Q

What is the stature and function of the flagellum?

A

A tail like structure that can rotate. It assist in mobility allowing the prokaryote cell to move around.

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18
Q

What is the stature and function of Pili?

A

Small protein like tubes. They enable prokaryote cells to attach to other cells.

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19
Q

What’s are the structure and function of ribosomes on prokaryotic cells?

A

70S ribosomes. They are the site of protein synthesis.

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20
Q

What is the structure and function of mesosomes?

A

They are infolding of the cell surface membrane that contain enzymes required for respiration. They aid in aerobic respiration, cell wall formation and DNA replication.

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21
Q

What is the structure and function of circular DNA?

A

Circular DNA is the genetic material of a prokaryote cell coasting of a singular strand of DNA that is not contained in a membrane bound nucleus. Found in the nucleoid.

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22
Q

What are the key differences between eukaryotic and prokaryotic cells?

A
  • eukaryotic cells are larger than prokaryotic cells.
  • eukaryotic cells Conway in linear DNA within a chromosome in a nuclear whereas prokaryotic contain circular no-linear DNA.
  • eukaryotic cells contained membrane bound organelles whereas prokaryotic don’t.
  • prokaryotic cells contain smaller ribosomes
  • eukaryotic cells have cellulose cell walls whereas prokaryotic have peptidoglycan walls.
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23
Q

What is the magnification equations (total magnification and magnification?

A

Total magnification = eyepiece lens magnification x object lens magnification
Magnification = image size / actual size

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24
Q

What is a gamete?

A

Gametes are the sex cells of an organism (sperm and egg). They fuse during fertilisation to form a zygote. Contains 23 single chromosomes in nucleus in humans.

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25
Q

How are sperm cells specialised for their function?

A
  • contains high amounts of mitochondria to provide enough energy for movement.
  • have a flagellum allowing them to swim efficiently
  • contain an acrosome that’s contains digestive enzymes to break down zona pellucida in the egg cell.
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26
Q

How are egg cells (ovum) specialised for their function?

A
  • contains a nutrients rich cytoplasm for the developing zygotes
  • have a jelly like layer called the zona pellucida that forms an impenetrable barrier after fertilisation prevent)no polyspermy.
    -follicle cells that form a protective coating.
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27
Q

What is fertilisation?

A

The fusion of the nuclei of the male gamete (sperm) and the female gamete (egg) forming a diploid zygote.

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28
Q

What is the acrosome reaction?

A

As the sperm moves towards the ovum (attracted by chemicals) it reaches it and the acrosome releases digestive enzymes causing the zona pellucida to hydrolysis allowing the nucleus to enter the ovum.

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29
Q

What is the cortical reaction?

A

After the nucleus of the sperm enters the cell, the cortical granules release their contents by exocytosis. Causing the zone pellucida to thicken and harder preventing any other sperm entering (polyspermy)

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30
Q

What is the nuclei fusion?

A

When the nucleus of the sperm fuse with the nucleus of the ovum to produce a diploid zygote which will then divide by mitosis to form an embryo.

31
Q

What is the locus?

A

The location of genes on a chromosome.

32
Q

What is gene linkage?

A

The closer the loci of the two genes the more they are (autosomally) linked and are therefor inherited together as they are less likely to be separated by crossing over.

33
Q

What is sex linkages and why are men more likely to inherit it?

A

A gene that is sex-linked occurs on the X chromosome of which men have only one. This means that men will only inherit one copy of the gene so only one recessive allele is required for the phenotype to be shown making it more commonly expressed in men.

34
Q

What is meiosis?

A

A type of cell division which goes through PMAT twice. The process results in the formation of 4 haploid gametes from a diploid cell. Happens int he ovaries and tested.

35
Q

How does meiosis result in genetic variation?

A
  • independent assortment
  • crossing over
36
Q

What is independent assortment?

A

The production of different combinations of allele in daughter cells due to the random alignment of homologous pairs along the equator of the spindle during meiosis I.

37
Q

What is crossing over?

A

Occurs during prophase 1 when homologous pairs meet at the centromere and large sections of DNA are exchanged between non-sister chromatids. Resulting in a new combination on chromosomes
The pint where the DNA is exchanged is called the chiasmata.

38
Q

What is the cell cycle and its three stages?

A

The regulated sequence elf event that occurs between one cell division and the next.
It has three phases
- interphase
- nuclear division (mitosis)
- cell division (cytokinesis)

39
Q

What is interphase?

A

During interphase the cell increases in mass and size
G1> the cell grows and all organelles are duplicated
S > the centrioles are duplicated, and DNA replication occurs (quality of DNA doubles)
G2 > the cell grows further, proteins are synthesised, and reorganisation of the cell takes place

40
Q

What is mitosis and its stages?

A

A type of cell division that is useful in plant for asexual reproduction and in humans for growth and to replace damaged tissues. It results in the formation of two identical diploid daughter cells.
- interphase
- prophase
- metaphase
- anaphase
- telophase

41
Q

What is interphase (mitosis)?

A

Cell organelles and DNA are duplicated.

42
Q

What is prophase?

A

The nuclear envelope and nucleolus breaks down, chromosomes condense and the centrioles are pulled to polar ends of the cell wall where they start to synthesis spindle fibres

43
Q

What is metaphase?

A

The chromosomes align at the cells equator and spindle fibres attach to the chromosomes centromeres.

44
Q

What is anaphase?

A

The spindle fibres contracts, splitting the centromere pulling one chromatid to each pole of the cell.

45
Q

What is telophase?

A

The chromosomes de-condense, the spindle fibres break down and a nuclear envelope forms between the two sets of chromosomes.

46
Q

What is cytokinesis?

A

Once the nucleus has divided into two genetically identical nuclei, the whole cell divides creating two genetically identical daughter cells.

47
Q

What is the importance of mitosis?

A

Growth of multicellular organisms > the production of clone cell means that zygotes can divide into multicellular organism.
Replacement and repair > damaged cells Ca; be replaces by cell division, and as cells are consistently dying they need to be continually replaced by genetically identical cells. (E.g. skin)
Asexual reproduction > production of new individuals by a single parent organism. The offspring are genetically identical. (Strawberry’s)

48
Q

What is a stem cell?

A

Undifferentiated cells that are capable of dividing to produce more stem cells and can differentiate into specialised cells to perform functions by switching genes ‘on’ and ‘off’.

49
Q

What is pluripotency?

A

Stem cells that can differentiate and give rise to many cell types as most of the genes are ‘switched off’
E.g. embryonic cells

50
Q

What is totipotency?

A

Stems cells which can differentiate and give rise to any cell type (including placenta) because all the genes within these cells are inactivated/switched ‘off’

51
Q

How can stem cells be used in medicine?

A

They have the ability to differentiate into other specialised cell type making them valuable in medical research and treatment as they can replace damaged tissues

52
Q

What are the advantage of using stem cells in medical research?

A
  • they can be used to grow transplant organs
  • they can be used to treat degenerative diseases and replace damaged tissue
  • they can be derived from the patients meaning there is no risk of infection/rejection as the cells are genetically identical.
53
Q

What are the disadvantages of using stem cells?

A
  • fertilised embryos have the potential, to become human life, making it unethical to cause the death of a foetus
  • embryonic stem cells carry a risk of infection/rejection/cancer as the cells are genetically different.
  • stem cell cultured in a lab may become infected with a virus such could be then transmitted inside a patient.
54
Q

Who controls the use of stem cells?

A

The use of stem cells in medical research is controlled by a regulatory body who judge what is acceptable, check the source of the stem cell and decide the maximum age that embryos are allowed for medical research.

55
Q

What are adult stem cells?

A

Adults stem cells are cells that can divide via mitosis an unlimited number of time but are only able to produce a limited range if cell types.
They are found in bone marrow (can make blood cells) and in the Brian (neural and glial cells)

56
Q

How do cells become specialised?

A
  1. A stem cells receives a stimulus (need to give example) e.g. chemical or hormonal
  2. This causes specific genes in the cells DNA to become activated
  3. The activated gene in transcribed by RNA polymerase to a mRNA strand
  4. The mRNA is translated forming a protein
  5. These proteins then modifies the cell (determining the structure and function), as modifications continue to take place the cell becomes increasingly specialised.
    The process is irreversible.
57
Q

What is the lac operon model?

A

The lac operon controls the production. Of the enzyme lactase and two other structural proteins.
Lactase breaks down the substrate lactose so it can be used as an energy source in the bacterial cell.

58
Q

What is the structure of the lac operon?

A

It is made up of several components
- promoter
- operator
- structural gene lacZ codes for lactase
- structural gene lacY which code for permease (allows lactose into the cell)
- structural gene lacA

59
Q

What happen in the lac operon when lactose is absent?

A
  1. The lac repressor protein binds to the operator region on the lac operon
  2. Due to the presence of the lac repressor protein RNA polymerase is unable to bind to the promoter region.
  3. Transcription of lactase cannot happen and the gene is inactive.
60
Q

What happens in the lac operon when lactose is present?

A
  1. There is an uptake of lactose by the bacterium
  2. Lactose binds to the secondary binding site on the repressor protein
  3. The repressor protein is distorted by the lactose so that is can no longer bind to the operator region
  4. RNA polymerase is then able to bind to the promoter region and transcription takes place.
  5. mRNA from all three structural genes is translated
  6. Enzyme lactase is produced and the lactose can be broken down and used for energy
61
Q

How are cells organised into tissues, organs and organ systems?

A

Cells have specific recognition proteins in their cell membrane which extends out and bind to complementary proteins on identical adjacent cells forming clusters of identical cells.

62
Q

What is a tissue?

A

A group of specialised cells that work together to perform a specific function. They usually have the same origin.

63
Q

What is an organ?

A

A group of tissues working together to perform a particular function.

64
Q

What is an organ system?

A

A group of organs working together to perform a particular function.

65
Q

What is epigenetics?

A

These are changes in a DNA that alter the expression of genes without changing the base sequence itself. It does this is two ways
- histone modification
- DNA methylation

66
Q

How does histone modification control gene expression?

A

This is the blinding of epigenetic markers (methyl or acetyl) which affects how tightly the DNA is wrapped around histone proteins.
When round tightly the genes RNA polymerase cannot access the DNA and the genes are inactive.
When round loosely RNA polymerase can transcribe the DNA into mRNA making a protein and the gene is therefor active.

67
Q

How does DNA methylation control gene expression?

A

Where methyl groups attach directly to DNA preventing RNA polymerase from binding, meaning transcription and translation of the protein in inhibited.

68
Q

What is the epigenome and how is it changed?

A

The epigenome is all the epigenetic markerss in an organism.
It can undergo changes due to certain environmental changes such as smoking, stress, exercise and diet. Additionally internal signalling from the body’s own cell can also cause modifications to occur.

69
Q

How are epigenetic changes inherited?

A
  1. Certain genes are activated or deactivated due to epigenetic changes
  2. These changes include histone modification and DNA methylation.
  3. These changes are then inherited and are present in daughter cells.
    One potential explanation is that if epigenetic changes occur in respond to an environment factor, it may be beneficial for the epigenetic change to also occur in the daughter cells/gametes.
70
Q

What is a phenotype?

A

The observable characteristics of an organism.

71
Q

What is polygenic inheritance?

A

Where more than one gene at different loci are responsible for the inheritance of a single characteristic or phenotype. This means each gene has an additive effect in the final phenotype giving rise to continuous variation.

72
Q

How to environmental factors give rise to continuous variation?

A

The environment that an organism lives in can also have an impact on its phenotype e.g. length of sunlight hours, supply of nutrients (food), availability of water, temperature range and oxygen levels. This will all change how an organism grows and develops.

73
Q

Variables of for practical 5 : observing mitosis

A

Control Variables > species of root tip, age of root tip, volume of solutions, time spend in solutions, temperature (water bath), light (use artificial p) and pH (buffers)
Dependent variables > number of cells undergoing mitosis (mitotic index’

74
Q

What is the method of core practical 5 : observing mitosis

A
  1. Cut 1cm of root tip
  2. Place root tip in alcohol (ethanol) for 5 minutes (stop the process of mitosis)
  3. Place the root tip in warm hydrochloric acid for 5 minutes to break down the pectin in the middle lamella.
  4. Place root tip of microscope slide and macerate
  5. Add a stain to highlight cell structure and add coverslip.
  6. View sample under light microscope at low and high power.
  7. Count number of cells undergoing mitosis and divide it by the total number of cells to calculate mitotic index.
  8. Repeat to calculate a mean, identify anomalies and increase validity.

A Level Biology (Salters-Nuttfield SNAB) (8 decks)

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