Cell Division+Immunology+transport Across Membranes Flashcards by yasin ahmed

Describe the appearance and behaviour of chromosomes during MITOSIS

(During prophase)
Chromosomes coil/condense/shorten and become visible
Appear as identical sister chromatids joined at the centromere

(Metaphase)
Chromosomes line up on the equator
Chromosomes attached to spindle fibres
By their centromere

(Anaphase)
Centromere splits
Spindle fibres contract
Sister chromatids move to opposite piles of the cell making v shape
(Telophase)
Chromosomes uncoil and unwind // cytokinesis also happens

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Describe and explain the processes that occur during meiosis that increase genetic variation

Homologus chromosomes pair up
Independent segregation
Maternal and paternal chromosomes pair up and reshuffled in random combination
Crossing over leads to exchange of non sister chromatids between homologous chromosomes
Both create new combination of alleles

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In which part of the cell cycle does dna replication take place

S-phase

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Describe the role of spindles during mitosis

Attachment of chromatids at centromere, separation of chromatids

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Importance of meiosis

Halves chromosome number
Diploid

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Describe the role of centromere in mitosis

Holds chromatids together
Attaches to spindle
Allows chromatids to be separated

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Odd number of chromosomes cannot produce fertile gametes as the chromosomes cannot pair

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To tell if cell undergoing mitosis in a picture

Chromsomes will be visible because they have condensed
Chromosome made up of 2 chromatids because dna replicated

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Suggest one advantage to a bacterium of secreting an extracellular

To digest proteins
So they can absorb amino acids for growth

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Processes that take place during G1 of the cell cycle are

• cell growth
• protein synthesis
• production of Rna
• production of organelles

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Reasons why a cell might not pass through G1 is

• Cell is not big enough
• Dna has been damaged
• Cell has not produced enough proteins/organelles
• environment does not contain enough nutrients

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Describe binary fission in bacteria

1) Replication of circular DNA
2) Replication of plasmids
3) Division of cytoplasm to produce daughter cells

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Differences between mitosis and meiosis

• Mitosis is 1 division, WHEREAS meiosis is 2 divisions
• In mitosis, daughter cells are genetically identical, WHEREAS in meiosis, daughter cells are genetically different
• In mitosis, 2 daughter cells are produced WHEREAS in meiosis, 4 cells produced
• In mitosis, diploid to diploid/haploid to haploid WHEREAS in meiosis diploid to haploid
Separation of homologous chromosomes only happens in meiosis
Independent segregation and crossing over only occur in meiosis

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Explain how the chromosome number is halved during meiosis

Homologous chromosomes (pair);
One of each (pair) goes to each (daughter)
cell / to opposite poles;

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Describe process of crossing over and explain how it increases genetic diversity

-homologous pairs of chromosomes form a bivalent
-chiasma form
-equal lengths of non-sister chromatids between homologous chromosomes are exchanged
-producing new combinations of alleles

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Describe the features of prophase

Nuclear membrane begins to breakdown;
Centrioles move to poles of the cell;
Chromosome condense;

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Describe the features of metaphase

spindle fibres form
spindle fibres attach
to the centromere of chromosomes
chromosomes align at the equator

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Describe the features of Anaphase

Spindle fibres shorten;
Centromere splits;
Sister chromatids are separated;
Pulled to opposite poles of the cell;

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Describe the features of telophase

Nuclear membrane begins to reform;
Chromosomes unwind

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Describe the role of the spindle during mitosis

Attachment of centromeres/chromosomes/chromatids; Separation of centromeres/chromatids/chromosomes;

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Importance of meiosis

Halves chromosome number
Increases variation within a population

Role of centromere during mitosis

Holds chromatids together
Attaches to spindle fibre
Allowing chromatids to be separated during anaphase

Antigen

Foreign protein
That stimulates an immune response leading to the production of an antibody

Antibody

Protein
Produced by plasma cells
In response to an antigen in an immune response

To check for Aids

Look for AIDS-related symptoms Check number of thelper cells

Children receive HIV antibodies from their mum so Test will always be positive

Elisa teat may contain a control well to see that only enzyme is causing a colour change and to see washing is effective

Give 2 ways pathogens can cause disease

• Release toxins which can directly damage tissue • can replicate and inside and destroy host cells

How do antibodies assist in the destruction of pathogens

• AGGLUTINATION- specific antibodies bind to the antigen and clump them together • Opsonisation- Marking pathogens so phagocytes recognise and destroy pathogens more efficiently • prevent pathogen replication

If a virus is inactive

• The cells arent being produced (link to the question- which cells have they talked about • Because virus is not replicating

Advantage of programmed cell death

Prevents replication of virus

What is a monoclonal antibody

Antibodies produced from the same B or plasma cell Or antibodies with the same tertiary structure

Give 2 cells other than pathogens that can cause disease

• Cancer cells • Cells from other organisms

What is the role of the disulfide bridge in forming the quaternary structure of an antibody?

Joins two different polypeptides together

Explain why these antibodies are only effective against a specific pathogen. (2)

Antibodies have a specific tertiary structure; Antigens are complementary to antibody

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how.

1. Vaccine contains antigen from pathogen; 2. Macrophage presents antigen on its surface; 3. T cell with complementary receptor protein binds to antigen; 4. T cell stimulates B cell; 5. (With) complementary antibody on its surface; 6. B cell secretes large amounts of antibody; 7. B cell divides to form clone all secreting/producing same antibody;

Describe the difference between active and passive immunity.

1. Active involves memory cells, passive does not; 2. Active involves production of antibody by plasma cells / memory cells; 3. Passive involves antibody introduced into body from outside / named source; 4. Active long term, because antibody produced in response to antigen; 5. Passive short term, because antibody (given) is broken down; 6. Active (can) take time to develop / work, passive fast acting;

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why. (3)

Specific primary structure; Specific tertiary structure; So only complementary to one antigen

Describe the structure of HIV

• RNA as genetic material • reverse transcriptase • protein capsid • viral envelope • attachment proteins

Deacribe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen

Th Cell binds to the antigen on the APC • This TH cell stimulates a specific B cell by the release of cytokines • B cell divides by mitosis • Forming plasma cells that release antibodies

Describe and explain the role of antibodies in stimulating phagocytosis

Bind to antigen and act as markers Antibodies cause agglutination and attract phagocytes

Describe how HIV is replicated

1. Attachment proteins attach to receptors on helper T cell/lymphocyte; 2. Nucleic acid/RNA enters cell; 3. Reverse transcriptase converts RNA to DNA; 4. Viral protein/capsid/enzymes produced; 5. Virus (particles) assembled and released (from cell);

What can change in chromosome number be cause by

Change in chromosome number can be caused in meiosis Homologous chromosomes fail to separate

Phagocytosis

Phagocyte engulfs pathogen Pathogen enters the cytoplasm of the phagocyte in a vesicle called phagosome Lysosomes fuse with vesicle releasing hydrolytic digestive enzymes Which hydrolyse pathogen Antigen presented on its cell surface membrane

Outline roles of organelles in production+transport+release of proteins in eukaryotic cells

Dna in nucleus codes for proteins Ribosomes produce protein Mitochondria produce ATP for protein synthesis Golgi body package and modify Vesicle/RER transports (remember RER can since its transporting proteins)

Give example of using monoclonal antibodies in medical treatment

Targets drugs Block antigens

Type of a white blood cell

Phagocyte

Interphase Where is majority of a life of a cell spent

Period between divisions Interphase G1

Where is genetic info carried in

Genes

How do mitochondria + chloroplast replicate

Binary fission

Genetic variation increases by

Crossing over Random fertilisation of gametes Mutatins

When does crossing over occur

During prophase+metaphase in 1st division