Biology topic 3

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Features of prokayrotic cells.
Infolding of cell surface membrane (respiration), ribosomes, circular DNA, cell wall of peptidoglycan, flagellum (movement), pili (allow the bacteria to stick to surfaces), capsule (to prevent dehydration and for protection), plasmid.
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Features of a eukaryotic cell.
centrioles (formation of the spindle fibres , transport in the cell cytoplasm), mitochondria (aerobic respiration), nucelus, rough ER, ribosomes, smooth ER (makes lipids and steroids), golgi apparatus (modifies proteins and packs them ), lysosome.
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Explain the process by which newly formed proteins leave the cell.
Vesicles pinnched off the rough ER contain the protein. The vesicles fuse with the flatterned sacs of the golgi apparatus. Proteins are modified in the golgi, vesicles pinched off the golgi contain the protein which fuses with the cell membrane.
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Explain the acrosome reaction.
The acrosome in the head of the sperm fuse with the cell surface membrane of the sperm and releases digestive enzymes. These break down the zona pellucida which allows the two nuclei to fuse.
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Explain the cortical reaction.
When the sperm penetrates the membrane surrounding the egg chemicals released by the ovum cause the zona pellucida to thicken preventing any other sperm from entering.
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How does meiosis create genetic variation?
Independent assortment, crossing over.
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Explain independent assortment.
During meosis only one chromsome from each pair ends up in the gamete. The chromosome that is selected from the pair is completely random.
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Explain crossing over.
During the first division of meiosis homologus chromosomes come into contact meaning all 4 chromotids come into contact. At these contact points known as chiasmata sections of DNA are exchanged between the chromosome pair.
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How does crossing over occur between the sex chromosomes?
It doesn't.
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What does it mean when two genes are linked?
One particular allele for a gene is inherited with another particular allele for a different gene.
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Why are some genes linked?
Any two genes with a locus on the same chromosome are linked.
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How can two alleles that are linked not be inherited together?
If crossing over occurs.
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Why do sex linked diseases occur?
As the Y chromosome is shorter than than the X chromsome so some genes dont have a locus on the Y chromosome. This means only one recessive allele needs to be passed on from the mother to the son to mean he is affected.
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Describe the different stages of the cell cycle.
Interphase contains G1 (creation of new organelles and membranes), S (DNA synthesis), G2 (new organelles and alleles). Mitosis and cytoplasmic division then occur.
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What stage affects the time it takes for the cell to replicate?
G1 (G2 and S are relatively constant in length)
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What are nucleoli?
The place in the nucleus where ribosomes are formed.
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What occurs during prophase?
Chromosomes condense and become shorter and thicker, forming two chromotids. The two chromatids are joined at the centromere. The centrioles move to the poles of the cell and spindle fibres attach to them.
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What occurs during metaphase?
The chromsomes move to the equator and their centromeres become attached to the spindle fibres.
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What occurs during anaphase?
The spindle fibres shorten and the centromeres split. One chromotid is pulled to each of the poles. The spindle then breaks down.
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What occurs during telophase?
Chromosomes unravel, nucleur envelope reforms. Cytoplasmic division then occurs.
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How do bacteria replicate?
Binary fission.
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What does the outer layer of the blastocyst become?
The placenta.
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What kind of potentcy do adult stem cells have?
Multipotent (can only specialize into a small range of cells)
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How does the epigenome work?
The epigenome influences which genes are transcribed in a cell. By adding methyl groups to the DNA is prevents RNA polymerase from binding to the DNA. DNA is wrapped around histones and by adding methyl groups it meand the DNA is bound more tightly.
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How does the lac operon model work with respect to lactose?
When lactose is not present a lactose repressor molecule binds to the operator gene. This means the RNA polymerase cannot bind to the promoter region so transcription cannot occur. If lactose is present it binds to the repressor molecule.
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How do cells organise themselves into tissues?
Cells have adhesion molecules on their cell surface membrane. These help the cells recognize other similar cells and bind to them. The exposed section of the molecule binds to complementary proteins on the other cell.
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What is discontinous variation?
When a characteristic is controlled by a single gene.
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What is it called when mutiple genes and the environment have an effect on a characteristic?
Multifactorial.
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How does melanin work?
Melanocyte stimulating hormone stimulates melanocytes to produce melanin. Melanin is packed into organelles called melanosomes. These collect around the nucleus of cells protecting them from uv light. People with darker skin have more receptors (MSH)
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What happens to the melanocyte cells when exposure to UV light increases?
More MSH is produced and more MSH receptors form so more melanin is produced.
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What are the different ways cancer can be caused?
physical factors such as UV light, chemicals (carcinogens), mutations caused when DNA incorrectly replicates. You can also inherite genes which increase the chance of you having cancer.
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Which two genes have a role in the cell cycle and are related to cancer?
Oncogenes (stimulates the transition from one stage in the cell cycle to the next), tumour suppressor genes (produces proteins which stop the cycle).
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Other cards in this set

Card 2

Front

Features of a eukaryotic cell.

Back

centrioles (formation of the spindle fibres , transport in the cell cytoplasm), mitochondria (aerobic respiration), nucelus, rough ER, ribosomes, smooth ER (makes lipids and steroids), golgi apparatus (modifies proteins and packs them ), lysosome.

Card 3

Front

Explain the process by which newly formed proteins leave the cell.

Back

Preview of the front of card 3

Card 4

Front

Explain the acrosome reaction.

Back

Preview of the front of card 4

Card 5

Front

Explain the cortical reaction.

Back

Preview of the front of card 5
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