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37 Cards in this Set
- Front
- Back
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What is the chance of Down's Syndrome? What chromosome is it on? |
1/1000 21 |
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When does down's syndrome occur? |
When nondisjunction occurs One daughter cell will have no chromosome 21 and not produce a viable embryo. The other has down’s syndrome |
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What is this called? How many chromosomes does the child have? |
This creates a trisomy of chromosome 21 The child has 47 chromosomes |
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What is the Down's syndrome where only part of the third chromosome joins the daughter cell? |
Translocation Down's |
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When does Translocation Down's occur? What % of Down's people have this? |
When part of chromosome 21 attaches to chromosome 14 5% |
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What is the name for cells with the correct number of chromosomes? |
Euploid |
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What is the name for cells with the wrong number of chromosomes? |
Aneuploid |
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What is it called when cells are more than 2n? |
Polyploid |
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How does accidental polyploidy happen? |
Defect in spindle fibres during meiosis (anaphase I+II) may cause all chromosomes to go to one end of the cell, this will create a triploid cell when fertilised. |
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What happens if two diploid gametes fuse?
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it becomes tetraploid (4n) |
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What is endomitosis? |
It is chromosome replication without cytokinesis after. |
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What can endomitosis produce? |
This can produce triploids which then might undergo endomitosis again to become hexaploid (6n).
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Give an example of a 3n organism |
Seedless watermelons |
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Give an example of an 8n organism |
Strawberries |
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What is a carcinogen? |
An agent that causes cancer |
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What is a tumour suppressor gene? |
A gene that regulates mitosis to prevent excessive division |
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What is a tumour? |
A bundle of cells after excessive division |
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What are the 2 types of tumour? |
Benign and Harmless or Malignant and Invasive |
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What are the 3 things that happen if a TSG is mutated? |
Doesn't repair DNA or Doesn't prevent cell from entering S phase or Doesn't initiate apoptosis if DNA damage isn’t repaired |
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What is a proto-oncogene?
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It is a gene that codes for a protein that contributes to cell division |
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What happens if mutated? |
May cause this to become an oncogene which causes excessive amounts of these proteins to be built |
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How may it become mutated? |
If chromosomes rearrange and it puts the proto-oncogene next to a permanently activated gene |
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Give another way it may become mutated? |
If there is an extra copy off the proto-oncogene. Too much protein will be made and excessive mitosis will occur |
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Define Variation |
Differences between members of the same species |
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What are the 3 causes of variation? |
Nature - Genetics Nurture - Environment Epigenetics |
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What is epigenetics? |
When the environment affects the expression of genes by altering how they are transcribed, without changing the nucleotide sequence |
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What are the 2 types of epigenetics? |
DNA methylation and Histone Modification |
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What is DNA methylation? |
When Cytosine becomes Methylcytosine and therefore is less likely to be transcribed as Guanine is less likely to attach |
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What is histone modification? |
Changes to histone proteins alter their interactions with DNA which makes the coiling around histones more relaxed |
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What is the effect of histone modification? |
Makes it more accessible to RNA polymerase which increases transcription |
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Histone modification, What amino acid should an Acetyl group affect? |
Lysine |
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Histone modification, What amino acid should a Methyl group affect? |
Lysine and Arginine |
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Histone modification, What amino acid should a Phosphate group affect? |
Serine and Threonine
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What is Progressive Differentiation? What can epigenetics do to this? |
During growth of cells from stem cells, only the correct enzymes are made for that cell's development. Change what proteins are made by each cell |
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What are 2 uses of Epigenetics? |
Genetic Imprinting X-Inactivation |
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What is genetic imprinting? |
It allows you to choose which parent’s genes are expressed so medical conditions are less likely |
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What is X-Inactivation? |
Turn one X chromosome off to stop codominance e.g. in fur colour speckles |
