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25 Cards in this Set
- Front
- Back
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What are autosomes?
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THe 22/23 chromosomes that are not sex chromosomes
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Females are X_ whilst Males are X_
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Female xx, male xy
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How many chromosomes does a gamete contain?
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23
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What is meiosis?
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Division of the cell
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What is the resulting cell when the sperm and ovum combine?
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Zygote
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What are gametes?
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The sperm and the ovum
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How many sperm are produced when meiosis is complete?
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4
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What is the likelihood that non twin siblings will be identical?
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1/ 700 trillion
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How many ovum are produced by meiosis?
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1
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What is another name for fraternal twins?
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dizygotic twins
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What factors are more likely to make an individual produce dizygotic twins?
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Age, IVF, Bad nutrition Family history, ethnicity
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What is another name for identical twins?
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monozygotic twins
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What is an allele?
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There are two forms of each gene at a chromosome - one from the mother and one from the father. Each form of these is called an allele
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If both alleles are alike, they are said to be
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Homozygous
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If both alleles are not alike they are said to be
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Heterozygous
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What is PKU?
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Recessive disorder tha affects how the body breaks down food, leading to high levels of phenylenanine, which causes mental retardation after 1 year
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Why are serious diseases caused by dominant alleles rare?
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Because if they had the dominant allele, then they were rarely live long enough to reproduce.
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Huntingonton's Disease is a rare example of a disorder that is caused by a dominant allele. Why does it continue to exist?
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Because symptoms usually do not appear until the age of 35 and the individual may have reproduced by then
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What is a mutation?
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A sudden but permanent change in a segment of DNA
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What is X- linked inheritance?
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When a harmful allele is carried on the X chromosome
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What sex is more likely to be affected by X-linked inheritance and why?
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Males because they only have 1 X chromosome
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What is genomic imprinting?
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It is when alleles are chemically marked so that one pair member is activated, regardlesss of its make up
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What is the difference between germline mutation and somatic mutation
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Germline is mutation of sex cells whilst somatic mutation is mutation of the body cells
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What is polygenetic inheritance?
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When many different genes influence the characteristic in question
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What causes down syndrome?
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95 percent of cases its the failure of chromsome 21 to seperate during meiosis, adding an extra chromosome or in other cases an extra broken piece of chromosome 21 is attached to another chromosome
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