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32 Cards in this Set
- Front
- Back
What does the nucleus of a cell contain?
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Chromosomes |
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What do chromosomes do? |
Carry genes
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How many sets of genes do the nuclei of males and female sex cells contain? |
One |
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How many sets of gens do offspring cells contain? |
Two |
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What are the two main causes of variation between individuals of the same kind of organism? |
environmental causes |
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Put these things into size order from largest to smallest: Genes, DNA and chromosomes |
One chromosome --> many genes --> lots of DNA |
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What are the features and characteristics of asexual reproduction?
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All genetic information from one parent. All offspring genetically identical to parent. Little variation. Identical copies produced by asexual reproduction are clones. |
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What are the features and characteristics of sexual reproduction?
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There is mixing of genetic information. Offspring show variation. In animals the sex cells are egg and sperm. Off spring are similar to both parents but not identical. Combination of two sets of genes. |
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Why is variation important to survival? |
Some characteristics may have a better chance of surviving than others. |
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How many pairs of chromosomes do humans have? |
23 |
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What chromosomes do human females have which make them female? |
Two X chromosomes (XX) |
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What chromosomes do human males have which make them male? |
An X and a Y chromosome (XY)
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What are alleles?
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A different form of a gene |
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What is the phenotype?
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Physical appearance of the characteristic (e.g. dimples or no dimples) |
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What is the genotype?
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The genetic make up (e.g. DD, Dd or dd) |
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What is meant when two alleles are homozygous? |
Both alleles are the same. DD = homozygous dominant dd = homozygous recessive |
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What is meant when two alleles are heterozygous?
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The two alleles are different (Dd)
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What is monohybrid inheritance?
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The inheritance of a single characteristic controlled by a pair of alleles |
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What did Gregor Mendel do? |
Observed patterns of inheritance in pea plants before chromosomes were discovered. Mendel realised that there are separate units of inheritance. |
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What are chromosomes made of? |
DNA |
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What is DNA made up of?
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DNA contains four compounds called bases. |
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What are genes? |
A sequence of three bases is the code for a particular amino acid. The order of the bases controls the order of the amino acids in the protein. |
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Is polydactyly dominant or recessive?
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Dominant |
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Is cystic fibrosis caused by the dominant or recessive allele?
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What does cystic fibrosis do? |
The allele affects cell membranes and causes the production of thick sticky mucus. |
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Is sickle-cell anaemia caused by the dominant or recessive allele? |
Recessive |
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What does sickle-cell anaemia do? |
people who are homozygous recessive normally do not survive. |
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What happens if you are heterozygous for the sickle-cell anaemia allele?
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The person has some sickle blood cells and this gives them protection from the malaria parasite.
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How is Down's syndrome caused? |
(A mistake during meiosis could lead to a cell with too many or too few chromosomes) |
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What are the results and problems that arise from screening embryos?
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Results of the test may give parents choices. In IVF the embryos are screened and only healthy babies are inplanted. some people may think that it is unethical to destroy unhealthy embryos. |
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How do gene probes work?
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A gene probe that will bind onto the gene for a specific disorder is produced. The gene probe has a fluorescent chemical attached to it. The probe is added to a mixture containing the DNA sample. UV light is used to detect the probe. If the probes have attached to the faulty allele and fluoresce, the embryo or foetus is affected by the condition. |
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What are the concerns about embryo screening?
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The reliability of the information of the screening process. Decisions about terminating the pregnancy. |