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mendalien genetics
unit test
| Question | Answer |
|---|---|
| homozygous | Has 2 of the same alleles (TT, tt) |
| heterozygous | Has 2 different alleles (Tt) |
| dominant | Allele that, if present, is always expressed |
| recessive | Allele that may be present, but not expressed (hidden) |
| monohybrid | A cross involving only one trait |
| dihybrid | A cross involving 2 traits |
| phenotype | Physical appearance of an organism |
| genotype | Genetic makeup of an organism |
| codominance | 2 alleles that are expressed equally |
| allele | Form of a gene for a trait |
| polygenic inheritance | Traits that are controlled by many genes |
| what are punnet squares used for? | To determine the probability of the outcome from a particular cross |
| define polyploidy. what is its effect on plants? on animals? | Polyploidy happens when an entire set of chromosomes undergoes nondisjunction during meiosis. In plants, it results in healthier plants with larger fruits. It is lethal in animals. |
| define phenylketonuria(pku). what cuases it? what is its result? how is it treated? | A metabolic disorder in which a person is missing the enzyme that breaks down the amino acid phenylalanine. It is caused by inheriting 2 recessive alleles. The result is mental retardation. It can be treated by following a diet low in phenylalanine. |
| how many chromosomes does a normal human have in each cell? how many pairs of sex chromosomes? how many pairs of autosomes? | Normal human cells contain 46 chromosomes. There is one pair of sex chromosomes, and 22 pairs of autosomes. |
| define incomplete dominance. give and example. | When the dominant allele doesn’t completely mask the recessive allele (genetic blending). A cross between red four o’clock flowers and white flowers results in pink flowers. |
| rule of dominance | there are 2 alleles that govern traits, one is always expressed and the other can be masked |
| Law of Segregation | alleles for traits are separated during meiosis, and are restored during fertilization |
| Law of Independent Assortment | alleles for different traits are inherited independently of each other |
| explain nondisjunction.what are the results? | Nondisjunction is the failure of homologous chromosomes to separate during anaphase of meiosis. It results in gametes that have too many or too few chromosomes. |
| explain the role of the enviroment in gene expression. | Genetic expression is heavily influenced by the environment.The external&internal environments of an organism can selectively turn on or off genes as needed. Ex. include tanning in the summer (external) & sexual development during puberty (internal). |
| sex linked disorders like hemophilia and color blindness are carried on which chromosome? which sex is more likely to express a sex-linked disorder?why? | Sex-linked traits are carried on the X chromosome. Males are more likely to expressed a sex-linked trait as they only have one X chromosome, while females have 2 and can be carriers. |
| what is meiosis? what is its significance within sexually reproduicing populations? | Meiosis is the process of creating gametes through 2 cell divisions. It is significant amongst sexually reproducing organisms as it ensures that the resulting offspring will have the correct number of chromosomes (prevents doubling). |
| what is sickle-cell anemia? how is it cuased? what ethnic group is most likely to have this disorder? | Sickle-cell anemia is a recessive genetic disorder where the red blood cells are abnormally shaped.caused by a mutation in the gene for hemoglobin,causing the abnormal hemoglobin.carried by those of African descent. |
| what is the advatages of sickle cell anemia? | advantage is that the allele is resistance to malaria. |
| diploid vs. haploid cells. | Diploid cells have 2 of each number of chromosome (2n). Haploid, or monoploid, cells have 1 of each number of chromosome (n). |
| what is crossing over? why is it important? | Crossing over is the exchange of genetic material between nonsister chromatids during prophase I of meiosis. It is important in that it provides genetic variability, ensuring the survival of the species in a changing environment. |
| what is down syndrome? how is it cuased? | Down syndrome is a genetic disorder where the person has inherited an extra chromosome 21 (trisomy 21). It is caused by nondisjunction during anaphase I of meiosis, |
| what are the results of down syndrome? | and results in a person of short stature, epicanthic folds of skin in the corners of the eyes, and mild to severe mental retardation. |
Created by:
giulianapie
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