PC705 Module 1

Age-dependent penetrance- - answer-when the phenotype appears normal until later in life when the genotype is expressed Oogonia - answerimmature female diploid germ cells Haploid - answerrefers to both chromosome number and DNA content Genotype - answerFull hereditary information Chromosomes - answercontain genes. Chromosomes are temporary but consistent state of condensed DNA for the purpose of cell division phenotype - answerThe outward appearance of an individual, which is the result of both genotype and the environment Genes - answerare composed of sequences of deoxyribonucleic acid (DNA) Two primary constituent of chromosomes are - answerDNA & proteins such as histones locus - answerEach gene occupies a position along a chromosome known as a _____--the "_____" is the location of the gene on the chromosome. The _____ is a "page" of the chapter in which the recipe is located. Allele - answeris a variant form of a given gene Ploidy - answeris the actual number of chromosomes present in a single-cell nucleus at mitosis dominant - answerThe allele whose effects are observable recessive - answerThe allele whose effects are hidden Codominance - answerwhen both alleles are expressed Carrier - answera person who has a disease-causing allele but is phenotypically normal Autosomal dominant (AD) - answerhave controlling gene alleles located on the autosomal chromosome, is expressed whether both alleles are dominant or only one allele is dominant Meiosis - answerthe conversion of diploid germ cells to haploid gametes Gametogenesis - answerrequired in converting diploid germ cells into haploid gametes, special cell division in which the chromosome number is reduced to half in the cells when does cell division start for oogonia? - answercell division starts in fetal life, by 9 wks the ovary has at least ½ million, by 5th month several million diploid oogonia are present in each of the ovaries Spermatogonia - answerimmature male germ cells Where are immature male germ cells produced? - answerproduced in the seminiferous tubules of the testes When are immature male germ cells produced? - answerlate in fetal development Mode of inheritance - answerhow a disease is passed on through generations how often do autosomal dominant genes occur? - answerrarely Sex-linked recessive - answera disease carried on the X chromosome that is recessive, male will be affected because they only have one X chromosome and the Y chromosome does not carry a normal allele Monogenic traits - answer(single gene traits) expression is determined by the input of the two alleles of a single gene Polygenic traits - answerinvolve the input of more than one gene Pedigree chart - answersummarizes family relationships and shows which members of a family are affected by a genetic disease Penetrance - answerthe percentage of individuals with a specific genotype who also exhibit the expected phenotype; how often a gene is expressed within a population when it is present Incomplete penetrance - answermeans the individuals who have a disease-causing allele may not exhibit the disease phenotype at all Recurrence risk-- - answerchance a child will have disease Expressivity - answeris the extent of variation in phenotype associated with a particular genotype, the gene is always expressed Factors affecting expressivity - answer--Genes at other loci can modify expression "modifier genes" --Environmental factors --Different types of mutations can affect severity Why are x-linked recessive disorders traits expressed more in males than females? - answer--Because males only have one X chromosome and the Y chromosome does not carry a normal allele to offset the abnormal one on the X chromosome. --Y chromosome has about 300 proteins encoding genes, most of which have to do with male characteristics --X chromosome has about 1500 single gene alleles most of which are not represented on the Y chromosome Regression to the mean - answerextremes of a condition or trait become more average over time in successive generations Another term for complex traits and diseases - answerAnother term for multifactorial traits and diseases Modifier genes - answergenes that contribute to a trait but are not the primary cause of its expression Risk alleles - answergene variants that increase a person's risk of developing the phenotype Threshold - answernumber of risk alleles needed to express the disorder has just been met Liability model - answerestimate of the risk of experiencing a complex disease based on the number of risk alleles in her/her kindred Triploidy - answeran entire extra SET of chromosomes Trisomy - answeran extra SPECIFIC chromosome environmental factors which can cause epigenomic changes - answerMother's diet Radiation exposure Foreign chemicals Even behaviors Developmental plasticity - answerability of the environment to cause different phenotypes from