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Genetics_CH2
Single-Gene Inheritance
| Question | Answer |
|---|---|
| gene discovery | finding the subset of genes in the genome that influence a property |
| single-gene inheritance | certain types of inheritance patterns that may be recognized in the progeny of controlled matings called crosses |
| crosses | controlled matings that biologists do to study certain inheritance patterns |
| mutants | individual organisms having some altered form of a normal property --> especially useful in identifying single-gene inheritance patterns |
| wild type (that which is found in the wild, nature) | the normal form of any type of any property of an organism |
| genetic dissection | the use of recombination and mutation to piece together the various components of a given biological function |
| finding mutants | screen a large number of individuals, looking for a chance occurence of mutations |
| Tay-Sachs disease and cystic fibrosis | the fundamental physical and functional unit of heredity which carries information from one generation to the next; a segment of DNA composed of a transcribed region and a regulatory sequence that makes transcription possible |
| genes | work through proteins |
| single-inheritance patterns | produced because genes are parts of chromosomes, and chromosomes are partitioned very precisely down through the generations |
| Pisum sativum | garden pea (Mendel's selected research organism) |
| seven properties of investigation (Mendel) | pea color, pea shape, pod color, pod shape, flower color, plant height, and position of the flowering shoot |
| character | a polymorphism (eye color) |
| phenotype | a form taken by a character (outward appearance) |
| pure lines | all offspring produced by matings within the members of the line were identical (yellow seeded parents made yellow seeded progeny) |
| self | special type of mating that is carried out by allowing the pollen of one flower to fall on its own stigma (crossing the genes of itself) |
| parental generations | two lines that are crossed to produce progeny |
| first filial generation | progeny from the parental generations |
| second filial generation | progeny from the intercrossed F1 generations |
| gene | a heredity factor |
| alleles | one or more different forms of a gene at a single locus |
| dominant | the phenotype shown by a heterozygote |
| recessive | an allele whose phenotype is not expressed by a heterozygote |
| Mendel's first law/ the law of equal segregation | The two members of a gene pair segregate from each other in meiosis; each gamete has an equal probability of obtaining either member of the gene pair |
| zygote | a fertilized egg, the first cell that developes into a progeny individual |
| homozygote | having a pair of identical alleles |
| heterozygote | having a pair of alleles that differ |
| monohybrid | a heterozygote for one gene |
| homozygous dominant | Y/Y |
| heterozygous | Y/y |
| homozygous recessive | y/y |
| geneotypes | allelic cominations underlying phenotypes |
| diagnostic of single-gene inheritance patterns | 1:1, 3:1, 1:2:1 ratios are diagnostic of single-gene inheritance and are based on equal segregation in a heterozygote |
| monohybrid cross | a cross of two heterozygous genotypes |
| pedigree analysis | scrutiny of medical records in the hop that informative matings have been made (such as monohybrid crosses) |
| propositus | a member of the family who first comes to the attention of a geneticist |
| autosomal recessive disorders | PKU, cystic fibrosis, and albinism |
| autosomal dominant disorders | pseudoachondroplasia (a type of dwarfism), Huntington disease (neural degeneration), polydactyly, and piebald spotting |
| polymorphism | the coexistence of two or more common phenotypes of a character |
| polymorphism (morphs) | alternative phenotypes are often inherited as alleles of a single autosomal gene in the standard Mendelian manner |
| dimorphism | simplest type of polymorphism (just two morphs) - ex. ability to tast the chemical phenylthiocarbamide (d0m. vs. rec. not tasting) |
| x-linked recessive disorders | red-green color blindness, hemophilia, Duchenne muscular dystrophy, testicular feminization syndrome aka androgen insensitivity syndrome |
| x-linked dominant disorders | hypophosphatemia (type of vitamin D-resistant rickets), and some forms of hypertrichosis (excess body and facial hair) |
| SRY gene | the gene that plays a primary role in maleness (testis determining factor) |
| product rule | the probability of two independent events both occurring is the product of their individual probabilities |
| gamete formation | cells divide as well as the chromosome pairs, carrying gene pairs |
| mitosis and meiosis | the two types of nuclear division that take place in eukaryotic cells |
| mitosis | ysomatic (body) cells divide to increase their number (can take place in diploids or haploids... either 2n --> 2n + 2n or n --> n + n) |
| meiocytes | specialized diploid cells that divide to produce sex cells such as sperm and egg in plants and animals or sexual spores in fungi or algae --> algae and fungi form transient diploid cell |
| meiosis | the two accompanying nuclear divisions to the two cell divisions (only occurs in diploid cells to produce haploid cells... 2n --> n + n + n + n) |
| gametophyte | small structure composed of haploid cells that will produce gametes (corn) |
| endosperm | nutritive tissure that surrounds the embryo which is derived from the zygote |
| synthesis (S phase) | DNA is replicated |
| sister chromatids | identical and produced from replication (paired) |
| meiosis | centromere does not divide in first division of meiosis |
| meiosis | homogous pairs of sister chromatids unite to form a bundle of four homolgous chromatids |
| synapsis | the joining of homologous chromatids that relies on the properties of a macromolecularassemblage called the synaptonemal complex (SC) which runs down the center of the pair |
| dyad | replicate sister chromosomes together |
| bivalent | the unit comprising the pair of synapsed dyads |
| tetrad | the four chromatids that make up a bivalent |
| crossing over | takes place at the tetrad stage and changes the combinations of alleles of several different genes but does not affect the single-gene inheritance patterns |
| products of meiosis | four haploid cells |
| spindle fibers | polymers of the molecule tubulin that pull the chromosomes apart |
| depolymerization | cause of the pulling apart of the chromosomes due to the shortening of the fibers |
| most mutations | alter the amino acid sequence of the gene's protein product, resulting in reduced or absent function |
| haploid organisms such as fungi and algae | show equal segregation directly in one individual meiocyte because products of meiosis are temporarily held in a type of sac, called an ascus |
| promoters | sites that are important in transition initiation |
| ascus | a membranous sac containing a tetrad with two genotypes of each or 4 spores |
| haploid genetics | requires the analysis of only one meiosis |
| diploid cross | requires the analysis of both the male and female parent |
| haploid | all alleles are expressed in the phenotype because there is no masking of recessives by dominant alleles on the other homolog |
| alleles | different forms of genes located at the same locus on the chromosome |
| alleles such as A and a | identical in most of their sequences and differ only at one or several nucleotides of the thousands of nucleotides that make up the gene |
| mutations | a change in the nucleotide sequence caused by a result of a rare chemical "accident" forming a new allele... can be a change, deletion or addition of a nucleotide |
| alleles with mutations | usually recessive because it usually takes only one copy of a wild-type gene to provide normal function |
| precedes both meiosis and mitosis | DNA molecule replication during S phase |
| restriction fragment length polymorphism (RFLP) | hybridizing a sequence with a probe, then a Southern hybridization will reveal if an enzyme cut DNA to a different length if the sequence codes for the cut (target site for the restriction enzyme) |
| PCR | also can be used to zero in on differences in chain length |
| molecular markers | can be used to track the inheritance of a segment of a chromosome at the some specific position in the same way that alleles of a gene do (PCR and RFLP) |
| primary phenotype of a gene | protein it produces |
| mutation in the gene encoding an enzyme | may alter the amino acid sequence in the vicinity of the enzyme's active site |
| exons | protein encoding regions |
| mutated alleles | code for a defective protein that no longer has normal function |
| important functional region of a gene | that encoding an enzyme's active site |
| intron mutations | usually prevent the processing of the normal RNA transcript --> alter splicing |
| null alleles | proteins encoded by these completely lack function |
| leaky mutations | mutant alleles that reduce the level of enzyme function (b/c some wild-type function seems to "leak" into the mutant phenotype) |
| silent mutatons | mutations that have no effect on enzyme function |
| haplosufficient | a copy of one of these genes in a diploid cell provides enough protein for normal function while the other copy of the gene is null |
| haploinsufficient | a null mutant allele will be dominant because a single copy of the wild-type gene does not provide enough protein for the normal function of the gene |
| recessive mutation ratio | a ratio of 3:1 (3 wild-type for every one mutant)... this would show that the mutant was a recessive alteration of a single gene |
| dominant mutation ratio | 1:1 (1 mutated for every one normal) |
| fungi | haploid |
| forward genetics | an approach to understanding biological function starting with random single-gene mutants and ending with detailed cell and biochemical analysis of them, oftne including genomic analysis |
| gene discovery analysis | observe phenotypic ratios in progeny --> deduce genotypes of parents (A/A, A/a, or a/a) or cross parents of known genotypes --> predict phenotypic ratios in progeny |
| testcross | the cross of an individual of unknown heterozygosity (for one gene or more) with a fully recessive parent or you can self the unknown and a 3:1 ratio will show it is heterozygous |
| tester | the fully recessive individual involved in a testcross |
| sex chromosomes | determines sex |
| X chromosomes | identical sex chromosomes in females |
| Y chromosome | considerably shorter than the X chromosome and is present in males |
| females | 44A + XX |
| males | 44A + XY |
| homogametic sex | female... during meiosis each egg receives one X chromosome |
| heterogametic sex | male... during meiosis each sperm has one X or one Y chromosome |
| sexually dimorphic | either female or male |
| drosophilia melanogaster | males have only one X chromosome and females have two X chromosomes |
| mammals | gender is determined by the presence of the Y chromosome... present = male and absence = female |
| dioecious species (plants) | showing animal-like dimorphism (females bearing flowers containing only ovaries and male plants bearing flowers containing only anthers |
| hemizygous | half zygous (X and Y) |
| X chromosome | contains many more genes than the Y chromosome |
| Y chromosome | has the gene for maleness (SRY) |
| differential regions | show sex-linked inheritance patterns |
| X linkage | shown in mutant X chromosomes (single-gene inheritance pattern) (differential region) |
| Y linkage | shown in mutant Y chromosome (differential region) |
| sex-linked gene | can show phenotypic ratios that are different in each sex |
| pseudoautosomal regions 1 and 2 | autosomal-like regions of the sex chromosomes (one or both of these regions pairs in meiosis and undergoes crossing over) |
| ZZ and ZW | genotypes of chickens and moths (females - ZW and males - ZZ) |
| trait | a form of a character (blue eyes) |
Created by:
Nicolekr
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