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Chapter 23a
| Question | Answer |
|---|---|
| differences in heritable traits. it is a prerequisite for evolution by natural selection ex. color variation in hypothetical beetle population | genetic variation |
| refers to the differences in genes or other DNA sequences among individuals | genetic variation |
| the product of inherited genotype and environmental influences | phenotype |
| occurs when the allele frequencies of a population change over time | evolution |
| what mechanisms can cause the evolution of populations? | natural selection, genetic drift, gene flow |
| phenotypic differences determined by a _____ can usually be classified on an “either-or” basis ex. pea flowers are either purple or white | single gene |
| phenotypic differences determined by _______ usually vary in gradations along a continuum ex. coat color in horses or height in humans | two or more genes |
| ____ is quantified by the percentage of heterozygous loci (14%) in a population (86%) | gene variability |
| ____ is quantified by comparing the nucleotide sequences of two or more individuals | nucleotide variability |
| ____rarely results in phenotypic variation 1. most nucleotide differences occur within non coding DNA segments (introns) 2. variations in coding regions (exons) rarely change the amino acid sequence of the encoded protein | nucleotide variability |
| phenotypic variation can result from_____, as well as genetic differences ex. differences in diet cause the variation between siblings | environmental influences |
| genetic variation originated when new genes and alleles arise by _______,______ or other processes ex. this occurs rapidly in organisms with short generation times | mutation, gene duplication |
| which organisms would exhibit greater replication frequency? | organisms with short generation times |
| which organisms would exhibit greater mutation frequency? | organisms with shorter generation time |
| _____can produce genetic variation by recombining existing alleles | sexual reproduction |
| new alleles arise by changing the nucleotide sequence. A _____ can form a new allele ______can be caused by replication errors or exposure to certain types of radiation or chemicals. even a point____can have a significant impact on phenotype | mutation |
| most ____ that alter phenotype are at least slightly harmful. harmful______ that are recessive can be hidden from selection in heterozygous individuals | mutations |
| carriers mask the affect of the mutated allele. this is called _______ ex. Ss (carrier) _____maintains a pool of alleles that could be beneficial if the environment changes ex. if malaria became a pandemic, then the mutation (Aa) could be beneficial | “heterozygote protection” |
| what percent of nucleotide alterations do not affect the exons | 1.5% |
| point mutations in _____ usually cause neutral variation, variation with no selective advantage or disadvantage ex. 98.5% code for no amino acid | noncoding regions |
| neutral variation in a ______(exon) can be silenced due to the redundancy in the genetic code | coding region |
| mutations that result in a change in phenotype are sometimes, though rarely, beneficial. in multicellular organisms, only _____in cell lines that produce gametes are passed to offspring | mutations |
| ______ or _____ can occur at large chromosomal mutations that delete, disrupt, or rearrange many loci. this is usually harmful | Altering Gene Number or Position |
| ____are usually harmful | Deletions ex. deletion in chromosome 5 causes mental retardation |
| _____of small segments of DNA, including genes, is a key potential source of genetic variation. if _____genes persist over generations, then mutations can accumulate, and new functions may arise | duplication ex. duplication of chromosome 1 causes distinctive facial features |
| ____(hox) encode transcription factors that regulate gene expression and specify the identity of body segments | homeotic genes |
| mutation rates are low in _____ and ____, averaging about one in every 100,000 genes per generation | animals and plants |
| _____have lower mutation rates, but shorter generation times allow mutations to accumulate rapidly | prokaryotes |
| mutations can accumulate rapidly in ___ due to short generation times and rapid mutation rates | viruses ex. omicron spreads more easily than earlier variants |
| most genetic variation in sexually reproducing organisms results from | recombination of alleles |
| new combinations of existing alleles occur through three mechanisms: | 1. crossing over (exchange of genetic material between homologous chromosomes during meiosis) 2. independent assortment (random distribution of chromosomes into gametes during meiosis) 3. fertilization (random combination of gametes) |
Created by:
Taylormorey