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AP Biology: Unit 4
AP Biology: Unit 4 (Ch.13, 14, & 15)
| Term | Definition |
|---|---|
| Genes | segments of DNA that code for basic units of heredity - offspring acquire genes from parents by inheriting chromosomes |
| Asexual Reproduction | - Produces clones (genetically identical) - Single parent - Little variation in population - only through mutations - Fast and energy efficient |
| Sexual Reproduction | - Meiosis produces gametes (sex cells) - 2 parents: male/female - Lots of variation/diversity - Slower and energy consumptive |
| Somatic (body) Cell | 2n = 46 chromosomes |
| Autosomes | 22 pairs of chromosomes that do not determine sex |
| Sex chromosomes | X & Y - Females: XX - Males: XY |
| Gametes (n=23) | 22 autosomes + 1 sex chromosome - Egg: 22 + X - Sperm: 22 + X/Y |
| Karyotype | a picture of an organism’s complete set of chromosomes - largest --> smallest pair |
| “Immortal” Cells | do not die after a few divisions |
| Life Cycle | reproductive history of organism, from conception --> production of own offspring |
| Meiosis | cell division that reduces # of chromosomes (2n --> n) - creates gametes - cells divide twice - result: 4 daughter cells, each with half as many chromosomes as parent cell purpose: to reproduce |
| Fertilization | combines gametes (sperm + egg) - fertilized egg: zygote (2n) |
| Zygote | fertilized egg - zygote divides by mitosis to make multicellular diploid organism |
| Meiosis 1: Interphase | chromosomes replicated/duplicated |
| Meiosis 1: Prophase 1 | crossing over at the chiasmata |
| Synapsis | homologous chromosomes pair up - Prophase 1 |
| Tetrad | 4 sister chromatids |
| Meiosis 1: Metaphase 1 | tetrads line up |
| Meiosis 1: Anaphase 1 | pairs of homologous chromosomes separate - sister chromatids still attached by centromere |
| Meiosis 1: Telophase 1 & Cytokinesis | haploid set of chromosomes in each cell - each chromosome = 2 sister chromatids - some species: chromatin & nucleus reforms |
| Meiosis 2: Prophase 2 | - no interphase - no crossing over - spindle forms |
| Meiosis 2: Metaphase 2 | chromosomes line up |
| Meiosis 2: Anaphase 2 | sister chromatids separate |
| Meiosis 2: Telophase 2 | - 4 haploid cells - nuclei reappear - each daughter cell genetically unique |
| Genetic Variation: crossing over | exchange genetic material - recombinant chromosomes - explains why some linked genes get separated during meiosis - meiosis: prophase 1 |
| Genetic Variation: independent assortment of chromosomes | random orientation of homologous pairs in Metaphase |
| Genetic Variation: random fertilization | any sperm + any egg - 8 million X 8 million = 64 trillion combinations! |
| P (parental) generation | true breeding plants |
| F1 (first filial) generation | offspring |
| F2 (second filial) generation | F1 offspring |
| Alleles | alternate versions of a gene - I^A, I^B, i |
| Dominant (P) | expressed |
| Recessive (p) | hidden |
| (Mendel's Principles) 1. Alternate version of genes (alleles) cause... | ...variations in inherited characteristics among offspring |
| (Mendel's Principles) 2. For each character... | ... every organism inherits one allele from each parent |
| (Mendel's Principles) 3. If 2 alleles are different... | ...the dominant allele will be fully expressed & the recessive allele will have no noticeable effect on offspring’s appearance |
| (Mendel's Principles) 4. Law of Segregation | the 2 alleles for each character separate during gamete formation |
| Homozygous | 2 same alleles (PP or pp) |
| Heterozygous | 2 different alleles (Pp) |
| Phenotype | expressed physical traits |
| Genotype | genetic make up |
| Punnet Square | device for predicting offspring from a cross |
| Testcross | determine if dominant trait is homozygous or heterozygous by crossing with recessive (pp) |
| Law of Independent Assortment | each pair of alleles segregates (separates) independently during gamete formation |
| Monohybrid cross | study 1 character |
| Dihybrid cross | study 2 characters |
| Complete Dominance | heterozygote and homozygote for dominant allele are indistinguishable |
| Incomplete Dominance | F1 hybrids have appearance that is between that of 2 parents |
| Codominance | phenotype of both alleles is expressed - I^A, I^B |
| Multiple Alleles | gene has 2+ alleles |
| Rh factor | protein found on RBC’s. - Rh+ = has protein - Rh- = no protein |
| Polygenic Inheritance | the effect of 2 or more genes acting upon a single phenotypic character |
| Nature and Nurture | both genetic and environmental factors influence phenotype |
| Pedigree | diagram that shows the relationship between parents/offspring across 2+ generations |
| Chromosome theory of inheritance | - genes have specific locations (loci) on chromosomes - chromosomes segregate and assort independently |
| Sex-linked gene | located on X or Y chromosomes - fathers passes to daughter, mother passes to both - males express recessive trait on the single X (hemizygous) - females can be affected or carriers |
| Sex-linked disorders | - colorblindness - Duchenne muscular dystrophy - hemophilia |
| Barr body | inactive X chromosome - regulate gene dosage in females during embryonic development |
| SRY gene | sex-determining region of Y |
| Genetic Recombination | production of offspring with a new combo of genes from parents - if offspring looks like parents: parental type - if different from parents: recombinants |
| Linked Genes | located on same chromosome & tend to be inherited together during cell division - contradicts Independent Assortment |
| Linkage Map | genetic map that is based on % of cross-over events - 1 map unit = 1% recombination frequency - express relative distances along chromosomes |
| 50% Recomnination | - far apart on same chromosome - on 2 different chromosomes |
| Genomic Imprinting | phenotypic effect of genes depends on whether from M or F parent |
| Methylation | silence genes by adding methyl groups to DNA |
| Amniocentesis | remove amniotic fluid around fetus to culture for karyotype |
| Chorionic villus sampling | insert narrow tube in cervix to extract sample of placenta with fetal cells for karyotype |
| Nondisjunction | chromosomes fail to separate properly in Meiosis 1 or Meiosis 2 - karyotyping can detect nondisjunctions - only in homologous chromosomes |
| Aneuploidy | incorrect # chromosomes |
| Polyploidy | 2+ complete sets of chromosomes - 3n or 4n |
| Diploid Cells | 46 |
| Haploid Cells | 23 |
| At the end of Meiosis 1, how many cells are there? | 2 haploid cells |
| True-Breeding | organism that will always pass down a specific phenotype trait |
| Locus | position of allele on a chromosome |
Created by:
tessamcelrone
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