Unit 5 Flashcards
Chapters 13, 14, + 15
Heredity
Transmission of traits from one generation to the next
Genetic Variation
The demonstrated differences between individuals of the same species
Genetics
The scientific study of heredity and variation
Locus
The specific position on a chromosome where certain genes are located
Asexual Reproduction
Reproduction that only requires a single individual’s DNA and produces identical offspring (clones)
Sexual Reproduction
Reproduction that requires 2 individual’s DNA to produce unique daughter cells with combinations of genes from both parents
Karyotype
An ordered display of the pairs of chromosomes in a cell
Homologous Chromosomes
Chromosomes that pair up and are about the same size/ contain the same genetic information (yet possibly different alleles)
Tetrad
The entire unit of homologs with 4 chromosomes total
Autosomes
The pairs of chromosomes that exclude the sex chromosomes (1-22 in humans)
Diploid Cells
Cells that have 2 sets of chromosomes (2n)
Haploid Cells
Cells that contain a single set of chromosomes (n)
Fertilization
The union of 2 gametes (1 from each parent) that produces a single diploid cell –> zygote
Alternation of Generations
Life cycles other organisms exhibit with both diploid and haploid multicellular stages
Chiasmata
X-shaped regions shared by homologous pairs were crossing over occurs in Prophase I
Synaptonemal Complex
Zipper-like structure that holds homologs together
Alleles
Different variations of gene expressions for a particular trait; dominant or recessive
Recombinant Chromosomes
The resulting chromosomes after crossing over
Random Fertilization
Process in which any sperm has the chance of fusing with any ovum (unfertilized egg); gametes undergoing meiosis are not chosen
Natural Selection
The evolutionary favoritism of genes that chance survival by environment
Character
A heritable feature that varies among individuals of the same species
Trait
Each variant for a character
True-Bred
Used to describe individuals that are in a long-line of homozygous phenotypes
Hybridization
Process of mating 2 contrasting true-bred individuals
P Generation
The true-bred parents
F1 Generation
The hybrid offspring
F2 Generation
Result of F1 individuals self-pollinating or cross-pollinating with other F1 individuals
Mendel’s Law of Segregation
During meiosis, the 2 alleles segregate and each gamete has equal probability of containing either allele
Dominant Trait
The allele that when heterozygous is present in the phenotype of the individual over the recessive phenotype; masks recessive trait
Recessive Trait
Allele that is masked by dominant allele when heterozygous, so only expressed phenotypically when homozygous for recessive
Homozygous
When an organism has 2 identical alleles for a character
Heterozygous
When an organism has 2 different alleles for a gene
Testcrossing
When an individual is bred with a homozygous recessive individual to determine the genotype as either heterozygous or homozygous dominant
Monohybrid
Offspring produced that are heterozygous for a character (F1 generation)
Dihybrid
When 2 true-breeding parents differing in 2 characters are crossed so the offspring is heterozygous for both traits
Mendel’s Law of Independent Assortment
Each pair of alleles on nonhomologous chromosomes separate independently of each other pair of alleles due to the random sorting of homologs along the metaphase plate (not all maternal DNA lines up one side and not all paternal DNA on the other)
Multicharacter Cross
When 2+ independent monohybrid crosses occur simultaneously
Incomplete Dominance
Heterozygous phenotypes reflect a mixture of the two homozygous phenotypes (no allele is completely dominant over the other)
Codominance
Both phenotypes are expressed when heterozygous
Plieotropy
Property of most genes to have multiple phenotypic effects
Epistasis
When a gene at one locus alters the phenotypic expression of a gene at another locus
Quantitative Characters
Characters that vary across a population
Polygenic Inheritance
Additive effect of multiple genes on a single phenotype
Multifactoral
Genes that can be influence by environmental influences during inheritance
Carriers
Heterozygous individuals that appear phenotypically normal but can pass down the recessive allele to their offspring (especially dangerous regarding sex-linked genes in heterozygous mothers)
Wild Type
Describes predominantly common phenotypes observed within a population
Mutant Phenotypes
Alternative traits from the wild type
Sex-Linked Genes
A gene that is located on either sex chromosome (X or Y); males have a higher chance of inheriting the recessive phenotype
Barr Body
A mass in the nucleus of female cells that is created from the inactive X chromosome condensing
Linked Genes
Genes located on the same chromosome that tend to be inherited together due to location; goes against Mendel’s second law
Parental Phenotypes
Inherited phenotypes that mirror the phenotypes expressed by the parents
Genetic Recombination
The production of offspring with a combination of traits differing from either parent –> recombinants
Genetic Map
An ordered list of the genetic loci along a particular chromosome
Linkage Map
A genetic map of a chromosome drawn based on recombination frequencies
Nondisjunction
When pairs of homologous chromosomes (or sister chromatids) do not separate correctly during meiosis
Aneuploidy
The result of fertilizing gametes in which nondisjunction has occurred; zygotes have abnormal (extra/missing) chromosomes
Polyploidy
Condition in which an organism has more than 2 complete sets of chromosomes
Genomic Imprinting
Variations in phenotypes that depend on which parent passed down the allele due to the silencing of genes caused by methylation of cysteine nucleotides
Extranuclear Genes
Genes found in the organelles in the cytoplasm (mitochondrial, chloroplast, and ribosomal DNA)
