Genetics Flashcards
Gene
the basic unit of heredity
Chromosomes
where genes are located
Alleles
the alternative forms of multiple genes
Genotype
the genetic makeup of an individual
Phenotype
the physical manifestation of the genetic makeup of an individual
Law of Segregation
- genes exist in alternative forms
- an organism has two alleles for each inherited trait (one from each parent)
- two alleles segregate during meiosis
- the expressed allele is the dominant one and the silent allele is the recessive
- organisms that contain two copies of the same allele are homozygous & organisms that carry two different alleles are heterozygous
- the dominant allele is expressed in the phenotype
Monohybrid Cross
- applies when only one trait is being studied in the particular mating
- parental generation: the individuals being crossed
- filial generation: the progeny generations
Punnett Square
- a way of predicting the genotypes expected from a cross drawing
Test Cross
-a diagnostic tool used to determine the genotype of an organism
Law of Independent Assortment
the inheritance of one such trait is completely independent of one another
Incomplete Dominance
if the phenotype of heterozygate is an intermediate of the phenotypes of the homozygates, blending occurs
Codominance
occurs when multiple alleles exist for a given gene and more than one of them is dominant, there is no blending
Sex Determination
- most chromosomes exist as pairs of homologous called autosomes
- all humans have 22 pairs of autosomes
- women: XX men: XY
- sex linked: genes located on the X or Y chromosomes
Sex Linkage examples
homophilia or color-blindness
Environmental Facts
- can affect the expression of a gene
- interaction between the environment and the genotype produces the phenotype
- temperature also influences the hair color
Cystoplasmic Inheritance
cytoplasmic genes may interact with nuclear genes and are important in determining the characteristics of their organelles
Nondisjunction
the failure of homologous chromosomes to separate properly during meiosis I or the failure of sister chromatids to separate during meisois II
Chromosomal Breakage
may occur spontaneously or be induced by environmental factors
Mutations
- changes in the genetic information coded in the DNA of a cell
- in somatic cells, it can lead to tumors
- in sex cells (gametes), it will be passed down to offspring
Mutagenic agents
- induce mutations (x-rays, UV rays, and radioactivity)
- inhibit spindle formation
- can be carcinogenic
Point Mutation
- a nucleic acid is replaced by another nucleic acid
- stop codons can be lethal
Frame Shift Mutation
nucleic acids are inserted into the genome sequence (lethal)
Phenylketonuna (PKU)
a molecular disease caused by the inability to produce the proper enzyme for the metabolism of phenylalanine
Sickle-cell anemia
a disease in which red blood cells become crescent shaped b/c they contain defective hemoglobin
Bacterialgenome
consists of a single circular chromosome located in the nucleic acid region of the cell
Replication
begins at a unique origin of replication and proceeds in both directions simultaenously
5’ to 3’ direction
Genetic Variance
-reproduce by binary fission (a sexual process)
Transformation
the process by which a foreign chromosome fragment (plasmid) is incorporated into the bacterial chromosome via recombination
Conjugation
- sexual mating in bacteria
- the transfer of genetic material between two bacteria that are temporarily joined
Transduction
occurs when fragments of the bacterial chromosome become packaged into the viral progeny produced during such a viral infection (bacteriophages)
Recombination
occurs when linked genes are spearated
Transcription
based on the accessibility to control DNA polymerase, which is directed by an operon - includes an operon region and a promoter region
Inducible systems
- the repressor binds to the operator, forming a barrier that prevents RNA polymerase from transcribing the structural genes
- for transcription to occur, an inducer must bind to the repressor (inducer-repressor complex)
- the inducer is usually the substrate
Repressible Systems
- the repressor in inactive until it combines with the corepressor
- corepressors are often end products of the biosynthetic pathways they control
