UNIT 1 | GENETICS + HEREDITY Flashcards
Law of Dominance
Some traits can mask other traits when both traits appear in the parents
Law of Segregation
During the formation of the reproductive cells the paired factors (genes) separate from one another and then recombine
Law of Independent Assortment
Each trait is inherited independent of one another
What is the one exception to the law of independent assortment
Blonde hair and blue eyes
Incomplete Dominance
Two alleles are neither dominant nor recessive. Both contribute to the phenotype of the offspring (a sort of blending). An example of this is snap dragons
Co-dominance and Multiple Alleles
Two alleles may contribute equally in the offspring and are both dominant
An example of this is a speckled offspring of a white chicken and a black rooster
Sex-Linked Traits
All organisms that reproduce sexually have a combination of X and Y chromosomes (Male, XY; Female, XX)
Non Disjunction
Failure of homologous chromosomes or sister chromatids to separate during cell division
What is a pedigree?
A diagram that shows the occurrence of a particular phenotype of a genetic trait from one generation to the next within a biological family
Describe a test cross
A genetic cross between homozygous recessive and a suspected heterozygous to determine the genotype
Describe a karyotype
A micrograph showing the number and visual appearance of the chromosomes
Describe meiosis
Cell division that results in four daughter cells each with half the chromosomes as the parent. The formation of gametes.
Name two cells that become a sperm and an egg
Oogonial (egg, ovary)
Spermatogonial (sperm, testes)
Both are diploid (2N)
P
F1
F2
Parental Generation
First filial generation
Second filial generation
Why do two heterozygous tall plants create three tall plants and one short plant?
The paired genes separate and recombine (law of segregation)
TtxTt=TT, Tt, Tt, tt (3:1)
Define heredity
The passing of traits from parent to offspring
Define factor
Describing a gene
Define gene
Trait
Define allele
A form of a trait
Define acquired trait
Trait that has been learned (ex scars or attitude)
Define inherited trait
Trait passed from parent or ancestor to offspring (ex eye colour)
Define autosome
Non sex chromosome
Define carrier
A female that caries a gene but does not express it in her phenotype (ex hemophilia; XRXr)
Define chromosome
Threadlike structure carrying genetic information in the form of genes
Define diploid
A cell that contains two sets of homologous chromosomes
Define fertilization
During sexual reproduction, an egg and sperm combine to form a zygote
Define gamete
Sex cell (sperm of egg)
Define genotype
Symbolic representation of a characteristic
Define haploid
A cell that contains only a single set of genes
Define heterozygous
Having two different alleles for a particular gene
Define homozygous
Having two identical alleles for a particular gene
Define homologous
Chromosomes in which one set comes from the male parent and one set from the female parent
Define multiple alleles
Three or more alternative forms of a gene
Define nondisjunction
Failure of homologous chromosomes or sister chromatids to separate during cell division
Define phenotype
Physical characteristic of an organism
Define tetrads
Four chromatids in groups of two formed in prophase one
Define synapsis
Fusion of chromosome pairs at the start of meiosis that enables crossing over to occur
Define autosomal recessive
Two copies of abnormal gene must be present in order to develop a disease
Define autosomal dominant
One copy of abnormal gene from one parent needed to get a disease
Define purebred
Organism that is the offspring of genetically similar parents that were both homozygous for a trait
Define hybrid
Organism that is the offspring of genetically dissimilar parents
Define dominant
Expressed in phenotype
Define recessive
Only expressed in phenotype when paired with another recessive allele
Define meiosis
Process in which a number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
