Genetics
Gene
(genetics) a segment of DNA that is involved in producing a polypeptide chain
Allele
Alternative form of a gene
Trait
A characteristic that an organism can pass on to its offspring through its genes.
Genotype
An organism’s genetic makeup.
Phenotype
An organism’s physical appearance, or visible traits.
Gamete
Haploid cells (n) produced by diploid cells (2n) for the purpose of sexual reproduction
Fertilization
Fusion of male and female gametes.
Dominant
An allele that is always expressed
Recessive
An allele that is masked when a dominant allele is present
homozygous
organisms that have two identical alleles for a particular trait, both alleles for a trait are the same
Heterozygous
An organism that has two different alleles for a trait
Monohybrid Cross
A cross between individuals that involves one pair of contrasting traits
Dihybrid Cross
hybridization using two traits with two alleles each
Law of Dominance
In many traits one allele is dominant over the other allele. The “weaker (recessive” allele is only expressed when it is paired with another recessive allele
Law of Segregation
Mendel’s law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
Law of Independent Assortment
Each pair of alleles segregates independently of each other pair of alleles during gamete formation
Incomplete Dominance
Cases in which one allele is not completely dominant over another
Co-Dominance
a condition in which both alleles for a gene are fully expressed
X-Linked Inheritance
A pattern of inheritance in which a recessive gene is carried on the X chromosome, so that males are more likely to be affected
Multiple Alleles
three or more forms of a gene that code for a single trait
Polygenic
combined effect of two or more genes on a single character
How is a genotype different from a phenotype?
A genotype is the genetic make-up and a phenotype is the physical appearance of the trait
How much does each parent contribute to a child’s genetic make-up?
50% from each parent
How many copies of an allele does somebody have to get to express the dominant trait?
this trait is 50% and the chance of the offspring having a recessive trait 50%
,so you only need one dominant allele for this trait to be expresses
,so you only need one dominant allele for this trait to be expresses
What is the phenotypic ratio for a dihybrid cross between two heterozygous parents?
9:3:3:1
Why do more men inherit x-linked recessive diseases/conditions than women?
because of X linked inheritance. Males only need one X to get the disease.
A white rabbit and black rabbit produced offspring that were black-and-white. Explain how the baby rabbits could have inherited this color fur.
Co-dominance
A red rose bush and white rose bush produced pink flowers. What could the parental genotypes be? What is the genotype for the offspring? What type of inheritance did this illustrate?
XRXr and XrY. Genotype for offspring: XRXr. Co-dominance. You get the red and some of the white, resulting in pink.