The scientific study of heredity
process in sexual reproduction in which male and female reproductive cells join to form a new cell
specific characteristic of an individual
The factors that are passed from parent to offspring
one of a number of different forms of a gene
How many alleles per trait would there be in a gamete in a pea plant?
There is only one allele per trait.
How can two alleles from different genes be inherited together?
Alleles of different genes tend to be inherited together when those genes are on the same chromosome.
How many alleles for a particular trait do pea plants inherit from each parent?
There is only one allele for a particular trait.
separation of alleles
the likelihood that a particular event will occur
Why are the principles of probability used for genetics?
They predict the traits of the offspring of the genetic crosses.
What is the probability of a penny coming up heads when flipped?
having two identical alleles for a trait
If an offspring is homozygous recessive, what do you know about the parents?
The offspring recieved one recessive allele from each parent.
having two different alleles for a trait
physical characteristics of an organism
Example of a phenotype in pea plants and list the genotype
50% tall and short; TT, Tt, tt; Pea plant height may be either tall or short.
the genetic makeup of an organism
How is a phenotype different from a genotype?
A phenotype is a physical characteristic of an organism and a genotype is the genetic makeup of an organism.
One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes
Situation in which the phenotypes produced by both alleles are completely expressed
one allele is not completely dominant over the other allele
a gene that has more than two alleles
trait controlled by two or more genes
term used to refer to chromosomes in which one set comes from the male parent and one set comes from the female parent
term used to refer to a cell that contains two sets of homologous chromosomes
What symbol is used to represent a diploid?
2N; N represents the single set of chromosomes found in a gamete.
If an organism's diploid number is 46, what is the number for haploid?
term used to refer to a cell that contains only a single set of genes
What symbol is used to represent a haploid?
process by which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
process in which homologous chromosomes exchange portions of their chromatids during meiosis
a fertilized egg
Where does an oganism get its unique characteristics?
An individual's unique characteristics are determined by factors that are passed from parent to offspring.
How are different forms of a gene passed to offspring?
When gametes are made, the alleles for each trait seperate from each other. That way each gamete carries only one allele for each gene.
How can we use probability to predict traits?
Punnett squares use probability to predict the combinations of alleles in a genetic cross.
How do alleles segregate when more than one gene is involved?
The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes
What did Gregor Mendel contribute to what we know about genetics?
Mendel's principles of heredity form the basis of modern genetics.
What are some exceptions to Mendel's principles?
Traits can be controlled by incomplete alleles and codominant alleles, or by genes with more than two possible alleles. Traits can also be controlled by several genes.
Does the environment have a role on how genes determine traits?
Environmental conditions can change the gene expression and influence genetically controlled traits.
How many sets of genes are found in most adult organisms?
The diploid cells of most adult organisms contain two complete sets of inherited chromosomes and so two complete sets of genes.
What happens during each phase of Meiosis I?
During prophase, each copied chromosome matches up with its homologous chromosome. Crossing-over increases the allele combinations on chromatids. In metaphase, spindle fibers form. In anaphase, chromatids seperate. In telophase, a nuclear membrane forms around the chromosomes. During cytokinnesis, the cells spilt, and two cells are made.
What happens during each phase of Meiosis II?
During prophase, the chromosomes become visible. During metaphase, the chromosomes line up in the middle of the cell. During anaphase, the chromatids seperate. During telophase and cytokinesis, four new haploid cells are formed.
How is meiosis different from mitosis?
Mitosis can be a form of asexual reproduction, does not change the number of chromosomes, and makes two identical diploid cells. Meiosis is a step in sexual reproduction, cuts chromosomes in half, and makes four different haploid cells.
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes
The fibers pull the homologous chromosomes toward opposite ends of the cell
Telophase I and Cytokinesis
Nuclear membranes form. The cell separates into two cells.
meiosis I results in two haploid daugther cells, each with half the number of chromosomes as the original cell
the chromosomes line up in a similar way to the metaphase stage of mitosis
the sister chromatids separate and move toward opposite ends of the cell
Telophase II and Cytokinesis
meiosis II results in 4 haploid daughter cells
Pure bred means that the plants self-pollinate and produce offspring identical to themselves.
A hybrid is the offspring that crosses between parents with different traits.
What does dominant mean?
The trait is visible whenever a dominant allele is present in the genotype such as TT or Tt(both tall)
What does recessive mean?
A trait is hidden unless the genotype is homozygous recessive such as a tt
Principle of Segregation
states that the pair of alleles for each parent seperate and only one allele passes from each parent to an offspring
Principle of independent assortment
states that genes for different traits can segregate independently during the formation of gametes
Why did Mendel use pea plants for his model organism?
They are small and are easy to grow
Why did Thomas Hunt Morgan use fruit flies for his model organism?
They produce hundreds of offspring.
Name the pattern of inheritance that would produce the speckled chicken with black and white feathers
What is the reason for codominance?
The phenotypes for both alleles are equally expressed in the offspring.
Describe a situation in flowers that show incomplete dominance
In four o'clock plants the R stands for red and W stands for white flowers. If a plant is RR, then the flower will be red. If WW, then the flower will be white.
A version of gene is the same thing as an what?
What patterns of inheirtance are illustrated by ABO Human Blood Types? Explain.
One pattern of inheirtance is codominance and the examples are A is equally dominant to B, so the blood type is AB. Multiple alleles have three possible alleles which are A,B,and O
What is meant by a polygenic trait?
A polygenic trait is a trait that is contolled by two or more genes and produce a wide range of possible phenotypes.
Example of a polygenic trait in humans.
Explain what causes the different colors in the wings of western white butterflies.
Western white butterflies that hatch in the spring have darker wing patterns than those who hatch in the summer.
Define homologous chromosomes
Chromosome pairs of the same length, centromere positions, and staining patterns for the same characteristics.
Explain how to determine the gametes for a dihybrid cross when the parent gamete is TtYy
TtYy; First: TY; Outside: Ty; Inside: tY; Last: Ty. The F.O.I.L. method determines all the possible allele combinations