Patterns of Inheritance- Genetics Flashcards
Character?
A heritable feature (flower colour)
Trait?
A variant of each character (purple or white)
Gene?
The instructional area of DNA on a chromosome that codes for a certain inheritable trait. Ex. Gene for eye colour, hair colour, and height.
Allele?
Two or more alternate forms of a gene, symbolized by letters. Each allele is located on the same position (Gene) on one of the pair of homologous chromosomes. Ex. Alleles for colour are blue or brown.
Dominant?
Allele that masks the other allele
Recessive?
Allele that is covered up
Homozygous?
Having two of the same allele (AA or aa); true-breeding.
Heterozygous?
Having two different alleles (Aa).
Genotype?
All of the organisms alleles (genetic information)’ both expressed and hidden. Represented by letters. Ex. Bb, BB, bb
Phenotype?
The visible, physical trait of the organism? Ex. Brown eyes.
Cross pollination?
One plant fertilizes a different plant.
Self pollination?
A plant fertilizes itself.
True-Breeding (pure bred)?
Synonymous with homozygous; plants that over several generations only produce plants like themselves. Ex. AA or aa
Hybrid?
Synonymous with heterozygous; carries two different alleles of the same gene. Ex. Aa
Parent Generation?
First organisms to breed; represented by the letters P1.
FIlial Generation?
The offspring resulting from the parent (P1) generation; represented by the letters F1 (first filial). The offspring that result from the F1 generation (first filial) are represented as the F2 generation (second filial).
What are the two influences that determine what an organisms will be like?
Hereditary and Environment
What is genetics?
The science of heredity
Gregor Mendel did some of the earliest work studying hereditary. He chose to use pea plants for his work because:
1) Pea plants have contrasting pairs of the same trait (homologous genes).
2) Peas can easily be cross pollinated.
Although peas usually___, Mendel was able to see Rudy how traits were inherited by using a process called___.
Self pollination
Cross pollination
In the process of cross pollination that Mendel used,___grains from the___of one plant would be transferred to the___of another. (Pollen grains form the___nuclei, egg cells are found at the base of the___of the pea flower).
Pollen, stamen, egg cells, sperm, pistil
What did Mendel observe?
That peas allowed to self-pollinate would consistently produce offspring identical to the parent plant. He then experimented with cross pollination to see what the offspring of parents plants that varied on only one trait would look like.
When Mendel experimented with cross pollination to see what the offspring of parent plants that varied on only one trait would look like what did he find?
Tall plants X short plants yielded tall;
Yellow seeds X green seeds yielded yellow;
Round seeds X wrinkled seeds yielded round
After Mendel’s experimented with cross pollination and parents that varied in only one trait what he did he wonder?
What happened to the characteristic lost when plants with different traits were cross-pollinated.
What was Mendel’s next experiment? What did he find in the F2 generation?
He allowed this first generation of cross bread plants (F1) to self pollinate. In the F2 generation, he found that 3/4 of the offspring exhibited the traits of the F1 generation, byt also that 1/4 of the offspring exhibited the “lost” trait of the original parent generation. He realized this meant the F1 generation must have still carried information needed for the lost trait but, for some reason, just did not show the trait. This thinking led him to propose three hypothesis.
What was Mendel’s first hypothesis?
Inherited Characteristics; The factors that Mendel referred to are now called genes.
What was Mendel’s second hypothesis?
What is the principle of dominance and recessiveness? What does this hypothesis explain What is a hybrid?
The Principle of Dominance and Recessiveness is one factor in a pair may mask the other.
This hypothesis explained why all the plants of the F1 generation were identical (the dominant trait masked the recessive trait).
A hybrid is an offspring of parents that differ in one or more traits. Hybrids express the dominant trait.
What was Mendel’s third hypothesis? What is the law of segregation? Why do we now know that this does occur? What does the first meitic division in a hybrid produce? What does the second meitic division in a hybrid produce?
The Law of Segregation is pairs of genees are separated.
We know know that this occurs as homologous chromosome are divided in the process of meiosis.
The first meitic division in a hybrid produces two different cells (one carries the dominant genes, the other the recessive).
The second meitic division in a hybrid produces four gametes with two arraign the dominant gene and two carrying the recessive gene?
What is the fourth hypothesis?
What did Mendel believe?
What has modern knowledge of chromosomes made it possible to present this hypothesis as?
What does this hypothesis mean?
The Law of Independent Assortment.
Mendel believed that genes separated and were distributed in a way independent of the other gene pairs.
Modern knowledge of chromosomes has made it possible to present this hypothesis as the Law of Independent Assortment. It means that many inherited traits are independent of other traits.
Genotype is the____.
Phenotype is____.
- actual gene
- how it works
If both genes for a trait are the same, the organisms is said to be____.
Homozygous
If the genes are not identical it is said to be____.
Heterozygous
Alleles are?
Genes that have contrasting effects on a trait. For example, T is an allele of t, and t is an allele of T.
What two things do punnet squares show?
- Probability of each resulting genotype
2. Results of each crosses phenotype
What is a monohybrid cross?
One pair of contrasting traits
What is a dihybrid cross?
One pair of contrasting traits.
What happens if heterozygous hybrid organisms are crossed in a monohybrid cross?
3/4 of the offspring will exhibit the dominant trait, and 1/4 offspring will exhibit the recessive.
What happened if heterozygous organisms are cross in a dihybrid cross?
There will be 9 possible genotypes.
