Genetics - Final Exam Flashcards
Law of Independent Assortment
Two different genes will randomly assort their alleles during the formation of haploid cells. Linked genes do not sort independently. More chromosomes = more diversity.
Phenotypic Ratio
Divide each total number of characteristic by the lowest number characteristic (usually the most recessive trait(s))
Genetic Recombination
Offspring receives a combination of alleles that differs from those in the parental generation.
2n
2 = one pair of chromosomes, while n = number of pairs.
Law of Segregation
The two copies of a gene segregate or separate from each other during transmission from parent to offspring. Only one copy of each gene is found in a gamete. At fertilization, two gametes combine randomly.
Loss-of-function
Defective copy of a gene that affects the phenotype. Recessive allele is usually loss-of-function.
Recessive Pattern of Inheritance
Must inherit two copies of mutant allele. Two heterozygous individuals will have 1/4 of offspring affected. Offspring of two affected individuals will be affected.
Dominant Pattern of Inheritance
Affected individuals will have inherited mutant allele from at least one affected parent.
Probability
P = Number of times outcome occurs / total # of possible outcomes.
Product Rule
EX: What is the probability that the couple’s first three offspring will have congenital analgesia? 1. Calculate individual probability of phenotype (1/4). 2. Multiply individual probabilities (1/4x1/4x1/4)
Product Rule Used for Combination of Different Offspring
EX: What is the probability that the first offspring will be unaffected, the second affected, and the third unaffected? (3/4 x 1/4 x 3/4)
Product Rule Used for Two or More Genes
EX: Individual with genotypes Aa Bb CC crossed with Aa bb Cc. What is probability of offspring having AA bb Cc? Do monohybrid cross for each genotype then multiply probabilities (1/4 x 1/2 x 1/2)
Binomial Expansion
Used to determine probability that certain proportion of offspring will be produced particular characteristics. What is the probability that two of five children have blue eyes?
Chi Square Test
Used to determine if a genetic hypothesis is consistent with the observed outcome of a genetic cross.
How to Set Up Chis Squared
- Determine hypothesis: is it segregated or assorted independently? 2. Calculate expected values: Determine ratio and determine probability. 3. Multiply probability with total. 4. Determine chi squared value and use chi square table. A P value less than 5% means the hypothesis is rejected.
X-Linked Inheritance`
Many genes found on X chromosome rather than Y chromosome. Genes on X chromosome govern eye color in fruit flies.
Chromosome Theory of Inheritance
Inheritance pattern of traits can be explained by transmission patterns of chromosomes during meiosis and fertilization. 1. Chromosomes contain genetic material that is transmitted from parent to offspring and from cell to cell. 2. Chromosomes replicate and are passed from generation to generation from parent to offspring. Each cell retains its individuality during cell division and gamete formation. 3. Nuclei of cells contain homologous pairs of chromosomes and are diploid. At meiosis, one of the two homologs segregates into a daughter cell nucleus. Gametes contain one set of chromosomes - they’re haploid. 4. During formation of haploid cells, nonhomologous chromosomes segregate independently. 5. Each parent contributes on set of chromosomes to offspring. Each set carries a full complement of genes.
Phases of Mitosis
Prophase, Prometaphase, Metaphase, Anaphase, Telophase
Prophase
After the chromosomes are decondensed (less tightly compacted) from interphase, mitosis begins with this stage. Chromosomes have replicated, resulting in 12 chromatids joined as 6 pairs of sister chromatids. Nuclear membrane begins to dissociate into vesicles. Nucleolus becomes less visable. Chromosomes move apart and mitotic spindle begins to form.
Prometaphase
Centrosomes move to opposite sides of cell. Spindle fibers interact with sister chromatids. Microtubules grow and are “captured” by kinetechores. Mitotic spindle is completely formed.
Metaphase
Sister chromatids align along metaphase plate. Metaphase begins once chromatids have alligned. Each pair of chromatids are attached to both poles by kinetechore microtubules.
Anaphase
Connection that holds sister chromatids together is broken. Each chromatid or monad, is linked to only one of the two poles. Chromatids move towards the pole they’re attached to. Kinetechore microtubules shorten. Poles themselves move farther apart due to elongation of polar microtubules and motor proteins.
Telophase
Chromosomes reach their perspective poles and decondense. Nuclear membrane reforms. Two nuclei with six chromosomes each.
Cytokinesis
Two nuclei and organelles are segregated into separate daughter cells. In animal cells, this occurs shortly after anaphase and a cleavage furrow is formed. In plants, a cell plate.