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Genetics Exam 2
Mendelian Genetics and Meiosis/Mitosis
| Question | Answer |
|---|---|
| How did people think inheritance occurred before Mendel? | Preformation and Blending Hypothesis |
| What made pea plants an excellent model system for Mendel to study inheritance? | Several varieties, easy to self and cross fertilize, relatively fast generation time, and they produce many offspring. |
| What is the Law of Segregation? | the two members of a gene pair segregate from each other in meiosis; each gamete has an equal probability of obtaining either member of the gene pair. Equal number of progeny types. |
| What is the Law of Independent Assortment? | Unlinked or distantly linked segregating gene pairs assort independently at meiosis. |
| What is the exception to the Law of Independent Assortment? | genes on the same chromosome generally do not assort independently because they are held together by the chromosome itself |
| What is the Chi Square test? What is it used for? | A statistical test which determines the probability of obtaining observed proportions by chance, under a specific hypothesis. Checks actual ratios against expected ratios in experimental situations. Observed results are compared to those by a hypothesis. |
| What are the features of an autosomal recessive disorder? | The disorder generally appears in the progeny of unaffected parents. The affected progeny affects both males and females |
| What are the features of an autosomal dominant disorder? | the Phenotype tends to appear in every generation. the affected progeny includes both males and females. |
| What is incomplete dominance? | A situation in which a heterozygote shows a phenotype quantitatively intermediate between the corresponding homozygote phenotypes. |
| What is incomplete penetrance? | not every individual with the genotype expresses the corresponding phenotype |
| What is Expressivity? | A measure for describing the range of phenotypic expression |
| What is overdominance? | a phenotypic relation in which the phenotypic expression of the heterozygote is greater than that of either homozygote |
| What is hybrid vigor? | a situation in which an F1 is larger or healthier than its two different pure parental lines |
| Explain codominance using rabbit coat color | the gene tyrosinase can convert the tyrosine into various forms of melanin. Codominance is when two alleles are dominant. The gene glycosyl transferase is both A and B dominant in ABO blood types |
| What are the features of a pedigree for a sex-linked trait? | affected individuals will rarely be females; affected males do not pass the trait to sons. |
| What are the features of a pedigree for a sex influenced trait? | mostly men would be affected, some women, and it can pass from father to son |
| What is epistasis? | alleles of one gene mask phenotype of another gene |
| What is complementation? | the production of a wild-type phenotype from parents with recessive phenotype |
| How does cell division occur in prokaryotes? | cell division can occur with binary fission; a process in which the parent cell splits into two daughter cells using septum formation |
| What are the four stages of interphase? | G1 phase, G0 phase, S phase, G2 phase |
| What processes make up M phase of the eukaryoticc cell cycle? | mitosis and cytokinesis |
| What are the key features of the mitotic spindle?? | centrosomes and microtubles which are polar/overlapping, have a kinetochore, and an aster on each end |
| What are the five stages of mitosis? | prophase, prometaphase, metaphase, anaphase, and telophase |
| Describe what happens in prophase | chromosomes become distinct and are condensed into spirals or coils |
| Describe what happens in prometaphase | the sister chromatids are joined at the centromere, the nucleoli disappear and the nuclear membrane begins to break down |
| Describe what happens in metaphase | the nuclear spindle is prominent, the chromosomes move to the equatorial plane where the centromeres attach to a spindle fiber from each pole |
| Describe what happens in anaphase | the pairs of sister chromatids separate,one to each pole, the centromeres separate creating V-shaped structures |
| Describe what happens in telophase | a nuclear membrane reforms around each daughter nucleus, the chromosomes uncoil, nucleoli reappear, the spindle disperses, cytoplasm is divided in two. |
| Explain the key differences between mitosis and meiosis | mitosis takes one nuclear division in somatic cells, meiosis takes two in reproductive cells. mitosis produces two diploid cells, meiosis produces four haploid cells. mitosis maintains chromosome number, meiosis reduces chromosomes by half. |
| How are metaphase 1 and metaphase 2 of meiosis different from mitosis? | Metaphase 1 is different because the centromeres do not divide. Metaphase 2 is different because the chromatids partly dissociate rather than being closely pressed together |
| What are the five steps in prophase 1 of meiosis? | Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis |
| What happens in Leptotene? | the chromosomes become visible as long, thin single threads. Chromosomes continue to contract, and centromeres develop along each chromosome |
| What happens in Zygotene? | active pairing of the threads. Each chromosome has a pairing partner and become paired along their lengths (synapsed) |
| What happens in Pachytene? | Chromosomes are fully synapsed. Nucleoli are pronounced. Chromomeres align in the paired homologs. Crossing over is complete (chiasmata) |
| What happens in Diplotene? | Each chromosome becomes a pair of sister chromatids. Chiasmata appear between nonsister chromatids. |
| What happens in Diakinesis? | Further chromosome contraction. The chromosome threads are replaced by compact units. |
| What is the Chromosome Theory of Inheritance? | Inheritance of traits can be explained by transmission of chromosomes during gametogenesis and fertilization |
| What is cytoplasmic inheritance? | inheritance through genes found in cytoplasmic organelles |
| Chloroplast genome | 100-200kb in size. 60-300 copies per cell |
| Mitochondrial genome | size varies greatly. 5-8 copies per cell. They are circular. |
| What is heteroplasmy? | a mix of mutant and wild type organelles that is due to cytoplasmic segregation |
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