12: Asexual and Sexual Reproduction in Eukaryotes
- Page ID
- 182446
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 12.0: Introduction
- This page covers asexual and sexual reproduction, highlighting chromosome segregation in mitosis and meiosis that leads to haploid gametes. It addresses organelle replication during eukaryotic cell division, emphasizing cytokinesis and the cell cycle stages. Key processes like DNA synthesis, cell growth decisions, and replication checkpoints are examined, along with the impact of mutations on these processes.
- 12.1: Ploidy during the cell cycle
- This page discusses the completion of DNA synthesis during the S phase, resulting in two chromosome copies as cells enter the G2 phase, where they can grow. It notes that ploidy remains consistent during asexual reproduction, and G2 cells are effectively tetraploid. The page raises questions about DNA damage detection, repair limitations, mutation effects, and variations in gene expression throughout the cell cycle.
- 12.2: Monitoring cellular processes- mitosis
- This page covers the mitosis process in eukaryotic cells, emphasizing the mitotic spindle's role and the critical function of cell cycle checkpoints to ensure proper chromosome alignment and distribution. It explains how replicated chromosomes connect with the spindle via kinetochores and describes the regulatory role of cyclin-dependent kinases (CDKs) in these checkpoints.
- 12.3: Sex-determination and its chromosomal basis
- This page covers two key topics: the mechanisms of sex determination in eukaryotes, including genetic and environmental factors, and the Holocene mammoth extinction, caused by climate change, habitat loss, and overhunting. It highlights the role of sexual reproduction in genetic diversity and evolution, while discussing the factors leading to the decline of woolly mammoths, shedding light on the effects of environmental changes on species survival.
- 12.4: Steps in meiosis- from diploid to haploid
- This page covers sexual reproduction in animals, focusing on how a diploid zygote forms from haploid gametes produced by the germ line. It distinguishes between male and female gametes and discusses sexual dimorphism and evolutionary implications. The page details meiosis in both sexes, resulting in sperm and eggs, and notes that fertilization initiates a genetically distinct organism's life, which continues in a changed form. Additionally, it defines germ cells and somatic cells.
- 12.5: Recombination and independent segregation
- This page discusses meiosis, highlighting its role in creating genetic diversity through processes like chromosome pairing, crossing-over, and independent assortment. It contrasts meiosis with mitosis and emphasizes the formation of unique gametes that, upon fertilization, contribute to new organisms and evolutionary potential. The text raises questions about the implications of genetic variation on traits and reproduction, stressing its significance in understanding inheritance and evolution.
- 12.6: Linkage and haplotypes
- This page discusses the significance of meiotic recombination in allele separation on chromosomes, its influence on allele frequencies under selection, and the unintended effects on neighboring alleles. It highlights the distance-dependent nature of these effects, measured in centimorgans, and the formation of haplotypes. The implications of these processes are connected to gene regulation and evolutionary outcomes for populations across generations.
- 12.7: X-inactivation and sex-linked traits
- This page discusses the XY chromosome-based system of sex determination, highlighting differences in genotypes between males and females and the resulting gene expression implications. It explains how mammals manage gene imbalance through X-inactivation in females, where one of the two X chromosomes is randomly silenced. The roles of the XIST gene, which induces inactivation, and the TSIX gene, which protects the active X, are detailed, ensuring only one X chromosome is expressed per cell.
- 12.8: X-linked diseases and mono-allelic gene expression
- This page explores genetic differences in X-linked traits between male and female cats, noting that males express recessive alleles due to having one X chromosome, while females exhibit mosaicism with potential expression of both X alleles. It also discusses random monoallelic expression in diploid cells, where transcriptional silencing can lead to the dominance of one allele, affecting cellular growth and survival, with ongoing research into the implications for development and disease.