Review Sheet Chapter 8

Review sheet – Chapter 8

 Understand that asexual reproduction involves the creation of a genetically-identical offspring from a single parent; no eggs or sperm (fertilization) are involved

 Understand that genetic diversity is sacrificed during asexual reproduction (all offspring are exact replicates of ‘parent’)

 Know that gametes are sex cells: eggs and sperm, which can combine to form a new, unique, genetically-distinctive offspring

 Know that prokaryotes reproduce via binary fission, where chromosomes are replicated and the cell splits in half into 2

 Know that prokaryotes have 1 chromosome, while human cells contain multiple chromosomes

 Know that chromosomes contain not only DNA, but also proteins which provide structure and control over the activity of genes

 Know that human cells contain 46 chromosomes, consisting of 22 pairs of autosomes and 1 pair of sex chromosomes

 Understand that before a cell can divide, its DNA (chromosomes) must first be replicated

 Know that a replicated chromosome consists of 2 “sister chromatids”

 Know that the cell cycle consists of interphase and the mitotic phase

 Understand that most of the cell spends its life in interphase – a period of growth and preparation for cell division

 Understand that DNA (chromosome) replication occurs during interphase

 Understand that interphase is made up of 3 stages: G1, S, and G2, with DNA replication occurring in the “S” phase

 Understand that the mitotic stage is made up of mitosis (nuclear division and distribution) and cytokinesis (the physical act of splitting 1 cell into 2)

 Understand that mitosis is made up of 5 stages:

o Prophase – mitotic spindle forms, chromatin condenses

o Prometaphase – nuclear envelope dissolves, chromosomes attach to spindle

o Metaphase – chromosomes align perpendicularly at center

o Anaphase – each sister chromatid of replicatec chromosome separates o Telophase – nuclear envelope reforms, chromatin uncoils, mitotic spindle disappears

 Understand that proteins regulate each step of the cell cycle

 Understand that cancer is a disease of the cell cycle, where the control over cell division becomes unchecked and unregulated

 Understand that meiosis is a type of cell division resulting in cells containing half the number of chromosomes as the ‘parent’ cell

 Know that meiosis occurs only in reproductive organs and produces gametes (sex cells) such as eggs, sperm, and pollen

 Understand that cells containing 2 sets of chromosomes are called diploid; cells containing only 1 set are called haploid

 Understand that sex cells (gametes) are haploid, but all other cells are diploid

 Understand that a homologous pair of chromosomes can bear 2 different kinds of genetic information for the same characteristics (different version of a gene)

 Understand that crossing over occurs only in meiosis (not mitosis) and results in genetically-new chromatids (chromosomes)

 Understand that most changes in chromosome number are harmful and some are fatal

 Know that Down’s syndrome (trisomy 21) results from having 3 copies of chromosome 21 (instead of 2)

 Understand that alterations in the number of chromosomes in sex chromosomes are not fatal

 Understand that females inactivate their extra (second) X chromosome to prevent a lethal overdose of genetic information; this inactivation is random and can result in different chromosomes (the X from the mother, or the X from the father) being inactivated in different cells (calico cats are an example)