BIO 111 Chapter Notes - Chapter 7: Wasatch Range, Asexual Reproduction, Dna Replication

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6 Feb 2017
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7.1: Different Life Cycles Use Different Modes of Cell Reproduction
Cell division a process by which a parent cell duplicates its genetic material and then
divides into two similar cells
o Important for growth, repairing tissues, and reproduction of all organisms
Asexual Reproduction through binary fission and mitosis
o Asexual reproduction a rapid and effective means of making new individuals
o Daughter cells are clones of the parent cell when without mutations
Mutations are alterations in DNA sequence caused by environmental
factors in DNA replication and allows for variation
o Reproduce through binary fission for prokaryotes, mitosis for eukaryotes
o Some multicellular eukaryotes can reproduce asexually
Aspen trees can reproduce sexually and asexually but most of the ones in
the Wasatch Mountains are just clones of each other because they
reproduced asexually
Sexual Reproduction through meiosis
o Sexual reproduction involves the fusion of two specialized cells called gametes
that when combined can have genetic variation from either parent
o Most diploid organisms use meiosis to make unique and varied gametes that
have half the usual amount of genetic material most cells have
This genetic material is DNA that is organized into chromosomes
Most cells (somatic cells) are not specialized, but the gametes are special
because they have only half the chromosomes as somatic cells
In somatic cells, there is two pairs of each chromosome diploid; one
from the mother and one from the father (46 all together) and they
occur in pairs called homologous pairs
The chromosomes in a homologous pair correspond to the same gene,
but might relay a different genotype
o The gamete is haploid and during sexual reproduction two gametes combine to
make a zygote in a process called fertilization. The gametes are haploid, but the
zygote is diploid
Sexual life cycles are diverse
o random selection of half of the diploid chromosome set allows for a lot of variety
and chances for evolution
7.2: Binary Fission and Mitosis
Both produce two genetically identical cells
To divide, the following events must occur:
o There must be reproductive signals initiating cell division
o DNA replication
o DNA segregation cell must distribute the replicated DNA to each of the two
new cells
o Cytokinesis cytoplasm must divide to form the two new cells
Binary fission
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o Reproductive signals: external factors such as environmental conditions and
nutrient concentrations that let the cell know whether they should divide
o DNA replication: prokaryotic cells have all genetic information on one circular
chromosome
ori: the site where replication of the circular chromosome starts (the
origin of replication)
ter: the site where replication ends (the terminus of replication)
chromosome replication takes place in a bunch of proteins, called the
repliatio ople
once replicated the two identical chromosomes separate and go to
opposite ends of the cell
o DNA segregation
Replication begins in the center of the cell, but as it is transcribed the ori
regions bind to proteins that move the chromosomes to opposite sides of
the cell
The proteins hydrolyze ATP in order to move the DNA
Cytoskeleton helps with this process
o Cytokinesis
Pinching in of the cell membrane caused by the contraction of a ring of
fibers on the inside surface of the membrane made of actin
While pinching the cell, new cell membrane materials are deposited until
the two cells are separate
Mitosis
o Reproductive signals
Eukaroti ells do’t ostatl diide heeer the eiroetal
conditions are adequate
“oe ells do’t even divide
Divide based on the function of the entire organism
o DNA replication
Have more than one chromosome, but otherwise pretty similar to
prokaryotic DNA replication
Occurs only during a specific stage of the cell cycle
o DNA segregation
Much more complicated than in prokaryotes because of the nuclear
envelope and a multitude of chromosomes that must equally be shared
in each of the new cells
o Cytokinesis
Different for plant cells and animal cells
Cell Cycle for eukaryotes
o M phase
Mitosis the set of processes in which the chromosome becomes
condensed and then segregates into two new nuclei
Cytokinesis the separation of the cytoplasm
o Interphase
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