Chapter 5 (Part 1) Flashcards by Tamara Smith

Sexual reproduction

new offspring arise through the combination of genetic information of two individuals of different sexes, creating a genetically unique individual.

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Asexual reproduction

new offspring are produced by a single parent. The offspring are
genetically identical to each other and to their parents.

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Prokaryotes reproduce…

asexually

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what is a plasmid

a much smaller, circular, extrachromosomal DNA molecule

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What is the function of plasmids

code for additional genes that may contribute to the survival of the bacterium.

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hereditary info in prokaryotes

stored in DNA
chromosome is a single circle of double-stranded DNA

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cell division in prokaryotes have a simple cell cycle which takes place in two stages

Copy the DNA (DNA replication)
Split the cell in two, forming two daughter cells. (Binary Fission)

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1st step of DNA replication in prokaryotes

Double-stranded DNA is ‘unzipped’
(breaking of H-Bonds)

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when DNA is copied starting at the…

origin of replication

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Enzyme DNA polymerase

uses original DNA molecule as a template to form new strands of DNA

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complementary nucleotides are added to…

the exposed DNA strands in each direction

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Binary Fission

after replication chromosomes move to either side. cytoplasm separates and the membrane pinches in. making two new cells

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conjugation

acquire DNA (plasmids) from other bacteria
- cell-to-cell through pili

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transduction

acquire DNA from viruses
- inserted into bacterium by bacteriophage

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transformation

acquire DNA from surroundings
- DNA fragments are taken up from enviroment

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DNA in eukaryotic cells are…

linear and packed into compact chromosomes

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Eukaryotic cells have two ways to to divide DNA depending on the cell type

Mitosis and Meiosis

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Mitosis

cell division mechanism that occurs in somatic cells
(also in undifferentiated stem cells which become somatic cells)
(Produces 2 cells with the same number of chromosomes

Meiosis

cell division mechanism that occurs in germ cells.
→ Involves 2 rounds of cell division
(Produces 4 cells with half the number of chromosomes

Stomatic cells

any cell in a multicellular organism that is not a germ cell or undifferentiated stem cell

Germ cells

aka sex cells. reside in the gonads (ovaries and testicles) for sexual reproduction.

interphase (G1, S, and G2 phases)

Cells spend most of their time here (normal function, growth, prep for mitosis).

Mitosis (M phase)

No protein synthesis. Chromosomes condense, line-up, and separate

Cytokinesis (C phase)

cell splitting

G0 Phase

cell cycle arrest, dormant (only occurs in some cells)

G1 Phase

* Cells spend most of their life here and perform normal cell functions. * Some organelles like mitochondria are replicated here.

S Phase

* Synthesis (of DNA) phase. * DNA is replicated here before cell division

G2 Phase

* Second growth phase. Preparation for mitosis. * Can be very short or may not occur at all. * The G2 checkpoint is very important to check for mutations after DNA replication.

T/F - the # of chromosomes determines the complexity of the organism

false

Homologous chromosomes

a pair of maternal and paternal chromosomes that align with each other during meiosis

Alleles

Homologs have the same genes in the same loci along each chromosome but have different variations of those genes

Sister chromatids

a result of DNA replication and are exact copies of each other

The sister chromatids are joined together by a structure called a...

centromere

humans have how many total chromosomes

how many pairs homologous chromosomes do humans have?

A Karyotype

a visual chromosome count of an organism showing what these chromosomes look like under a light microscope

Mitosis is a continuous process, but it is divided into four distinct stages

1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

Prophase

- condensed chromosomes become visible - The nucleolus disappears - Centrioles separate and migrate to opposite ends (“poles”) of the cell

centrioles form...

a network of spindle fibers (made uo of microtubles)

spindle fibers grow from each pole until attached to...

a kinetochore (a centromere at a protein attachment site)

Metaphase

Chromosomes align at the centre of the cell. Chromosomes align along an imaginary plane that divides the cell in half.

Anaphase

sister chromatids separate (enzymes break the cohesin and the kinetochores). The microtubules of the spindle are dismantled, starting at the poles. (This pulls the chromatids toward the poles.)

Telophase

→ The spindle is dismantled → A nuclear envelope starts to form around the set of chromosomes at each pole → The chromosomes begin to uncondensed → The nucleolus reappears

Cytokinesis

occurs at the end of mitosis. is the division of the cytoplasm into equal halves. occurs by actin filaments contracting and pitching the cell into 2