Cell division and DNA 1. Parent cell 2. DNA Replication 3. Daughter Cells

General idea: As organisms grow their cells must multiply ‘Parent’ cells give rise to ‘_______’ cells DNA inside parent cells must be duplicated One copy for each daughter cell First, need to understand chromosomes & DNA

Chromosomes: coiled strands of DNA Number varies among species __ in humans, __ HOMOLOGOUS PAIRS Each pair=1 from ___ + 1 from ___ Fruit fly Human karyotype One homologous pair Muntjac deer From father From mother Rat

Chromosomes can occur singly or in duplicate Called a chromosome in ______ case Unreplicated chromosome ________ chromosome ________ chromosomes Sister ________ (identical) centromere

Two types of cell division: MITOSIS: creation of ________ cells For _______ and replacement MEIOSIS: creation of ____ cells Topic of our next lecture Cell division

Mitosis is a part of the overall Cell Cycle Cell division Growth phases not addressed in later slides Cell division

(uncoiled chromosomes) Interphase - Preparation for _____ cell division - DNA ________, seen as ________ (cloudy) - Centrioles clustered together Nucleus Cell membrane Chromatin (uncoiled chromosomes) Centrioles Sketch 1 Cell division > mitosis > interphase

X x Mitosis is studied in phases Early Prophase of Mitosis Sketch 2 - Chromatin condenses into ___________ chromosomes - Centrioles move apart - Spindle fibers extend toward _________________ This organism has only _ pairs of chromosomes X x Spindle fibers ____________ pair of chromosomes (one from mother, another from father) One _______ chromosome (a pair of sister chromatids) Sketch 2 Cell division > mitosis > prophase

X X x x Late Prophase of mitosis: - Nuclear envelope __________ - Spindle fibers connect to _____________ X x centromere X x Sketch 3 Cell division > mitosis > prophase

X X x x Metaphase: Spindle fibers pull chromosomes to _____________ metaphase plate Sketch 4 Cell division > mitosis > metaphase

        Anaphase: - Sister chromatids get separated Become ________ chromosomes         Daughter chromosome Sketch 5 Cell division > mitosis > anaphase

        5) Telophase: Two nuclear membranes develop Cytoplasm becomes divided     Daughter cells are ________ identical     Sketch 6 Cell division > mitosis > telophase

In animals, ___________________separates daughter cells Telophase differs in plant & animal cells In animals, ___________________separates daughter cells In plants, a _________ develops between cells Cell division > mitosis > telophase

DNA = Deoxyribonucleic Acid DNA molecule Chromosome histone proteins one base pair Human DNA: ~ 2 m (~6 ft) long – in each cell! ~ 20,000-25,000 genes (genetic traits) ~ 3 billion pairs of monomers (___________) DNA

Genome maps A record of all base pairs & ________ of a species E.g., Human chromosome #2: Known genes:

The monomers of DNA are ___________ Nucleotides have 3 parts: Nitrogenous ____ Phosphate _____ Deoxyribose _____ Adenine Nitrogenous base can be 1 of 4 types: Guanine, Cytosine, Adenine or Thymine DNA > monomers

Nucleotides are linked by _____________ backbone Phosphates Bases Sugars P Cytosine S P Adenine S P S Guanine DNA > sugar-phosphate backbone

DNA is a ‘double-spiral’ molecule A ladder-like “___________” Variation in sequence of ________ produces variation in ‘genetic code’ E.g., the codes AGTA and GATA code for different information DNA is a ‘double-spiral’ molecule A ladder-like “___________” Bonded pairs of nitrogenous bases Sugar-phosphate backbones The double strand is twisted cork-screw-like DNA > double helix

James Watson (American, 23) and Francis Crick (Brit, 35) won the 1953 Nobel Prize for describing the ____________ structure of DNA Very short: move up to end of mitosis, make lecture 10 all meiosis Introns & exons DNA > double helix

DNA strands are held together by ________ bonds Hydrogen bonds Only ___________ base pairs bond together Complementary base pairs: Adenine & Thymine (A-T); use __ hydrogen bonds Cytosine & Guanine (C-G); use __hydrogen bonds DNA > replication

DNA replication (during __________): Chromosomes unravel, appear as cloudy ________ Helicase enzyme “_______” DNA strands Breaks hydrogen bonds binding the strands Creates a “replication _______” A C G T Helicase A C G T DNA > replication > unzipping

DNA Polymerases build new daughter strands Attach _____________ nucleotides to each DNA strand A C G DNA polymerase T __ __ A C G T DNA > replication > daughter strands

DNA POLYMERASES build new daughter strands Attach complementary nucleotides to template A C G T A C G T DNA > replication > daughter strands

A C G T A C G T DNA > replication > daughter strands

Each with ½ ___ and ½ ___ DNA G T 2 daughter DNAs A C G T Identical Each with ½ ___ and ½ ___ DNA Ensures accurate replication of DNA for both new _______ cells DNA > replication > daughter strands

Replication can not continue to ____ base pairs ________ are non-coding end-caps where shortening occurs 2nd DNA polymerase lags behind first Leaves a bit of single-stranded DNA at ends _______ chromosome with each replication Become shorter with each replication – with ____ After telomeres become completely eroded: - _____ genes become eroded - genetic ______ occur